Showing papers in "Journal of Economic Entomology in 2004"
TL;DR: Results indicated a several-fold advantage for the males-only strain as measured by the level of induced sterility, especially at the very high release ratios of 100:1 recorded in 1997.
Abstract: The effect of releases of bisexual (males and female) and unisexual (male only) sterilized medflies was compared in three large field evaluations over a 3-yr period (1995–1997) in southwestern Guatemala. The two strains tested were a genetic sexing strain, Vienna-4/Tol-94, carrying the temperature sensitive tsl gene to eliminate females in the egg stage, and the standard bisexual Petapa strain. Flies were mass-reared, sterilized by irradiation as pupae, shipped to a field center, and released by air as young adults over 2 km by 2 km core areas in the centers of separate 6 km by 6 km test plots. Strain performance was monitored weekly by trapping sterile and wild male adults in core and buffer areas and by collecting eggs from coffee berries to determine induced sterility. Results indicated a several-fold advantage for the males-only strain as measured by the level of induced sterility, especially at the very high release ratios of 100:1 recorded in 1997. During that final test year, sterile-fly release rates were increased to provide high sterile:wild (S:W) fly ratios in the field, and egg sterility reached levels in excess of 70% in plots were the male-only strain was used. However, in the plots where the bisexual strain was released, induced sterility only reached 12% despite S:W ratios above 1,000:1.
263 citations
TL;DR: Beekeepers in temperate climates should combine late autumn management strategies with treatment protocols that keep the mite population at low levels before and during the period when the winter bees emerge.
Abstract: The ectoparasitic mite Varroa destructor (Anderson & Trueman) is the most destructive pest of the honey bee, Apis mellifera L., in Europe and the United States. In temperate zones, the main losses of colonies from the mites occur during colony overwintering. To obtain a deeper knowledge of this phenomenon, we studied the mites’ impact on the vitellogenin titer, the total protein stores in the hemolymph, the hemocyte characteristics, and the ecdysteroid titer of adult honey bees. These physiological characteristics are indicators of long-time survival and endocrine function, and we show that they change if bees have been infested by mites during the pupal stage. Compared with noninfested workers, adult bees infested as pupae do not fully develop physiological features typical of long-lived wintering bees. Management procedures designed to kill V. destructor in late autumn may thus fail to prevent losses of colonies because many of the adult bees are no longer able to survive until spring. Beekeepers in temperate climates should therefore combine late autumn management strategies with treatment protocols that keep the mite population at low levels before and during the period when the winter bees emerge.
237 citations
TL;DR: It is proposed that nonpathogenic bacteria can be used as a probiotic to enhance honey bee immunity, helping bee larvae, and other life stages, survive attacks from pathogens in the field.
Abstract: To explore immune system activation in the honey bee, Apis mellifera L., larvae of four ages were exposed through feeding to spores of a natural pathogen, Paenibacillus larvae larvae, to cells of a diverse set of related nonpathogenic bacteria, and to bacterial coat components. These larvae were then assayed for RNA levels of genes encoding two antibacterial peptides, abaecin and defensin. Larvae exposed to either P. l. larvae or a mix of nonpathogenic bacteria showed high RNA levels for the abaecin gene relative to controls. First instars responded significantly to the presence of the nonpathogenic mix within 12 h after exposure, a time when they remain highly susceptible to bacterial invasion. This response was sustained for two successive instars, eventually becoming 21-fold higher in larvae exposed to probiotic spores versus control larvae. The mixture of nonpathogenic bacteria is therefore presented as a potential surrogate for assaying the immune responses of different honey bee lineages. It also is proposed that nonpathogenic bacteria can be used as a probiotic to enhance honey bee immunity, helping bee larvae, and other life stages, survive attacks from pathogens in the field.
211 citations
TL;DR: The hypothesis that diatomaceous earth enhances the efficacy of B. bassiana against larval T. castaneum, at least in part by damaging the insect cuticle, thus increasing conidial attachment and making nutrients more available to conidia for their germination is supported.
Abstract: This research tested the suppressive ability of Beauveria bassiana (Balsamo) Vuillemin alone and in combination with diatomaceous earth against the red flour beetle, Tribolium castaneum (Herbst). Adults did not show a dose response to B. bassiana, and the addition of diatomaceous earth (DE) did not result in a significant increase in mortality. Against larvae, however, DE at 190 mg/kg grain enhanced the efficacy of B. bassiana at all concentrations ranging from 33 to 2,700 mg of conidia per kilogram of grain. The presence of DE resulted in 17- and 16-fold decreases in the median lethal concentration of B. bassiana at 56 and 75% RH, respectively. No significant differences in larval mortality in response to B. bassiana and diatomaceous earth alone or in combination were found between 56 and 75% RH. Conidial attachment to larvae was significantly greater with 190 mg/kg DE than without it. The partial analysis of lipids taken up by DE from the larvae revealed the removal of phospholipids and long-chain fatty acids. These results support the hypothesis that diatomaceous earth enhances the efficacy of B. bassiana against larval T. castaneum, at least in part by damaging the insect cuticle, thus increasing conidial attachment and making nutrients more available to conidia for their germination.
171 citations
TL;DR: Results indicate that the mode of delivery of these essential oils was largely a result of action in the vapor phase via the respiratory system, and merit further study as potential fumigants for T. urticae control.
Abstract: Fifty-three plant essential oils were tested for their toxicity against eggs and adults of Tetranychus urticae Koch as well as adults of Phytoseiulus persimilis Athias-Henriot, by using a filter paper diffusion bioassay without allowing direct contact. Responses varied according to oil type and dose, and mite species. In a plastic container (4.5 by 9.5 cm) bioassay at 14 x 10(-3) microl/ml air, caraway seed, citronella java, lemon eucalyptus, pennyroyal, and peppermint oils gave > 90% mortality against adult T. urticae, whereas 82 and 81% mortality was observed with sage and spearmint oils, respectively. With the exception of sage oil, the other six essential oils were highly effective against T. urticae eggs at 9.3 x 10(-3) microl/ml air. Against adult P. persimilis, these six test oils caused > 90% mortality at 7.1 x 10(-3) microl/ml air. Particularly peppermint oil at 4.7 x 10(-3) microl/ml air was highly toxic. In an acrylic cage (30 by 30 by 40 cm ) test, lemon eucalyptus, pennyroyal, peppermint, and spearmint oils were highly effective against adult T. urticae at 1.4 x 10(-3) microl/ml air. These results indicate that the mode of delivery of these essential oils was largely a result of action in the vapor phase via the respiratory system. The essential oils described herein merit further study as potential fumigants for T. urticae control.
162 citations
TL;DR: The optimal temperature for soybean aphid growth and reproduction on soybean under controlled conditions was determined, using a modification of the nonlinear Logan model, to be 34.9 and 27.8°C.
Abstract: Soybean aphid, Aphis glycines Matsumura, is now widely established in soybean, Glycine max L., production areas of the northern United States and southern Canada and is becoming an important economic pest. Temperature effect on soybean aphid fecundity and survivorship is not well understood. We determined the optimal temperature for soybean aphid growth and reproduction on soybean under controlled conditions. We constructed life tables for soybean aphid at 20, 25, 30, and 35°C with a photoperiod of 16:8 (L:D) h. Population growth rates were greatest at 25°C. As temperature increased, net fecundity, gross fecundity, generation time, and life expectancy decreased. The prereproductive period did not differ between 20 and 30°C; however, at 30°C aphids required more degree-days (base 8.6°C) to develop. Nymphs exposed to 35°C did not complete development, and all individuals died within 11 d. Reproductive periods were significantly different at all temperatures, with aphids reproducing longer and producing more progeny at 20 and 25°C than at 30 or 35°C. Using a modification of the nonlinear Logan model, we estimated upper and optimal developmental thresholds to be 34.9 and 27.8°C, respectively. At 25°C, aphid populations doubled in 1.5 d; at 20 and 30°C, populations doubled in 1.9 d.
160 citations
TL;DR: In cross-resistance assays with both neonicotinoids, the strain that had been selected with thiamethoxam for 12 generations demonstrated almost no cross- Resistance to acetamiprid, whereas the acetamIPrid-selected strain exhibited high cross-Resistance of >500-fold to thiamETHoxam.
Abstract: The dynamics of resistance in the sweetpotato whitefly, Bemisia tabaci (Gennadius), to the neonicotinoids acetamiprid and thiamethoxam was studied extensively in cotton fields in Israel during the cotton-growing seasons 1999–2003. Whitefly strains were collected in early and late seasons mainly in three locations in northern, central, and southern Israel. The whiteflies were assayed under laboratory conditions for susceptibility to neonicotinoids, as part of the Israeli cotton insecticide resistance management strategy. Selections to both acetamiprid and thiamethoxam and cross-resistance between them also were conducted in the laboratory. Although no appreciable resistance to acetamiprid was observed up to 2001, a slight increase of approximately five-fold resistance was detected during 2002 and 2003. However, from 2001 to 2003 thiamethoxam resistance increased >100-fold in the Ayalon Valley and Carmel Coast cotton fields. In cross-resistance assays with both neonicotinoids, the strain that had been selected with thiamethoxam for 12 generations demonstrated almost no cross-resistance to acetamiprid, whereas the acetamiprid-selected strain exhibited high cross-resistance of >500-fold to thiamethoxam.
157 citations
TL;DR: Observations of aphid behavior on leaves indicated that aphids departed from the leaves of resistant plants 8-24 h after being placed on them, whereas they remained indefinitely on leaves of susceptible cultivars and developed colonies.
Abstract: The fecundity, longevity, mortality, and maturation of the soybean aphid, Aphis glycines Matsumura (Homoptera: Aphididae), were characterized using three resistant soybean, Glycine max (L.) Merrill, genotypes ('Dowling', 'Jackson', and PI200538 'Sugao Zarai') and two susceptible genotypes ('Pana' and 'Loda'). Antibiosis in the resistant genotypes was demonstrated by a significant decrease in fecundity and longevity and increased mortality of A. glycines. Aphid fecundity, measured as number of offspring produced in the first 10 d by each viviparous aptera, was higher on Pana than on the resistant genotypes. Aphid longevity, the mean number of days a 1-d-old adult lived, was 7 d longer on Pana than on Dowling and Jackson. The mortality of both viviparous apterae and nymphs on resistant genotypes was significantly higher than on susceptible genotypes. A greater number of first instars survived to maturation stage (date of first reproduction) on susceptible plants than on resistant plants. None of the first instars placed on Dowling and PI200538 leaves survived to maturation. Observations of aphid behavior on leaves indicated that aphids departed from the leaves of resistant plants 8-24 h after being placed on them, whereas they remained indefinitely on leaves of susceptible cultivars and developed colonies. Reduced feeding due to ingestion of potentially toxic compounds in soybean may explain the possible mechanism of resistance to the soybean aphid.
153 citations
TL;DR: Provesta bait containing spinosad was evaluated against two parasitoids of tephritid fruit flies and Parasitoids were less susceptible than fruit flies to such a degree that use ofspinosad in bait spray should be compatible with these parasitoid species.
Abstract: The feeding toxicity of the natural insecticide spinosad in Provesta protein bait was evaluated for three economically important fruit fly species, the Mediterranean fruit fly, Ceratitis capitata (Wiedemann); the melon fly, Bactrocera cucurbitae Coquillett; and the oriental fruit fly, Bactrocera dorsalis Hendel. Both females and males were evaluated. Spinosad was remarkably similar in toxicity to all three fruit fly species. Male C. capitata (24 h LC50 values and 95% fiducial limits = 2.8 [2.60–3.0] mg/liter spinosad) were significantly, although only slightly more susceptible to spinosad than females (4.2 [3.8–4.6] mg/liter). Male (5.5 [4.7–6.6] mg/liter) and female (4.3 [3.7–4.9] mg/liter) B. cucurbitae were equally susceptible to spinosad. Female (3.3 [3.1–3.6] mg/liter) and male (3.1 [2.9–3.3] mg/liter) B. dorsalis also were equally susceptible to spinosad. Provesta bait containing spinosad also was evaluated against two parasitoids of tephritid fruit flies, Fopius arisanus (Sonan) and Pysttalia fletcheri (Silvestri). These parasitoids did not feed on the bait, so a contact toxicity test was conducted. Significant amounts of mortality were found only after exposure of parasitoids to spinosad-coated glass vials with concentrations ≥500 mg/liter spinosad. Parasitoids were less susceptible than fruit flies to such a degree that use of spinosad in bait spray should be compatible with these parasitoid species. Because the fruit flies tested in this study were so susceptible to spinosad, this product seems to be promising as a bait spray additive and a replacement for malathion for control of these species.
127 citations
TL;DR: The results indicate that high gossypol in host cotton had an antibiotic effect on A.gossypii and showed a positive effect on growth and development of P. japonica at the third trophic level, which suggests compatibility between one form of host plant resistance and biological control by predators.
Abstract: The effects of three cotton cultivars with low ('ZMZ13'), medium ('HZ401'), and high ('M9101') gossypol contents on the development, reproduction, and survival of Aphis gossypii Glover and its predator Propylaea japonica (Thunberg) were investigated. Developmental duration and immature survivorship did not vary between aphids on the three cultivars, whereas A. gossypii feeding on M9101 (high gossypol cultivar) displayed significantly shorter adult longevity and lower fecundity than aphids fed on 'ZMS13' and 'HZ401'. Free fatty acid content in cotton aphids reared on 'M9101' was greater than in those reared on 'HZ401' and 'ZMS13'. No significant differences in survival and lifetime fecundity of P. japonica were observed between P. japonica fed cotton aphids reared on the three different cultivars. P. japonica fed aphids from 'M9101' showed a significantly shorter developmental period and greater adult weight than those fed aphids from the other two cultivars. The decreased larval developmental duration and increased adult weight of P. japonica fed cotton aphids reared on the high gossypol-containing cultivar might have been caused by the high fatty acid content of the prey aphids. Our results indicate that high gossypol in host cotton had an antibiotic effect on A. gossypii and showed a positive effect on growth and development of P. japonica at the third trophic level. This suggests compatibility between one form of host plant resistance and biological control by predators. The allelochemical contents should be taken into account in integrated pest management for their effects on both herbivores and entomophagous insects.
118 citations
TL;DR: Red imported fire ant, Solenopsis invicta Buren were relatively the most abundant heliothine predators observed and lady beetles included the convergent lady beetle, Hippodamia convergens Guérin-Méneville; the sevenspotted lady beetle; and the multicolored Asian lady beetle occurred in cover crops and cotton during both years of the experiment.
Abstract: In fall 2000, an on-farm sustainable agricultural research project was established for cotton, Gossypium hirsutum L., in Tift County, Georgia. The objective of our 2-yr research project was to determine the impact of several cover crops on pest and predator insects in cotton. The five cover crop treatments included 1) cereal rye, Secale cereale L., a standard grass cover crop; 2) crimson clover, Trifolium incarnatum L., a standard legume cover crop; 3) a legume mixture of balansa clover, Trifolium michelianum Savi; crimson clover; and hairy vetch, Vicia villosa Roth; 4) a legume mixture + rye combination; and 5) no cover crop in conventionally tilled fields. Three main groups or species of pests were collected in cover crops and cotton: 1) the heliothines Heliothis virescens (F.) and Helicoverpa zea (Boddie); 2) the tarnished plant bug, Lygus lineolaris (Palisot de Beauvois); and 3) stink bugs. The main stink bugs collected were the southern green stink bug, Nezara viridula (L.); the brown stink bug, Euschistus servus (Say); and the green stink bug, Acrosternum hilare (Say). Cotton aphids, Aphis gossypii Glover, were collected only on cotton. For both years of the study, the heliothines were the only pests that exceeded their economic threshold in cotton, and the number of times this threshold was exceeded in cotton was higher in control cotton than in crimson clover and rye cotton. Heliothine predators and aphidophagous lady beetles occurred in cover crops and cotton during both years of the experiment. Geocoris punctipes (Say), Orius insidiosus (Say), and red imported fire ant, Solenopsis invicta Buren were relatively the most abundant heliothine predators observed. Lady beetles included the convergent lady beetle, Hippodamia convergens Guerin-Meneville; the sevenspotted lady beetle, Coccinella septempunctata L.; spotted lady beetle, Coleomegilla maculata (DeGeer); and the multicolored Asian lady beetle, Harmonia axyridis (Pallas). Density of G. punctipes was higher in cotton fields previously planted in crimson clover compared with control cotton fields for all combined sampling dates in 2001. Intercropping cotton in live strips of cover crop was probably responsible for the relay of G. punctipes onto cotton in these crimson clover fields. Density of O. insidiosus was not significantly different between cover crop and control cotton fields. Lady beetles seemed to relay from cover crops into cotton. Conservation of the habitat of fire ants during planting probably was responsible for the higher density of red imported fire ants observed in all conservation tillage cotton fields relative to control cotton fields. Reduction in the number of times in which economic thresholds for heliothines were exceeded in crimson clover and rye compared with control fields indicated that the buildup of predaceous fire ants and G. punctipes in these cover crops subsequently resulted in reduction in the level of heliothines in conservation tillage cotton with these cover crops compared with conventional tillage cotton without cover crops.
TL;DR: Three populations of the leafminer, Liriomyza trifolii (Burgess), were collected from commercial ornamental production greenhouses in the United States and tested for susceptibility to three commercial insecticides and resistance to these three insecticides was unstable.
Abstract: Three populations of the leafminer, Liriomyza trifolii (Burgess), were collected from commercial ornamental production greenhouses in the United States and tested for susceptibility to three commercial insecticides. A leaf dip bioassay of leaves containing young (1–2-d-old) larvae was used. Based on larval mortality and compared with a susceptible laboratory reference colony, the three strains varied in spectrum and level of resistance to the insecticides. CA-1, collected from Gerbera daisy, was moderately resistant to cyromazine (18.1-fold) and abamectin (22.0-fold), but highly resistant to spinosad (>188-fold). CA-2, collected from chrysanthemums, was not resistant to abamectin, had a low level of resistance to cyromazine (8.2-fold), but was extremely resistant to spinosad (1,192-fold). GA-1, collected from chrysanthemums, had very low levels of resistance to cyromazine (5.4-fold) and spinosad (1.9-fold) but was moderately resistant to abamectin (30.6-fold). When reared in the absence of insecticide selection pressure, all three strains reverted to approximately the level of the reference strain. The CA-1 strain reverted in nine generations to cyromazine; however, the lowest levels of abamectin and spinosad resistance reverted to was 3.1-fold at F8 and 3.2 at the F10, respectively. The CA-2 strain reverted in five generations to both cyromazine and spinosad. GA-1 reverted in five generations to abamectin. Based on the results, resistance to these three insecticides was unstable. Additionally, there was no cross-resistance among these three insecticides.
TL;DR: Results indicate that gossypol increased the magnitude and dominance of some fitness costs, which could improve the ability to design refuges for managing insect resistance to Bt crops.
Abstract: Fitness costs associated with insect resistance to Bacillus thuringiensis (Bt) crops may help to delay or prevent the spread of resistance alleles, especially when refuges of non-Bt host plants are present. The potential for such delays increases as the magnitude and dominance of fitness costs increase. Here, we examined the idea that plant secondary chemicals affect expression of fitness costs associated with resistance to Bt cotton in Pectinophora gossypiella (Saunders). Specifically, we tested the hypotheses that gossypol affects the magnitude or dominance of fitness costs, by measuring performance of three independent sets of pink bollworm populations fed artificial diet with and without gossypol. Each set had an unselected susceptible population, a resistant population derived by selection from the susceptible population, and the F1 progeny of the susceptible and resistant populations. No individuals completed development on diets with gossypol in one set, suggesting that these individuals partially lost the ability to detoxify this chemical. In the other two sets, costs affecting survival did not support the hypotheses, but costs affecting pupal weight did. Adding gossypol to diet increased the magnitude and dominance of costs affecting pupal weight. In one of the two sets with survivors on diet with gossypol, costs affecting development time were less recessive when gossypol was present in diet. These results indicate that gossypol increased the magnitude and dominance of some fitness costs. Better understanding of the effects of natural plant defenses on fitness costs could improve our ability to design refuges for managing insect resistance to Bt crops.
TL;DR: It is shown for the first time that transgenic virus resistance in wheat can indirectly influence R. padi life history and nymphal development was significantly longer on the transgenic genotypes infected with BYDV, compared with noninfected transgenic plants.
Abstract: The life history of Rhopalosiphum padi (L.) was monitored on transgenic and untransformed soft white winter wheat plants that were infected with Barley yellow dwarf virus (BLDV), noninfected, or challenged with virus-free aphids under laboratory conditions. Two transgenic soft white winter wheat genotypes (103.1J and 126.02) derived from the parental variety Lambert and expressing the barley yellow dwarf virus coat protein gene, and two untransformed varieties, virus-susceptible Lambert and virus-tolerant Caldwell, were tested. R. padi nymphal development was significantly longer on the transgenic genotypes infected with BYDV, compared with noninfected transgenic plants. In contrast, nymphal development on Lambert was significantly shorter on BYDV-infected than on noninfected plants. Nymphal development on noninfected Lambert was significantly longer than on noninfected transgenics. No significant difference in nymphal development period was detected between virus-infected and noninfected Caldwell. Aphid total fecundity, length of reproductive period, and intrinsic rate of increase were significantly reduced on BYDV-infected transgenic plants compared with BYDV-infected Lambert. In contrast, reproductive period, total adult fecundity, and intrinsic rate of increase on noninfected Lambert were significantly reduced compared with noninfected transgenics. Transgenic plants infected with BYDV were inferior hosts for R. padi compared with infected Lambert. However, noninfected transgenics were superior hosts for aphids than noninfected Lambert. Moderate resistance to BYDV, as indicated by a significantly lower virus titer, was detected in the transgenic genotypes compared with the untransformed ones. Results show for the first time that transgenic virus resistance in wheat can indirectly influence R. padi life history.
TL;DR: Differences in oviposition between the potential trap crops and cabbage were likely due to host volatiles, leaf morphology and color, or a combination of these factors, rather than to total leaf areas, leaf shape, or plant architecture.
Abstract: Potential trap crops for the diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), were evaluated through a series of ovipositional preference and larval survival experiments in outdoor screenhouses in 2002 and 2003. Hosts examined as trap crops were glossy and waxy collards, Brassica oleracea L. variety acephala; Indian mustard, Brassica juncea (L.) Czern; and yellow rocket, Barbarea vulgaris (R. Br.) variety arcuata. More eggs were laid on the potential trap crops, with the exception of waxy collards, than on cabbage. When P. xylostella was offered multiple hosts at the same time, numbers of eggs laid on glossy collards, Indian mustard, and yellow rocket were 3, 18, and 12 times greater than on cabbage, respectively. Similarly, when P. xylostella was offered a single trap crop host and cabbage, numbers of eggs laid on glossy collards, Indian mustard, and yellow rocket were 300, 19, and 110 times greater than on cabbage, respectively. Our studies suggest differences in oviposition between the potential trap crops and cabbage were likely due to host volatiles, leaf morphology and color, or a combination of these factors, rather than to total leaf areas, leaf shape, or plant architecture. Two-choice tests with a Y-tube olfactometer indicated that plant volatiles were major factors in P. xylostella host preference. The percentage larval survival from egg to pupation was 22.2% on cabbage, 18.9% on waxy collards, and 24.4% on Indian mustard, whereas survival was significantly lower on glossy collards (6.7%) and yellow rocket (0%). Based on our tests, it seems that yellow rocket may be the best candidate for use as a trap crop for P. xylostella because it is highly attractive for oviposition, but larvae do not survive on it.
TL;DR: Both thymol formulations, after the treatments, reduced significantly the levels of mite infestations of adult bees and sealed brood, but their efficacy, expressed as percentage of mortality, was lower for both products than the efficacy previously obtained with the same products in other experimental conditions.
Abstract: An apiary trial on the use of two acaricide formulations (gel-Apiguard and vermiculite and Api Life VAR) in the control of Varroa destructor (Anderson & Trueman) was conducted in summer 2001 in Sardinia (Italy). The main goals were 1) to determine their effectiveness against V. destructor, taking into account natural mite mortality in control hives; and simultaneously 2) to determine the persistence of both formulations and residues in honey and wax, by using a new extraction method. Both thymol formulations, after the treatments, reduced significantly the levels of mite infestations of adult bees and sealed brood, but their efficacy, expressed as percentage of mortality, was lower for both products (Api Life VAR 74.8 ± 13.1 and 81.3 ± 15.5, Apiguard 90.4 ± 8.3 and 95.5 ± 8.7 for sealed brood and adult bees, respectively) than the efficacy previously obtained with the same products in other experimental conditions. Moreover, a considerable colony-to-colony variability was recorded, and a significant negative effect of the thymol treatments on colony development was observed. During 2 wk of treatment, the bees removed nearly 95% of all the applied product (gel or vermiculite). Residues found in honey collected from the nest varied from 0.12 to 4.03 mg/kg for Api Life VAR and from 0.40 to 8.80 mg/kg for Apiguard. The residues were relatively higher in wax (Api Life VAR = 21.6 ± 13.0; Apiguard = 147.7 ± 188.9) than in honey, because thymol is a fat-soluble ingredient.
TL;DR: Melon fly was the most tolerant of the three species to irradiation, and oriental fruit fly was more tolerant than Mediterranean fruit fly, and larvae were more tolerant when irradiated in fruit compared with artificial diet.
Abstract: Currently approved irradiation quarantine treatment doses for Bactrocera cucurbitae (Coquillet), melon fly; Ceratitis capitata (Wiedemann), Mediterranean fruit fly; and Bactrocera dorsalis (Hendel), oriental fruit fly, infesting fruits and vegetables for export from Hawaii to the continental United States are 210, 225, and 250 Gy, respectively. Irradiation studies were initiated to determine whether these doses could be reduced to lower treatment costs, minimize any adverse effects on quality, and support a proposed generic irradiation dose of 150 Gy for fruit flies. Dose-response tests were conducted with late third instars of wild and laboratory strains of the three fruit fly species, both in diet and in fruit. After x-ray irradiation treatment, data were taken on adult emergence, and adult female fecundity and fertility. Melon fly was the most tolerant of the three species to irradiation, and oriental fruit fly was more tolerant than Mediterranean fruit fly. Laboratory and wild strains of each species were equally tolerant of irradiation, and larvae were more tolerant when irradiated in fruit compared with artificial diet. An irradiation dose of 150 Gy applied to 93,666 melon fly late third instars in papayas resulted in no survival to the adult stage, indicating that this dose is sufficient to provide quarantine security. Irradiation doses of 100 and 125 Gy applied to 31,920 Mediterranean fruit fly and 55,743 oriental fruit fly late third instars, respectively, also resulted in no survival to the adult stage. Results support a proposed generic irradiation quarantine treatment dose of 150 Gy for all tephritid fruit flies.
TL;DR: The laboratory resistance and cross-resistance data developed here should provide useful tools and information for designing an insecticide management strategy for controlling this fruit fly in the field.
Abstract: Oriental fruit flies, Bactrocera dorsalis (Hendel), were treated with 10 insecticides, including six organophosphates (naled, trichlorfon, fenitrothion, fenthion, formothion, and malathion), one carbamate (methomyl), and three pyrethroids (cyfluthrin, cypermethrin, and fenvalerate), by a topical application assay under laboratory conditions. Subparental lines of each generation treated with the same insecticide were selected for 30 generations and were designated as x-r lines (x, insecticide; r, resistant). The parent colony was maintained as the susceptible colony. The line treated with naled exhibited the lowest increase in resistance (4.7-fold), whereas the line treated with formothion exhibited the highest increase in resistance (up to 594-fold) compared with the susceptible colony. Synergism bioassays also were carried out. Based on this, S,S,S-tributyl phosphorotrithioate displayed a synergistic effect for naled, trichlorfon, and malathion resistance, whereas piperonyl butoxide displayed a synergistic effect for pyrethroid resistance. All 10 resistant lines also exhibited some cross-resistance to other insecticides, not only to the same chemical class of insecticides but also to other classes. However, none of the organophosphate-resistant or the methomyl-resistant lines exhibited cross-resistance to two of the pyrethroids (cypermethrin and fenvalerate). Overall, the laboratory resistance and cross-resistance data developed here should provide useful tools and information for designing an insecticide management strategy for controlling this fruit fly in the field.
TL;DR: For both species, progeny production in the treated grains was significantly reduced in comparison with the untreated grains, whereas significant differences were noted among commodities, formulations, and dose rates.
Abstract: Bioassays were conducted in the laboratory to assess the effect of the diatomaceous earth (DE) formulations Insecto, SilicoSec, and PyriSec, on stored oat, rye, and triticale, against adults of the rice weevil, Sitophilus oryzae (L.), and the confused flour beetle, Tribolium confusum Jacquelin du Val. The DEs were tested at three dose rates, 0.75, 1, and 1.5 g of DE/kg of grain. Adults of the two aforementioned species were exposed to all combinations of grain-formulation-dose rate, at 26°C and 60% RH. Mortality in DE-treated commodities was recorded after 24 h, 48 h, 7 d, and 14 d of exposure for S. oryzae and T. confusum and after 21 d for T. confusum. In S. oryzae, adult mortality was almost 100% after 7 d of exposure in all three grains examined. The mortality of T. confusum adults in DE-treated grains did not reach 100%, even after 21 d of exposure. Generally, the application of DE in rye caused higher adult mortality of T. confusum than in the other two products. All three dose rates tested provided the same mortality level of S. oryzae adults after 7 d of exposure. In contrast, 1.5 g of DE resulted in significant higher adult mortality of T. confusum, in comparison with the other dose rates, even after 21 d of exposure. All formulations were equally effective after 7 d of exposure against S. oryzae, but at 48 h of exposure, PyriSec caused significantly higher mortality than the other two formulations. For both species, progeny production in the treated grains was significantly reduced in comparison with the untreated grains, whereas significant differences were noted among commodities, formulations, and dose rates. No progeny were recorded in the treated rye for either species or in the treated triticale for S. oryzae.
TL;DR: The abundance and diversity of natural enemies was greatest at sites that adopted IPM and least at sites practicing conventional pest management strategies, correlating greater P. xylostella mortality at these sites.
Abstract: Maximizing the contribution of endemic natural enemies to integrated pest management (IPM) programs requires a detailed knowledge of their interactions with the target pest. This experimental field study evaluated the impact of the endemic natural enemy complex of Plutella xylostella (L.) (Lepidoptera: Yponomeutidae) on pest populations in commercial cabbage crops in southeastern Queensland, Australia. Management data were used to score pest management practices at experimental sites on independent Brassica farms practicing a range of pest management strategies, and mechanical methods of natural enemy exclusion were used to assess the impact of natural enemies on introduced cohorts of P. xylostella at each site. Natural enemy impact was greatest at sites adopting IPM and least at sites practicing conventional pest management strategies. At IPM sites, the contribution of natural enemies to P. xylostella mortality permitted the cultivation of marketable crops with no yield loss but with a substantial reduction in insecticide inputs. Three species of larval parasitoids (Diadegma semiclausum Hellen [Hymenoptera: Ichneumonidae], Apanteles ippeus Nixon [Hymenoptera: Braconidae], and Oomyzus sokolowskii Kurdjumov [Hymenoptera: Eulophidae]) and one species of pupal parasitoid Diadromus collaris Gravenhorst (Hymenoptera: Ichneumonidae) attacked immature P. xylostella. The most abundant groups of predatory arthropods caught in pitfall traps were Araneae (Lycosidae) > Coleoptera (Carabidae, Coccinelidae, Staphylinidae) > Neuroptera (Chrysopidae) > Formicidae, whereas on crop foliage Araneae (Clubionidae, Oxyopidae) > Coleoptera (Coccinelidae) > Neuroptera (Chrysopidae) were most common. The abundance and diversity of natural enemies was greatest at sites that adopted IPM, correlating greater P. xylostella mortality at these sites. The efficacy of the natural enemy complex to pest mortality under different pest management regimes and appropriate strategies to optimize this important natural resource are discussed.
TL;DR: The results suggest that a greenhouse integrated pest management (IPM) program using a botanical such as UDA-245 could effectively control infestations of major pests present while having a negligible effect on biological control agents.
Abstract: The emulsifiable concentrate UDA-245 based on an essential oil extract from Chenopodium ambrosioides variety near ambrosioides, a North American herbaceous plant, was compared with commercially available pesticides for their effectiveness to control green peach aphid, Myzus persicae (Sulzer) (Homoptera: Aphididae), western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), and greenhouse whitefly, Trialeurodes vaporariorium (Westwood) (Homoptera: Aleyrodidae). Side effects on the whitefly parasitoid Encarsia formosa Gahan (Hymenoptera: Aphelinidae) also were determined. With green peach aphid, UDA-245 at 0.5% concentration was significantly more effective than the control (water) treatment in a laboratory bioassay and significantly more effective than neem oil and the control treatment and as effective as insecticidal soap in a greenhouse assay. With the western flower thrips, UDA-245 at 0.5% was significantly more effective than neem oil, insecticidal soap and the control treatment in a laboratory bioassay, whereas in a greenhouse assay, UDA-245 at 1.0% was the only treatment that maintained control of the western flower thrips 2 wk after the last treatment period. UDA-245 at 0.5% (laboratory bioassay) was significantly more effective in managing greenhouse whitefly than neem oil, endosulfan, and the control treatment and as effective as insecticidal soap. Insecticidal soap proved to be toxic to the parasitoid E. formosa (71.9% mortality), whereas UDA-245 at 0.5% was not significantly more toxic than the control (11.2 and 4.6% mortality, respectively). Our results suggest that a greenhouse integrated pest management (IPM) program using a botanical such as UDA-245 could effectively control infestations of major pests present while having a negligible effect on biological control agents.
TL;DR: There was a significant reduction in the survival of postdiapausal adults from the resistant strain and the F1 strains, indicating that there is a nonrecessive overwintering cost associated with Cry1A resistance in H. armigera.
Abstract: Glasshouse and laboratory experiments were conducted to evaluate the relative fitness of Cry1A-susceptible and laboratory-selected resistant strains of Helicoverpa armigera (Hubner). Life history parameters of H. armigera larvae feeding on young cotton plants showed a significant developmental delay of up to 7 d for the resistant strain compared with the susceptible strain on non-Bacillus thuringiensis (Bt) cotton. This fitness cost was not evident on artificial diet. There was no developmental delay in the F1 hybrid progeny from the reciprocal backcross of the resistant and susceptible strains, indicating that the fitness cost is recessive. In two cohorts tested, survival to pupation of resistant larvae on Bt cotton expressing Cry1Ac was 54 and 51% lower than on non-Bt cotton, whereas all susceptible and F1 larvae tested on Cry1Ac cotton were killed. Mortality of susceptible larvae occurred in the first or second instar, whereas the F1 larvae were able to develop to later instars before dying, demonstrating that resistance is incompletely recessive. The intrinsic rate of increase was reduced by >50% in the resistant strain on Cry1Ac cotton compared with the susceptible strain on non-Bt cotton. There was a significant reduction in the survival of postdiapausal adults from the resistant strain and the F1 strains, indicating that there is a nonrecessive overwintering cost associated with Cry1A resistance in H. armigera.
TL;DR: It is suggested that chinch bug feeding leads to a loss in catalase activity in susceptible buffalograsses, and resistantbuffalograss may be able to tolerate chinchbug feeding by increasing their peroxidase activity.
Abstract: This research investigated the role of oxidative enzymes in the defense response of buffalograss, Buchloe dactyloides (Nuttall) Engelmann, to Blissus occiduus Barber. Changes in catalase and peroxidase activity were observed in both resistant and susceptible buffalograsses in response to chinch bug feeding. Susceptible plants were shown to have a lower level of catalase activity compared with their respective control plants. By contrast, catalase activities of resistant plants were similar between infested and control buffalograsses throughout the study. Resistant plants had higher levels of peroxidase activity compared with their control plants, whereas peroxidase activities for control and infested susceptible plants remained at similar levels or were slightly lower for infested plants. These findings suggest that chinch bug feeding leads to a loss in catalase activity in susceptible buffalograsses. In contrast, resistant buffalograsses may be able to tolerate chinch bug feeding by increasing their peroxidase activity. Polyphenol oxidase activities were similar between control and infested plants for the buffalograsses evaluated. Among the enzymes examined, no differences in isozyme profiles for peroxidase and polyphenol oxidase were detected between control and infested 378, NE91-118, Cody, and Tatanka plants. Gels stained for catalase identified differences in the isozyme profiles of infested and uninfested 378 plants; however, infested and control NE91-118, Tatanka, and Cody plants has similar isozyme profiles. No differences in protein profiles were observed between chinch bug-infested 378, NE91-118, Cody, and Tatanka plants and their respective uninfested controls.
TL;DR: Investigating the effect of probiotic adult diets on the pheromone-calling activity, mating success, life expectancy, and survival of mass-reared male Mediterranean fruit flies, Ceratitis capitata, found that males reared on the probiotic yeast-enhanced agar, sy, had a significant mating advantage over competitors fed the standard s agar or noninoculated sy agar.
Abstract: The aim of the current study was to investigate the effect of probiotic adult diets, i.e., adult diets containing viable symbiotic intestinal bacteria, on the pheromone-calling activity, mating success, life expectancy, and survival of mass-reared male Mediterranean fruit flies, Ceratitis capitata (Wiedemann), as an avenue for improving the field performance of sterile males in release programs to eradicate, suppress, or prevent spread of wild populations. The effect of inoculation of two standard adult diets (sugar-yeast granulate [SY] and sugar agar [s]) and two experimental formulations (yeast-reduced granulate [Sy] and yeast-enhanced sugar agar [sy]) with Enterobacter agglomerans and Klebsiella pneumoniae (typically occurring in the gut of wild flies) on the different fitness components was assessed in the laboratory and on field-caged host trees. We found that, in the laboratory, males reared on the probiotic yeast-enhanced agar, sy, had a significant mating advantage over competitors fed th...
TL;DR: Boric acid, imidacloprid, and thiamethoxam in sucrose aqueous baits had different delayed toxicities to worker Argentine ants, Linepithema humile (Mayr), and the negative impact of fast-acting toxicants on trail following, recruitment, trophallaxis, and control of Argentine ants is discussed.
Abstract: Boric acid, imidacloprid, and thiamethoxam in sucrose aqueous baits had different delayed toxicities to worker Argentine ants, Linepithema humile (Mayr). The concentrations required to produce an LT50 (time required to produce 50% mortality) within 1Ð 4 d were 3.63Ð 0.55% boric acid, 9.2 10 3 to 7.1 10 4 % imidacloprid, and 3 10 4 to 2 10 5 % thiamethoxam. The three toxicants were not repellent. Other laboratory trials showed that 1% boric acid, 5 10 4 to 5 10 3 % imidacloprid, and 1 10 5 to 1 10 3 % thiamethoxam had delayed toxic effects, whereas 0.5% boric acid and 5 10 3 % imidacloprid did not. Baits that provided an LT50 between days 1 and 4 were considered to have delayed toxic effects. The utility of aqueous sucrose baits and toxicants soluble in such systems and the negative impact of fast-acting toxicants on trail following, recruitment, trophal- laxis, and control of Argentine ants are discussed.
TL;DR: The Cincy strain produced significantly smaller oothecae and lower numbers of eggs in each egg capsule than the nonaverse Jwax and Dorie strains of cockroaches, suggesting fitness costs are associated with resistance.
Abstract: A gel bait-resistant German cockroach, Blattella germanica (L.), strain Cincy was collected in Cincinnati, OH. This strain exhibited a high level of behavioral resistance to Avert (0.05% abamectin) and Maxforce FC (0.01% fipronil) gel baits. Topical application assays indicated moderate levels of physiological resistance of the Cincy strain to abamectin and fipronil. Resistance ratios (based on LD50 values from topical applications) to abamectin and fipronil were 2.5 and 8.7, respectively. The Cincy strain of had a significantly lower LD50 value to abamectin than a nonaverse field strain (Dorie) and similar LD50 values to fipronil as the Dorie strain. The aversion behavior (avoidance of gel baits) was therefore caused by food ingredients in the gel baits. The Cincy strain showed avoidance of agar containing fructose, glucose, maltose, and sucrose, which are phagostimulants to the laboratory strain. Modifications of the inert ingredients in the Maxforce FC gel bait significantly improved the efficacy against the Cincy strain. The Cincy strain produced significantly smaller oothecae and lower numbers of eggs in each egg capsule than the nonaverse Jwax and Dorie strains of cockroaches, suggesting fitness costs are associated with resistance.
TL;DR: Ginger oil has potential as a protectant of tomato seedlings against B. argentifolii, but issues of phytotoxicity and coverage need to be addressed.
Abstract: The whitefly Bemisia argentifolii Bellows & Perring is an economically important pest of tomatoes, Lycopersicon esculentum Mill., inducing an irregular ripening disorder of fruit and transmitting plant pathogenic viruses. With the goal of investigating ginger oil as a protectant for tomato plants, we tested the effects of concentration of ginger oil and application methods on repellency to whitefly in a vertical still-air olfactometer. In choice and no-choice experiments conducted in a greenhouse, we evaluated whether ginger oil would protect tomato seedlings from whitefly settling and oviposition. Ginger oil repelled whitefly adults in the vertical olfactometer. The repellency of ginger oil was attributed to its odor, effective at the concentrations used over a distance of 1-2 mm. Tomato leaf disks dipped in ginger oil repelled whiteflies at concentrations of 0.5, 0.75, and 1%, but not at concentrations <0.5%, in a dose-response experiment conducted in the olfactometer. Repellency increased with increasing ginger oil concentration when leaf disks were dipped in ginger oil but not when ginger oil was sprayed onto the leaf disks. Higher quantities of monoterpenes and sesquiterpenes were deposited on leaf disks dipped in ginger oil than on sprayed leaf disks according to gas chromatographic quantification. In the greenhouse, both choice and no-choice tests were conducted with tomato seedlings dipped in 0.25% ginger oil solution or 2% Tween 20, as treatment and control, respectively. In the choice test, 35-42% fewer whitefly adults settled and 37% fewer eggs were laid during the 24-h exposure period on tomato plants dipped in ginger oil solution than on plants dipped in 2% Tween 20. In the no-choice test, 10.2-16.7% fewer whiteflies settled on treated plants compared with control plants but no significant differences were detected in the number of eggs laid. Higher concentrations of ginger oil could not be used without causing severe wilting of tomato leaves. Ginger oil has potential as a protectant of tomato seedlings against B. argentifolii, but issues of phytotoxicity and coverage need to be addressed.
TL;DR: Multivariate analysis of fungi complex composition showed that the frequency of fungal was species significantly influenced by the kind of seed, which may heighten the risk of occurrence of mycotoxins in food and feed stuffs and cause mixed contamination by fungal and mite allergens.
Abstract: Toxigenic and allergen-producing fungi represent a serious hazard to human food and animal feed safety. Ninety-four fungal species were isolated from mite-infested samples of seeds taken from Czech seed stores. Fungi were isolated from the surface of four kinds of seeds (wheat, poppy, lettuce, and mustard) and from the gut and external surface of five species of mites (i.e., Acarus siro L., 1758, Caloglyphus rhizoglyphoides (Zachvatkin, 1973), Lepidoglyphus destructor (Schrank, 1781), Tyrophagus putrescentnae (Schrank, 1781) and Cheyletus malaccensis Oudemans 1903) separately. Multivariate analysis of fungi complex composition showed that the frequency of fungal was species significantly influenced by the kind of seed. Fungal frequencies differed between mites gut and exoskeleton surface and between the surfaces of mites and seeds. Three groups of fungal species were recognized: 1) mite surface-associated fungi: Penicillium brevicompactum, Alternaria alternata, and Aspergillus versicolor; 2) mite surface- and seed-associated fungi: Aspergillus niger, Penicillium crustosum, Penicillium aurantiogriseum, Penicillium chrysogenum, and Aspergillus flavus; and 3) seed-associated fungi: Cladosporium herbarum, Mucor dimorphosporus f. dimorphosporus, Botrytis cinerea, Penicillium griseofulvum, and Eurotium repens. Mite-carried species of microfungi are known to produce serious mycotoxins (e.g., aflatoxin B1, cyclopiazonic acid, sterigmatocystin, ochratoxin A, and nephrotoxic glycopeptides) as well as allergen producers (e.g., A. alternata and P. brevicompactum). Storage mites may play an important role in the spread of some medically hazardous micromycetes. In addition, these mite-fungi associations may heighten the risk of occurrence of mycotoxins in food and feed stuffs and cause mixed contamination by fungal and mite allergens.
TL;DR: Fertility was not different from that of controls in all treatments, and males were not involved in the reduction of oviposition, and Align proved to be harmless to newly emerged adults irrespective of the mode of exposure.
Abstract: A commercial formulation of azadirachtin (Align) was tested on Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) adults to determine its effects on reproduction. Three methods of exposure were carried out in the laboratory (residual, direct contact and ingestion) with concentrations close to the maximum field recommended concentration in Spain (48 mg AI/liter). Align proved to be harmless to newly emerged adults irrespective of the mode of exposure. Nevertheless, fecundity was reduced in a reversible way in females that have ingested azadiracthin after the onset of oviposition. Fertility was not different from that of controls in all treatments. Additional tests showed that males were not involved in the reduction of oviposition. Electron microscopy studies pointed out that Align interfered with vitellogenin synthesis and/or its uptake by developing oocytes; thus, growing follicles in treated females were significantly smaller that those of the controls. The role of azadirachtin as a compound that may influence several hormonal and protein titers involved in reproduction is also discussed.
TL;DR: In autumn, it seems that H. axyridis is an opportunist, taking advantage of previously damaged fruit, caused by other agents, and shows a preference for damaged fruits over undamaged fruits.
Abstract: The objective of this study was to assess the potential pest status of Harmonia axyridis (Pallas) on autumn-ripening fruit. In autumn, H. axyridis has been observed feeding on pumpkins, apples, grapes, and raspberries in Minnesota. To determine whether H. axyridis can inflict primary feeding damage to fruit (i.e., breaking the skin of the fruit), we conducted laboratory feeding experiments with undamaged pumpkins, apples, grapes, and raspberries. The only fruit that H. axyridis was able to damage directly was raspberry. Laboratory choice tests were conducted to determine whether H. axyridis exhibits a preference between damaged and undamaged fruit, between cultivars of fruit, and between sugar water and water alone. For all fruits tested, H. axyridis showed a preference for damaged fruits over undamaged fruits. H. axyridis also exhibited a strong preference for sugar water over water alone. However, few differences were exhibited in preference between cultivars of fruit. In autumn, it seems that H. axyridis is an opportunist, taking advantage of previously damaged fruit, caused by other agents.