Showing papers in "Journal of Economic Entomology in 1988"
TL;DR: Colonies of Indianmeal moth, Plodia interpunctella (Hubner), and almond moth, Cadra cautella (Walker), reared in the laboratory on diet treated with Bacillus thuringiensis , became resistant to B. thurringiensis but resistance did not progress at the same rate or to the same extent in all of the colonies.
Abstract: Colonies of Indianmeal moth, Plodia interpunctella (Hubner), and almond moth, Cadra cautella (Walker), reared in the laboratory on diet treated with Bacillus thuringiensis , became resistant to B. thuringiensis . However, resistance did not progress at the same rate or to the same extent in all of the colonies. Resistance in five Indianmeal moth colonies increased from 2- to 29-fold within three generations, and from 15- to 100-fold in ca. 40 generations under relatively low selection pressure. With higher selection pressure, resistance in one colony increased >250-fold. Resistance in an almond moth colony increased only ca. 7-fold in 21 generations of intensive selection. Resistance was stable when selection was discontinued after the resistance levels reached a plateau, but declined if selection was discontinued earlier. The resistance was partially recessive in the five Indianmeal moth colonies, but not to an equal extent. The resistance assorted independently of the recessive genetic markers copper, golden , and white-eye .
171 citations
TL;DR: In a food preference chamber, fewer adults of red flour beetle settled in rice grain treated with 100, 500, or 1,000 ppm of the oil of turmeric Curcuma longa, sweetflag Acarus calamus, neem Azadirachta indica A. Juss, or “Margosan-O” (a commercial neem-based insecticide).
Abstract: In a food preference chamber, fewer adults of red flour beetle ( Tribolium Castaneum Herbst) settled in rice grain treated with 100, 500, or 1,000 ppm of the oil of turmeric Curcuma longa (L.), sweetflag Acarus calamus (L.), or neem Azadirachta indica A. Juss, or “Margosan-O” (a commercial neem-based insecticide). Repellency increased with increasing concentrations of the oils and Margosan. In another choice test, filter paper strips treated with turmeric oil or sweetflag oil at 200, 400, or 800 µg/cm2 repelled insects during the first 2 wk; thereafter, repellency decreased more rapidly than with neem oilor Margosan- O. Tribolium castaneum adults fed wheat flour, which had been treated with the test materials at 200 ppm, produced fewer and underweight larvae, pupae, and adults compared with the control.
123 citations
TL;DR: Nematophagous micro arthropods are a biotic factor that could limit survival of field-applied entomogenous nematodes as well as a significant difference between LD50 estimates obtained when mites were present or absent.
Abstract: Potential for nematophagous mites and Collembola to reduce survival of entomogenous nematodes was tested in laboratory studies. The majority of the arthropods tested were observed feeding on Steinernema feltiae Filipjev (Breton strain) and Heterorhabditis heliothidis (Khan, Brooks, and Hirschmann) (NC strain) infective stage juveniles. Phoresy of S. feltiae infectives on many of the mites was observed, with infectives forming rafts of tightly packed nematodes on the dorsum of some of the larger mites. Such infectives remained viable and could move off the mite to kill prepupae of the greater wax moth, Galleria mellonella (L.). Only one species of mesostigmatid mite, Gamasellodes vermivorax Walter, was able to complete development on infectives, and survival was poor. An endeostigmatid mite, Alycus roseus Koch, and a collembolan, Hypogastura scotti Yosii, were able to complete development from late-instar nymph to adult and to produce viable eggs on S. feltiae . In laboratory studies, there was a negative correlation between G. vermivorax number and greater wax moth prepupal mortality, demonstrating lossin nematode efficacy caused by predation by the mesostigmatid mite. There was also a significant difference between LD50 estimates obtained when mites were present or absent. Thus, nematophagous micro arthropods are a biotic factor that could limit survival of field-applied entomogenous nematodes.
118 citations
TL;DR: The use of CLIMEX to assist with the assessment of potential establishment and spread of two exotic pests, Mediterranean fruit fly, Ceratitis capitata (Wiedemann), and Colorado potato beetle, Leptinotarsa decemlineata (Say), in New Zealand is demonstrated.
Abstract: A computer-based system for matching climates in ecology (CLIMEX) may assist in answering questions concerning the likelihood of establishment of exotic pests in any locality. CLIMEX compares the relative potential for growth and persistence of poi-kilotherms at different times and places by providing temperature and moisture parameters that describe the response of the organism to its environment. Although CLIMEX has broad application and much potential in entomology, it is particularly useful for summarizing current knowledge and giving insight when detailed biological or climatological information is scarce. Such lack of information may confront the scientist dealing with insect quarantine problems. The use of CLIMEX to assist with the assessment of potential establishment and spread of two exotic pests, Mediterranean fruit fly, Ceratitis capitata (Wiedemann), and Colorado potato beetle, Leptinotarsa decemlineata (Say), in New Zealand is demonstrated. Information available in the literature was used to determine CLIMEX parameters for each insect. To refine initial parameters, selected overseas locations where each insect is found were examined for correspondence of CLIMEX output with favorable periods of population development and probable relative abundance. Established parameters were then used to examine 286 meteorological sites throughout New Zealand. Potential favorable areas of population establishment are identified.
115 citations
TL;DR: Buprofezin affected embryo genesis and larval stages, while fenpropathrin especially affected adults and oviposition, and at concentrations of 125 and 250 mg/liter under field conditions, buprofezin strongly suppressed infestation by SPWF.
Abstract: Buprofezin (2- tert -butylimino-3-isopropyl-5-phenyl, 3,4,5,6 tetrahydro-2-thiadiazine-4-one) sprayed on cotton seedlings under greenhouse conditions suppressed embryo genesis and progeny formation of the sweet potato whitefly (SPWF), Bemisia tabaci (Gennadius). The estimated concentration for 50% inhibition of egg hatch applied through adults was ca. 15 mg/liter and that for 50% cumulative larval mortality was 6 mg/liter. Length of female exposure to buprofezin correlated well with the effect on embryo genesis, resulting in total suppression at exposure time >24 h. Buprofezin was persistent under greenhouse conditions; spraying concentrations of 62.5 and 125 mg/liter resulted in 50% inhibition of egg hatch at 4 and 7 d after application, respectively, and suppression of >95% of progeny formation up to 26 d after application. In comparative assays with fenpropathrin, buprofezin affected embryo genesis and larval stages, while fenpropathrin especially affected adults and oviposition. At concentrations of 125 and 250 mg/liter under field conditions, buprofezin strongly suppressed infestation by SPWF.
99 citations
TL;DR: The absence of a carbohydrate source (e.g., honey or honeydew) at the time of field release may limit the effectiveness of T. platneri, which lived longer with than without honey whether or not host eggs were present.
Abstract: The effects of Sitotroga cerealella (Olivier) and Trichoplusia ni (Hubner) eggs on the size, fecundity, and longevity, and of honey on the fecundity and longevity of Trichogramma platneri Nagarkatti were investigated. Variation in the average length of the hind tibiae (HTL), a measure of a wasp’s body size, accounted for 72% of the variance in the number of mature eggs present in the ovaries of a 24-h-old T. platneri . Females with longer HTLs produced significantly more eggs and lived longer than did those with shorter HTLs. Large females (HTL = 0.21 ± 0.009 mm, x ± SD) produced 2.3 times more offspring than medium-sized females (HTL =0.17 ± 0.009 mm) and 5.5 times more than small females (HTL = 0.15 ± 0.004 mm). Females reared from S. cerealella eggs were significantly smaller (HTL = 0.14 ± 0.006 mm) than those reared from T. ni eggs (HTL = 0.17 ± 0.020 mm) and produced fewer offspring (18.2 ± 13 eggs versus 42.6 ± 25 eggs, respectively); hence, S. cerealella eggs apparently produce low-quality T. platneri females. Furthermore, T. Platneri lived longer with than without honey whether or not host eggs were present. Thus, the absence of a carbohydrate source (e.g., honey or honeydew) at the time of field release may limit the effectiveness of T. platneri .
95 citations
TL;DR: This study determined toxicities of 13 insecticides representing three classes to a prey-predator complex consisting of spined soldier bug and its lepidopterous prey, velvetbean caterpillar, fall armyworm, and corn earworm.
Abstract: This study determined toxicities of 13 insecticides representing three classes to a prey-predator complex consisting of spined soldier bug ( Podisus maculiventris (Say)) and its lepidopterous prey, velvetbean caterpillar ( Anticarsia gemmatalis (Hubner)), fall armyworm ( Spodoptera frugiperda (J. E. Smith)), and corn earworm ( Heliothis zea (Boddie)). The stink bug was generally more susceptible to organophosphorus and carbamate insecticides but was more tolerant of pyrethroids such as permethrin, cypermethrin, and fenvalerate compared with its prey. The organophosphate tetrachlorvinphos had no apparent toxicity to the stink bug at concentrations ≤100 µg per insect but was very toxic to some of the prey. Reasons for the selective toxicities are suggested and discussed.
73 citations
TL;DR: The strength and variability of sublethal effects found in this and other studies indicate that sub lethal effects must be considered to evaluate accurately the selectivity of pesticides in favor of parasitoids.
Abstract: Sublethal effects of insecticides on the parasitoid Aphytis melinus DeBach were investigated. Longevity, daily rate of progeny production per female, and size and sex ratio of offspring were measured for parasitoids exposed to rates near the LC50’s of carbaryl, chlorpyrifos, dimethoate, malathion, and methidathion. Survivors of the exposure to carbaryl exhibited no significant sublethal effects. Exposure to each of the organophosphorous materials reduced longevity by 73-85% and temporarily depressed progeny production. Chlorpyrifos also shifted the sex ratio of offspring toward more males. The strength and variability of sublethal effects found in this and other studies indicate that sublethal effects must be considered to evaluate accurately the selectivity of pesticides in favor of parasitoids.
68 citations
TL;DR: Because use of DEF, PB, and TPP did not increase the toxicity in the resistant strain to that of the susceptible strain, an unidentified resistance factor, possibly insensitive acetylcholinesterase, may be of importance in OP resistance.
Abstract: A field strain of Bemisia tabaci (Gennadius) from California, resistant to malathion, methyl parathion, sulprofos, permethrin, and DDT, showed increases in resistance levels (ranging from 1.1- to 8.9-fold) in a subsequent survey. Selective synergists were used to study the involvement of hydrolytic or oxidative enzymes (or both) in the resistance mechanism of the resistant strain. Resistance levels were decreased markedly when DEF (S,S,S-tributyl phosphorotrithioate) synergized three organophosphate (OP) compounds (malathion, methyl parathion, and sulprofos) and one pyrethroid (permethrin), suggesting the involvement of increased detoxication by esterases as part of the resistance mechanism. In addition, malathion was synergized by triphenyl phosphate (TPP), indicating the influence of carboxylesterases in malathion resistance. No highly active esterases were associated with organophosphate (OP) resistance. Piperonyl butoxide (PB) synergized the three OPs, permethrin, and DDT to different degrees in both susceptible and resistant strains, thus indicating the importance of enhanced oxidative metabolism in B. tabaci resistance. Because use of DEF, PB, and TPP did not increase the toxicity in the resistant strain to that of the susceptible strain, an unidentified resistance factor, possibly insensitive acetylcholinesterase, may be of importance in OP resistance. DEF antagonized DDT toxicity in the resistant strain, which increased the resistance ratio from 12.0- to 16.7-fold. DDT was synergized to a limited extent by diethyl maleate (DEM), thus suggesting limited metabolism by DDT-dehydrochlorinase in the resistant strain. A nonmetabolic knockdown resistance mechanism (kdr) may be a factor in DDT resistance because neither PB nor DEM supressed resistance completely.
65 citations
TL;DR: A technique that allows the staining and observation of whole leafhopper salivary sheaths left behind in plant tissue is described, and is reliable in recovering known sheaths and is applicable to several hemipteran sheath-feeders.
Abstract: A technique that allows the staining and observation of whole leafhopper salivary sheaths left behind in plant tissue is described. A derivation of McBride’s acid fuchsin stain for fungal hyphae was used, followed by clearing of the plant tissue for observation under a dissecting microscope. Data gathered included the shape and location of sheaths, and the orientation of sheaths to veins. The technique simultaneously stained eggs present ill the plant tissue. Thus, measures of both feeding and oviposition were acquired from the same plant. This method is reliable in recovering known sheaths and is applicable to several hemipteran sheath-feeders. The method should be useful to researchers studying host plant resistance and other aspects of the feeding of haustellate insects.
62 citations
TL;DR: The reinvasion potential of termites shown in this study suggests that either nematode application should be made frequently or that the entire colony rather than only the feeding site must be treated.
Abstract: The potential of the entomogenous nematode Steinernema feltiae Filipjev (=Neoaplectana carpocapsae Weiser), Breton strain, for control of a subterranean termite, Reticulitermes tibalis (Banks), was tested in laboratory and field trials. Termite workers were susceptible to nematodes in laboratory tests, but large numbers of nematodes were required for mortality. LD50 was estimated at 1.5 x 10(4) nematodes per termite in standard filter paper assays. Nematodes were applied to the soil directly beneath baited traps at a rate of 1 x 10(7) per m2 in field trials. There was a significant difference between treated and untreated traps in number of termites per trap, and protection was provided for a period of 2-3 wk. Termites attacking traps on treated sites entered traps at a corner or from the top, suggesting that termites may be avoiding contact with entomogenous nematodes. The reinvasion potential of termites shown in this study suggests that either nematode application should be made frequently or that the entire colony rather than only the feeding site must be treated.
TL;DR: 5-31183, 2-[1-methyl-2-(4-phenoxyphenoxy) ethoxyl pyridine, was highly effective in inhibiting normal development of mosquito larvae into adults in laboratory and field trials and appears to be compatible with the environment.
Abstract: 5-31183, 2-[1-methyl-2-(4-phenoxyphenoxy) ethoxyl pyridine, was highly effective in inhibiting normal development of mosquito larvae into adults in laboratory and field trials. Late fourth instars were the most sensitive stage. Mortality occurred in the pupal stage and, at lower doses, resulted in formation of abnormal adults. In highly polluted water, 5-31183 adsorbed onto organic matter and its biological activity persisted for 2 mo after application of 0.11 kg (AI)/ha (0.1 lb/acre). Its persistence in water in the absence of organic matter declined as temperature and sunlight exposure simultaneously increased. Its persistence in relatively “clean” field waters and soil was of short duration. No long-term bioaccumulation problem was apparent following dynamic or static exposures to fish. Nontarget aquatic organisms that coexist in mosquito breeding habitats were not affected adversely by treatments which were effective against mosquitoes. These results indicate efficacy against mosquito larvae, a high degree of safety to associated nontarget organisms, and chemical persistence properties that appear to be compatible with the environment.
TL;DR: In laboratory experiments, concentrations of 0.4, 0.8, and 1.2% neem-seed extract inhibited feeding of adult and larva of Colorado potato beetle, Leptinotarsa decemlineata (Say), and feeding of larvae and adults was inhibited to a greater extent by addition of the synergist piperonyl butoxide (PBO).
Abstract: In laboratory experiments, concentrations of 0.4, 0.8, and 1.2% (wt/vol) neem-seed extract inhibited feeding of adult and larva of Colorado potato beetle, Leptinotarsa decemlineata (Say), on treated potato foliage, Solanum tuberosum L. Adult mortality did not exceed 25% in any neem treatment; however, 73% of larvae were dead 72 h after feeding on foliage treated with 1.2% neem extract. Toxicity of neem extract to larvae was enhanced, and feeding of larvae and adults was inhibited to a greater extent by addition of the synergist piperonyl butoxide (PBO) at a ratio of 10:1 (PBO/azadirachtin). In field experiments, spray applications of neem extract significantly reduced numbers of L. decemlineata larvae and adults in treated plots on all sample dates. The effectiveness of neem extract against L. decemlineata was signifcantly improved on two dates by addition of PBO. The 1.2% neem + PBO treatment resulted in low tuber yield, suggesting possible phytotoxic effects.
TL;DR: Results suggest strong cross-resistance between the pyrethroids and DDT.
Abstract: Bioassays were conducted with a range of insecticides to assess the degree of resistance in a strain of Heliothis armigera (Hubner) collected from the field in Thailand. A susceptible laboratory strain which had LD50’s similar to those of susceptible field populations was used as a reference strain for comparisons. The Thailand strain had high levels of resistance at LD50’s-resistance factors of 102-fold to cis -cypermethrin, 82-fold to trans -cypermethrin, 51-fold to fenvalerate, 125-fold to DDT and 28-fold to carbaryl. The strain had 2-fold resistance to diazinon, monocrotophos and endosulfan. These results suggest strong cross-resistance between the pyrethroids and DDT.
TL;DR: In the R strain, DEF synergized cypermethrin and permethrin, causing almost complete elimination of resistance to both pyrethroids, suggesting that esterases are involved in the mechanism of pyrethroid resistance in SPWF.
Abstract: Adults of sweetpotato whitefly (SPWF), Bemisia tabaci (Gennadius), from susceptible (S) and field (R) strains were treated in the laboratory with cypermethrin, permethrin, methyl parathion, and sulprofos, alone or in combination with S,S,S-tributyl phosphorotrithioate (DEF). Females were significantly less sensitive than males to all insecticides tested, the difference being greatest (20-fold) with permethrin. The highest level of resistance in females (63.2-fold) was found with permethrin, while a moderate level (13.3-fold) was found with suiprofos. High synergism was obtained with cypermethrin and permethrin. In the S strain, the synergism ratio of cypermethrin/DEF (1:1) was 31.2 for females and 18.2 for males, while that of permethrin/DEF (1:5) was 15.8 for females and 1.8 for males. In the R strain, DEF synergized cypermethrin and permethrin, causing almost complete elimination of resistance to both pyrethroids. This synergistic effect suggests that esterases are involved in the mechanism of pyrethroid resistance in SPWF. The link between arrhenotoky and resistance in SPWF is discussed.
TL;DR: Techniques are described for capturing and analyzing volatiles that emanate from newly established galleries of scolytid beetles in on-tree or phloem sandwich preparations, demonstrating how pheromone production can vary in relation to a beetle’s sex, behavior, mating status, and stage of gallery development.
Abstract: Techniques are described for capturing and analyzing volatiles that emanate from newly established galleries of scolytid beetles in on-tree or phloem sandwich preparations. They include an air input system that collects volatiles from the gallery entrance, a micro-Porapak Q trap, and gas-liquid chromatography through a 60-m, fused-silica capillary column. In studies on Dendroctonus ponderosae Hopkins, D. rufipennis Hopkins, and Ips pini (Say), the techniques have proven to be useful in determining simultaneously the quantity and quality of all semiochemicals produced by host tissue and individual beetles; demonstrating how pheromone production can vary in relation to a beetle’s sex, behavior, mating status, and stage of gallery development; and establishing behaviorally optimal and environmentally acceptable release rates for semiochemicals used in pest management programs.
TL;DR: Yield losses in ‘Rough Rider’ winter wheat, Triticum aestivum L., and ‘Cougar” winter rye, Secale cereale L., caused by feeding of Schizaphis graminum, Rhopalosiphum padi, and Macrosiphum avenae were measured for 3 yr in South Dakota fields.
Abstract: Yield losses in ‘Rough Rider’ winter wheat, Triticum aestivum L., and ‘Cougar’ winter rye, Secale cereale L., caused by feeding of Schizaphis graminum (Rondani), Rhopalosiphum padi (L.), and Macrosiphum avenae (F.) were each measured for 3 yr in South Dakota fields. Caged plots were artificially colonized with aphids for 10 d when plants were in three different growth stages; losses in components of yield were measured at harvest. Greatest losses of yield were caused when aphids fed during the seedling (2-3 leaf) stage in autumn; mean densities of 25-30 aphids per stem caused reductions of 50% in some components of yield at this stage. Lower yield losses were recorded for similar aphid population densities when they fed in spring during the boot stage (immature in florescence invested in leaf sheath), and no losses were observed when aphids fed on mature (dough stage) plants. Schizaphis graminum and R. padi were more damaging than M. avenae at similar population densities. Winter wheat was more vulnerable than rye to yield losses caused by aphid feeding.
TL;DR: The toxicity of the juvenile hormone analog (JHA) 2-[1-methyl-2-(4-phenoxyphenoxy) ethoxy] pyridine (MPEP), was evaluated on California red scale, Aonidiella aurantii, Ceroplastes floridensis Comstock, and the ectoparasite Aphytis holoxanthus DeBach.
Abstract: The toxicity of the juvenile hormone analog (JHA) 2-[1-methyl-2-(4-phenoxyphenoxy) ethoxy] pyridine (MPEP), was evaluated on California red scale (CRS), Aonidiella aurantii (Maskell); Florida wax scale (FWS), Ceroplastes floridensis Comstock; and the ectoparasite Aphytis holoxanthus DeBach. Treatment with 25 ppm inhibited the development of first- and 3-d-old second-instar CRS nymphs. The development of older second-instar CRS female nymphs was not arrested by a rate of 600 ppm, but the resulting females failed to reproduce following a 100 ppm application. A. aurantii females were not affected by the JHA treatment. When exposed to 50 ppm of MPEP, the three FWS nymphal stages ceased growing or failed to oviposit as adults. Treatment with 100 and 200 ppm resulted in 68.7 and 97.5% mortality of 3- to 10-d-old FWS females, respectively. Surviving young females ceased growing but began oviposition as morphologically immature scales; the number of eggs per female scale was significantly reduced and egg sterility was induced by the JHA treatment. Oviposition and egg viability of mature C. floridensis female scales were not affected by MPEP application. JHA treatment had no adverse effect on larval and pupal development of A. holoxanthus or on successful adult emergence and female fecundity.
TL;DR: A positive correlation was confirmed between poor sanitation and higher cockroach populations and improved sanitary conditions increased the efficacy of some insecticide treatments.
Abstract: The efficacy of several insecticides for controlling the German cockroach, Blattella germanica (L.), was compared in field and laboratory tests. Based on trap catch before and after treatment in a multiunit public housing complex, 0.2% cypermethrin was more effective than 0.5% chlorpyrifos or 1.1% propoxur. Up to 3 mo of residual activity was achieved with cypermethrin. A positive correlation was confirmed between poor sanitation and higher cockroach populations. Improved sanitary conditions increased the efficacy of some insecticide treatments. Cockroaches collected from apartments where these tests were done were > 100 times as resistant to propoxur and bendiocarb, and 4.51, 1.34, and 1.84 times as resistant to cypermethrin, chlorpyrifos, and diazinon, respectively (continuous exposure surface contact test).
TL;DR: Major plant sources of greenbug resistance were evaluated against two new greenbug isolates, Oklahoma (SCO) and Texas (WCT), to demonstrate that these isolates should be designated as biotypes.
Abstract: Major plant sources of greenbug, Schizaphis graminum (Rondani), resistance were evaluated against two new greenbug isolates, Oklahoma (SCO) and Texas (WCT), to demonstrate that these isolates should be designated as biotypes. Host plant reactions to the isolates were compared with those of biotypes E and F. The SCO isolate (biotype G) had two plant resistance relationships distinct from any previously described biotypes. Biotype G damaged all known sources of greenbug resistance in wheat, Triticum aestivum L., but did not damage ‘Wintermalt,’ a barley, Hordeum vulgare L., variety previously reported to be susceptible to all greenbug biotypes. The WCT isolate (biotype H) caused host plant responses on wheat that were similar to those of biotype E. However, biotype H was avirulent on all sorghum, Sorghum bicolor (L.) Moench, varieties and severely damaged ‘Post,’ a barley variety resistant to all previously described biotypes. Damage ratings for varieties infested with biotypes E and F were consistent with other studies and verified greenbug resistance in our plant sources. Both biotypes G and H lack the middorsal dark green abdominal stripe characteristic of biotypes B, C, and E but have the general appearance of biotype F.
TL;DR: A technique for developing and using multiple-species economic injury levels (EILs) is proposed, discussed, and evaluated, showing the usefulness of the technique in assessing host injury, in economic terms, from multiple insect pests.
Abstract: A technique for developing and using multiple-species economic injury levels (EILs) is proposed, discussed, and evaluated. Grouping insects into injury guilds, based on the plant’s physiological response to the injury, forms the theoretical basis for the multiple-species approach. In addition, a method for estimating crop injury, using an injury equivalency system, is proposed as a technique for refining the accuracy of EIL-based decision making. A detailed discussion concerning the theory and assumptions behind multiple-species EILs and injury equivalency is presented. As an example of the usefulness of the proposed system, we present data on a leaf-mass consuming insect guild on determinate soybeans. The paradigm includes an extensive review of defoliation-yield loss relationships for soybean and the calculation of EILs at four crop growth stages. Consumption data for five common soybean defoliators were also reviewed. These data were converted to equivalency coefficients based on the relative consumption potential of each species. With this system, each species within a guild can be related to every other species on the basis of its ability to contribute to overall injury. Finally, we present actual data for a leaf-mass soybean consuming guild and relate sampling information to the EIL. The result is a refined estimate of injury when species and size class consumption differences are incorporated in the estimate. Perhaps more significant, however, is the usefulness of the technique in assessing host injury, in economic terms, from multiple insect pests.
TL;DR: A system for acoustically detecting internal-feeding insect larvae in grain is described, finding that larvae produced detectable sounds 71-90% of the time until pupation, where the infestation rate was strongly correlated to number of sounds as counted by a frequency counter.
Abstract: A system for acoustically detecting internal-feeding insect larvae in grain is described. Larvae of the lesser grain borer, Rhyzopertha dominica (F.); rice weevil, Sitophilus oryzae (L.); and Angoumois grain moth, Sitotroga cerealella (Olivier), produced sounds loud enough to be detected 13-19 d after oviposition, depending upon the species. After first detection, larvae produced detectable sounds 71-90% of the time until pupation. Infestation rates could be estimated, at least in the range of 1-20 infested kernels per 100 ml of grain, where the infestation rate was strongly correlated to number of sounds as counted by a frequency counter.
TL;DR: Comparisons of the proportion of squares damaged by lygus bugs between the terminal 5 nodes, terminal 10 nodes, and all nodes on one to three dates per location indicate that the terminal5 nodes provide a reliable estimate of L. Hesperus feeding damage to squares.
Abstract: Numbers of Lygus Hesperus Knight per 50 net sweeps and numbers of abscised and lygus bug damaged squares per cotton plant terminal were counted weekly. Square abscission and square damage showed a high positive correlation with L. hesperus numbers ( r = 0.92, n = 7, for week of count and r = 0.69, n = 63, for June through July) and with square age ( r = 0.96, n = 20); fruit set on first and second sympodial branch positions showed a high negative correlation with L. Hesperus numbers ( r = -0.65, n = 25, for zero to six bugs per 50 sweeps). Comparisons of the proportion of squares damaged by lygus bugs between the terminal 5 nodes, terminal 10 nodes, and all nodes on one to three dates per location indicate that the terminal 5 nodes provide a reliable estimate of L. Hesperus feeding damage to squares. Our calculations indicate that before 1 August each lygus bug collected in the sweep net indicates a potential for 23,400 abscised plus damaged squares per hectare on the day of sample. Boll retention in relation to lygus bug numbers is presented. This information is expected to provide guidance when developing management strategies for L. hesperus on cotton. Square damage and loss can be used to estimate need for pesticide use and for refining the lygus bug: square ratio as an estimator of treatment threshold.
TL;DR: Populations of Phylis melinus detach, a parasitic of California red scale, in citrus, were artificially selected for increased tolerance to five insecticides commonly used in citrus IMP, producing gradual, small to moderate increases in resistance.
Abstract: Populations of Phylis melinus detach, a parasitic of California red scale, Aonidiella aurantii (Haskell), in citrus, were artificially selected for increased tolerance to five insecticides (carbonyl, chlorpyrifos, dimethoate, malathion, and mediation) commonly used in citrus IMP. Selection produced gradual, small to moderate increases in resistance, accompanied in 3 of 12 selected lines with apparent decreases in genetic variation for pesticide tolerance. LC50’s for carbonyl increased to >5 times that of the original field population and approximately 20 times that of a susceptible natural population. Major resistance phenotypes were not detected in large field samples of A. melinns , suggesting that such phenotypes are either present at low frequencies ( 50% survival of the carbaryl-selected strain as early as 18 d after treatment, whereas the unselected colony continued to suffer >86% mortality on 75-d-old residues (the oldest tested). Because larval A. melinus are protected from insecticides within their scale insect hosts, this observed increase in carbonyl tolerance of adults may enable the carbaryl-resistant A. melinns populations to persist in groves treated with carbaryl.
TL;DR: The fruit fly, Drosophila melanogaster (Meigen), is uniquely suited as a model insect to investigate the classical, population, and molecular genetics of resistance evolution.
Abstract: Although the biochemical basis of insect resistance to many pesticides is understood reasonably well, little is known of the genetic mechanisms underlying the evolution of resistance. A major reason for this shortcoming is difficulty with genetic manipulations of most insect pests. The fruit fly, Drosophila melanogaster (Meigen), is uniquely suited as a model insect to investigate the classical, population, and molecular genetics of resistance evolution. The advantages and disadvantages of D. melanogaster for this work are discussed. Cloned sequences from D. melanogaster resistant genes can be used to identify and study homologous genes in pest species.
TL;DR: The fixed-precision sequential sampling plans of Kuno and Green were used to develop monitoring plans for the pea aphid, Acyrthosiphon pisum, and tested with sequential sampling bootstrap simulations of six independent data sets, demonstrating the stochastic nature of each stop-line plan.
Abstract: The fixed-precision sequential sampling plans of Kuno and Green were used to develop monitoring plans for the pea aphid, Acyrthosiphon pisum (Harris), and tested with sequential sampling bootstrap simulations of six independent data sets. For both sampling plans, and population densities from 0.87 to 96.5 aphids per stem, actual precision levels were not fixed at the desired level but fluctuated considerably depending on the particular set of samples selected for any given simulation run. For each set of simulation runs ( n = 100) at the intermediate densities of four and eight aphids per stem, actual precision levels were better than the desired fixed level 99-100% of the time. Corresponding sample sizes for these situations were usually higher than necessary, and the plans were therefore more conservative than stated. Conversely, at the low (0.87 aphids per stem) and high (>24.5 aphids per stem) densities tested, actual precision levels were poorer than the desired level (39-49% of the time). In these situations, too few samples were taken, and the plans were more liberal than stated. These studies clearly demonstrate the stochastic nature of each stop-line plan and emphasize the need for sequential sampling simulations to validate sampling plans before field implementation. As a result of the simulation studies with A. pisum , we used Kuno’s stop-line plan with precision levels (D) = 0.30 for low (≤3/stem) and high (> 1S/stem) aphid densities and D = 0.35 for intermediate densities (3.I-IS/stem). These stop lines were selected to maintain an average actual precision level of D ≅ 0.25 across all density ranges.
TL;DR: This occurrence of resistance is unusual because it appeared the first time this population was exposed to diflubenzuron without previous exposure to related chemicals, whereas the population in another similarly treated orchard retained a high degree of susceptibility after approximately 8 yr of exposure to d IFZ.
Abstract: Codling moth, Cyndia Pomona ella (L.), from pear in the Bedford, Oreg., area showed resistance to the chitin synthesis inhibitor diflubenzuron in laboratory and orchard studies. In the orchard this was shown in 1984 and 1985 as 54.5-63.6% damage at harvest compared with 0.8-2.0% damage occurring in another similarly treated orchard. Concentration-mortality studies later in 1985 and early 1986 showed about a 2-fold difference in susceptibility (LC30= 52.6 and 59.1 mg [All/liter versus 37.9 and 28.2 mg [All/liter) between the two populations based on the response of eggs of the F3. and F4. laboratory-reared generations to residues on the treated fruits. When results from exposure of eggs to a single discriminating concentration of diflubenzuron (112.3 mg [All/liter) were compared, the diflubenzuron-resistant population showed a significantly higher survival (≤29.2-fold). Studies in the same orchard in 1986 again showed a lack of control (35% damage) with a normal concentration. Higher concentrations of 2 times and 4 times normal showed 15% and 8% damage, respectively. This is the first report of resistance to diflubenzuron in the codling moth. This occurrence of resistance is unusual because it appeared the first time this population was exposed to diflubenzuron without previous exposure to related chemicals, whereas the population in another similarly treated orchard retained a high degree of susceptibility after approximately 8 yr of exposure to diflubenzuron. The causes or mechanisms for this develpment of resistance to diflubenzuron in the codling moth remain to be determined.
TL;DR: It is suggested that N, plant population, and soil moisture levels are contributing factors in WCR larval survival and recovery of the corn plant root system.
Abstract: A 2-yr field study was used to examine the main effects and interactions of western corn root worm (WCR), Diabrotica virgifera virgifera LeConte, infestations, nitrogen (N), and corn plant population levels on larval survival and damage, and root growth response. Nitrogen application and higher plant density treatments increased adult emergence, although there were significant N by plant density interactions both years. In 1985, root damage ratings increased with moderate N application but decreased with high N levels. Plant density treatments had no effect on damage ratings. Nitrogen application in 1985 decreased lodging by 44% in plants injured by WCR. Increased N and low to moderate plant population levels resulted in larger root systems and greater regrowth and brace root development. A significant N by plant density interaction indicated that a high plant population level negated the positive response of brace root development to increased N application. WCR infestation promoted root regrowth and brace root development. Decreased adult emergence, root damage ratings, lodging, and increased root regeneration were observed in 1984, a year characterized by excessive June rainfall and saturated soil conditions. These results suggest that N, plant population, and soil moisture levels are contributing factors in WCR larval survival and recovery of the corn plant root system.
TL;DR: For both insects, eggs were the stage most susceptible to cold in oranges, and no significant difference in cold tolerance was seen between young and old larvae, and the effectiveness of 16 d storage at 1.0°C (±0.5°C) against both insects was demonstrated.
Abstract: The presence in Australia of the Queensland fruit fly, Dacus tryoni (Froggatt), and Mediterranean fruit fly, Ceratitis capitata (Wiedemann), restricts access for Australian oranges to some world markets because of plant quarantine regulations. Oranges infested with eggs, young larvae, or old larvae of these insects were stored for various periods at 1 or 1.5°C. For both insects, eggs were the stage most susceptible to cold in oranges, and no significant difference in cold tolerance was seen between young and old larvae. D. tryoni larvae were generally less cold-tolerant than those of C. capitata . The effectiveness of 16 d storage at 1.0°C (±0.5°C) against both insects was demonstrated by 100%mortality on treating more than 90,000 D. tryoni larvae and more than 40,000 C. capitata larvae in oranges.
TL;DR: A cage technique to screen sorghum cultivars for resistance to Contarinia sorghicola under no-choice conditions is described, and TAM 2566 and DJ 6514 were the most resistant cultivars.
Abstract: A cage technique to screen sorghum cultivars for resistance to Contarinia sorghicola under no-choice conditions is described. Forty adults, collected from flowering sorghum panicles in Andhra Pradesh, India, and introduced to the cage at the top- to half-anthesis stage for 2 consecutive days, resulted in maximum damage in the susceptible cultivar CSH 1. Use of a wire-framed cage covered with a blue bag resulted in the greatest damage in CSH 1. This technique was useful for verification of resistance under field conditions. The resistance of 21 cultivars to C. sorghicola was compared under no-choice cage and natural conditions for 4 seasons. Of 15 cultivars reported to be resistant under natural conditions, only 3 (DJ 6514, TAM 2566, and IS 12666C) showed repeatable levels of resistance under no-choice conditions. TAM 2566 and IS 12666C were less attractive to adults (<4 adults/5 panicles) than the susceptible hybrid CSH 1 (19 adults/5 panicles) under field conditions. Fourteen cultivars which were either less attractive to adults or had <12% florets with larvae under natural conditions, showed a susceptible reaction under no-choice testing in the cage. Cultivar reactions were stable over 4 seasons (except IS 2328). TAM 2566 and DJ 6514 were the most resistant cultivars. Sources of resistance placed in groups could be used to increase levels of resistance by hybridization among cultivars belonging to different groups.