Showing papers in "Environmental Entomology in 2001"
TL;DR: The timing of peak trap collections during April coincided with peak tree attacks, and the collection of some species like X. germanus in trap collections may be a more important indicator of tree attack than abundance in the trap, have significance to the nursery industry.
Abstract: Ambrosia beetles can be important pests of nursery production. The beetles are difficult to control with insecticides, requiring that pesticides be closely timed before tree attack, applied repeatedly, or have long residual activity. The goal of this project was to improve management decisions for ambrosia beetle control in nurseries. This study used ethanol-baited traps, field observations of tree attacks, and emergence cages over beetle galleries to determine the following: (1) composition of ambrosia beetle fauna in middle Tennessee, (2) species responsible for attacks on chestnut (Castanea mollissima Blume), a susceptible tree species, (3) timing of tree attacks and progeny emergence, and (4) the relationship between tree attacks, progeny emergence, and beetle collections in ethanol-baited traps. Ambrosia beetles were surveyed using ethanol-baited Lindgren traps at the Tennessee State University Nursery Crop Research Station in McMinnville, TN, and at two commercial nurseries near Dibrell and...
171 citations
TL;DR: The ability of spirea aphid to feed and develop on a wide range of host plants increases its chance to infest citrus and thereby spreading the citrus tristeza virus.
Abstract: The development, survivorship, longevity, reproduction, and life table parameters of the spirea aphid, Aphis spiraecola Patch, were evaluated at 25°C on seven commonly grown plants (Polyscias crispata (Bull) Merrill cultivar chicken-gizzard aralia, P. scutellaria (Burman) Fosberg, Vibernum suspensum Lindley, grapefruit (Citrus paradisi Macfadyen), rough lemon (C. jambhiri Lushington), pineapple orange [C. sinensis (L.) Osbeck variety pineapple orange], orange jessamine [Murraya paniculata (L.) Jack]) in the laboratory. Spirea aphid failed to survive on orange jessamine. The developmental times for the immature stages ranged from 7.9 d on P. scutellaria to 9.9 d on grapefruit or pineapple orange. The immature survival varied from 92.7% on P. scutellaria to 78.8% on pineapple orange. The average number of nymphs reproduced per female were 42.7, 35.7, 28.7, 22.3, 18.0, and 11.7 on P. crispata, P. scutellaria, V. suspensum, grapefruit, rough lemon, and pineapple orange, respectively. Female adults li...
133 citations
TL;DR: Testing 13 species of phytoseiid mites for prey preferences between eggs and larvae of twospotted spider mite showed no differences in prey-stage preferences when compared with individuals from long-term reared laboratory strains of the same species, however, individuals of one field-collected strain of G. occidentalis showed a stronger preference for eggs than individuals from three other strains ofThe same species.
Abstract: We tested 13 species of phytoseiid mites for prey preferences between eggs and larvae of twospotted spider mite, Tetranychus urticae Koch In general, oligophagous, specialized spider mite predators preferred eggs whereas more polyphagous, generalist predators showed no prey-stage preference or preferred larvae: Phytoseiulus macropilis (Banks), P persimilis Athias-Henriot, Neoseiulus longispinosus (Evans), and Neoseiulus fallacis (Garman) preferred eggs; Kampimodromus aberrans (Oudemans), Galendromus occidentalis (Nesbitt), N barkeri Hughes, N californicus (McGregor), N cucumeris (Oudemans), and Typhlodromus pyri Scheuten showed no prey-stage preference; and Amblyseius andersoni Chant, Euseius finlandicus (Oudemans) and E hibisci (Chant) preferred larvae When the ratio of spider mite eggs to larvae was altered, adult females of E finlandicus, G occidentalis, N fallacis, and P persimilis maintained relatively constant feeding ratios, resulting in slight negative prey-stage switching due
127 citations
TL;DR: The lower and upper developmental thresholds as well as the optimal temperatures and thermal constant for the preoviposition period and all immature stages were estimated by fitting the observed developmental rates versus temperature with a nonlinear model and two linear models.
Abstract: Developmental rates of the B- and Q-biotypes of Bemisia tabaci (Gennadius, 1889) were studied at seven constant temperatures (17, 20, 23, 26, 30, 33, and 35°C) on sweet pepper, Capsicum annuum L. (‘Morron’). The egg incubation period and the times required to complete development at all immature stages decreased with increasing temperature up to 33°C, but at 35°C were found to be greater than at 33°C. The relationships between developmental rate of B. tabaci and temperature were influenced by the insect biotype. The lower and upper developmental thresholds as well as the optimal temperatures and thermal constant for the preoviposition period and all immature stages were estimated by fitting the observed developmental rates versus temperature with a nonlinear model and two linear models. For all stages, graphs obtained by plotting the reciprocal of development times against temperature could be described by the modification 2 of the Logan’s model. The simple linear model tT = K+ct suffices for pre...
124 citations
TL;DR: The ability of aphid populations to adapt to high temperatures in the Iberia peninsula is suggested, suggesting the role of temperature as a key factor in determining aphid population dynamics in the northeastern Iberian peninsula.
Abstract: The development, reproduction and longevity of corn aphids Rhopalosiphum padi (L.), Sitobion avenae (Fabricius) and Metopolophium dirhodum (Walker) were studied at 18, 22, 25, 27.5 and 30°C. Only nymphs of R. padi survived at 30°C, but the adult reproductive capacity was very low. Rhopalosiphum padi performed better than M. dirhodum at all temperatures tested, and better than S.avenae over the range of 22–27.5°C. The better performance of R. padi was due to a lower nymphal mortality, lower developmental and prereproductive times and a higher intrinsic rate of increase (rm). Sitobion avenae had a higher rm than M. dirhodum at all temperatures. The most suitable temperature for population development was ≈28.5°C for R. padi, 26.5°C for S. avenae and 24.5°C for M. dirhodum, suggesting the ability of aphid populations to adapt to high temperatures in the Iberian peninsula. The role of temperature as a key factor in determining aphid population dynamics in the northeastern Iberian peninsula is discussed.
124 citations
TL;DR: A dynamic model of colony growth with two time steps per day was formulated that operates by colony area, S, and alate production, a to predict the future range of the fire ant Solenopsis invicta Buren within the United States based on climate and its current extreme distributions.
Abstract: We predict the future range of the fire ant Solenopsis invicta Buren within the United States based on climate and its current extreme distributions. To reach that goal, a dynamic model of colony growth with two time steps per day was formulated that operates by colony area, S, and alate production, a. Colony growth rate depended on daily maximum and minimum soil temperatures. Temperature records at 4,537 meteorological stations within the current (near 1.5 million km2) and potential range of S. invicta were obtained from NOAA’s National Climatic Data Center. At each station, a colony was allowed to grow and lifetime female alate production was calculated. Estimated alate production was then examined at current extremes of the fire ant distribution at selected locations in Arkansas, Tennessee, and Oklahoma. Estimates from these locations were used to define four zones of colony proliferation success: certain, possible, undemonstrated, and improbable. An annual precipitation limit (510 mm) was sel...
123 citations
TL;DR: Both the field experiment and a laboratory experiment showed that extrafloral nectar provides nutritional benefits that extend beyond those provided by a simple water source and promote substantial longevity of first-instar lacewing larvae.
Abstract: We examined the role of extrafloral nectar in the ecology of a larval common green lacewing, Chrysoperla plorabunda (Fitch). Larval lacewings were observed foraging freely in cotton fields and almond orchards to quantify their consumption of extrafloral nectar. Extrafloral nectar was a major component of the diet of neonate lacewing larvae foraging on cotton. Extrafloral nectar consumption increased strongly as the local availability of aphid prey declined. Lacewing larvae also fed frequently on extrafloral nectar when foraging in almond orchards. A manipulative diet experiment in the field demonstrated that in the absence of arthropod prey, extrafloral nectar contributed only slightly to neonate lacewing growth and did not support lacewing development. Nevertheless, extrafloral nectar did promote substantial longevity of first-instar lacewing larvae, which were able to maintain a high level of searching activity. Both the field experiment and a laboratory experiment showed that extrafloral nectar provides nutritional benefits that extend beyond those provided by a simple water source. Lacewing larvae are highly omnivorous: they feed on plant-based resources (extrafloral nectar), on herbivorous arthropod prey (e.g., aphids), and on other predatory or omnivorous arthropods.
118 citations
TL;DR: Recent cultural practices in California cotton include higher rates of nitrogen fertilization, which increases nitrogen content of plants, which is an important factor contributing to the increased severity of the cotton aphid as a pest of California cotton during the midseason.
Abstract: Field experiments were conducted from 1996 to 1998 to assess the effects of nitrogen fertilization rates and planting dates on the population dynamics of the cotton aphid, Aphis gossypii Glover, during the midgrowing season of California cotton. Cotton aphids reached higher densities in high nitrogen fertilized plants (227 kg N/ha, rate currently used by cotton growers) than in low nitrogen fertilized plants (57 kg N/ha). In addition, late-planted cotton (May–June), which had more nitrogen content, also harbored higher aphid populations than early plantings (April). Overall, aphid abundance was positively correlated with plant nitrogen content. In a moderate aphid pressure year (1996), planting the cotton early (April) was effective in keeping the aphid population below the midseason economic threshold. However, in a high aphid pressure year (1997), it was necessary to drastically reduce the nitrogen fertilization to 57 kg N/ha to maintain the aphid density under this threshold. Recent cultural practices in California cotton include higher rates of nitrogen fertilization, which increases nitrogen content of plants. The current data suggest that this practice (i.e., high fertilization) is an important factor contributing to the increased severity of the cotton aphid as a pest of California cotton during the midseason.
109 citations
TL;DR: The results indicate that the mechanisms by which UV-deficiency protects covered crops from insect infestation and spread of viruses are that the lack of UV interferes with insect flight orientation; and that the loss of UV radiation alters the normal behavior of the invading insects, resulting in reduced dispersal activity.
Abstract: The effect of a UV-deficient environment on the attraction and dispersal behavior of whiteflies, Bemisia argentifolii (Bellows & Perring), and on the transmission efficiency of the whitefly-borne tomato yellow leaf curl geminivirus, was tested under field conditions and through controlled experiments. We found that the rate of tomato yellow leaf curl virus-disease spread to tomato plants grown under walk-in tunnels covered with regular greenhouse plastic sheets increases sharply with time, whereas the virus infection-rate under UV-absorbing sheets proceeds at a very slow pace. Average number of whiteflies trapped under regular plastic sheet tunnels was significantly higher than numbers trapped in UV-absorbing plastic sheet tunnels. Similarly, the average number of whiteflies trapped on yellow-sticky traps placed on the outside walls of tunnels covered with regular plastic was higher than the number trapped on the outside walls of tunnels covered with UV-absorbing plastic sheets. No differences were found in the whitefly's ability to transmit tomato yellow leaf curl virus under the two types of plastic covers. Whitefly dispersal pattern under the two types of plastic covers was examined using a release-recapture experiment. In each type of walk-in tunnel we established a grid of yellow-sticky traps forming two concentric circles: an inner and an external. Under UV-absorbing tunnels, significantly higher numbers of whiteflies were captured on the internal circle of traps than the external circle. The fraction of whiteflies that were captured on theexternalcirclewasmuchhigherunderregularcovers,whencomparedwithUV-absorbingcovers, suggesting that filtration of UV light hindered the ability of whiteflies to disperse inside these plastic tunnels. Our results indicate that the mechanisms by which UV-deficiency protects covered crops from insect infestation and spread of viruses are that the lack of UV interferes with insect flight orientation; and that the lack of UV radiation alters the normal behavior of the invading insects, resulting in reduced dispersal activity.
106 citations
TL;DR: It is demonstrated that Mi-mediated aphid resistance is isolate-specific, and it may not extend to all aphid species, and that virulent potato aphids are geographically widespread, and, unlike virulent nematode isolates, are relatively common.
Abstract: Mi is a dominant locus in tomato that confers resistance to both root knot nematodes, Meloidogyne spp., and potato aphids, Macrosiphum euphorbiae (Thomas). The goal of this study was to investigate the breadth of Mi-mediated aphid resistance. To examine variability in potato aphid response, the effect of Mi on seven isolates of the potato aphid from California, New Jersey, North Carolina, France, and The Netherlands was measured in greenhouse bioassays. Assays were also performed to determine if Mi impacted another aphid species that attacks tomato, Myzus persicae (Sulzer). Tomato varieties carrying Mi had a profound negative impact on the potato aphid isolates from France and The Netherlands. In contrast, other potato aphid isolates from New Jersey, North Carolina, and California proved to be virulent, or capable of overcoming Mi. Mi-mediated resistance also did not extend to the green peach aphid isolates tested. These results demonstrate that Mi-mediated aphid resistance is isolate-specific, a...
104 citations
TL;DR: Investigations reveal that M. carolinensis larvae may act as facultative intraguild predators of larvae of other phloem inhabiting species, and possibly related cerambycid species associated with bark beetles.
Abstract: Larvae of the Carolina sawyer Monochamus carolinensis (Olivier) (Cerambycidae) and bark beetle larvae (Scolytidae) often simultaneously feed in phloem of recently killed pine trees. Our investigations reveal that M. carolinensis larvae may act as facultative intraguild predators of bark beetle larvae. Phloem sandwiches were used in four experiments to examine inter- and intraspecific interactions. We discovered that all sizes of M. carolinensis larvae killed bark beetle larvae. Seventy-six percent of the killed bark beetle larvae were consumed by M. carolinensis, including 58% that were entirely ingested. Cannibalism in M. carolinensis occurred in every experimental trial. Based on this evidence, M. carolinensis, and possibly related cerambycid species associated with bark beetles, are facultative intraguild predators of larvae of other phloem inhabiting species. The consequences of this behavior may have important implications for bark beetle population dynamics.
TL;DR: Data analysis of the first year study of population dispersal of Anoplophora glabripennis in Gansu Province, China, has shown that surveys for adult beetles and infested trees at a minimum of 1,500 m from previously infested Trees would assist in preventing continued colonization in the current U.S. infestations.
Abstract: As a basis for the development of both eradication and management strategies for control of Anoplophora glabripennis Motschulsky (Asian longhorned beetle) investigations of A. glabripennis dispersal were undertaken in Gansu Province, China, in 1999. Data analysis of the first year study of population dispersal, in which >16,000 adult A. glabripennis were marked and released (mass-mark recapture method), has shown that the mean dispersal distance for A. glabripennis was ≈266 m, whereas the 98% A. glabripennis recapture radius was 560 m. More notably, A. glabripennis dispersal potential over a single season was found to be 1,029 m and 1,442 m, for male and gravid female beetles, respectively, which is well over the previously reported distances. There was also a directional bias in dispersal. These results indicate that surveys for adult beetles and infested trees at a minimum of 1,500 m from previously infested trees would assist in preventing continued colonization in the current U.S. infestation...
TL;DR: Development time and percent survival of the silverleaf whitefly, Bemisia argentifolii Bellows & Perring, were determined at five constant temperatures ranging from 20 to 35°C on two cultivars of cotton, cantaloupe, and pepper.
Abstract: Development time and percent survival of the silverleaf whitefly, Bemisia argentifolii Bellows & Perring (formerly referred to as B strain of sweetpotato whitefly), were determined at five constant temperatures ranging from 20 to 358C on two cultivars of cotton, cantaloupe, and pepper (Capsicum sp.). Fecundity was recorded at 308C during the first 10 d of adulthood. Developmental, survival, and fecundity rates were not significantly different between cultivars within crops of either cotton or cantaloupe, but varied between crops. Development time from egg to adult at 20—328C ranged from 14.6 6 0.8 (mean 6 SE) to 36.0 6 1.0 d on cantaloupe and from 16.3 6 0.7 to 37.9 6 2.1 d on cotton, respectively. Whiteflies did not develop at 358C or on pepper at any temperature. Minimum developmental thresholds and degree-days requirements from egg to adult were 11.18C and 312.5 DD on cotton and 13.28C and 250.0 DD on cantaloupe, respectively. Immature survival was high (76.5 6 11.5—100%) on cantaloupe, intermediate (37.3 6 13.3—64.4 6 10.2%) on cotton, and very low (0—8.3 6 8.3%) on pepper from 20—328C. Fecundity ranged from 153.3 6 10.8—158.3 6 9.3 eggs per female on cantaloupe, from 117.0 6 6.0—117.5 6 22.1 eggs per female on cotton, and from 2.1 6 0.7—40.5 6 5.8 eggs per female on pepper, at 308C.
TL;DR: In this paper, a commercial formulation of Bacillus thuringiensis subsp kurstaki (Dipel ES) was incorporated into a meridic diet used to feed European corn borer larvae; they then were offered as food to O. insidiosus nymphs.
Abstract: Laboratory feeding studies were conducted to determine the effects on Orius insidiosus nymphs of feeding on 1-d-old European corn borer, Ostrina nubilalis (Hubner), larvae that had ingested a diet containing Bt toxins. A commercial formulation of Bacillus thuringiensis subsp kurstaki (Dipel ES) was incorporated into a meridic diet used to feed European corn borer larvae; they then were offered as food to O. insidiosus nymphs. Immediately after adult eclosion, O. insidiosus sex was determined, body weight and length were measured, and developmental time was calculated. Another feeding study was conducted to determine the effect of Bt corn silk on mortality of immature O. insidiosus. Fresh silks of Bt and non-Bt corn plants were offered to O. insidiosus nymphs until they reached adulthood. Mortality counts were made daily. Finally, visual counts of O. insidiosus were made on Bt and non-Bt corn in fields at three locations in Kansas. The numbers of O. insidiosus nymphs and adults were recorded on 40...
TL;DR: Based on the dispersal results from this study, at least in Iowa, the recommendation for placement of nontransgenic corn as refuge in the Corn Belt is a half mile or closer to Bacillus thuringiensis Berliner (Bt)-corn if the refuge corn is not sprayed and a quartermile or closer when the Refuge corn is sprayed.
Abstract: To observe the aggregation and dispersal behavior of adult European corn borer, Ostrinia nubilalis (Hubner), males in search of mates, two populations were marked, each with a different dye. One population was continuously reared in the laboratory (>5 yr) and the other was collected annually from the field. From 1986 to 1988, marked adults were released in two release sets per year, with three to five releases per release set, coinciding with the spring and summer flights of European corn borer in central Iowa. Traps for recapture contained lures baited with 40 μg of synthetic 97:3 Z:E-11-tetradecenyl acetate. Traplines extended from 200 m to 48 km. Each trap was assigned a compass direction. Males from the laboratory-reared population dispersed similarly to males just 1 generation from the wild. European corn borer males and females dispersed 23–49 km and some were recovered 14 km from the release site within 100 min after release. Sampling of aggregation sites demonstrated that on the nights of...
TL;DR: The importance of sampling along a vertical gradient to assess the effects of silvicultural treatments on insect fauna in managed forests differing in vertical structure was evaluated.
Abstract: Unbiased samples from insect traps are dependent on the placement of traps to account for variation in the spatial distribution of insect fauna. In forests, the spatial distribution of insects reflects forest vertical structure. However, comparative studies of insect diversity in managed forests have traditionally focused a single forest stratum (e.g., forest floor, canopy). We evaluated the importance of sampling along a vertical gradient to assess the effects of silvicultural treatments on insect fauna. We compared the catch from flight-intercept traps suspended at 1, 3, 5, 7, 9, and 11 m above the forest floor in eight forest stands representing three management types: two clearcut stands, two shelterwood stands, and four selection stands. The vertical distribution of insects was significantly different across the three management systems. A greater proportion of the insect fauna was recovered close to the forest floor in clearcut stands than in selection and shelterwood stands. Some insect taxa were restricted to the higher traps; whereas other taxa showed different height associations across the three management systems. Therefore, vertical sampling is important to compare the insect fauna in managed forests differing in vertical structure.
TL;DR: The Logan nonlinear model provided the best estimates of grape berry moth field development, and an improved degree-day model should use 8.41°C as a minimum base temperature threshold and 423.9 as the egg-to-adult degree- day requirement.
Abstract: We modeled development in grape berry moth, Endopiza viteana (Clemens), which exploits wild and cultivated Vitis. Laboratory experiments were used to derive the temperature-dependent developmental curve for eggs, larvae, and pupae. We used linear interpolation to estimate stage-specific base temperature thresholds and degree-day requirements under laboratory conditions. We also estimated parameters of the Logan and Lactin nonlinear developmental models. Lastly, we conducted field experiments to evaluate the conventional degree-day model, which has a base threshold of 10°C; an improved degree-day model that was based on our laboratory observations; and nonlinear developmental models in predicting seasonal grape berry moth development. We concluded that the Logan nonlinear model provided the best estimates of grape berry moth field development, and an improved degree-day model should use 8.41°C as a minimum base temperature threshold and 423.9 as the egg-to-adult degree-day requirement. Also, after...
TL;DR: The established stage emergence models should be useful in building a C. sasakii population model that will describe its seasonal occurrence pattern and population dynamics under various orchard systems.
Abstract: Temperature-dependent development of Carposina sasakii Matsumura was studied, and its stage emergence models were developed. The development times of C. sasakii decreased with increasing temperature up to 32°C in eggs, up to 28°C in larvae, and up to 30°C in pupae. The estimated low-threshold temperatures were 11.0, 9.4, and 10.3°C for eggs, larvae, and pupae, respectively. Thermal constants of eggs, larvae, and pupae were 104.2, 270.3, and 188.7 degree-days, respectively. The stage emergence models of C. sasakii, which simulate the proportion of individuals shifted from a stage to the next stage, were constructed using the modified Sharpe and DeMichele model and the two-parameter Weibull function. In field validation, a degree-day model for the prediction of egg hatch time showed the bias of <1 d between prediction and observation. The stage emergence models predicted the patterns of C. sasakii stage emergences in the field. Also, the established stage emergence models should be useful in building a C. sasakii population model that will describe its seasonal occurrence pattern and population dynamics under various orchard systems.
TL;DR: Observations imply that, although an insect population’s spatial structure may be difficult to characterize due to its dynamic nature, there is a consistent and predictable pattern in L. decemlineata spatial structure that is linked to its population phenology.
Abstract: Integrating global positioning systems technology with a visual canopy survey, a 1-m level of sampling support was used to explore within-field spatial organization of the Colorado potato beetle, Leptinotarsa decemlineata (Say), in potatoes. Spatially referenced counts of adult and large larvae (third and fourth instar) L. decemlineata were made in four '1.5-ha untreated potato fields during two Pennsylvania growing seasons. The presence and nature of spatial structure varied with developmental stage. Overwintered, immigrating adults established 'trends' or 'drift' in the mean density, but spatial dependency (covariance structure) was not detected. This, coupled with a high incidence-to-mean density relationship, suggests a within-field dispersive role for the colonizers. Large larvae and F1 adults, in contrast, displayed spatial dependency (covariance structure), at times accounting for up to '45% of the variation. Their relatively lower incidence-to-mean density relationship suggests less within-field mobility during the reproductive phase of the population cycle. These observations imply that, although an insect population's spatial structure may be difficult to characterize due to its dynamic nature, there is a consistent and predictable pattern in L. decem- lineata spatial structure that is linked to its population phenology.
TL;DR: This work gave opportunities to better understand interactions of the plant-aphid-lady beetle tritrophic model and demonstrated that successful biological control of pests must integrate the environmental aspects of each trophic level.
Abstract: Secondary plant substances, also called allelochemicals, play a major role in pest infestations. Glucosinolates (GLS) and their degradation products are powerful phagostimulants for herbivores feeding on Brassicaceae and deter the noncrucifer feeders but are tolerated by some generalist phytophagous insects such as the peach-potato aphid, Myzus persicae Sultzer. Do the allelochemical substances only effect the herbivores or do they also influence the predators of the pest? Broad bean, Vicia faba L. (GLS free), oilseed rape, Brassica napus L. (low GLS level), and white mustard, Sinapis alba L. (high GLS level), were used in this work as host plant for the prey. Although the two latter Brassicaceae species had positive effects on aphid reproductive rates, host plants displayed mixed influences on the performance of the predaceous twospotted lady beetle, Adalia bipunctata L. Both rape and mustard shortened development duration and increased adult weight of the twospotted lady beetle. No significant difference of lady beetle mortality was observed, depending on the prey host plant. Whereas, rape-fed M. persicae enhanced larger egg production and larvae emergence, mustard-fed M. persicae induced lower fecundity and egg viability of the beetles. Fitness of M. persicae on high GLS plant-fed A. bipunctata was lower than the other plants. Biological parameters of aphid predators are closely linked to chemical composition of Brassicaceae species. This work on allelochemical impact gave opportunities to better understand interactions of the plant-aphid-lady beetle tritrophic model and demonstrated that successful biological control of pests must integrate the environmental aspects of each trophic level.
TL;DR: Fewer ants, lower number of species, and lower ant diversity were found at sites with higher elevation and soil moisture, while more ant species and individuals were found on ridges than in valleys.
Abstract: The relationship between ants and their habitats was examined in oak-dominated mixed forests in the central Appalachian mountains. Ants were sampled using pitfall traps over the summers of 1995, 1996, and 1997. Principal component and correlation analysis indicated that ant diversity (Shannon’s H′), species richness, and abundance were closely correlated with habitat principal components. Fewer ants, lower number of species, and lower ant diversity were found at sites with higher elevation and soil moisture. Diversity (H′) of ants and species richness decreased by 0.1 (R2 = 0.75) and 2.2 (R2 = 0.57) when the elevation increased 100 m, respectively. As the elevation increased, there were relatively less Formica neogagates Emery and more Aphaenogaster rudis (Emery). More ant species and individuals were found on ridges than in valleys.
TL;DR: Results indicated that the release of partially sterile male (and fully sterile female) codling moths does not result in increased fruit injury and that the lower dose of radiation used to partially sterilize males results in insects that are more active, disperse greater distances and are generally more competitive.
Abstract: Season-long field studies were conducted in Washington apple orchards that compared the following: (1) twice per week releases of partially sterile codling moths, Cydia pomonella (L.), treated with either 100 or 250 Gy, and (2) combinations of mating disruption plus the release of partially sterile (100 Gy) codling moths, to control wild codling moth populations. No significant differences in the level of fruit damage at either midseason or harvest were found between any of the treatments, or between the treatments and the inside controls. Damage in all plots was <0.1%. In both studies, trap data suggest that the movement of the 100 Gy-treated moths into the other treatments and the inside controls may have masked treatment effects. However, fruit damage was significantly lower in all treatment plots when compared with control plots located outside of the treatment areas. Results indicated that the release of partially sterile male (and fully sterile female) codling moths does not result in increased fruit injury and that the lower dose of radiation used to partially sterilize males results in insects that are more active, disperse greater distances and are generally more competitive.
TL;DR: This is the first experimental evidence that heteroblasty in Eucalyptus affects insect reproductive behavior and is discussed in relation to subsequent studies on psyllid performance in this system that found that the epicuticular wax plays a primary role in the preferences of these psyllids species for the juvenile versus adult shoots.
Abstract: Heteroblasty describes plants whose juvenile and adult vegetative shoots differ morphologically. In Eucalyptus, heteroblasty is a common source of within-plant variation and an expression of ontogenetic aging that affects the within-tree distribution of psyllids. Using Eucalyptus globulus Labillardiere as a model system, we studied the reproductive behavior of adults of two Australian psyllid species (Ctenarytaina eucalypti Maskell and C. spatulata Taylor) on the glaucous, simple-shaped juvenile leaves and the glossy, sickle-shaped adult leaves under field conditions. We compared the ovipositional preferences and mating site preferences of the psyllids in caged pairs of juvenile and adult shoots, as well as the behavior of the psyllids after they landed on both types of shoots. Ctenarytaina eucalypti oviposited only on juvenile shoots and C. spatulata oviposited only on adult shoots. Ctenarytaina eucalypti mated primarily (88% of the time) on juvenile shoots, and C. spatulata mated only on adult shoots. After landing on both shoot types, C. eucalypti remained longer than C. spatulata on juvenile shoots, but C. spatulata remained longer than C. eucalypti on adult shoots. This is the first experimental evidence that heteroblasty in Eucalyptus affects insect reproductive behavior. These results are discussed in relation to subsequent studies on psyllid performance in this system that found that the epicuticular wax (present only on the juvenile leaves) plays a primary role in the preferences of these psyllid species for the juvenile versus adult shoots.
TL;DR: The effect of habitat transformation on dung beetle assemblages in the north-western Free State was investigated by comparing the fauna of a nature reserve with that on neighboring farms, finding definite habitat preferences and high abundance of a few dominant, highly effective competitors.
Abstract: The effect of habitat transformation on dung beetle assemblages in the north-western Free State was investigated by comparing the fauna of a nature reserve with that on neighboring farms. Dung beetle sampling was done in four different localities within two different habitat types, a grassveld area and a bushveld (savanna) area. In these two habitat types, dung beetle assemblages in Sandveld Nature Reserve (27° 37′ S, 25° 46′ E) and on farms were compared. Eighty-three species belonging to 26 genera were captured in the study area. Doube’s classification was used to divide the dung beetles into functional groups according to the manner in which they use and disturb dung. The grassveld habitats were dominated by larger dung beetles belonging to functional groups I and II, whereas in the bushveld habitats smaller dung beetles belonging to functional groups IV and V were dominant. There were definite habitat preferences, with the larger dung beetles belonging to functional group I and II preferring the grassveld habitats and having higher abundance in the natural rather than the disturbed habitats. The smaller dung beetles, belonging to functional group V, preferred the bushveld habitats. The better competitors (the larger dung beetles) occurred more abundantly in the grassveld habitats and also more abundantly in the natural grassveld habitat than in the disturbed habitat. None of the indices measuring species richness nor dominance showed significant differences between the four habitats. The dung beetle assemblages in all four habitats showed a log series pattern, with high abundance of a few dominant, highly effective competitors and a large number of ‘rare’ species, which were assumed to be less effective competitors. This does not, however, imply that the dung beetles were similarly affected by the different habitats, because the biomass of dung beetles was higher in the grassveld than the bushveld habitats and also higher in the natural habitats. A change in vegetational ground cover caused by overgrazing and trampling has a greater effect on the larger, more effective competitors in the assemblage, whereas the smaller less effective competitors do not seem to be affected by this change.
TL;DR: Coccinellid population densities closely tracked those of cotton aphids during both years of the study, and coccinellids are a valuable component of the cotton aphid’s natural enemy complex.
Abstract: Four treatments were evaluated during 1997 and 1998 to determine the effects of pesticides on coccinellid densities: (1) untreated control, (2) foliar applications of a systemic insecticide, imidacloprid (Provado 1.6 F), when spray thresholds of aphid numbers were exceeded in all plots, (3) weekly foliar applications of a fungicide, chlorothalonil (Bravo 720), and (4) weekly foliar applications of imidacloprid (Provado 1.6 F). The coccinellids observed in Georgia cotton during the study included Hippodamia convergens Guerin-Meneville, Scymnus spp., Harmonia axyri- dis (Pallas), Coccinella septempunctata L., and Coleomegilla maculata (Mulsant). During 1997, H. convergens and Scymnus spp. comprised 75 and 15%, respectively, of all coccinellids observed during the study. During 1998, Scymnus spp. comprised 44% of all coccinellids, and H. convergens comprised 33%. Coccinellid population densities closely tracked those of cotton aphids during both years. Cotton aphid and coccinellid densities were greatest in the chlorothalonil treatment during both years of the study. In functional feeding response experiments, fourth-instar and adult Scynmus creperus exhibited a type II functional response to A. gossypii density under laboratory conditions. Fourth instars exhibited a higher search rate and shorter handling time than adult S. creperus. Collectively, coccinellids are a valuable component of the cotton aphid's natural enemy complex.
TL;DR: Verbenone was an interruptant for some nontarget insects, especially Coleoptera, and none were consistently attracted to verbenone, but both systems have promise for use in forest stands, depending on management objectives and land use.
Abstract: We tested two formulations of verbenone for efficacy in protecting ponderosa pine trees from attack by the red turpentine beetle, Dendroctonus valens LeConte: (1) polyethylene bubblecaps filled with 800 mg of neat verbenone, and (2) a sprayable water suspension of microencapsulated verbenone. We baited artificial trees (cardboard cylinders coupled with Lindgren pheromone traps) with host kairomones and the verbenone formulations. Efficacy was measured by numbers of beetles captured in baited traps. Both release systems significantly reduced trap catch, and there was no significant difference between them. Both systems have promise for use in forest stands, depending on management objectives and land use. Verbenone was an interruptant for some nontarget insects, especially Coleoptera, and none were consistently attracted to verbenone. We report on verbenone as an interruptant to host attraction in the red turpentine beetle, and also on the efficacy of a microencapsulated scolytid semiochemical.
TL;DR: Examination of Formosan subterranean termites, Coptotermes formosanus Shiraki, for possible biological control agents revealed the presence of 15 bacteria and one fungus associated with dead termites from New Orleans, LA, USA.
Abstract: Examination of Formosan subterranean termites, Coptotermes formosanus Shiraki, for possible biological control agents revealed the presence of 15 bacteria and one fungus associated with dead termites from New Orleans, LA, USA. All but one of the bacteria species were gram-negative bacteria. Bacterial isolates from dead termites were primarily Serratia marcescens Bizio that caused septicemia in C. formosanus and also appeared to contain proteolytic enzymes. Multiple strains of S. marcescens were isolated. Six of the eight strains of S. marcescens were red, probably not pathogenic in humans, and candidates as biological control agents for C. formosanus. Bacteria isolated from termite substrata included Corynebacterium urealyticum Pitcher, Acinetobacter calcoacet/baumannii/Gen2 (Beijerinck), S. marcescens, and Enterobacter gergoviae Brenner. Some of these bacteria are potential human pathogens. Forced exposure bioassays demonstrated that the T8 strain of S. marcescens killed 100% of C. formosanus by day 19.
TL;DR: It is concluded that diamondback moth may be more likely to be controlled by intercropping than leek moths.
Abstract: We compared the effect of intercropping on oviposition and emigration behavior of two related specialist moth species. The effect of height of the intercrop species (red clover) on oviposition was studied in field cages, using the leek moth, a specialist on Allium species, and the diamondback moth, a specialist on Brassica species. The moths were also evaluated in an open field experiment. Emigration of both moths was studied in the laboratory and in the field in cages with host plants, red clover (nonhost), host plant and red clover, and bare soil. The possible influence of noncontact stimuli was also studied in the laboratory. The leek moth laid the same amount of eggs in monoculture as in intercroppings with high and low clover. White cabbage intercropped with high clover received fewer eggs of the diamondback moth compared with a cabbage monoculture. Intercropping with low clover did not reduce the amount of eggs laid. Intercropping did not appear to affect the emigration of either the leek moth or the diamondback moth. Leek moths were less likely to emigrate than diamondback moths during the first 4 h of the study. We conclude that diamondback moth may be more likely to be controlled by intercropping than leek moths.
TL;DR: It is indicated that peach trees are attractive to both predators and parasitoids and therefore may be a valuable addition to apple orchards to enhance the abundance of biological control species.
Abstract: Limb jarring samples were taken in four experimental apple orchards (one completely unmanaged; one with horticultural management and no pest management; one with horticultural management, no pest management, and interplanted with peach and sour cherry; and one under conventional commercial management practices) at hourly intervals over a 24-h period at four times in 1991. A total of 1,176 individual predators belonging to seven orders and 22 families was collected. The most abundant species was Coniopteryx sp. (Coniopteryigidae: Neuroptera), and the most abundant family was Coccinellidae (Coleoptera). A total of 396 adult parasitoids was collected from 26 families of Hymenoptera and one Diptera family, with Encyrtidae being the most abundant. All other individuals were classified as potential food items and were identified only to order or, in some instances, family. A total of 5,812 potential food items was collected. Diversity of predators and parasitoids was greatest in May and June. Diversity of predators was highest on apple trees that were inter-planted with peach and cherry trees, whereas parasitoid diversity was greatest on peach trees and on insecticide treated apple trees. Chrysopids (Neuroptera), clerids (Coleoptera), and Leptothrips mali (Fitch) (Phlaeothripidae: Thysanoptera) were most commonly collected at dawn or during the night, suggesting that their role in orchards may be underestimated by sampling only during daylight hours. With the exception of Scelionidae and Platygastridae (Hymenoptera), parasitoids were most commonly collected during the night. Results indicate that peach trees are attractive to both predators and parasitoids and therefore may be a valuable addition to apple orchards to enhance the abundance of biological control species.
TL;DR: Water-soluble ibuprofen sodium salt demonstrated a protective effect that was unexpected in light of the increased termite mortality observed with the relatively water insoluble, free acid form, and was insufficient to prove the hypothesis that the termites’ immune systems were suppressed by these compounds.
Abstract: The biological control of termites may be facilitated if their highly evolved immune systems can be suppressed. Eicosanoids are C20 polyunsaturated acids that are of widespread biochemical importance, including their role in protecting insects from bacterial infection. In laboratory experiments, the eicosanoid biosynthesis inhibitors dexamethasone, ibuprofen, and ibuprofen sodium salt were each provided along with a red-pigmented isolate of Serratia marcescens Bizio, a bacterial pathogen, to the Formosan subterranean termite, Coptotermes formosanus Shiraki, by means of treated filter paper. The increased mortality that resulted with dexamethasone and ibuprofen supported, but alone was insufficient to prove, the hypothesis that the termites’ immune systems were suppressed by these compounds, making the insects more vulnerable to infection by S. marcescens. This effect on mortality was noted only at 3.4 × 1010 colony-forming units per milliliter, a high treatment level. A significant amount of the infection and subsequent mortality may have resulted from direct contact with the bacterium and the remainder from its ingestion. Water-soluble ibuprofen sodium salt demonstrated a protective effect that was unexpected in light of the increased termite mortality observed with the relatively water insoluble, free acid form.