Showing papers in "Environmental Entomology in 1991"
TL;DR: Hemlock woolly adelgid severely reduced the growth and survival of Tsuga canadensis (L.) Carriere, which had a major impact on the subsequent performance and population dynamics of this insect.
Abstract: Studies in a hemlock plantation and in four hemlock forests in Connecticut revealed that hemlock woolly adelgid, Adelges tsugae Annand, severely reduced the growth and survival of Tsuga canadensis (L.) Carriere, which had a major impact on the subsequent performance and population dynamics of this insect. The presence of adelgids at all but relatively low densities ( 93% of the adelgids produced in each of the subsequent 3 yr became sexuparae; in the fourth year only sexuparae were produced. Density-dependent production of the unsuccessful sexuparae played a major role in the decline of A. tsugae populations on their deteriorating host.
322 citations
TL;DR: The ubiquitous entomopathogenic fungus Beauveria bassiana (Balsamo) Vuillemin colonized the corn plant at whorl stage, moved within the plant, and persisted to provide season-long suppression of O. nubilalis.
Abstract: The ubiquitous entomopathogenic fungus Beauveria bassiana (Balsamo) Vuillemin was applied to whorl-stage corn plants, Zea mays L., by foliar application of a granular formulation of conidia and by injection of a conidial suspension. Plants were analyzed at harvest for presence of B. bassiana and for the amount of tunneling by laboratory-reared European corn borer larvae, Ostrinia nubilalis (Hubner). In 1989, 98.3% of the foliarly treated plants, 95.0% of the injected plants, and 33.3% of the nontreated plants were colonized by B. bassiana at harvest. In 1988, there were no significant differences between treatment effects on O. nubilalis tunneling in plants. In 1989, when environmental conditions were more conducive to fungal growth, tunneling was significantly greater in the control plants, followed by the injected and foliarly treated plants. When applied to foliage, B. bassiana provided the greatest amount of O. nubilalis suppression. The entomopathogenic fungus colonized the corn plant at whorl stage, moved within the plant, and persisted to provide season-long suppression of O. nubilalis .
273 citations
TL;DR: D. frontalis outbreaks are driven not by stochastic fluctuations of weather, but by some unknown population process acting in a delayed density-dependent manner, which provides a starting point for a current study that will experimentally test various hypotheses concerning the role of natural enemies in D.frontalis cycles.
Abstract: It is widely believed that population outbreaks of the southern pine beetle ( Dendroctonus frontalis Zimm.) are caused by vagaries of climate, such as periods of severe drought. According to this view, D. frontalis population dynamics are dominated by density-independent processes. We have statistically analyzed a 30-yr record of D. frontalis activity in east Texas and have assessed the relative roles of density-independent and density-dependent factors in beetle population fluctuations. Regressions of the rate of population change on three climatic variables were not significant. By contrast, both time-series and regression analyses provided strong and consistent evidence for delayed density regulation of D. frontalis populations. Thus, in contrast to previous analyses, we conclude that D. frontalis outbreaks are driven not by stochastic fluctuations of weather, but by some unknown population process acting in a delayed density-dependent manner. This result provides a starting point for a current study that will experimentally test various hypotheses concerning the role of natural enemies in D. frontalis cycles.
145 citations
TL;DR: Tests in Maryland demonstrated that parasitic tachinid flies use the Euschistus unsaturated methyl-ester as a host-finding kairomone, and it is not yet clear what role minor volatile components of EusChistus play in reproductive isolation.
Abstract: Methyl (2 E ,4 Z )-decadienoate was isolated and identified as the major male-specific volatile of Euschistus conspersus, E. tristigmus, E. servus, E. politus , and E. ictericus . In a sixth species, E. obscurus , this ester is a relatively minor male-specific component, with the major component being tentatively identified as methyl 2,6-dimethyltetradecanoate. Females, males, and nymphs of E. conspersus, E. tristigmus, E. servus , and E. politus were significantly attracted to methyl (2 E ,4 Z )-decadienoate in field tests conducted in California and Maryland. Tests in Maryland also demonstrated that parasitic tachinid flies use the Euschistus unsaturated methyl-ester as a host-finding kairomone. It is not yet clear what role minor volatile components of Euschistus play in reproductive isolation.
135 citations
TL;DR: A method of quantifying insect paths in the field for use in ecological and behavioral studies is described and illustrated with a study of individual movements in a hilltopping butterfly, Euphydryas editha Boisduval.
Abstract: We describe a method of quantifying insect paths in the field for use in ecological and behavioral studies. First, we discuss how continuous and curvilinear paths traced by moving insects can be approximated with a series of connected straight lines. Next we describe our procedure for following insects under field conditions and for recording their behaviors (and the timing of behavioral events) with a hand-held TRS-80 computer. We discuss how successive positions of a followed insect can be recorded by triangulation and then translated into spatial coordinates. Finally, we illustrate the method with a study of individual movements in a hilltopping butterfly, Euphydryas editha Boisduval.
113 citations
TL;DR: It is concluded that entomopathogenic nematodes do not adversely affect nontarget arthropods when used for short-term control of insect pests.
Abstract: The effect of entomopathogenic nematodes on nontarget arthropods in the laboratory, field soils, and a stream were assessed. In the laboratory, adult predators were less susceptible to the nematodes Steinernema carpocapsae (Weiser) (Rhabditida: Steinernematidae) and Heterorhabditis bacteriophora Poinar (Rhabditida: Heterorhabditidae) than the immature stages. In field tests, entomopathogenic nematodes that had significantly suppressed pest populations ( Popillia japonica Newman, Japanese beetle, Scapteriscus vicinus Scudder, tawny mole cricket, Otiorhynchus sulcatus (F.), black vine weevil, Delia radicum (L.), cabbage maggot, and Diabrotica virgifera virgifera LeConte, western corn rootworm) did not adversely affect the numbers of nontarget soil arthropods in comparison with the untreated control. In contrast, broad-spectrum chemical insecticides (isofenphos, ethoprop, or chlorpyrifos used as chemical checks) significantly reduced or showed a tendency to reduce nontarget arthropod populations. In a stream trial, S. carpocapsae significantly reduced black fly larval populations, but the nontarget insects often increased in the treatment sites. Decreases in nontarget populations were matched by approximately equal or greater reductions in the upstream controls. We conclude that entomopathogenic nematodes do not adversely affect nontarget arthropods when used for short-term control of insect pests.
112 citations
TL;DR: These solutions provide tools for the more accurate quantification of parasitism as a mortality factor in insect life systems and compare their relative usefulness for systems of varying types of biologies and sampling constraints.
Abstract: An earlier forum article identified a need for new analytical methods for obtaining stage-specific estimates of losses from parasitism for life table, population dynamics, and evaluation studies. A discussion of the conceptual framework for recently developed solutions to this problem is presented. Classes of solutions considered include recruitment, stage frequency, and death rate analyses. We present the rationale and methodology for each and compare their relative usefulness for systems of varying types of biologies and sampling constraints. These solutions provide tools for the more accurate quantification of parasitism as a mortality factor in insect life systems
110 citations
TL;DR: No correlation was observed between levels of total free amino acids in healthy and infected plants and rates of oviposition or survival, and this suggests that B. tabaci does not assess host suitability to regulate Oviposition with respect to the projectedhost suitability for offspring survival.
Abstract: In some cases, infection by plant viruses can alter host plant quality for homopterous insects. In these experiments, adult whiteflies from a population of Bemisia tabaci (Gennadius) that had been reared continuously on pumpkin plants for more than five years, were exposed to six plant species infected with one of four whitefly-transmitted plant viruses. The life history traits of whiteflies on virus-infected hosts were compared to those of whiteflies exposed to corresponding healthy hosts. Significant differences were found in progeny survival and oviposition rate among the six healthy hosts. Survival on healthy hosts ranked as follows: zucchini > cantaloupe = cotton = pumpkin > lettuce = tomato. Oviposition and immature survival rates varied between healthy and virus-infected host plants. The mean proportion of eggs surviving to adulthood was higher on pumpkin plants infected with watermelon curly mottle strain of squash leaf curl virus (WCMoV/SLCV) than on healthy pumpkin. Significantly lower mean proportion of offspring survived to adulthood on WCMoV/SLCV-infected zucchini, chino del tomate virus-infected tomato, and cotton leaf crumple virus-infected cotton compared to whiteflies on healthy control plants. For other virus-infected–healthy combinations, there were no significant differences in survival rates. No correlation was observed between levels of total free amino acids in healthy and infected plants and rates of oviposition or survival. The lack of correlation between oviposition and survival rates on healthy and infected plants, suggests that B. tabaci does not assess host suitability to regulate oviposition with respect to the projected host suitability for offspring survival.
99 citations
TL;DR: Eggs were an adequate (but not optimal) diet for larval development and adult oviposition relative to M. persicae or corn pollen, and females did not prefer either prey at low prey densities, but they preferred aphids over eggs at high densities.
Abstract: Feeding responses that influence the effectiveness of a polyphagous endemic coccinellid, Coleomegilla maculata (DeGeer), for biological control of Colorado potato beetle, Leptinotarsa decemlineata (Say), in potato were examined in the laboratory. Consumption rate, functional response, prey preference, and the effect of alternate prey were studied for C. maculata adult females feeding upon eggs of Colorado potato beetle; Myzus persicae (Sulzer) and corn pollen were alternate food sources. C. maculata females continuously supplied with eggs attacked an average of 20.8 eggs per 48 h, and introduction of M. persicae significantly reduced but did not eliminate egg feeding. Females starved for 24 h showed a Type II functional response to egg density when offered 10–70 eggs per 24 h in small cages at 26 ± 2°C. Data fit well to the Holling disk equation, which predicted maximum egg consumption of 31.5 eggs per 24 h. The functional response curve showed suppression of egg feeding at high egg densities when aphids were present as alternate prey, but no effect was evident at low egg densities. There was no change in functional response with corn pollen as the alternate food. When Colorado potato beetle eggs and aphids were available in equal numbers, females did not prefer either prey at low prey densities, but they preferred aphids over eggs at high densities. Eggs were an adequate (but not optimal) diet for larval development and adult oviposition relative to M. persicae or corn pollen. Some implications for ecology and effectiveness of C. maculata for control of Colorado potato beetle in potato are discussed.
98 citations
TL;DR: Soils from 351 sites representing ecologically diverse habitats from six Hawaiian Islands were assessed for entomopathogenic nematodes using the Galleria baiting technique, and heterorhabditids were highly correlated with ocean beaches within 100 m of seashore (0 m elevation).
Abstract: Soils from 351 sites representing ecologically diverse habitats from six Hawaiian Islands (sea level to 4,200 m) were assessed for entomopathogenic nematodes using the Galleria baiting technique. Twenty-four sites (6.8%)were positive for entomopathogenic nematodes. Twenty-two sites (6.3%) were positive for a Heterorhabditis sp. from the islands of Kauai (6), Oahu (5), Maui (4), Molokai (1), and Hawaii (6), and two sites were positive for a Steinernema sp. from Maui. No entomopathogenic nematodes were recovered from soils on the island of Lanai. Heterorhabditids were highly correlated with ocean beaches within 100 m of seashore (0 m elevation). These positive sites had soils containing sand grains from coral and shells with moderately alkaline pH (8.0) and low organic content (12%). The steinernematid isolates came from inland areas in silty clay and silt loam soils with higher organic content (15–35%).
93 citations
TL;DR: Results indicated that a population of irradiated flies released from a single point dispersed in a manner that may be modeled as if the population consisted of two subpopulations, one of which was dispersing in a diffusionlike pattern and the other was not dispersing, and that the fraction of the population in the nondispersing subpopulation increased.
Abstract: One of the most common methods of studying insect dispersal is the recapture of members of a population released at a single time from a single location. This procedure especially lends itself to quantitative analysis. Quantitative studies of the dispersal of insects released in this manner may be divided into the following three general categories: (1)statistical studies in which certain dispersal parameters such as average distance flown are estimated without assuming any particular model; (2) curve fits to an empirical model having a predetermined functional form, such as an exponential; and (3) fits to a fundamental biological model such as a diffusion-based model. Each of these methods of analysis serves a purpose. For example, the first and second methods are often useful in developing control strategies for invasive pest species, whereas the third is useful for understanding the biological process driving dispersal. The article presents a quantitative analysis of the dispersal of irradiated Mediterranean fruit flies, Ceratitis capitata (Wiedemann) in a macadamia nut orchard near Hilo, Hawaii. All three of the methods described above are used in the analysis. The article had three primary objectives. The first was to review and contrast the three methods of analyzing data on the dispersal of insects from a point source. The second was to illustrate how these methods may be applied to insect recapture data using the example of released Mediterranean fruit flies. The third was to use the quantitative analysis to compare the results of the present release study with other studies on related species and to draw general conclusions about the nature of the dispersal of released sterile Mediterranean fruit flies. Results indicated that a population of irradiated flies released from a single point dispersed in a manner that may be modeled as if the population consisted of two subpopulations, one of which was dispersing in a diffusionlike pattern and the other was not dispersing, and that the fraction of the population in the nondispersing subpopulation increased. The dispersal pattern appeared to be little influenced by prevailing wind and to remain centered near the release point. The pattern had almost complete circular symmetry.
TL;DR: Data on the natural control of cereal aphids, Diuraphis noxia (Mordvilko), Metopolophium dirhodum (Walker), and Sitobion avenae (F.), by entomophthoralean fungi and hymenopterous parasitoids on furrow-irrigated spring wheat in southwestern Idaho are presented.
Abstract: Data on the natural control of cereal aphids, Diuraphis noxia (Mordvilko), Metopolophium dirhodum (Walker), and Sitobion avenae (F.), by entomophthoralean fungi and hymenopterous parasitoids on furrow-irrigated spring wheat in southwestern Idaho are presented. The important fungi involved were Pandora neoaphidis (Remaudire & Hennebert) Humber and Conidiobolus spp., including C. obscurus (Hall and Dunn) Remaudire, C. thromboides Drechsler, and C. coronatus (Constantin) Batko. During 1986–1989, M. dirhodum and S. avenae populations usually reached or exceeded economic levels. D. noxia did not enter the region until late June 1987. It was the first aphid found infesting the crop in 1988 and reached high densities that summer but was not found in 1989, perhaps because of mortality during an extremely cold winter. Fungal infection occurred ≍2,3, and 6 wk after colonization of the crop by M. dirhodum, S. avenae , and D. noxia, respectively. Epizootics occurred each summer but usually after the crop was damaged by large aphid populations. An exception occurred during 1987 when M. dirhodum and S. avenae populations were effectively suppressed by mycoses, apparently enhanced by unusually frequent rainfall during late May and June. M. dirhodum experienced much higher mortality from fungal infection than did S. avenae and D. noxia. P. neoaphidis was the dominant fungus infecting M. dirhodum and D. noxia, whereas Conidiobolus spp. were most important on S. avenae. Entomophthora chromaphidis Burger & Swain and two Zoophthora species sporadically infected cereal aphids. Parasitoids, mainly Aphidius ervi Haliday for S. avenae and M. dirhodum and Diaeretiella rapae (M'Intosh) for D. noxia, usually attacked cereal aphids earlier than the fungi but were less influential during the decline of host populations. Multiple regression and correlation analysis indicated that mycoses and parasitoids made significant contributions to the reduction of peak populations of each aphid species compared with the influence of crop maturation. Weak correlation between fungal infection and host density and climatic factors ( r2 ranging from 0.35 to 0.53) was found. Development of fungal infection seemed to be better correlated with host density than with climatic factors. Precipitation was more associated with fungal infection of S. avenae, which inhabits upper portions of the host crop, but had little effect on that of M. dirhodum and D. noxia, which inhabit more humid microenvironments. No other climatic factors were significantly correlated with fungal infection. A hypothesis is proposed that the site on a wheat plant typically occupied by an aphid species influences the development of mycoses.
TL;DR: Data on growth rate, survival, and fecundity of the two strains reared on HD-73 delta-endotoxin were used to set parameters of a Single-locus genetic model to predict the rate at which H. virescens populations would adapt to B. kurstaki or its endotoxin when exposed to it in choice and no-choice situations.
Abstract: A commercial formulation of Bacillus thuringiensis var. kurstaki Berliner (Dipel 2X) and purified HD-73 delta-endotoxin were evaluated for effects on the growth, behavior, and fitness of susceptible and toxin-adapted strains of Heliothis virescens (F.) by incorporation of the materials into artificial diets at varying concentrations. Neonate larvae were placed in experimental arenas where they could choose a diet containing toxin and a control diet, or were placed in arenas where the only diet available contained a toxin. The difference between the strains in growth and survival was much more pronounced when larvae could not choose to feed on the control diet. Both strains avoided moderate and high concentrations of the toxins. At the lowest concentration of HD-73, neither strain avoided the diet that contained the endotoxin. At the two lowest concentrations of Dipel 2X, only the susceptible strain avoided the diet containing Dipel. Data on growth rate, survival, and fecundity of the two strains reared on HD-73 delta-endotoxin were used to set parameters of a Single-locus genetic model to predict the rate at which H. virescens populations would adapt to B. thuringiensis var. kurstaki or its endotoxin when exposed to it in choice and no-choice situations. Results from the model generally predict much more rapid adaptation in no-choice situations.
TL;DR: When a Beauveria -infected host was included in a choice test, nematodes tended to occur more frequently at the host not infected with B. bassiana, which may minimize antagonistic interactions between entomogenous nematode and B.bassiana in soil.
Abstract: Laboratory experiments were conducted to determine the effect of soil texture and condition of Galleria mellonella larvae (infected with Beauveria bassiana , uninfected and alive, or uninfected and killed by freezing) on host-finding by the entomogenous nematodes, Heterorhabditis bacteriophora and Steinernema carpocapsae, H. bacteriophora was more motile than S. carpocapsae in organic and fine sandy loam soils, but less motile in clay soil. In soil-filled tubes, H. bacteriophora and S. carpocapsae usually occurred more frequently near healthy hosts when healthy hosts were present in choice tests. When a Beauveria -infected host was included in a choice test, nematodes tended to occur more frequently at the host not infected with B. bassiana . This behavior may minimize antagonistic interactions between entomogenous nematodes and B. bassiana in soil.
TL;DR: The effect of fruit species on parasitization of Anastrepha ludens (Loew) by Diachasmimorpha longicaudata (Ashmead) was studied and the roles of fermenting fruit volatiles, size, and color in host habitat selection by this parasitoid were investigated.
Abstract: The effect of fruit species on parasitization of Anastrepha ludens (Loew) by Diachasmimorpha longicaudata (Ashmead) was studied. The roles of fermenting fruit volatiles, size, and color in host habitat selection by this parasitoid also were investigated. The lowest percentage parasitism was recorded for larvae in grapefruit, Citrus paradisi Macf. On the other hand, grapefruit volatiles and size proved most attractive to D. longicaudata . Greater percentage parasitism was recorded for larvae in smaller and apparently less attractive fruit. The length of the parasitoid's ovipositor, depth of the fruit pulp, and host larval behavior could explain these contrasting results. Citrus volatiles attracted almost twice as many female parasitoids as volatiles of mango, Mangifera indica L., or peach, Prunus persica L. Fruit >5 cm in diameter were equally attractive to D. longicaudata . Selection of colors by D. longicaudata was not statistically different among colors tested.
TL;DR: Photoperiod influenced nymphal development and diapause induction in a laboratory culture of Orius insidiosus and duration of the preoviposition period was inversely related to photoperiod.
Abstract: Photoperiod influenced nymphal development and diapause induction in a laboratory culture of Orius insidiosus (Say). At 20°C, development of nymphs was significantly faster at a photoperiod of 10:14 (L:D) than at 12:12, 13:11, 14:10, or 15:9. Subsequently, diapause induction exhibited a typical long-day response; nearly 100% of adult females entered reproductive diapause when reared under short photoperiods (10:14 [L:D]), whereas at longer photoperiods (12:12, 13:11, 14:10, 15:9 [L:D]), fewer insects initiated diapause (56.8, 29.7, 5.3, 12.9%, respectively). The critical photoperiod fell between 12:12 and 13:11 (L:D). Duration of the preoviposition period was inversely related to photoperiod.
TL;DR: Among-sample spatial variation in gypsy moth egg mass population density was quantified from four databases and specific recommendations were developed for the spacing of spatially stratified egg mass samples in area-wide management systems.
Abstract: Among-sample spatial variation in gypsy moth egg mass population density was quantified from four databases: the Melrose Highlands data (104 plots [0.0405 ha] sampled throughout coastal New England over a 20-yr period in the early 1900s; maximum point separation of ≍250 km), Massachusetts state survey data (150 plots of 20 banded trees located throughout Massachusetts and sampled from 1985 to 1987; maximum point separation ≍300 km), Fox Chapel Survey Data (517 plots [0.0101 ha] sampled throughout Fox Chapel Borough, Pennsylvania from 1988 to 1990; maximum point separation ≍8 km) and Cape Cod within-stand data (groups of 169 plots [0.008 ha] located in a 25-m grid; maximum point separation ≍1 km). Sample semivariograms were calculated that quantified spatial dependency in density at a variety of spatial scales. Both the Melrose and Massachusetts data showed evidence of spatial contagion in density at distances ranging from 20 to 100 km. The range and magnitude of this spatial dependence varied considerably from year to year. The extent of small-scale (<200 m) spatial contagion of egg mass densities in the Cape Cod data was also quite variable. Some of the sites in some years showed evidence of spatial dependence at various distances, whereas data from other years and other sites showed no spatial contagion. In contrast, semivariograms from the Fox Chapel plots were quite similar: in each of the 3 yr the maximum distance of spatial dependence (“range”) was ≍1 km. In summary, we quantified spatial dependency in egg mass densities at scales ranging from 25 m to 100 km. There was little evidence of spatial dependency at greater distances. The ordinary kriging procedure can use these semivariograms to generate maps of interpolated estimates of egg mass densities. These maps may be valuable in area-wide gypsy moth management programs. Specific recommendations were developed for the spacing of spatially stratified egg mass samples in area-wide management systems.
TL;DR: The results differed sharply with previous field measures of predation by P. maculiventris, indicating that attack rates in a simple laboratory arena are limited by different behaviors than are important in the field.
Abstract: Laboratory experiments were conducted to measure the functional response of Podisus maculiventris (Say) in a simplified arena. Predators were isolated singly for 24 h in 9-cm Petri dishes with either 1, 2, 4, 8, 12, or 16 third-instar larvae of Mexican bean beetle ( Epilachna varivestis Mulsant). Results showed a typical type II response, with up to 9 prey attacked when 16 were provided. Holling's disk equation was fitted to the data to give estimates of handling time and the maximum number of prey that could be attacked in 24 h. The results differed sharply with previous field measures of predation by P. maculiventris , indicating that attack rates in a simple laboratory arena are limited by different behaviors than are important in the field. As a result we suggest that measuring functional response must be done in an appropriate test arena if the results are to be used to predict the impact of the predator on field populations of prey.
TL;DR: The spatial and temporal foraging dynamics of western harvester ant colonies, Pogonomyrmex occidentalis (Cresson), in a shrub–steppe ecosystem in southwestern Wyoming were studied and composition of forage returned by ants differed seasonally and according to daily changes in surface temperature.
Abstract: The spatial and temporal foraging dynamics of western harvester ant colonies, Pogonomyrmex occidentalis (Cresson), in a shrub–steppe ecosystem in southwestern Wyoming were studied. Ant foraging was spatially organized by permanent trunk trails that were formed by workers traveling in corridors between shrubs. An exponential decline was observed in forager flows with distance along trails, a pattern which changed when foragers were recruited to experimental seed patches. Trails also differed in seasonal forager activity and the seed species returned by ants. Soil surface temperature was a significant contributor to variation in forager departure rates in 70% of the 48 samples taken across months and colonies during the 2-yr study. Densities of soil seeds in the foraging areas of P. occidentalis colonies were significantly correlated with seasonal ant activity levels. The composition of forage returned by ants differed seasonally and according to daily changes in surface temperature.
TL;DR: A new multiple embedded nuclear polyhedrosis virus was isolated from a fourth-instar celery looper, Anagrapha falcifera (Kirby) collected from cabbage in central Missouri in May 1985 and patented by the U.S. Government Patent and Trademark Office.
Abstract: A new multiple embedded nuclear polyhedrosis virus was isolated from a fourth-instar celery looper, Anagrapha falcifera (Kirby) collected from cabbage in central Missouri in May 1985. Characterization and comparison to other multiple embedded nuclear polyhedrosis viruses via restriction endonuclease analysis indicated a unique baculovirus with a molecular weight of 85.6 × 108 Daltons. This baculovirus (AfMNPV) was propagated in cabbage looper larvae and tested against a variety of insect species in laboratory bioassays. More than 31 species of Lepidoptera from 10 families demonstrated susceptibility when allowed to feed ad libitum on substrates (artificial or natural) contaminated with occlusion bodies (OB) at 10 or 100 OB/mm2. Helicoverpa (= Heliothis) zea and H. virescens did not demonstrate differential susceptibility to AfMNPV (LC50, 0.36 and 0.39 OB/mm2, respectively) as compared to the alfalfa looper, Autographa californica , multiple embedded nuclear polyhedrosis virus (AcMNPV) LC50, 10.3 and 0.45 OB/mm2, respectively). No other currently known natural or genetically engineered baculovirus infects as many cosmopolitan, economically important insect species or causes mortality as quickly at low concentrations. This is the first baculovirus patented by the U.S. Government Patent and Trademark Office (no. 4,911,913, issued 27 March 1990).
TL;DR: The mated female adults of A. cucumeris were the most effective predatory stage, whereas all male stages were ineffective predators, and use of this information for improving and predicting the outcome of biological control of F. occidentalis on greenhouse crops is discussed.
Abstract: The functional response for various stages of the predatory mite, Amblyseius cucumeris (Oudemans), on first instars of western flower thrips, Frankliniella occidentalis (Pergande), was determined. The predation trials were conducted on greenhouse cucumber and sweet-pepper leaf disks over a 24-h period at 26 ± 1°C and 12:12 (L:D) photoperiod. Prey densities ranged from 1 to 40 larvae per leaf disk. The mated female adults of A. cucumeris were the most effective predatory stage, whereas all male stages were ineffective predators. Use of this information on the predator-prey relationship between A. cucumeris and F. occidentalis for improving and predicting the outcome of biological control of F. occidentalis on greenhouse crops is discussed.
TL;DR: First instars of the eucalyptus longhorned borer, Phoracantha semipunctata (F), were not capable of colonizing bark of vigorous standing trees of two EucalyPTus species, and bark moisture content plays a critical role in the resistance of eucallyptus trees against colonization by E. longhorn borer larvae.
Abstract: First instars of the eucalyptus longhorned borer, Phoracantha semipunctata (F.), were not capable of colonizing bark of vigorous standing trees of two Eucalyptus species. The lack of a kino gum reaction after the introduction of larvae into the bark of E. grandis Hill ex Maiden and E. tereticornis Small strongly indicates that this gum does not play an important role in the initial defense against borer attack. Larvae were also not able to colonize the bark of logs that were maintained at high moisture content but were able to colonize the bark of dry logs and artificially water-stressed trees that had reduced bark moisture content. We propose that bark moisture content plays a critical role in the resistance of eucalyptus trees against colonization by eucalyptus longhorned borer larvae.
TL;DR: The data suggested that pest injury is less likely to exceed economic injury levels in polycultures than in monocultures, and the conditions for vegetational diversity to improve yields were examined.
Abstract: Five methods were evaluated for measuring the effects of arthropod pests on crop yields in vegetationally diverse agroecosystems, and the conditions for vegetational diversity to improve yields were examined. Two methods measured absolute yield benefits in which polyculture yields were higher than yields in monocultures. A review of the literature indicated that absolute yield benefits occurred only rarely and only when the arthropod pests caused severe yield losses in monocultures. One method was judged of limited use. The remaining two methods measured marginal yield benefits, in which yield loss in polycultures is less than that in monocultures. Statistical tests for factorial experiments that estimate this marginal benefit are proposed. A review of 41 cases suggested that this benefit occurred only if polycultures had lower pest populations than monocultures, and even then, it occurred intermittently. Severe competition from the other plants in the polyculture might limit the ability of the crop to compensate for pest injury and crop tolerance, or resistance to pest injury might otherwise limit yield losses in polycultures. In addition, the data suggested that pest injury is less likely to exceed economic injury levels in polycultures than in monocultures.
TL;DR: Changes in the distribution of borer larvae and their predators are discussed in relation to prey and pollen availability in different corn plant microhabitats.
Abstract: In western Maryland, the European corn borer, Ostrinia nubilalis (Hubner), exhibited three flight periods (from late May to mid-September 1986–1988) but completed only two generations in corn. Oviposition by corn borer moths increased when the tassels emerged and shed pollen. Peak density of the predators Orius insidiosus (Say) and Coleomegilla maculata (DeGeer) coincided with peak density of the borer's second-generation eggs and neonates. Second-generation egg masses and second and older instars were randomly distributed between plants in the field where first instars were aggregated. Corn borer females of the second flight period deposited most eggs (82%) on the ventral surfaces of leaves in the middle sections of plants near silking ears (76.7%). The emerging neonates initially dispersed randomly on the leaves. However, 30 min after emergence, most neonates cued on leaf axils, which served as the most common microhabitat for young larvae. Larval microhabitat differed substantially between the nonoverwintering and overwintering forms and between early and late instars of the nonoverwintering form. Leaf axils were the preferred microhabitat of young larvae, but preference shifted to stalks and ears as larvae matured. Overwintering larvae inhabited almost only stalks. Similarly, O. insidiosus adults and nymphs changed their within-plant distribution throughout the season. These changes in the distribution of borer larvae and their predators are discussed in relation to prey and pollen availability in different corn plant microhabitats.
TL;DR: Results suggest that inundative release of entomopathogenic nematodes where B. bassiana occurs may result in greater control of soilborne insect pests than application of nematode alone.
Abstract: Laboratory experiments were conducted to assess the reproductive success of Steinernema carpocapsae (Weiser) or Heterorhabditis bacteriophora Poinar in soilborne Spodoptera exigua (Hubner) previously exposed to Beauveria bassiana (Bals.) Vuill. Treatments of H. bacteriophora plus B. bassiana resulted in higher total mortality of S. exigua in soil than treatments with either nematode alone or fungus alone. For S. carpocapsae plus B. bassiana , insect mortality was not significantly different compared with S. carpocapsae alone. In treatments with nematode plus fungus, percentage mortality of S. exigua from S. carpocapsae and H. bacteriophora was reduced relative to the treatments with nematodes alone. These results suggest that inundative release of entomopathogenic nematodes where B. bassiana occurs may result in greater control of soilborne insect pests than application of nematodes alone.
TL;DR: Factors that influenced the structure and function of the new experimental ponds appeared to be: lack of connection to colonized waters, small size, and simple, homogeneous habitat and food resources.
Abstract: Benthic macroinvertebrate colonization of 12 0.04-ha experimental ponds was studied for 1 yr. The ponds were filled in late January 1988 and artificial substrate samples were retrieved at 4-wk intervals from 25 February 1988 to 25 February 1989. The first organisms ( Chironomus and Ceratopogonidae) were collected in the first set of samples 4 wk after filling. The colonization sequence was Diptera (primarily several genera of chironomids), followed by Coleoptera, Ephemeroptera, and Odonata. The arrival of taxa corresponded to adult flight periods. Noninsect taxa (Oligochaeta, Nematoda, Amphipoda) were collected in relatively low numbers late in the year. Twenty-nine taxa were collected, 13 of which were present in all 12 ponds. Mean number of taxa, diversity, and evenness increased rapidly during the first 7 mo, but never became very high. Mean density increased slowly throughout the spring and summer to about 200 individuals per sampler and then increased rapidly during the autumn to about 600 individuals per sampler. Community structure was dominated by Chironomidae (≈85%) and Ephemeroptera (≈9%). Trophic function was dominated by detritus-feeding collectors (≈79%). Factors that influenced the structure and function of the new experimental ponds appeared to be: lack of connection to colonized waters, small size, and simple, homogeneous habitat and food resources.
TL;DR: It is suggested that C. floridana that choose plants with higher nitrogen content under natural conditions enjoy a selective advantage and that choice within a host-plant species (and perhaps among species) is correlated with host- plant nitrogen content.
Abstract: Cameocephala floridana Ball is an oligophagous leafhopper that switches host plants seasonally and feeds primarily on the salt-marsh cord grass, Spartina alterniflora Loiseleur-Deslongchamps, during the winter. In the laboratory, we examined how variation in foliar nitrogen of S. altemiflora influenced the choice of cord-grass culms by C. floridana as feeding and oviposition sites. We also examined the effects of host-plant nitrogen on leafhopper oviposition rate, body size, and fecundity. Given a choice among cord-grass culms grown under four fertilization regimes, groups of adult female leafhoppers preferentially fed on culms that were higher in foliar nitrogen. Although the total number of eggs laid was highest on plants of superior quality (as measured by nitrogen content), the rate of oviposition did not differ among plants of different nitrogen levels. Leafhoppers reared from first instar to adult on highly fertilized plants were significantly larger (had higher dry body weight) than those reared on unfertilized or minimally fertilized plants. A significant relationship between body weight and maternal sibship was also found for males, but not for females. Larger body size is advantageous because larger adult females have higher daily oviposition rates than smaller ones. We suggest that C. floridana that choose plants with higher nitrogen content under natural conditions enjoy a selective advantage and that choice within a host-plant species (and perhaps among species) is correlated with host-plant nitrogen content.
TL;DR: Specific hunger and effects of specific hunger on attractiveness of three types of olfactory feeding attractants to a laboratory strain of Mexican fruit fly, Anastrepha ludens, were investigated in laboratory bioassays and greenhouse flight chamber experiments.
Abstract: Specific hunger and effects of specific hunger on attractiveness of three types of olfactory feeding attractants to a laboratory strain of Mexican fruit fly, Anastrepha ludens (Loew), were investigated in laboratory bioassays and greenhouse flight chamber experiments. Newly emerged flies (up to 4 d old) fed preferentially on sugar over protein, whereas 5–9–d–old flies undergoing sexual maturation fed about equally on sugar and protein. Sugar or protein deprivation increased feeding preference for sugar or protein, respectively, whereas constant access to sugar or protein decreased preference for the respective nutrient. Sugarv hunger, whether age-dependent or deprivation-induced, increased attractiveness to flies of CEH, a fruit-derived attractant consisting of 1,8-cineole, ethyl hexanoate and hexanol, relative to two proteinaceous lures. Protein hunger dramatically increased attractiveness of bacteria, a purported protein source for fruit flies, relative to CEH. Protein hunger also increased attractiveness of torula yeast, a commonly used proteinaceous lure, compared with CEH, although attractiveness of torula yeast did not become greater than attractiveness of CEH. Combinations of torula yeast and CEH were not more attractive than CEH alone to any age-feeding history groups of flies. Combinations of CEH and bacterial odor were never more attractive than bacterial odor alone to protein-hungry flies and were actually less attractive then CEH alone to the one group of sugar-hungry flies (2–3–d–old unfed) that was tested.
TL;DR: Results suggest that C. maculata can contribute to the control of both early and late generations of Colorado potato beetle and efforts to conserve this natural enemy will help reduce the need for chemical control.
Abstract: Mortality to the egg stage of Colorado potato beetle, Leptinotarsa decemlineata (Say), from endemic predators was assessed in unsprayed plots within commercial potato fields in western Massacusetts in 1986 and 1987. Direct measurement of recruitment into the egg stage and of losses to predation gave estimates of total stage-specific mortality for each generation of Colorado potato beetle and daily mortality rates. Abundance of endemic egg predators was measured through direct observation and trapping. Coleomegilla maculata (DeGeer), a coccinellid, was the most abundant predator and the only one consistently present whenever Colorado potato beetle eggs were in the field. Total mortality to eggs from predation was 39.9% in the second generation of 1986 and 37.8% and 58.1% in the first and second generations of 1987, respectively. Daily mortality rate did not change significantly during large fluctuations in prey density. Results suggest that C. maculata can contribute to the control of both early and late generations of Colorado potato beetle and efforts to conserve this natural enemy will help reduce the need for chemical control.
TL;DR: The results suggest that subtle behavioral or developmental shifts may allow some bark beetles to temporarily escape from predators that exploit scolytid pheromones as kairomones.
Abstract: The numbers and distributions of pine engraver, Ips pini (Say), predators, and secondary subcortical associates responding to racemic ipsdienol in Wisconsin were analyzed over 4 yr with regard to date, height in the canopy, and distance from the margin of previously killed trees. The largest difference in response patterns between predators and I. pini was in seasonal occurrence. Most I. pini were caught late in the season, whereas most predators were caught much earlier. Additional differences were observed in spatial distributions and time by space interactions. These results suggest that subtle behavioral or developmental (or both) shifts may allow some bark beetles to temporarily escape from predators that exploit scolytid pheromones as kairomones. Factors contributing to discrepancies between predator and prey trap catch can also be exploited in pest management. Semiochemically based control treatments can be scheduled to greatly reduce the proportion of beneficial insects caught without substantially reducing efficacy. Additionally, this information can be used to improve population estimates of predators and guide natural enemy introduction strategies.