Female Pupal Weight Research Articles

Feeding and Growth Response of Fall Armyworm Spodoptera frugiperda (Lepidoptera: Noctuidae) towards Different Host Plants.

The fall armyworm, Spodoptera frugiperda, is a major migratory polyphagous insect pest of various crops. The essential nutrient and mineral profile of the host plants determines the feeding fitness of herbivorous insects. As a result, the growth and development of insects is affected. To determine the effect of the nutrient and mineral profile of different host plants (maize, castor bean, cotton, cabbage, okra, and sugarcane) on the growth and development of S. frugiperda, biological parameters like larval weight, pupal weight (male/female), and feeding and growth indices were calculated. The proximate compositions such as crude protein, crude fat, crude fibre, and ash and mineral contents of the tested host plants showed significant differences (p < 0.05). The feeding indices on these host plants also differed significantly (p < 0.05). The maximum relative growth rate (RGR), relative consumption rate (RCR), and consumption index (CI) were recorded in S. frugiperda larvae that fed on maize and castor bean leaves. The crude protein, dry matter, and ash contents in maize and castor bean were significantly higher and positively correlated with the RGR and RCR of S. frugiperda larvae. The larval, male and female pupal weights were the maximum in the larvae feeding on the castor bean host plant. These findings provide novel information based on nutritional ecology to develop sustainable integrated pest management strategies using selective crop rotation.

Study on Biology of Fall Armyworm, Spodoptera frugiperda (J.E. Smith) on Maize, Zea mays L. in Manipur, India

Aim: To study the biology and morphometric parameters of different stages of fall armyworm, Spodoptera frugiperda.&#x0D; Study Design: Experimental study.&#x0D; Place and Duration of Study: PG laboratory, Department of Entomology, College of Agriculture, Iroisemba, CAU (Central Agricultural University), Imphal, June-August 2022.&#x0D; Methodology: The egg masses collected from maize fields were transferred to sterilized petri plates containing maize leaves and reared under laboratory conditions (25±2°C, 70±10% RH). Duration and morphometric parameters of different stages of fall armyworm were recorded regularly.&#x0D; Results: The mean incubation period of eggs was observed to be 1.90 days. The larval period of six instars were recorded to be 2-4, 2-5, 2-3, 2-3, 2-3, 2-3 and 3-6 days, respectively. The mean larval length of six instars were 1.91, 3.38, 6.15, 9.78, 18.60 and 32.30 mm, respectively. The mean larval width of six instars were 0.33, 0.74, 1.31, 2.26, 2.92 and 3.53 mm, respectively. The average larval weight of six instars were 0.0031, 0.0214, 0.0420, 0.0503, 0.0576 and 0.0652 gm, respectively. The total larval duration was observed to be 16.70 days. The male and female pupal period was found to be 7.60 and 7.10 days, respectively. The average male pupal length, width and weight were 14.79±0.18 mm, 4.54±0.14 mm and 0.17±0.01 gm, respectively. The average female pupal length, width and weight were 13.0-18.20 mm, 4.0-5.2 mm and 0.18±0.01 gm, respectively. The ovipositional period was found to be 1-6 days. Mean longevity of males and females were observed to be 8.70 and 9.00 days, respectively. The total life cycle of male and female lasted 34.90 and 35.60 days, respectively.&#x0D; Conclusion: This study clearly provides basic information about the biology of this recently invaded pest. To prevent the potential devastating occurrence, compatible integrated pest management strategies are needed at the early stages of FAW infestation.

Reproductive Biology of Muga Silk Moth &lt;i&gt;Antheraea assamensis&lt;/i&gt; Helfer

Results of morphological and morphometric study of male and female reproductive systems of Antheraea assamensis Helfer (Saturniidae: Lepidoptera), a silk moth cultivated exclusively in the North Eastern Region of India are reported herein along with some observations on its reproductive performance in four seasons. The male reproductive system consists of a pair of testes, paired vasa deferentia, seminal vesicle, ductus ejaculatorius duplex, ductus ejaculatorius simplex, an aedeagus and a pair of male accessory glands. The female reproductive system consists of a pair of ovaries, each with four ovarioles, paired lateral oviducts, a common oviduct which has a dorsal protrusion, the vestibulum, a bursa copulatrix, a spermatheca and a pair of female accessory glands with their reservoirs. Fecundity has been found to be positively correlated with female pupal weight in each season. Hatching % of eggs has been found lowest and significantly different (p&lt;0.001) in summer as compared to autumn, winter and spring seasons. Morphology of eupyrene and apyrene sperm bundles and sperm has also been reported.

Temperature and host plant species affect the performance and immunocompetence of an outbreak defoliator in northwestern Patagonia

Abstract Rising temperature has been associated with increased occurrence of herbivorous insect outbreaks, explained by several direct and indirect mechanisms. Whereas natural enemies are known key drivers of forest‐defoliating insect cycles, indirect effects of temperature on insect's ability to defend against pathogens and parasitoids (e.g., immunocompetence), as well as the interaction with other mechanisms (e.g., diet), remain less explored. The aim of this study is to evaluate the effect of temperature and diet on the performance and immune response of the model lepidopteran system Ormiscodes amphimone (Saturniidae) and its host plants Nothofagus spp. (Nothofagaceae). Larvae of O. amphimone were reared under two temperature conditions (ambient 18:6°C and warmed, 21:6°C; light: dark, 14:10 h) and on leaves of two of their preferred Nothofagus host plants, which vary in quality (lower N. antarctica–higher N. pumilio). We measured developmental time, female pupal weight as a proxy of fitness, relative growth rate, nutritional indices and melanisation of a monofilament as a proxy of immune response. Results showed that an average rise of 2°C favours larval immunocompetence, potentially decreasing mortality exerted by parasitoids. Moreover, depending on diet, an increase in temperature can either maintain (on more nutritious N. pumilio leaves) or enhance (on less nutritious N. antarctica leaves) larval nutritional efficiency, performance and female pupal weight. Hence, an increase in temperature could enhance O. amphimone population growth, through attenuating differences caused by diet and enhancing immunocompetence, favouring outbreak frequency, severity and area.

The Addition of Sterols and Cryoprotectants to Optimize a Diet Developed for Eldana saccharina Walker (Lepidoptera: Pyralidae) Using the Carcass Milling Technique.

Simple SummaryDespite being essential for growth, insects cannot synthesize sterols. Naturally, sterols are obtained from insects’ host plants, but in artificial diets are sometimes missing or not optimal, leading to reduced growth. By adding 1.0 g of stigmasterol, and a combination of 0.2 g each of cholesterol and stigmasterol to two standard minimum specification (MS) diets for Eldana saccharina, pupation was faster (72% and 70%, respectively) than the control diet (15%), 20 days after neonate inoculation. Nevertheless, a reproductive mass reared insect could become a poor field performer, as reproductive output and field performance might be traded off. To increase E. saccharina’s cold performance, cryoprotectants were added to a standard MS diet. Males from MS diets containing both concentrations of a proline/trehalose mix, and the highest concentration of trehalose, recovered 30–33% faster from chill coma than males from the remaining diets. Fertility of females that entered chill coma was reduced (<44%) when fed as larvae on cryoprotectant supplemented diets. Females not exposed to chilling treatment had 84% fertility when mated with males from the same source. The MS diet plus 0.2 g each of cholesterol and stigmasterol should become the standard diet, as larval development time was decreased by 60% without obvious trade-offs.Various combinations and concentrations of cholesterol (C) and stigmasterol (S) were added into a base diet developed for Eldana saccharina. Survival of inoculated neonate was high on all diets (>92% at day 20 and >95% at day 27). Fastest larval development occurred on the minimum specification (MS) (+1.0 gS) and MS (+0.2 gC: 0.2 gS) diets (72 and 70% pupation respectively at day 20). Significantly slower development (15% pupation) occurred on the control diet at day 20. Female pupal weight increased when larvae fed on the MS (+0.1 gC), (+0.1 gS) and (+0.2 gC:0.2 gS) diets (0.2143 ± 0.00 g, 0.2271 ± 0.01 g and 0.2252 ± 0.01 g, respectively) as compared with the control diet (0.1886 ± 0.00 g). Adult emergence was significantly higher (100%) from the MS (+0.1 gS) and MS (+0.2 gC:0.2 gS) diets, as compared with the remaining sterol (95%) and control diets (97%). To potentially increase E. saccharina’s cold tolerance, inclusion of cryoprotectants L-proline (P) and trehalose (T) into the MS diet was investigated. Males from the MS (0.2 gP:0.2 gT), MS (0.5 gP:0.5 gT) and MS (1.0 gT) diets recovered fastest from chill coma treatment (204 ± 44 s, 215 ± 7 s and 215 ± 9 s, respectively) than those from the remaining cryoprotectant diets (305 ± 22 s). The addition of cryoprotectants severely reduced female fertility (<44%) when mated with non-chill coma exposed males. In contrast, eggs from females not exposed to chilling treatment were 84% fertile when mated with males from the same source. The MS (0.2 gC:0.2 gS) diet is the preferred choice to replace the currently used diet, reducing the larval growth period by 60% without negative effects on key life cycle parameters of E. saccharina.

Defensive responses of Erianthus arundinaceus against sugarcane shoot borer, Chilo infuscatellus (Snellen) (Crambidae: Lepidoptera)

A total of eight field screened Erianthus arundinaceus genotypes against sugarcane shoot borer, Chilo infuscatellus was further screened under laboratory conditions along with a ruling variety Co 86032 for their confirmation of resistance and susceptibility. A significant reduction of C. infuscatellus larval and pupal survival; larval and female pupal weight; adult longevity; fecundity rate (eggs/female) and extended larval and pupal duration was recorded in the genotypes IJ 76 370, IJ 76 364 and IK 76 78, respectively. Biochemical parameters viz., total phenols, poly phenol oxidase and proteinase inhibitors and total proteins were highest in the genotypes IJ 76 370 and IJ 76 364 which indicates the presence of antibiosis mechanism of resistance against C. infuscatellus. The total soluble sugars were significantly lower in all genotypes. The genotypes IJ 76 364 and IK 76 84 fed – C. infuscatellus showed lowest larval total carbohydrate and protein content, respectively. The study identified two elite E. arundinaceus IJ 76 370 and IJ 76 364, that could be used as new genetic stocks for the possible utilization in the future resistant breeding programme against sugarcane shoot borer.

High temperature tolerance and thermal-adaptability plasticity of Asian corn borer (Ostrinia furnacalis Guenée) after a single extreme heat wave at the egg stage

Abstract Due to ongoing climate change, short-term extreme heat waves in the summer are expected to be more frequent. Insect eggs are sensitive to thermal stress. This raises the question of whether herbivore insects' thermal adaptability would be changed after a single extreme heat wave at the egg stage. In this study, we examined the developmental performance of Ostrinia furnacalis Guenee at 25 °C, 27 °C, 29 °C or 31 °C after a single extreme heat wave (42 °C) for 0 h (control), 1 h, 2 h, or 3 h at the egg stage. The results showed that O. furnacalis at the egg or larval stage was more sensitive to a single heat wave than it was at the pupae or adult stage. After a single heat wave, O. furnacalis showed a reduced egg-hatching rate or reduced larval survival rate, but the optimum temperature for egg hatching and larval survival was higher than that in the control. The upper temperature threshold and optimum temperature for larval development in the control were higher than that after a single extreme heat wave. Both male and female pupal weight decreased with increasing temperature, and pupal weight decreased faster in females than in males. The Cox proportional hazard model showed that when O. furnacalis developed at 25 °C, the instantaneous death risk of adults with a 3 h heat wave at the egg stage was higher than that of the control, but when O. furnacalis developed at 29 °C and 31 °C, the instantaneous death risk of adults after a heat wave was significantly lower than that of the control. Our study highlights the effect of a single heat wave on O. furnacalis eggs and the subsequent development of survival individuals.

Effects of elevated CO2 on the fitness and potential population damage of Helicoverpa armigera based on two-sex life table

We evaluated the direct effects of three different atmospheric CO2 concentrations (380 ppm, 550 ppm and 750 ppm) on the population parameters of the cotton bollworm, Helicoverpa armigera fed an artificial diet. The life history and fitness of H. armigera were analyzed using an age-stage, two-sex life table. Our results showed significantly longer larval durations and lower female pupal weight under elevated CO2 than under ambient CO2. Additionally, the fecundity of H. armigera was lower under elevated CO2 than under ambient CO2. H. armigera reared under elevated CO2 conditions showed lower intrinsic and finite rates of increase but higher net consumption and finite consumption rates than H. armigera reared under ambient CO2 conditions. According to population projections, a much smaller total population size and reduced consumption capacities would be expected in an elevated CO2 atmosphere due to higher mortality and lower growth rate compared with ambient CO2 levels. These results indicate that the fitness of and potential damage caused by H. armigera would be affected by increased CO2 relative to ambient CO2 concentrations. Additional studies on the long-term direct and indirect effects of elevated CO2 levels on H. armigera are still needed.

Spruce Budworm (Lepidoptera: Tortricidae) Oral Secretions I: Biology and Function

The potential roles of the oral secretions (OS) of spruce budworm (SBW; Choristoneura fumiferana Clemens) larvae and factors that may affect the volume of OS disgorged were investigated in the laboratory. Experiments revealed that diet-fed SBW larvae readily disgorge OS when induced ("milked"), with minimal overall cost to their development and eventual pupal weight. Exposure of conspecific larvae to OS throughout larval development negatively affected survival and male pupal weight; however, male development time was faster when exposed to OS. Female pupal weight and development time were not affected. Preliminary experiments suggested that OS had a repellent effect on a co-occurring herbivore, the false hemlock looper, Nepytia canosaria (Walker). OS produced by larvae that fed on three host tree species and on artificial diet significantly increased the grooming time of ants (Camponotus sp.), indicating that SBW OS have an anti-predator function. The volume of OS is significantly greater in L6 than in L4 or L5, with the volume produced by L6 depending on weight and age as well as feeding history at time of milking. These findings indicate that SBW OS function as both an intra- and interspecific epideictic pheromone and as an anti-predator defensive mechanism, while incurring minimal metabolic costs.

Effects of pathogen exposure on life-history variation in the gypsymoth (Lymantria dispar).

Investment in host defences against pathogens may lead to trade-offs with host fecundity. When such trade-offs arise from genetic correlations, rates of phenotypic change by natural selection may be affected. However, genetic correlations between host survival and fecundity are rarely quantified. To understand trade-offs between immune responses to baculovirus exposure and fecundity in the gypsy moth (Lymantria dispar), we estimated genetic correlations between survival probability and traits related to fecundity, such as pupal weight. In addition, we tested whether different virus isolates have different effects on male and female pupal weight. To estimate genetic correlations, we exposed individuals of known relatedness to a single baculovirus isolate. To then evaluate the effect of virus isolate on pupal weight, we exposed a single gypsy moth strain to 16 baculovirus isolates. We found a negative genetic correlation between survival and pupal weight. In addition, virus exposure caused late-pupating females to be identical in weight to males, whereas unexposed females were 2-3 times as large as unexposed males. Finally, we found that female pupal weight is a quadratic function of host mortality across virus isolates, which is likely due to trade-offs and compensatory growth processes acting at high and low mortality levels, respectively. Overall, our results suggest that fecundity costs may strongly affect the response to selection for disease resistance. In nature, baculoviruses contribute to the regulation of gypsy moth outbreaks, as pathogens often do in forest-defoliating insects. We therefore argue that trade-offs between host life-history traits may help explain outbreak dynamics.

Asynchrony between Host Plant and Insects-Defoliator within a Tritrophic System: The Role of Herbivore Innate Immunity.

The effects of asynchrony in the phenology of spring-feeding insect-defoliators and their host plants on insects’ fitness, as well as the importance of this effect for the population dynamics of outbreaking species of insects, is a widespread and well-documented phenomenon. However, the spreading of this phenomenon through the food chain, and especially those mechanisms operating this spreading, are still unclear. In this paper, we study the effect of seasonally declined leafquality (estimated in terms of phenolics and nitrogen content) on herbivore fitness, immune parameters and resistance against pathogen by using the silver birch Betula pendula—gypsy moth Lymantria dispar—nucleopolyhedrovirus as the tritrophic system. We show that a phenological mismatch induced by the delay in the emergence of gypsy moth larvae and following feeding on mature leaves has negative effects on the female pupal weight, on the rate of larval development and on the activity of phenoloxidase in the plasma of haemolymph. In addition, the larval susceptibility to exogenous nucleopolyhydrovirus infection as well as covert virus activation were both enhanced due to the phenological mismatch. The observed effects of phenological mismatch on insect-baculovirus interaction may partially explain the strong and fast fluctuations in the population dynamics of the gypsy moth that is often observed in the studied part of the defoliator area. This study also reveals some indirect mechanisms of effect related to host plant quality, which operate through the insect innate immune status and affect resistance to both exogenous and endogenous virus.

Responses of leaf beetle larvae to elevated [CO₂] and temperature depend on Eucalyptus species.

It is essential to understand the combined effects of elevated [CO2] and temperature on insect herbivores when attempting to forecast climate change responses of diverse ecosystems. Plant species differ in foliar chemistry, and this may result in idiosyncratic plant-mediated responses of insect herbivores at elevated [CO2] and temperature. We measured the response of the eucalypt leaf beetle Paropsis atomaria (Coleoptera: Chrysomelidae) feeding on Eucalyptus tereticornis and Eucalyptus robusta. Seedlings were grown at ambient (400 µmol mol(-1)) or elevated (640 µmol mol(-1)) [CO2] and ambient (26/18 °C day/night) or elevated (ambient + 4 °C) temperature in a greenhouse for 7 months. Larvae fed on flush leaves from egg hatch to pupation while being directly exposed to these conditions. Elevated [CO2] reduced foliar [N] and [P], while it increased total nonstructural carbohydrates and the C:N ratio. Elevated temperature increased foliar [N] in E. robusta but not E. tereticornis. Plant-mediated effects of elevated [CO2] reduced female pupal weight and increased developmental time and leaf consumption. Larval survival at elevated [CO2] was impacted differently by the two host plant species; survival increased on E. robusta while it decreased on E. tereticornis. Elevated temperature accelerated larval development but did not impact other insect parameters. We did not detect a CO2 × temperature interaction, suggesting that elevated temperature as a combined direct and plant-mediated effect may not be able to ameliorate the negative plant-mediated effects of elevated [CO2] on insect herbivores. Our study highlighted host-plant-specific responses of insect herbivores to climate change factors that resulted in host-plant-specific survival.

Dominant fitness costs of abamectin resistance in Plutella xylostella

The TH-Abm strain of Plutella xylostella, exhibiting 23 670-fold resistance to abamectin, was selected from a field-evolved multiresistant population. By repeated backcrossing to a susceptible strain (Roth) and selection with abamectin, the resistance trait of TH-Abm was introgressed into Roth to generate a near-isogenic strain (Roth-Abm). Fitness costs associated with abamectin resistance were examined in Roth-Abm. Compared with Roth, Roth-Abm obtained 11 500-fold resistance to abamectin and 364 000-, 12- and 12-fold cross-resistance to emamectin benzoate, spinosad and fipronil respectively. Roth-Abm has a significantly longer pupal development time, lesser female pupal weight and lower larval survival than Roth. Female fecundity and egg viability are significantly lower in Roth-Abm than in Roth. All of the above fitness components of the F1 progeny from Roth × Roth-Abm are similar to those of Roth-Abm and are significantly lower than those of Roth. By comparing with the net replacement rate (R0 ) of Roth, the fitness of Roth-Abm, F1a (Roth male × Roth-Abm) and F1b (Roth female × Roth-Abm) are 0.50, 0.50 and 0.53 respectively. Abamectin resistance in Roth-Abm results in significant fitness costs, and the fitness costs are autosomal and dominant. Rotation of abamectin with other insecticides without cross-resistance could be especially useful for delaying abamectin resistance in P. xylostella.

Effects of High-Quality Aromatic Rice Varieties on the Fitness of the Striped Stem Borer, Chilo suppressalis (Walker) in Central China

The striped stem borer (SSB), Chilo suppressalis (Walker) (Lepidoptera: Pyralidae), is a major pest of rice in China. Variation in host-plant quality may affect the body size of herbivorous insects, which in turn, can determine their life-history parameters such as survival, fecundity and fitness. In this study, we tested the effects of high-quality aromatic rice varieties on the fitness of SSB in China. Results showed that 1st instar larvae had higher penetrating rates and survival rates on the high-quality aromatic rice varieties (EX-1 and WX-988) than that on the non-aromatic rice varieties (EZ-5 and LYP-9). In addition, shorter developmental periods, greater female pupal weights and higher of other life-history parameters (hatching rate, pupation rate, eclosion rate and increase index) were found on the high-quality aromatic rice varieties, although only female pupal weight showed a significant difference between the two varieties. The highest dead heart rate was found on the aromatic rice variety of EX-1. These results indicate that SSB sustains a lower fitness cost when consuming the high-quality aromatic rice varieties (EX-1 and WX-988) than on the non-aromatic rice varieties (EZ-5 and LYP-9) in Central China.

Rapid induced resistance of silver birch affects both innate immunity and performance of gypsy moths: the role of plant chemical defenses

In this study we tested the effects of rapid induced resistance of the silver birch, Betula pendula, on the performance and immune defense of the gypsy moth, Lymantria dispar. We also measured the effects of defoliation on the concentrations of plant secondary metabolites, particularly on phenolics and terpenoids. It was found that severe natural defoliation (by moth larvae) of silver birch led to an increase in lipophilic flavonoids on the leaf surface. The concentration of some simple phenolics and monoterpenes (linalool and geraniol) also increased, while that of several glycosides of quercetin decreased. The female pupal weights and survival rates of moths decreased, and larval development time increased, when the insects fed on defoliated trees. However, the feeding of caterpillars with the leaves of defoliated trees led to an increase in lysozyme-like activity in their hemolymph, with an increase in their ability to encapsulate potential parasites. Our data show that the silver birch deploys a rapid chemical defense against gypsy moth larvae. We suggest that lipophilic flavonoids are important compounds in the direct silver birch defense against L. dispar caterpillars. The increased strength of immune defense of insects exposed to trees that had deployed a rapid induced resistance may be an adaptation of the herbivores to resist the rising density of parasites when host population density is high.

Relationship Between Behavior and Physiology in an Invasive Pest Species: Oviposition Site Selection and Temperature-Dependent Development of the Oriental Fruit Moth (Lepidoptera: Tortricidae)

Oviposition site selection is crucial for the reproductive success of a herbivore insect species with relatively sedentary larvae. The optimal oviposition theory, i.e., the preference-performance hypothesis, has thus far mainly been tested with a focus on nutritional quality of the host. This study investigates whether female oriental fruit moth Grapholita (Cydia) molesta choose a microhabitat for oviposition characterized by a temperature range within which their offspring perform best. Thermal preferences of females during oviposition were assessed in a circular temperature gradient arena. Offspring performance and survival were assessed under different constant temperature conditions. Females preferred oviposition sites of approximately 30 degrees C over lower and higher temperatures. At this temperature, egg, larval, and pupal development was significantly faster than at 22 and 25 degrees C, and larval development was also faster than at 33 degrees C. At 30 degrees C and at the lower temperatures tested, survival of eggs and larvae was significantly higher than at 33 degrees C, whereas development was precluded at 35 degrees C. Furthermore, female pupal weight attained at 30 and 33 degrees C exceeded that reached at the lower temperatures tested. Considering the potentially reduced predation risk caused by the shorter developmental time of eggs and larvae, the laboratory data suggest that this species maximizes its fitness by selecting a thermally optimal environment for its offspring, supporting the optimal oviposition theory. Conversely, it is known that the codling moth (C. pomonella) lacks a mechanism to avoid temperatures lethal to progeny development, which may reflect the differences in geographic ranges of these tortricids.

Rapid induced resistance and host species effects on gypsy moth, Lymantria dispar (L.): Implications for outbreaks on three tree species in the boreal forest

Field pupal weight, development time, and survival of gypsy moth, Lymantria dispar (L.), larvae on three defoliated (50%) and undefoliated tree species that are common to the forest of the Great Lakes basin were compared for one season in 1988. Host species and defoliation affected female pupal weight; male pupal weight was affected only by host species. The smallest and largest pupae of both sexes, from both defoliated and undefoliated trees, came from larvae that fed on red oak, Quercus rubra L., and trembling aspen, Populus tremuloides Michx., respectively; pupal weight of larvae that fed on white birch, Betula papyrifera Marsh., were intermediate. Development time was affected only by tree species; the shortest and longest development occurred on trembling aspen and red oak, respectively; development time on white birch was medial. Gypsy moth survival was not affected by defoliation or host species. Superficially, these data obviously suggest that both defoliated and undefoliated trembling aspen and white birch are more nutritious, and will support higher gypsy moth fitness than its traditional hosts like red oak. However, we argue that outbreaks of gypsy moth will not occur in aspen and birch stands because its tri-trophic fitness is lower there due in part to the higher efficacy of certain gypsy moth natural enemies. We hypothesize that outbreaks on these two tree species will be limited by the nuclear polyhedrosis virus, Entomophagus maimaiga, and key physical features (e.g. light trunk color) of the host that deter larval host-seeking/accepting behavior. More than 20 years of gypsy moth outbreak records in North America support this hypothesis.

Influence of Cytoplasmic Male Sterility on Expression of Different Mechanisms of Resistance in Sorghum to &lt;I&gt;Atherigona soccata&lt;/I&gt; (Diptera: Muscidae)

Atherigona soccata (Rondani) (Diptera: Muscidae) is one of the most important pests of sorghum, Sorghum bicolor (L.) Moench, in Asia, Africa, and the Mediterranean Europe. Exploitation of cytoplasmic male sterility (CMS) for hybrid production has resulted in considerable narrowing of the genetic base and may increase the vulnerability of this crop to insect pests. Therefore, we studied the expression of different mechanisms of resistance in sorghum to A. soccata in CMS (A) and maintainer (B) lines of 12 genotypes under field and greenhouse conditions. The CMS lines of A. soccata-resistant genotypes were preferred for oviposition (78.5 versus 71.5% plants with eggs) and suffered greater deadheart incidence (47.6 versus 41.6%) than the corresponding maintainer lines, whereas such differences were not apparent in CMS lines belonging to the susceptible genotypes (92.7 versus 92.3% plants with eggs and 75.6 versus 74.6% deadhearts) under multichoice field conditions. Similar differences also were observed under controlled conditions in the greenhouse. The larval period (9.0 versus 8.8 d) and pupal mortality (18.4 versus 13.4%) were greater on maintainer lines than that on the CMS lines in the resistant group. The male and female pupal weights, fecundity, and antibiosis index were greater on the CMS than on the maintainer lines. The maintainer lines showed better recovery resistance than the CMS lines, but no such differences were observed in tiller deadhearts. The differences in susceptibility to A. soccata were greater in the A. soccata resistant CMS and maintainer lines than in the CMS and maintainer lines belonging to susceptible genotypes. Conversion of A. soccata-resistant genotypes into alternate less susceptible cytoplasmic backgrounds may be undertaken for developing sorghum hybrids with stable resistance to A. soccata.

Fecundity Study of Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae) on Various Host Plants

This study has shown that the S. exigua female fecundity was influenced by the host plant which was fed during the larval stage. The number of eggs laid by the female when larvae were fed on shallot was higher than lady's finger. Whereas S. exigua reared on cabbage and long beans laid intermediate number of eggs. Further, the female pupal weight was also influenced by the host plant which was fed during the larval stage. The female pupal weight was heavier when larvae were fed on shallot than on cabbage and lady's finger, whilst long beans was intermediate. Furthermore, there are significant relationships between female pupal weight and adult fecundity. © 2006 Academic Journals Inc.

Early-Season Host Plant Fruit Impacts on Reproductive Parameters of the Oriental Fruit Moth (Lepidoptera: Tortricidae)

Oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), a cosmopolitan pest of tree fruits, has been a significant pest in the United States since its introduction in the early 20th Century. Grapholita molesta historically has been a major pest of stone fruit. However, since the mid to late 1990s, outbreaks in commercial apple orchards in the eastern United States have become common place. This study examined the effects of larval host (e.g., apple vs. peach) on G. molesta reproduction, as a means to better understand the increased importance of G. molesta as an apple pest in the midAtlantic region. In laboratory investigations, G. molesta adults reared on apple fruit had approximately 2-fold higher fecundity than those reared on peach (F = 10.98; df = 3,101; P &amp;lt; 0.001). In two separate studies, when larvae were reared under either crowded or noncrowded feeding conditions, female adult longevity and oviposition period were significantly greater among moths reared as larvae on apple than those reared on peach (2001: P = 0.019 and 0.009, respectively; 2002: P = 0.031 and 0.001, respectively). Female pupal weight was significantly higher in individuals reared on apple than those reared on peach, in both studies (2001 and 2002: P &amp;lt; 0.001). Similar host-influenced impacts on G. molesta reproductive phenomena could affect population dynamics of G. molesta, especially late in the season when apple fruit are a preferred feeding site.