Survival Of Instars Research Articles

The Effect of Wood Ash and Soil Applications on the Behavior and Survival of Spodoptera frugiperda (Lepidoptera: Noctuidae) Larvae on Maize.

Cryptic feeding inside maize whorls makes it difficult to control fall armyworm (FAW). Smallholder farmers use alternative methods of control, of which the efficacy is uncertain. We determined the efficacy of wood ash and soil for the control of FAW and recorded its effect on larval preference and ballooning. Maize plants were artificially infested with larvae of different instars and treatments were either soil, wet ash, or dry ash, applied as single preventative or curative applications. Larvae exhibited non-preference for treated leaves in choice tests. The efficacy of treatments varied largely between experiments. Under laboratory conditions, ash treatments resulted in significant mortality of 1st and 5th instars. Dry and wet ash as curative applications for 1st instars resulted in 67 and 66% mortality, respectively, compared to mortality recorded in the control (22%). Under field conditions, survival of 3rd instars on treated plants was low (21-34%), compared to 70% on untreated plants. Due to the high variability in efficacy, the use of these alternative methods does not guarantee effective control. They do, however, have a place in IPM systems if applied as soon as infestations are observed and when larvae as still small. Recommendations on the use of ash and soil as spot treatments against FAW are provided.

Entomopathogenicity of Ascomycete Fungus Cordyceps militaris on the Cotton Bollworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae)

This study investigated the exposure of the cotton bollworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) to a novel pathogenic fungal agent historically associated with human medicinal value, a commercial strain of Cordyceps militaris ((L.) Fr.) Vuill. (Hypocreales). A series of comparative studies were conducted to evaluate the efficacy of two different exposure methods using four concentrations (n × 109, n × 108, n × 107, n × 106) of C. militaris, where n × 109 provided a concentration of approximately 420 ± 37 spores per mm2 with 398 ± 28 viable spores. Survival of cotton bollworms of all stages was not affected by C. militaris at any concentration 1 d post-exposure. The greatest reduction in survival and highest sporulation rates were observed primarily on or after 7 d post-exposure for early instars (first and second). Significant declines in the survival of early instars were observed for all concentrations at 7 d, and 95% mortality by 10 d, with the exception of the fifth instars that experienced a less severe reduction in survival (35%) when exposed to any concentrations used in the study. Survival of late instars (third to fifth) ranged from 44% to 68% on day 10, while adult survival was near 99% across the duration of the experiment. The relatively narrow range observed for both the lethal concentration and sporulation of second, third, and fifth instar cotton bollworms exposed to the C. militaris strain may demonstrate potential field application for control of larval populations of cotton bollworms.

Impact of Stocking Density on the Survival, Growth and Injury of Narrow-Clawed Crayfish (Pontastacus leptodactylus) Reared in a Flowing Brackish Water System

The crayfish population dramatically declined in most lakes and dams in Türkiye; hence, crayfish culture is a possible option to increase the supply. This study aimed to determine the effects of stocking density on the growth performance and survival of newly-hatched third instars of narrow-clawed crayfish (Pontastacus leptodactylus) in a flowing brackish water system. The third instars were randomly stocked in nine tanks (area: 1.7 ) for 120 days with three densities of 10, 50, and 100 crayfish/. The results indicated that the stocking density significantly affected the growth performance, survival rate, proportion of the cheliped injury, biomass, length distribution, and feed conversion ratio (FCR). The mean final weights and total lengths were 2.27, 1.40, and 1.08 g and 4.83, 3.73 and 3.51 cm according to the densities, respectively. The highest stocking density increased the total biomass yield and proportion of the cheliped injury but reduced the survival, growth, molting frequency and regeneration of the appendage. The survival (86.3%) and specific growth rate (1.16 cm/day) in the 10 individuals/ group were significantly higher than the other groups. The cheliped injury was also found to be the lowest in the 10 individual/ group (p<0.05). Our study results showed that significant differences in FCR value were observed at different stocking densities. In summary, higher stocking density at the end of this study increased the frequency and severity of aggressive interactions of crayfish, limiting molting frequency and growth performance. A density of 10-50 crayfish/ is recommended for better growth parameters while 100 crayfish/ is suggested for higher biomass yield.

Toxicity assessment of two IGR insecticides on eggs and larvae of the ladybird Eriopis connexa.

Eriopis connexa is an important predator in the Neotropical region, associated with pests of economic relevance on horticultural crops in Argentina. The use of broad-spectrum insecticides could reduce the biodiversity of these natural enemies in agroecosystems and put at risk its conservation. New, selective "risk reduced" insecticides could be an alternative to conventional chemical control to promote sustainable agriculture. The goal of this work was to assess the lethal and sublethal effects of two insect growth regulator (IGR) insecticides on eggs and two larval instars of E.connexa exposed to insecticides. Pyriproxyfen and cypermethrin significantly affected egg hatching by 28.8% and 70.4%, respectively. Pyriproxyfen reduced the survival of larvae that emerged by ≈52% from Day (D3)3 after hatching and caused the lengthening of developmental time for both larval and pupal stages. By contrast, teflubenzuron did not reduce hatching and survival but shortened the developmental time of the pupae stage. Cypermethrin reduced the survival of 2nd (L2 ) and 4th (L4 ) larval instars by 36.4% and 74.6%, respectively, and lengthened the development time of L2 . Pyriproxyfen lengthened the development time of L4 and reduced the fecundity and fertility of females. Teflubenzuron reduced survival of L2 and L4 larval instars by 46.9% and 28.6%, respectively, and lengthened the total development time for the larval stage. In addition, teflubenzuron reduced the fecundity and fertility of females. Both eggs and larvae were susceptible to exposure to IGR, showing lethal and sublethal effects. This study highlights, once again, the higher toxicity of cypermethrin to E.connexa. The toxicity of both IGR insecticides could impair the performance of E.connexa as a biological control agent in agroecosystems. © 2022 Society of Chemical Industry.

Effect of Vegetable Host Plant Type on Halyomorpha halys (Hemiptera: Pentatomidae) Nymphal Development.

The brown marmorated stink bug, Halyomorpha halys (Stål), is an invasive pest introduced to North America in the mid-1990's that has caused economic losses to a wide range of commodities. In vegetables, H. halys feeding damage has been well described, but the effect of different vegetable hosts on H. halys fitness is less understood. We caged 2nd instar H. halys on different vegetable hosts (e.g., tomato, sweet corn, eggplant, bell pepper, and snap bean) and monitored their development until adulthood to compare the effects of vegetable host type on H. halys nymph survival and development time. Experiments were replicated nine times over a two-year period. Survival of 2nd instars from F1 generation (early-season) eggs was low (<30%) on all vegetables resulting in no significant treatment effect. However, H. halys nymphs collected from F2 generation (late-season) eggs had higher survivorship on all vegetables except tomato. The percentage of H. halys 2nd instars that reached adulthood was greatest on corn (53%) and pepper (45%), followed by snap bean (24%), and significantly lower on eggplant (9%) and tomato (2%). Total development time from 2nd instar to adult was fastest on corn and slowest on peppers, although tomatoes were not tested due to the low survival. Trends in development rate were not seasonally-dependent. Our study compares H. halys survivability on several vegetable commodities, and provides insights into H. halys developmental success and dependence on various host plants over the season.

Susceptibility of Different Life Stages of Kudzu Bug Megacopta cribraria (F.) (Hemiptera: Plataspidae) to Two Different Native Strains of Beauveria bassiana.

This is the first study that examined and compared the survival, LC50, and RR50 estimates of Megacopta cribraria F. (Hemiptera: Plataspidae) nymphs and adults that were exposed to two native Beauveria bassiana isolates (Previously codified as NI8 and KUDSC strains) at four concentrations. The greatest reduction in survival and mortality was observed primarily on or after 10 d post-exposure to B. bassiana isolates. Survival of early instars (2nd, 3rd) were not affected by either strains or concentration at 3 d and 5 d post-exposure. Survival of later instars (5th) and adults was significantly reduced when exposed to the KUDSC strain at all concentrations. Comparison of dose–mortality values (LC50) using resistance ratios (RR50) were significantly different between life stages of the kudzu bug for both strains of B. bassiana. The LC50 values showed that kudzu bug adults are more susceptible than any other life stage when exposed to either strain. The KUDSC strain was more pathogenic than NI8 10 d after exposure, but NI8 exhibited significantly higher pathogenicity than KUDSC 20 d after exposure. Our results suggest potential field application of B. bassiana for kudzu bug control and their integration into pest management strategies to suppress them before they cause economic damage to soybean crops.

Effect of background tank color in combination with sand substrate and shelters on survival and growth of Scylla tranquebarica instar

Effect of tank color in combination with substrate-shelters on the survival and growth of the instar of purple mud crab, Scylla tranquebarica (initial body weight of 28.7 ± 2 mg) was investigated. Ten treatments were tested in triplicate with black (B) and white (W) tanks were set as the control, while other tanks were provided with a combination of sand substrate (S), and/or polyvinyl chloride pipes (P) as horizontal and nets (N) as vertical shelter, referred as B, BS, BSP, BSN, BSPN, W, WS, WSP, WSN and WSPN, respectively. Survival of the instar in black tanks (26.7 to 60.0%) was higher than in white tanks (20.0 to 46.7%) (P = 0.052). Survival in the horizontal shelter treatments (46.7 and 63.3%) exceeded that in the vertical shelter groups (30.0 and 50.0%) (P = 0.068). The final body weight of the instar in black tank (2.4 to 3.8 g) was significantly lower than white tank (2.6 to 4.8 g) (P = 0.02). Specific growth rate was significantly greater in sand substrate treatments (8.4 to 9.1%/day) than in controls (7.9 and 8.0%/day) (P = 0.015). In conclusion, horizontal shelter was better than vertical type, and black tank with substrate and horizontal shelter was more suitable for culture of purple mud crab instar.

Temperature and Humidity Interact to Influence Brown Marmorated Stink Bug (Hemiptera: Pentatomidae), Survival.

High-temperature events can influence insect population dynamics and could be especially important for predicting the potential spread and establishment of invasive insects. The interaction between temperature and environmental humidity on insect populations is not well understood but can be a key factor that determines habitat range and population size. The brown marmorated stink bug, Halyomorpha halys (Stål), is an invasive agricultural pest in the United States and Europe, which causes serious economic damage to a wide range of crops. This insect's range continues to expand. It has recently invaded the Central Valley of California, which has a hotter and drier climate compared with the Eastern United States where this insect is established. We investigated how high-temperature events and relative humidity would impact the survival and reproduction of H. halys. Using incubators and humidity chambers, we evaluated the impact of humidity and short-term (2 d) high-temperature exposure on the survival and development of H. halys eggs, nymphs, and adults. We found that high temperatures significantly reduced H. halys survival. The impact of humidity on H. halys survival was dependent on temperature and life stage. Low humidity decreased first-instar survival but not third- to fourth-instar survival. High humidity increased first instar survival but decreased third- to fourth-instar survival. Humidity did not influence adult or egg survival. We also found that high temperatures decreased H. halys reproduction. Our findings have important implications for understanding the invasive ecology of H. halys and may be used to improve models predicting H. halys range expansion.

Effect of gamma irradiation and subsequent cold storage on the development and predatory potential of seven spotted ladybird beetle Coccinella septempunctata Linnaeus (Coleoptera; Coccinellidae) larvae

Seven spot ladybird beetle, (Coccinella septempunctata) is a widely distributed natural enemy of soft-bodied insect pests especially aphids worldwide. Both the adult and larvae of this coccinellid beetle are voracious feeders and serve as a commercially available biological control agent around the globe. Different techniques are adopted to enhance the mass rearing and storage of this natural enemy by taking advantage of its natural ability to withstand under extremely low temperatures and entering diapause under unfavorable low temperature conditions. The key objective of this study was to develop a cost effective technique for enhancing the storage life and predatory potential of the larvae of C. septempunctata through cold storage in conjunction with the use of nuclear techniques, gamma radiations. Results showed that the host eating potential of larvae was enhanced as the cold storage duration was increased. Gamma irradiation further enhanced the feeding potential of larvae that were kept under cold storage. Different irradiation doses also affected the development time of C. septempuntata larvae significantly. Without cold storage, the lower radiation doses (10 and 25 GY) prolonged the developmental time as compared to un-irradiated larvae. Furthermore, the higher dose of radiation (50GY) increased the developmental time after removal from cold storage. This study first time paves the way to use radiation in conjunction with cold storage as an effective technique in implementation of different biological control approaches as a part of any IPM programs

Double-stranded RNA targeting vATPase B reveals a potential target for pest management of Henosepilachna vigintioctopunctata

The development of genetic based techniques, specifically RNA interference (RNAi), has emerged as a powerful tool in novel pest management strategies for pestiferous coleoptera. The 28-spotted ladybird beetle, Henosepilachna vigintioctopunctata, is a dynamic foliar pest of solenaceous plants, primarily potato plants, and has quickly become one of the most important pests attacking many crops in Asian countries. In this study, we demonstrate the efficacy of dietary RNAi targeting vATPase B, which led to significant gene silencing. Downstream effects of vATPase B silencing appeared to be both time- and partial dose-dependent. Our results indicate that silencing of vATPase B caused a significant decrease in survival rate, as well as reduced the food stuffs consumption and inhibited the overall development of H. vigintioctopunctata. Furthermore, results demonstrate expression of insect melanism related genes, TH and DDC, was significantly up regulated under the dsvATPase B (RNAi molecule designed against vATPase B) treatment. The impact of oral dsvATPase B delivery on the survival of 1st, 3rd instars, and adults was investigated through bacterially expressed dsRNA. The effectiveness of RNAi-based gene silencing in H. vigintioctopunctata provides a powerful reverse genetic tool for the functional annotation of its genes. This study demonstrates that vATPase B may represent a candidate gene for RNAi-based control of H. vigintioctopunctata.

Growth rate and fatty acid composition of orange mud crab instars, Scylla olivacea, reared at different temperatures

The objective of the present study was to examine the effect of different rearing temperatures on growth, survival, instar development, and fatty acid (FA) composition of orange mud crab instars, Scylla olivacea. The experiment was conducted at four different water temperatures of 24 °C, 28 °C, 32 °C and 36 °C using instar stage 1 (C1) in temperature-controlled recirculating rearing systems and lasted for 30 days. The study findings revealed that higher temperatures (≥32 °C) significantly reduced intermolt duration, whereby most crabs reached instar stages C6-C7, although 10.3% were still in the C2−C3 developmental stage. In addition, at temperature 36 °C all crabs were dead after three days of culture. Surprisingly, at constant temperature of 28 °C, total Polyunsaturated Fatty Acid were lower (0.52) compared to those at lower, 24 °C (0.71) and higher temperature of 32 °C (0.74). However, the direct effects of temperature on total fatty acids composition in crabs could not be distinguished from indirect effects of variable crab size and molt number. In conclusion, high temperature of 32 °C negatively affects instars growth and may induce molting, especially in S. olivacea.

Host Plant and Thermal Stress Induce Supernumerary Instars in Caterpillars.

Environmental stressors may induce variation in the number of larval instars of holometabolous insects. Host plant quality and ambient temperature can both induce this life history shift in the silver-spotted skipper, Epargyreus clarus (Cramer 1775) (Lepidoptera: Hesperiidae). To better understand this phenomenon, we raised larvae on high-quality (kudzu) or low-quality (wisteria) host plants in growth chambers under three temperature regimes (20, 26, and 32°C) that were either constant or diurnally fluctuating (T ± 5°C), and recorded survival and incidence of supernumerary instars. Larvae feeding on the low-quality host and/or experiencing thermal stress were more likely to show supernumerary development (SD). A subset of treatments yielded a mix of SD and TD (typical development) individuals, allowing for comparisons between phenotypes. Under the most stressful treatment (20 ± 5°C, wisteria), development time was 9 days longer in SD than in TD individuals; by contrast, at typical summer temperatures (26 ± 5°C), also on wisteria, total development time did not differ between these two phenotypes. Head capsules of both second and third instars were smaller in SD individuals. A retrospective logistic regression analysis indicated that third-instar head capsule size could be used to predict expression of the SD phenotype. By the ultimate instar, however, there were no detectable differences in head capsule size, and SD and TD individuals did not differ in pupal mass, strongly suggesting that the SD phenotype functions as a compensatory mechanism allowing E. clarus larvae to achieve the same size at metamorphosis (a strong fitness correlate) as TD larvae.

Effect of postemergence fomesafen application on common milkweed (Asclepias syriaca) growth and utilization by monarchs (Danaus plexippus)

Field experiments were conducted to investigate impacts of herbicide injury to common milkweed (Asclepias syriaca L.) on oviposition preference of monarch butterflies (Danaus plexippus Linnaeus). Common milkweed seedlings were transplanted in patches containing five plants spaced 25 cm apart in a no-till soybean field shortly after soybean planting in 2016. Herbicide treatments included an untreated control and 0.14 kg ha−1 fomesafen plus 0.5% crop oil concentrate applied postemergence. The experiment was repeated in the same area in 2017 by planting soybean no-till prior to common milkweed emergence. Common milkweed leaves displayed chlorosis and necrotic lesions five days after fomesafen application during both years. Two weeks following application many leaves damaged by fomesafen dehisced, and plants averaged an injury rating of 3.4 (visual scale of 1 = healthy and 5 = dead). Leaves emerging from the apical meristem following fomesafen application appeared normal, and four weeks after application injury ratings decreased to an average of 2.6. Dry weight of common milkweed ten weeks after application was not affected by fomesafen in either year. Common milkweed plants were examined for monarch eggs and larval instars weekly from May to August. In 2016, patches averaged 0.8 eggs, whereas in 2017 patches averaged 45.2 eggs. Fomesafen did not affect oviposition preference by monarch butterflies in either year. Larval instars on the milkweed patches were recorded throughout 2017. Presence and survival of instars were not affected by fomesafen, with patches averaging 7.5 and 0.1 first and fifth instars, respectively. In greenhouse experiments, common milkweed survived fomesafen rates up to 0.28 kg ha−1, twice the rate typically used in soybean, and plants showed signs of recovery within two weeks of application.

Effect of the eucalypt lerp psyllid Glycaspis brimblecombei on adult feeding, oviposition‐site selection, and offspring performance of the bronze bug, Thaumastocoris peregrinus

AbstractOviposition‐site selection may be greatly affected by competitive plant‐mediated interactions between phytophagous insects but these interactions have been poorly investigated on trees. Here, we evaluated the potential interaction between two invasive pests of Eucalyptus trees, the red gum lerp psyllid, Glycaspis brimblecombeiMoore (Hemiptera, Sternorrhyncha: Aphalaridae), and the bronze bug, Thaumastocoris peregrinusCarpintero et Dellapé (Heteroptera: Thaumastocoridae). We assessed the effect of the co‐occurrence of G. brimblecombei on the selection of feeding and oviposition sites by T. peregrinus females using dual‐choice bioassays. We compared developmental time and survival of the first instar of nymphs reared on healthy Eucalyptus tereticornisSmith (Myrtaceae) leaves and on leaves infested with the lerp psyllid, either with or without lerps (i.e., white conical sweet‐tasting structures, secreted during the nymphal stage). Bronze bug females prefer to oviposit on lerp‐carrying leaves but we found no difference in feeding preference when compared to healthy leaves. Infestation with the lerp psyllid hampered nymphal performance in terms of developmental time and survival, although the presence of lerps reverted the effect in survival and shortened the duration of the initial instar. These results display an interaction between these two insect species that affects both the oviposition preference of T. peregrinus females and the nymphal performance. Although there seems to be a discrepancy between mother preference and offspring performance, feeding on the lerps may prove beneficial to the offspring under long‐term conditions and multiple infestation by other pests and diseases.

Effects of Aschersonia aleyrodis on the life table and demographic parameters of Bemisia tabaci

The present study reports the sublethal effects of the entomopathogenic fungus, Aschersonia aleyrodis (Webber) on Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae). A fungal suspension of A. aleyrodis isolate Aa005 containing 1×107 conidia mL−1 was sprayed against B. tabaci on eggplant leaves under greenhouse conditions. The effects of fungal application on survival as well as life table parameters of the whitefly were observed at different post inoculation periods. The results indicated that A. aleyrodis can significantly affect the survival of 1st, 2nd, and 3rd nymphal instars of B. tabaci. Developmental periods of different instar nymphs were not affected by fungal application. A. aleyrodis spores persisted well and significantly affected the survivorship of young instar nymphs of B. tabaci at different post incubation periods. Life table results suggested that A. aleyrodis has no impact on general fecundity and longevity of B. tabaci. When the pathogen was exposed to the open environment and maintained for a relatively longer period, a reduction in the reproductive rate and intrinsic rate of increase was caused by the fungal spores, though the sublethal effects were not as good as the control treatment. The results suggest that the ability of spores to suppress an increase in whitefly population persists well after incubation of spores to the external environment (up to 9 days).

Postharvest Irradiation Treatment for Quarantine Control of the Invasive Lobesia botrana (Lepidoptera: Tortricidae).

Irradiation is a postharvest treatment option for exported berries and berry-like fruits to prevent movement of the quarantine pest European grape vine moth, Lobesia botrana (Denis & Schiffermüller) (Lepidoptera: Tortricidae). The effects of irradiation on egg, larval, and pupal development in L. botrana were examined. Eggs, neonates, third and fifth instars, and early- and late-stage pupae were irradiated at target doses of 50, 100, 150, or 200 Gy or left untreated as controls in replicated factorial experiments, and survival to the adult stage was recorded. Tolerance to radiation generally increased with increasing age and developmental stage. A dose of 150 Gy prevented adult emergence in eggs and larvae. Pupae were more radiotolerant than larvae, and late-stage pupae were more tolerant than early-stage pupae. In large-scale validation tests, 150 Gy applied to fifth instars in diet prevented adult emergence, but some survival occurred in fifth instars irradiated in table grapes; however, 250 Gy prevented fifth instar survival in grapes. For most commodities, the fifth instar is the most radiotolerant life stage likely to occur with the commodity; a minimum radiation dose of 250 Gy will prevent adult emergence from this stage. For traded commodities such as table grapes that may contain L. botrana pupae, 325 Gy applied to mature female pupae sterilized emerging adults and may provide quarantine security. Radiotolerance in L. botrana is comparable to other tortricids, and the data reported here support a generic dose of 250 Gy for eggs and larvae of this group.

Performance of Early Instar Monarch Butterflies (Danaus plexippusL.) on Nine Milkweed Species Native to Iowa

Over the past two decades, the population of monarch butterflies east of the Rocky Mountains has experienced a significant decline. Habitat restoration that includes milkweed plants is crucial to boost population numbers in the breeding range. Monarch butterfly larvae use milkweeds as their only host plant, but larval performance on different milkweed species is not well documented. We examined early instar survival and growth on nine milkweed species native to Iowa. These included Asclepias exaltata (poke milkweed), A. hirtella (tall green milkweed), A. incarnata (swamp milkweed), A. speciosa (showy milkweed), A. sullivantii (prairie milkweed), A. syriaca (common milkweed), A. tuberosa (butterfly milkweed), A. verticillata (whorled milkweed), and Cynanchum laeve (honey vine milkweed). In laboratory and greenhouse experiments, larval survival on all nine milkweed species did not differ. Larvae that fed on C. laeve plants were an instar behind larvae that fed on any other species, while larvae that fed on A. verticillata weighed more than larvae that fed on any other species. Our results show that early instar larvae can survive on all nine milkweed species.

Estimating Density and Temperature Dependence of Juvenile Vital Rates Using a Hidden Markov Model.

Organisms in the wild have cryptic life stages that are sensitive to changing environmental conditions and can be difficult to survey. In this study, I used mark-recapture methods to repeatedly survey Anaea aidea (Nymphalidae) caterpillars in nature, then modeled caterpillar demography as a hidden Markov process to assess if temporal variability in temperature and density influence the survival and growth of A. aidea over time. Individual encounter histories result from the joint likelihood of being alive and observed in a particular stage, and I have included hidden states by separating demography and observations into parallel and independent processes. I constructed a demographic matrix containing the probabilities of all possible fates for each stage, including hidden states, e.g., eggs and pupae. I observed both dead and live caterpillars with high probability. Peak caterpillar abundance attracted multiple predators, and survival of fifth instars declined as per capita predation rate increased through spring. A time lag between predator and prey abundance was likely the cause of improved fifth instar survival estimated at high density. Growth rates showed an increase with temperature, but the preferred model did not include temperature. This work illustrates how state-space models can include unobservable stages and hidden state processes to evaluate how environmental factors influence vital rates of cryptic life stages in the wild.

Feeding Preference and Performance ofHelicoverpa zea(Lepidoptera: Noctuidae) Larvae on Various Soybean Tissue Types

Abstract Helicoverpa zea Boddie (Lepidoptera: Noctuidae) feeding preference and performance on soybean tissue types is poorly understood. We assessed preference by looking at feeding behavior and resulting performance of 2nd and 4th instar H. zea larvae on leaves, flowers, and pods in no-choice and choice assays. Consumption indices were calculated and observed feeding behaviors were used to indicate preference; survival, growth rate, and larval body mass were recorded as measures of performance. Second instars performed better when fed leaf tissue than when fed other tissue types. In no-choice assays, 32% of 2nd instars that fed exclusively on newly emerging trifoliates reached the pupal stage, and 50% of those that fed exclusively on fully emerged leaf trifoliates survived to pupation. Early instar survival was poor (ranging from 0 to 3%) on all other tissue types, including flowers, stems, and pods. However, when given a choice of tissue types throughout their larval lifetime, 2nd instars preferred to ...

Effects of Postharvest Cold Storage on the Development and Survival of Immature Drosophila suzukii (Diptera: Drosophilidae) in Artificial Diet and Fruit.

Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) attacks a wide range of host plants, including crops such as blueberries, cherries, caneberries, and strawberries. We evaluated the influence of three temperatures (1.1, 3.9, and 5.0 °C) and four exposure durations (6, 12, 24, and 72 h) that were selected to represent typical grower practices on survival and development time of immature D. suzukii in artificial diet and one temperature and duration (1.67 °C for 72 h) in fruit (blueberries and raspberries). Cold storage at 1.1 °C for 24 h decreased larval survival, but shorter durations generally did not affect larval survival. No eggs or young larvae survived when held for 72 h at 1.1 °C, and fewer older larvae survived after 72 h at 1.1, 3.9, and 5.0 °C than at 20 °C (control). Development time in diet was longer for all life stages following at least 12 h at any of the storage temperatures. In blueberries, no eggs survived to pupation when stored at 1.67 °C for 72 h, and survival of third instars was reduced by 41%. In raspberries, egg, second instar, and third instar survival was significantly reduced following storage at 1.67 °C for 72 h. Drosophila suzukii larval development time was shorter in raspberry than in blueberry, but it was significantly longer in both fruits when stored at 1.67 °C for 72 h. Our results indicate that cold storage can reduce survival and increase development time of immature D. suzukii, and it could be a useful part of an integrated program to manage D. suzukii infestation.