Low Larval Density Research Articles

Impact of phytohormones on wheat resistance to Hessian fly under heat stress

The Hessian fly (HF, Mayetiola destructor) is one of the most destructive pests of wheat and wheat-related cereals. Wheat resistance and/or susceptibility to HF are often affected by the levels of phytohormones in plants. In this study, we tested the impact of phytohormones on Molly wheat resistance to HF biotype GP by externally applying phytohormones, including salicylic acid (SA), jasmonic acid (JA), 12-oxophytodienoic acid (OPDA), and auxin (indole acetic acid, IAA) to wheat seedlings under heat conditions. Our results indicated that the impact of externally applied phytohormones on wheat resistance to HF depends on the timing of phytohormone application and/or HF larval density at HF feeding sites in the plants. The early application of SA, OPDA, and IAA enhanced wheat resistance to HF under heat stress at low larval density, while the delayed application of SA, OPDA, and IAA did not affect wheat resistance to HF at high larval density.

Control Efficacy of the Bt Maize Event DBN3601T Expressing Cry1Ab and Vip3Aa Proteins against Beet Armyworm, Spodoptera exigua (Hübner), in China.

The beet armyworm, Spodoptera exigua (Hübner), is a major pest of maize, cotton, soybean, and many other crops globally. Despite the widespread deployment of Bt transgenic maize for pest control worldwide, the efficacy of Bt lepidopteran-resistant transgenic maize in managing S. exigua remains rarely studied. In this study, we quantified the expression level of pyramided Cry1Ab and Vip3Aa toxins in Bt maize (event DBN3601T) and evaluated their control efficiency against S. exigua under both laboratory and field conditions. The enzyme-linked immunosorbent assay (ELISA) results showed that the expression levels of Cry1Ab and Vip3Aa proteins in DBN3601T maize tissues followed a decreasing order as follows: V5-leaf > V8-leaf > VT-tassel > R2-kernel > R1-silk. Diet-overlay assay results showed that the LC50 values of Cry1Ab and Vip3Aa proteins against S. exigua larvae were 11.66 ng/cm2 and 27.74 ng/cm2, respectively, with corresponding GIC50 values at 1.59 ng/cm2 and 7.93 ng/cm2. Bioassay using various tissues of the DBN3601T maize indicated that after 7 days of infestation, mortality rates of neonates and third-instar larvae ranged from 86% to 100% and 58% to 100%, respectively. Mortality was highest on V5 and V8 leaves, followed by R2-kernel, VT-tassel, and R1-silk. Field trials demonstrated that DBN3601T maize exhibited significantly lower larval density, damage rate, and leaf damage score compared to non-Bt maize. Field cage trial showed that the control efficacy of DBN3601T maize at the vegetative stage could reach 98%. These findings provide a theoretical basis for utilizing Bt transgenic maize to enhance the sustainable management of S. exigua in Asia.

Intercropping organic broccoli with Rhododendron tomentosum and Fagopyrum esculentum: a test of bottom-up and top-down strategies for reducing herbivory

Brassicaceous plants are attacked by a wealth of specialist herbivores that include the Diamondback moth (DBM) Plutella xylostella L. (Lepidoptera: Plutellidae), control of which requires novel biocontrol strategies. DBM is a cosmopolitan pest causing damage that varies yearly in Finland depending on the timing and extent of their migration. Intercropping with companion plants can hamper host location by herbivores or attract their natural enemies. We tested two sustainable companion plant-based protection strategies on field-grown broccoli (Brassica oleracea var. italica), which comprised 1) aromatic and repellent-releasing Rhododendron tomentosum (RT) (bottom-up strategy), and 2) nectar-producing buckwheat Fagopyrum esculentum (FE) (top-down strategy) combined with an early-season floating row cover (mechanical control) (MC + FE). In addition, a control (no companion plant or cover) and mechanical control (MC) without FE were included. DBM adults on yellow sticky traps and larvae on plants were counted, and feeding damage on leaves was quantified. Volatile organic compounds emitted by broccoli plants in control and RT plots, and emitted by boundary RT plants in RT plots, were identified and quantified. There was a mass outbreak of DBM in early summer with a population peak in mid-July when the second adult generation emerged. DBM adult densities were significantly lower in RT and MC + FE than in control plots. Broccoli in RT plots had a lower larval density and lower damage intensity than in control plots in the early-season. Larval densities and damage intensities were the highest in the latter half of July. Control plots had the highest number of larvae followed by RT, MC, and MC + FE plots. Damage intensities in control plots were significantly higher than in all other treatments throughout the season. Damage intensity was lower in MC and MC + FE plots than in RT plots at the end-of-July. R. tomentosum emitted two characteristic sesquiterpene alcohols, palustrol and ledol, but no evidence of adsorption and re-release of these compounds from Brassica plants grown in RT plots was found. We conclude that incorporating RT as a boundary plant and using a mechanical row cover reduces DBM damage on broccoli, but further multi-year trials under varying degrees of pest pressure are needed.

Effects of larval crowding on the transcriptome of Drosophila simulans.

Larval crowding is one common ecological stressor for many insect species. In Drosophila, high larval density alters multiple widely-studied phenotypes including life-history traits, morphology and behavior. Nevertheless, we still miss a holistic view of the full range of phenotypic changes and the underlying molecular mechanisms. In this study, we analyzed the adult transcriptomes of high and low larval density fly cohorts, and highlighted the molecular basis of the plastic traits. Increased cellular energy metabolism and locomotion, along with reduced reproductive investment, are key responses to high larval density. Moreover, we compared the expression changes among cohorts with different developmental delays caused by larval crowding. The majority of genes induced by larval crowding showed the strongest expression alterations in cohorts with intermediate delay. Furthermore, linear expression changes were observed in genes related to nutrition and detoxification. Comparing different high-density cohorts could provide insights into the varied responses to distinct larval crowding-induced stresses such as space competition, food degradation and waste accumulation.

Heterocypris incongruens maintains an egg bank in stormwater habitats and influences the development of larval mosquito, Culex restuans.

Dormant propagules can provide a rapid colonization source for temporary aquatic habitats and set the trajectory for community dynamics, yet the egg banks of stormwater management systems have received little attention. We asked which species hatched from the sediment of drainage ditches in Champaign County, IL, and found bdelloid rotifers and ostracods (Heterocypris incongruens) to be the most common taxa. These sites also are colonized by mosquitoes, and we established laboratory experiments to examine interspecific interactions between common co-occurring taxa. Culex restuans larvae were reared in the presence or absence of H. incongruens at two intra- and interspecific densities (20 or 40 total individuals) and their survivorship to adulthood, development time to adulthood, adult body size, and sex ratio were determined. Survival for Cx. restuans was significantly lower at high larval density than at low larval density in both treatments. Culex restuans larvae reared in the presence of H. incongruens had a shorter development time to adulthood and emerged as larger adults compared to those reared in the absence of H. incongruens. The sex ratios in the H. incongruens treatments were female-biased whereas those in the Culex-only treatments were male-biased. These differences may have epidemiological implications, as only female mosquitoes serve as disease vectors. Our results emphasize the importance of understanding interspecific interactions in influencing larval mosquito development traits.

High larval densities and high temperatures lead to a stronger immune response in the black soldier fly

Organisms are expected to invest more in their immune function when the risk of disease infection is high. However, induction of a robust immune response is costly and may not be achievable in suboptimal environments. High conspecific density could simultaneously imply high infection risk and a suboptimal environment for many insect species. We focus on the economically important dipteran species (black soldier fly, BSF) that represents the insect order that has been ignored in previous research on density effects on immunity. The experimental part of the study was carried out to evaluate the effect of larval density (three density treatments: 1, 5 and 10 larvae/cm2) and temperature (three thermal treatments: 23, 27 and 30 °C) on the immune function of BSF larvae. The larvae that were reared at high compared to low larval densities and at higher than lower temperatures had significantly higher activity of phenoloxidase, an enzyme that plays an essential role in insect immune function. Sex did not have a significant effect on phenoloxidase activity and prepupal mass, pupal mass and adult mass were not affected by the levels of phenoloxidase activity of fifth instar larvae. In addition, we give an overview of larval density effects on insect immunity and show that density-dependent prophylaxis (stronger immune response in high larval density environments) is indeed common in the results of published case studies. However, cases with no correlation between density and immunity traits were as frequent. Moreover, in more than half of the studies, qualitatively different within-species patterns in different immunity traits were observed. We conclude that BSF larvae exhibit density-dependent prophylaxis, and larvae invest more into their immune system at high larval densities and temperatures than they do at low larval densities and temperatures.

Habitat value of constructed breeding pools for the endangered Sonoma population of California tiger salamander

AbstractHabitat creation is a common element of efforts to recover populations threatened by altered habitat. Unfortunately, human‐created habitats do not necessarily support re‐establishment of target species. We investigated the value of constructed vernal pools as breeding habitat for the endangered Sonoma County population of California tiger salamanders (Ambystoma californiense) by conducting 19 years of larval surveys in 118 pools that were natural (n = 40), constructed (n = 70), or natural with substantial human alterations (human‐altered, n = 8). California tiger salamander larval densities in human‐altered and natural pools declined over the study period, while larval densities in constructed pools showed non‐negative trends. Larval declines in natural pools may be attributed to long‐term degradation of the surrounding terrestrial habitat. Mean larval densities over the course of the study were equivalent between constructed and natural pools, when corrected for pool morphometry. In contrast, human‐altered pools had lower larval densities. To assure consistent California tiger salamander breeding, pools needed to be ≥30 cm deep and 240 m2 in area, with deeper (50–70 cm) and larger (1,600–1,800 m2) pools providing increased larval productivity. Over the study, there was no evidence of decrease in the rate of colonization of new pools. We conclude that constructed pools can be important tools in the recovery of imperiled pool‐breeding amphibians if proper design elements for the target species are considered.

Cold winters drive consistent and spatially synchronous 8-year population cycles of cabbage stem flea beetle.

Population cycles have been observed in mammals as well as insects, but consistent population cycling has rarely been documented in agroecosystems and never for a beetle. We analysed the long-term population patterns of the cabbage stem flea beetle Psylliodes chrysocephala in winter oilseed rape over 50 years. Psylliodes chrysocephala larval density from 3045 winter oilseed rape fields in southern Sweden showed strong 8-year population cycles in regional mean density. Fluctuations in larval density were synchronous over time across five subregional populations. Subregional mean environmental variables explained 90.6% of the synchrony in P. chrysocephala populations at the 7-11year time-scale. The number of days below -10°C showed strong anti-phase coherence with larval densities in the 7-11year time-scale, such that more cold days resulted in low larval densities. High levels of the North Atlantic Oscillation weather system are coherent and anti-phase with cold weather in Scania, Sweden. At the field-scale, later crop planting date and more cold winter days were associated with decreased overwintering larval density. Warmer autumn temperatures, resulting in greater larval accumulated degree days early in the season, increased overwintering larval density. Despite variation in environmental conditions and crop management, 8-yearcycles persisted for cabbage stem flea beetle throughout the 50 years of data collection. Moran effects, influenced by the North Atlantic Oscillation weather patterns, are the primary drivers of this cycle and synchronicity. Insect pest data collected in commercial agriculture fields is an abundant source of long-term data. We show that an agricultural pest can have the same periodic population cycles observed in perennial and unmanaged ecosystems. This unexpected finding has implications for sustainable pest management in agriculture and shows the value of long-term pest monitoring projects as an additional source of time-series data to untangle the drivers of population cycles.

Effect of Variations in the Pretreatment of Organic Waste on The Growth of Black Soldier Flies (BSF) Larval

This study was conducted to see the effect of size and freshness variations of organic waste on BSF growth. The research was conducted on laboratory-scale research at campus of Pasundan University and field-scale research on Pojok Kang Pisman at Bandung City-hall. In laboratory-scale research, the organic waste used is artificial organic waste whose composition is close to organic waste from market. Meanwhile in field-scale research, the organic waste used is from market organic waste. Variations in pretreatment were carried out by varying the organic waste size and freshness in laboratory-scale research and comparison in order of chopping and fermentation of organic waste in various cocopeat thickness in field-scale research. Maggot/BSF growth analysis was carried out by calculating the waste reduction index, Efficiency of Conversion Digested Feed, survival rate, and maggot protein tests. The results of the laboratory study showed that the smaller the size of the waste influenced increasing the WRI, SR and ECD values but had little effect on the protein content of the larvae. The protein content of larvae is suitable for chicken feed (19-21%). However, when the waste was fermented, there was a significant increase in WRI and SR, and the protein content of the larvae increased (32-34%), suitable for tilapia and catfish feed. Field research results with higher larval density in fermented waste resulted in higher WRI and ECD values compared to laboratory results with lower larval density. In addition, the treatment of chop-fermentation and fermentation-chopped sequences gave different water content values ​​which affected the WRI and ECD values. The higher the water content, the lower the WRI and ECD values. The protein content of larvae in the field study was almost the same as in the laboratory study, ranging from (31-34%).

Priority effects and density promote coexistence between the facultative predator Chrysomya rufifacies and its competitor Calliphora stygia

Highly competitive ephemeral resources like carrion tend to support much greater diversity relative to longer-lived resources. The coexistence of diverse communities on short-lived carrion is a delicate balance, maintained by several processes including competition. Despite this balance, few studies have investigated the effect of competition on carrion, limiting our understanding of how competition drives coexistence. We investigated how priority effects and larval density influence coexistence between two blowfly species, the facultative predator Chrysomya rufifacies and its competitor Calliphora stygia, which occupy broadly similar niches but differ in their ecological strategies for exploiting carrion. We examined how adult oviposition, larval survival, developmental duration, and adult fitness were affected by the presence of differently aged heterospecific larval masses, and how these measures varied under three larval densities. We found C. rufifacies larval survival was lowest in conspecific masses with low larval densities. In heterospecific masses, survival increased, particularly at high larval density, with priority effects having minimal effect, suggesting a dependency on collective exodigestion. For C. stygia, we found survival to be constant across larval densities in a conspecific mass. In heterospecific masses, survival decreased drastically when C. rufifacies arrived first, regardless of larval density, suggesting C. stygia is temporally constrained to avoid competition with C. rufifacies. Neither species appeared to completely outcompete the other, as they were either constrained by density requirements (C. rufifacies) or priority effects (C. stygia). Our results provide new mechanistic insights into the ecological processes allowing for coexistence on a competitively intense, ephemeral resource such as carrion.

Diet quality and conspecific larval density predict functional trait variation and performance in a polyphagous frugivorous fly

AbstractDiet quality and the presence and abundance of conspecifics feeding on the same food resource are critical factors that affect functional traits of many animal species and influence ecological processes.We hypothesized that in insects whose larvae live in groups of varying sizes in ephemeral and nutritionally variable environments, extreme macronutrient content in the feeding substrate is a barrier for optimal performance that can be overcome by the collective feeding behaviour of large numbers of larvae.We experimentally examined how multiple immature and adult traits of the polyphagous tephritid fruit fly,Anastrepha ludens, vary as a function of the quality of its larval diet (protein + carbohydrate [P + C] content of 8.0%–12.6% w/w, and protein‐to‐carbohydrate [P/C] ratio of 1.8–0.11) across extreme levels of conspecific larval densities (60–600 larvae/60 g of diet).Overall, we found positive effects on survival of immature and adult stages, the duration of the larval stage, pupal weight and adult emergence of flies, as dietary P + C content increased, followed by negative effects when the diet had extremely high carbohydrate‐biased macronutrient content. Larval density had positive, negative and curvilinear effects depending on the macronutrient composition of the food, resulting in a range of fly responses through a continuous scale of macronutrient content and larval density combinations. Optimal performance ofA.ludens, in terms of larval development time, body weight and survival to adulthood, was found when the diet consisted of low P + C content and high P/C ratios, and low larval densities.Our findings point to a diet‐mediated relationship between density and survival to the adult stage, suggesting that large numbers (up to a point) of larvae can balance negative effects of conspecific competition when food is characterised by high macronutrient content and low P/C ratios. We conclude that diet quality and conspecific density interact in complex ways to shape trait expression and performance in a frugivorous fly. Addressing this interaction is key to advance the understanding of the mechanisms behind changes in population dynamics in insect species living in groups confined in isolated and ephemeral resources.Read the freePlain Language Summaryfor this article on the Journal blog.

Temperature-modified density effects in the black soldier fly: low larval density leads to large size, short development time and high fat content

The effects of biotic and abiotic factors on insect life histories have been extensively studied. However, the impact of some crucial aspects, such as larval density (crowding) and the effects of environmental interactions, have often been overlooked. This study aims to determine the effects of larval density and temperature on life-history traits in the black soldier fly (BSF). Our results showed an increase in prepupal mass, pupal mass, prepupal-to-pupal mass loss, survival, prepupal fat content, adult mass, adult longevity and a reduction in larval and pupal development time at low densities. Larval density was maintained throughout the entire larval period and larval survival was determined at the 4th instar and at prepupation. Larvae were reared at three different larval densities (1, 5 and 10 larvae/cm2), at three temperature treatments (23, 27 and 30 °C) and food was provided ad libitum. High densities, on the contrary, resulted in an increase in development time, mortality and a decrease in prepupal mass loss. Temperature significantly affected all studied traits except survival, prepupal fat content and adult longevity, and notably modified the larval density effects on prepupal mass, pupal mass, adult mass, prepupal-to-pupal mass loss, prepupal fat content, duration of larval period, and adult longevity. Males and females differed in all studied life-history traits except adult mass. We conclude that density and temperature and their interaction-related effects during larval development considerably affect BSF larval life-history traits. Therefore, these effects should be carefully considered when planning for insect mass rearing.

Budworm-linked warblers as early indicators of defoliation by spruce budworm: A field study

Outbreaks of eastern spruce budworm (Choristoneura fumiferana; hereafter SBW) are a major natural disturbance in coniferous forests of eastern North America. These outbreaks provide a superabundant source of food for insectivorous birds. Three species, referred to as budworm-linked warblers, exhibit strong positive numerical responses to early increases of SBW density: Tennessee Warbler (Leiothlypis peregrina), Cape May Warbler (Setophaga tigrina), and Bay-breasted Warbler (S. castanea). Their abundance increases even before defoliation is visible from aerial surveys. Budworm-linked warblers may detect new epicenters of SBW outbreaks through natal dispersal, as this movement is typically much more extensive than subsequent (breeding dispersal) movements. Our main objectives were, thus, (1) to determine whether sudden increases in the abundance of budworm-linked warblers could be used to detect early stages of SBW outbreaks, and (2) to examine age-specific responses of budworm-linked warblers to local and landscape-level habitat characteristics, in order to investigate the potential role of natal dispersal in the detection of new epicenters. To do so, we estimated the abundance of each species of budworm-linked warbler in 75 study plots sampling a gradient of SBW density and related them to 7 stand variables and landscape metrics with generalized additive mixed models. We also compared the responses of yearling (second-year; SY) and older (after-second-year; ASY) individuals to the density of SBW larvae and habitat variables at different spatial scales. We captured 31 Tennessee Warblers, 27 Cape May Warblers, and 57 Bay-breasted Warblers. The abundance of all three species of budworm-linked warblers increased with SBW larval density, but the numerical response of Bay-breasted Warbler was initiated earlier and it varied with age. SY individuals tended to be associated with stands supporting lower larval densities than ASY individuals and, as suggested by other authors, Bay-breasted Warbler appeared to be more efficient at exploiting SBW larvae at low density. For that reason, this species represents an early indicator of stands undergoing SBW outbreaks and we propose to use its abundance as an indicator to orient labour-intensive ground surveys of SBW larvae.

Factors affecting the seasonal variability of planktonic shrimps (Dendrobranchiata) along an estuary–ocean gradient on the Amazon continental shelf

AbstractDendrobranchiata shrimp taxonomic composition and spatial and temporal distribution on the Amazon continental shelf (ACS) were investigated along a transect between the sources of the Amazon and Pará Rivers, encompassing an extension of ~250 km towards the continental slope. Plankton was collected with oblique trawls (200 μm mesh size), and nine taxa were found; 59.4% were larvae (mysis or decapodid stages) and 40.6% were juveniles or adults. Acetes was negatively related to chlorophyll-a and temperature, and Luciferidae were positively correlated with months. This study provides novel information on the density distribution of dendrobranchiate shrimps, thus helping to pave the way to characterize a large-scale, hugely relevant area that is poorly studied. As in other tropical coastal areas, there is here an increase in number of taxa with increased distance from the coast. Luciferidae, Solenoceridae and Penaeidae were the most frequent families whereas Sicyoniidae and Sergestidae had the lowest frequency of occurrence nearer the slope. Despite the low larval density of penaeid shrimps, their presence in all months and at all sampling sites along the ACS proves the importance of this area for shrimps with socioeconomic relevance, as well as its importance as a nursery and growth habitat for dendrobranchiate shrimps.

The response of sycanus aurantiacus ishikawa et okajima (hemiptera: reduviidae) to color polymorphisms larvae of spodoptera exigua (hubner) (lepidoptera: noctuidae)

his study aims to evaluate the predatory behavior, preference and functional response of S. aurantiacus in color polymorphism larvae of S. exigua. The predatory behavior and preference test of S. aurantiacus using green and dark brown color larvae of S. exigua. Functional response test was carried out with 5 treatments of larvae population density with 10 replications. The results showed that S. aurantiacus prefers to dark brown larvae of S. exigua than green. The time taken by predators to find the first and subsequent prey was faster in dark brown larvae than in green, both on low or high larval density. The search time for the first prey on dark brown larvae was 22.7 minutes (at high density) and 39.3 minutes (at low density) while those on green larvae were 26.5 minutes and 42.7 minutes. S. aurantiacus showed type-II functional response to the density rate of S. exigua larvae both dark brown and green with the line equation respectively Y = 1,284x / 1 + 0,056x; R2: 0.96; a: 0,107; Th: 0.52 (dark brown larvae) Y = 1.32x / 1 + 0.063x; R²: 0.952; a: 0,109; Th: 0.58 (green larvae).

Applying a Selection Experiment to Test for Fitness Costs of Bt Resistance in Western Corn Rootworm (Coleoptera: Chrysomelidae) and the Effect of Density on Fitness Costs.

Western corn rootworm, Diabrotica virgifera virgifera LeConte, is a serious pest of corn and is often managed with transgenic corn producing insecticidal toxins from the bacterium Bacillus thuringiensis (Bt). This pest has developed field-evolved resistance to all commercially available Bt traits, beginning with Cry3Bb1 in 2009. Fitness costs may accompany Bt resistance, where individuals with alleles for Bt resistance have reduced fitness on non-Bt corn compared to Bt-susceptible individuals. In conjunction with non-Bt refuges, fitness costs can delay the evolution of Bt resistance. Importantly, ecological factors may affect the presence and magnitude of fitness costs. For western corn rootworm, available data suggest that fitness costs of Bt resistance may be present in some cases. Using two Cry3Bb1-resistant western corn rootworm strains (Hopkinton and Cresco), a fitness-cost experiment was performed by rearing rootworm in the absence of Bt for six generations to test for fitness costs of Cry3Bb1 resistance and the effect of larval rearing density on fitness costs. Fitness costs were detected for both strains; however, strains were still resistant to Cry3Bb1 corn at the end of the experiment. Cresco experienced a greater loss of resistance at low versus high density, but no effect of density was detected in Hopkinton. Our study shows that fitness costs can accompany Bt resistance in western corn rootworm and may be more pronounced under low larval density. Even though fitness costs were present, it appears that rootworm populations may remain resistant to Cry3Bb1 corn for years after resistance has evolved.

First Report Using a Native Lacewing Species to Control Tuta absoluta: From Laboratory Trials to Field Assessment.

The South American tomato pinworm, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), a destructive pest on tomato, has invaded most Afro-Eurasian countries. Recently invaded by the pest, most tomato crops in greenhouses and open fields in Tajikistan are currently suffering major damage. While failure in management using chemical insecticide has been frequently observed, alternative options such as biological control is urgently needed. In this study, we evaluated the effectiveness of the common green lacewing Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) against T. absoluta. In controlled laboratory conditions, C. carnea showed high predation rate on both T. absoluta eggs (i.e., 36 ± 2 eggs within 24 h and 72 ± 4 eggs within 48 h) and larvae, especially it can attack the larvae both inside and outside the leaf galleries (i.e., an average of 22% of the larvae was killed inside, and an average of 35% was killed outside). In a cage exclusion experiment, T. absoluta showed relatively low larval density in the cages with pre-fruiting release of C. carnea, whereas the larval density was four to six times higher in the “no release” cages. In the “post-fruiting release” cages, the pest population that had already built up during the pre-fruiting stage eventually crashed. In an open-field experiment, the tomato crops in control plots were fully destroyed, whereas low levels of larvae density and damage were observed in the biocontrol plots. Moreover, the field release of C. carnea resulted in significantly higher tomato yield than those without release, despite no differences between the “pre-fruiting release” and “post-fruiting release” treatments. We conclude that the local commercial biocontrol agent C. carnea could be promising for the management of T. absoluta in Tajikistan. It is also one of the first reports showing the management of T. absoluta using a lacewing species. The effectiveness should be validated by further field trials in larger area of commercial crops and various locations.

Host Plant Effects on Winter Moth (Lepidoptera: Geometridae) Larval Development and Survival.

The winter moth, Operophtera brumata (L.) is an invasive forest and agricultural pest in North America that causes severe defoliation to a wide range of host species. This study examines the differential larval densities, development, and survival on seven host species in midcoast Maine: red oak (Quercus rubra L., Fagales: Fagaceae), apple (Malus domestica L., Rosales: Rosaceae) and crab apple (Malus sp. L., Rosales: Rosaceae), red maple (Acer rubrum L., Sapindales: Sapindaceae), pin cherry (Prunus pensylvanica L., Rosales: Rosaceae), white birch (Betula papyrifera L., Fagales: Betulaceae), wild lowbush blueberry (Vaccinium angustiflolium L., Ericales: Ericaceae), and highbush blueberry (Vaccinium corymbosum L., Ericales: Ericaceae). We also explore the degree of synchrony between selected host plants and larval hatch and its effect on survival. We found that densities, development, and survival were significantly greater on red oak (Quercus rubra) and apple (Malus sp.) than on all other target species and were lowest on pin cherry (Prunus pennsylvanica). We found low larval densities in open, wild lowbush blueberry fields; however, larvae successfully fed and developed on wild lowbush blueberry in a laboratory setting. This suggests that winter moth is a potential pest to wild lowbush blueberry in Maine if the outbreak expands to include areas with wild lowbush blueberry production.

Influence of a Foliar Endophyte and Budburst Phenology on Survival of Wild and Laboratory-Reared Eastern Spruce Budworm, Choristoneura fumiferana on White Spruce (Picea glauca)

A manipulative field study was carried out to determine whether the foliar endophyte fungus, Phialocephala scopiformis DAOM 229536, decreased the performance of eastern spruce budworm, Choristoneura fumiferana larvae developing on white spruce trees. Overwintered second-instar budworm larvae from a laboratory colony or from a wild population were placed on endophyte positive or negative trees one or two weeks before budburst. The presence of the endophyte in the needles reduced the survival of C. fumiferana from both a wild population and a laboratory colony. Survival for budworm juveniles up to pupation and to adult emergence was 13% and 17% lower, respectively, on endophyte positive trees. The endophyte did not influence the size or sex of survivors and budworm survival was not influenced by any two- or three-way interactions. Budworm survival was higher for wild than for laboratory-reared budworm and for budworm placed on trees a week before budburst. This may be the first field study to demonstrate the efficacy of an endophytic fungus against wild individuals of a major forest insect pest. The efficacy of the endophyte at low larval densities suggests that it could be a useful tactic to limit spruce budworm population growth in the context of an early intervention strategy.

Increasing the stocking density in Paracentrotus lividus larviculture: Effects on survival and metamorphosis rates

The development of sustainable methods for sea urchin juvenile production is currently constrained by high mortality rates during larval growth and the high costs of larval rearing systems management. With the aim of developing a method for the production of juveniles of the purple sea urchin Paracentrotus lividus in a medium-scale recirculating system, the present study focused on the effects of high stocking densities on larval growth. Plutei larvae were reared at three different densities (up to 7 ind/ml) in a semi-static culture system. Larval survival and metamorphosis success were evaluated in order to identify the most effective density range. The highest metamorphosis rates (80%–95%) were obtained at 4 and 7 larvae/ml. These results are comparable with (and in some cases higher than) those reported for the same species at much lower larval densities. In conclusion, the rearing conditions tested here show for the first time that a significantly higher (4 ind/ml) stocking density than those of traditional P. lividus rearing methods (based on large volumes and low densities) can be adopted, thus supporting the feasibility of an increase in the final output of competent larvae with no increase in rearing volumes.