Egg Mass Density Research Articles

Damage analysis of Pochazia shantungensis (Hemiptera: Ricaniidae) in persimmons.

An invasive species, Pochazia shantungensis (Hemiptera: Ricaniidae), causes serious economic damage to fruit trees. In Korea, this pest is mainly managed using chemical insecticides. However, the management timing and insecticides for P. shantungensis negatively affect honeybee populations. Thus, this study estimated the decision-making level for P. shantungensis in persimmons to decrease insecticide application and increase management efficiency. We determined which developmental stage (i.e., egg, nymph, and adult) affected the damage-related factors (numbers of new shoots and fruit formations, and harvest amount) of persimmons using both spatial analyses and linear relationships. The distribution of P. shantungensis eggs was spatially correlated with the one of persimmon fruit number. However, we did not find any linear relationships between the densities of P. shantungensis eggs and damage-related factors of persimmons. Instead, we found that the density of P. shantungensis correlated with the death of oviposited branches. From the developed model of branch death possibility based on egg mass density, 5.75 egg masses per newly developed branch were proposed as the decision-making level. The findings would help increase the efficiency of P. shantungensis management in persimmon orchards and develop decision-making levels for other insects.

Seasonal differences in amounts of oviposition habitat and egg‐laying by caddisflies in rivers with regulated versus unregulated flows

Abstract Few studies consider spatio‐temporal variation in egg‐laying for benthic insects in streams. However, such variation can have lasting effects on the numbers and distribution of offspring and subsquent life‐cycle stages. For species that require specific egg‐laying habitats, such as rocks that protrude from the water surface (emergent rocks, ER), densities of egg‐laying habitat can affect densities of benthic eggs and even larvae for some species. For such species, changes in water levels alter the spatio‐temporal distribution of ER and can affect densities of eggs and, potentially, larvae. Below dams, modified flow regimes may alter the temporal availability of ER. In this study we tested whether river regulation altered the availability of oviposition habitat and changed the phenology of oviposition compared to unregulated rivers. At multiple sites in two regulated (Murrumbidgee, Tumut) and three unregulated (Goobarragandra, Goodradigbee, Micalong) rivers (south‐east Australia), we surveyed densities of ER and egg masses of five species of caddisflies (family Hydrobiosidae) seasonally over 3 years (2019–2021). Samples of adults also were collected during two seasons using light traps. High flows in both regulated rivers submerged all rocks during spring and summer and low‐flow releases stranded rocks above the waterline at all (Murrumbidgee River) or most (Tumut River) sites during autumn and winter. No ER or egg masses were observed on any date in the Murrumbidgee River, despite relatively large catches of adults. On the Tumut River, low densities of ER and egg masses were twice observed at one site, during seasons (winter, autumn) when oviposition was low in the unregulated rivers. In unregulated rivers, ER and egg masses (five species, four genera) were present at all sites but with lower densities in winter than in other seasons. During peak oviposition periods, densities of egg masses per site were not strongly related to densities of ER. In summer 2019, ER in two unregulated rivers were blanketed by sheets of algae and sediment that appeared to prevent oviposition because no egg masses were observed at this time. In regulated rivers, aseasonal flows precluded egg‐laying by submerging (summer, autumn) or stranding (winter, spring) all or most ER. In contrast, ER were available all year in the unregulated rivers and egg‐laying occurred all year, except when ER were blanketed by algae and sediment. Within seasons, local densities of egg masses may be limited by numbers of gravid females, rather than numbers of ER, which differs from previous research. Identifying impediments to reproduction is critical to understanding variability in population numbers in natural and altered systems. Our observations of oviposition failure downstream of dams present a new hypothesis for why some insect species are absent from channels where flows are regulated for irrigation. Blankets of algae may similarly preclude reproduction in rivers with low‐flow conditions, but this remains untested.

Parasitoids and pathogens in a collapsingLymantria dispar(Lepidoptera: Erebidae) population in Lower Austria

AbstractA local population outbreak of the spongy moth,Lymantria disparL. (Lepidoptera: Erebidae), in Lower Austria, resulted in the defoliation of an oak forest in 2018 and 2019. In the study year 2020, the population density was still high but was expected to decline. In the present work, the role of parasitoids and pathogens in the collapse of the population was investigated. In total, 20 egg masses, 680 larvae and 12 pupae ofL. disparwere collected in the field from April to July 2020 and reared until the emergence of adult moths or death. Causes of mortality were determined based on emerging parasitoids and on microscope inspection of non‐parasitized cadavers. Stage‐specific mortality rates were calculated for eggs, larval stages (L1–L6) and pupae. Seven parasitoid species and three pathogens were responsible for the premature death of spongy moths. The egg parasitoidAnastatus disparis(Hymenoptera: Eupelmidae) emerged from 19% of all eggs. Larval parasitoids caused stage‐specific mortality rates from 15% to 61%. The dominant parasitoid of young and intermediate instars was the solitary waspGlyptapanteles porthetriae(Hymenoptera: Braconidae). Mature larvae were mainly parasitized by the parasitic fliesBlepharipa pratensis(Diptera: Tachinidae) andParasetigena silvestris(Diptera: Tachinidae). Pathogens caused stage‐specific mortality rates from 11% to 41%. The nuclear polyhedrosis virus (LdNPV; Lefavirales: Baculoviridae) was the dominant pathogen in all instars. The introduced fungusEntomophaga maimaiga(Entomophthorales: Entomopthoraceae)—detected for the first time in Austria in 2019—caused low mortality rates in older larvae. Starting from high egg mass densities in spring, the spongy moth population declined to negligible levels until summer.

Metabarcoding of canopy arthropods reveals negative impacts of forestry insecticides on community structure across multiple taxa

Abstract Insecticides used to combat outbreaks of forest defoliators can adversely affect non‐target arthropods. Forestry insecticides typically suppress Lepidoptera larvae which are the cornerstone of the canopy community of deciduous oak forests. The abrupt removal of this dominant component of the food web could have far‐reaching implications for forest ecosystems, yet it is rarely investigated in practice owing to several methodological shortcomings. The taxonomic impediment and the biased nature of arthropod sampling techniques particularly impede the assessment of insecticide impacts on diverse communities. To tackle this issue, we propose an experimental approach combining sampling by pyrethrum knockdown and species determination via DNA metabarcoding, using community subsampling to derive estimates of species abundances. We applied this protocol to investigate the short‐term effects of the insecticides diflubenzuron (DFB) and Bacillus thuringiensis var. kurstaki (BTK) on canopy‐dwelling arthropod communities in German oak woodlands. Our approach allowed us to detect most of the diversity and integrate species abundances in our analyses. By classifying arthropod species into assemblages based on their expected sensitivity rather than coarse taxonomic groupings, we could unveil substantial effects of DFB across multiple taxa 5 weeks after application. Although strong effects on single species appear related to direct toxicity, substantial impacts of DFB on parasitoids and xylophagous beetles suggest that anti‐defoliator treatments can have previously unsuspected indirect effects on some components of forest arthropod communities. The impacts of BTK on community structure were consistent with that of DFB though much weaker. Synthesis and applications. Comparing diversity patterns in the arthropod communities of sprayed and unsprayed oak canopies, our results show that selective insecticides can alter species diversity in presumably non‐sensitive taxa. Even though the ecological significance of these impacts has yet to be assessed in an operational setting, their existence calls for increased regulatory scrutiny on indirect effects. As community approaches become more attainable with the rapid development of DNA metabarcoding, we suggest the inclusion of community‐level end points as regulatory requirements for the approval of forest‐use insecticides.

Development of conventional sampling plans for egg masses and nymphs of citrus blackfly Aleurocanthus woglumi Ashby (Hemiptera: Aleyrodidae)

The citrus blackfly Aleurocanthus woglumi Ashby (Hemiptera: Aleyrodidae) is an important pest in orange crops. A conventional sampling plan is the first step in generating integrated pest management programs. However, there are currently no sampling plans defined for A. woglumi. Therefore, the aim of this study was to develop conventional sampling plans for egg masses and nymphs of A. woglumi in orange orchards. For that purpose, the densities of egg masses and nymphs were evaluated in commercial orchards to determine the best sampling unit, the required number of samples, and the time and cost of the sampling plan. The third most basal leaf of the branch was the best sampling unit for egg masses, while the second most basal leaf was the ideal site for sampling A. woglumi nymphs. The sampling plans developed are composed of 54 samples for egg masses and 35 samples for nymphs. These plans do not require long sampling times (less than 1 h) and cost less than US$ 3. Thus, the sampling plans developed allow quick and efficient decision-making.

Foothill yellow-legged frog breeding biology in a semiregulated river, Humboldt County, CA

River-breeding foothill yellow-legged frogs (Rana boylii) are endemic to California and Oregon. Across this wide geographic range, many populations have declined due habitat loss, non-native competitors and predators (e.g., American bullfrogs [Lithobates catesbeianus], Centrarchid fish), and disrupted water flow due to dams. Even when flow conditions are not extensively regulated, managers still require basic and region-specific information about the breeding biology of this species to prevent further decline. To document spatiotemporal dynamics of reproductive output during drought and high flow years, we surveyed a 13.5 km reach of the lower Mad River, Humboldt County, CA approximately 70 km downstream of Matthews Dam. We found relatively high densities of egg masses (39 to 59 masses / km). Egg masses were generally laid on small cobbles (mean ±SE diameter = 11 ± 0.24 cm) at depths between 0 and 20 cm, and 95% of egg masses were laid within 6 m of the wetted edge. Egg masses were disproportionately found in the tailouts of fast runs and glides, and found less often than expected in side arms, runs, and riffles than would be expected by chance. Breeding timing appeared to be more related to rapid decreases in stream flow variance than air temperature. Taken with previous information about the species, our results suggest that R. boylii rely on multiple cues to initiate breeding. Our results can be used to help inform breeding timing and habitat use by R. boylii breeding under natural flow regimes in Northern California. Our recommendations for future research include further investigating upland habitat use by post-metamorphic life stages factors that influence breeding site selection.

Features of forecasting of leaf-eating insects distribution in the forests of Zhytomyr Polissia

Foliage damage by leaf-eating insects during mass reproduction causes deterioration of the sanitary state of forest and a decrease in its increment. Timely detection of pest foci allows reducing the cost of their elimination and preventing negative consequences for stands. The purpose of this study was to identify the species composition of leaf-eating insects on the territory of State Enterprise Zhytomyrske Forestry and the subcompartments with the greatest threat of foci development of the dominant species – Tortrix viridana, taking into account forest site conditions and stand structure. During the feeding period, the species composition of leaf-eating insects was identified, and after the end of oviposition, the density of Tortrix viridana egg masses was assessed on tree branches selected in subcompartments with different forest site conditions, age, the relative crop density, and proportion of oak in the stand composition. The database of forest inventory (Ukrderzhlisproekt) and the score assessment of the preferences of stands for foci development were used. Eleven species of leaf-eating insects from order Lepidoptera were identified, including 9 species from the family Tortricidae, of which Tortrix viridana dominated. The highest egg mass density of this pest was assessed in fresh dubrava conditions (D2 ), in pure oak plantations aged 40-80 years with a low relative crop density. The average score of stand preference for Tortrix viridana was assessed by forest site conditions (2.93 and 2.88 for seed plantations and coppice forest, respectively), age (3.65), the relative density of stocking (2.6), and oak participation (3.3) in the State Enterprise Zhytomyrske Forestry. The list of subcompartments with a very high and high threat of an outbreak of Tortrix viridana has been established. A survey in these subcompartments would allow timely detection of pest population increase and prevent its development

Nondestructive Sampling for Spotted Lanternfly (Hemiptera: Fulgoridae) Egg Masses in Woodlands Based on Fixed-Radius Plots.

A nondestructive sampling method was developed for Lycorma delicatula egg masses based on fixed-radius plot (100 m2) in 2020. All trees >1.0 cm DBH (diameter at breast height, 1.37 m in height) on each plot were visually inspected from the ground 4 m from the tree with binoculars. Egg masses found on trees were separated into six within-tree positions (lower trunk, middle trunk, upper trunk, first branch, second branch, above second branch) and recorded by cardinal directions, whereas those laid on shrubs/vines and stones were recorded without such separation. In total, 146 trees were inventoried at 28 plots over seven study sites (four plots per site). Egg masses were found on 19 tree species plus summer grape (Vitis aestivalis) and stone. Of the 421 total egg masses recorded, 31.1% were on Norway maple (Acer platanoides), followed by tree-of-heaven (Ailanthus altissima; 14.7%), black birch (Betula lenta; 12.6%), tuliptree (Liriodendron tulipifera; 11.9%), and American beech (Fagus grandifolia; 10.2%). Egg mass density per tree was positively correlated with tree diameter, and egg mass density per plot was positively correlated with plot basal area. Egg mass density after conversion ranged from 600 to 3,930 eggs masses/ha with no significant difference among study sites. Cardinal direction had no effect; however, significantly more egg masses were found on the first branches and upper trunks than other within-tree positions. Overall, branches were better than trunks in predicting egg mass number for the tree. The role of distance and late season adult aggregation on oviposition substrate selection are discussed.

Biopesticide and Parasitoid Effects on Megacopta cribraria (Hemiptera: Plataspidae) Life Stage Density and Egg Parasitism in Soybean

Biopesticide and Parasitoid Effects on <i>Megacopta cribraria</i> (Hemiptera: Plataspidae) Life Stage Density and Egg Parasitism in Soybean

Oviposition Substrate Selection, Egg Mass Characteristics, Host Preference, and Life History of the Spotted Lanternfly (Hemiptera: Fulgoridae) in North America.

Oviposition substrate selection, egg mass characteristics, host preference, and life history of Lycorma delicatula (White) (Hemiptera: Fulgoridae) were studied in Pennsylvania between 2016 and 2017. Twenty-four substrate types (trees, shrubs, and nonliving materials) were selected by females for oviposition. Tree-of-heaven, black cherry, black birch, and sweet cherry were favored at 62.5% of the types and accounted for 68.5% of the egg masses based on survey results 200 cm above ground. Egg mass density ranged between 0.2 and 75.2 egg masses/m2 with no significant difference among substrate types. Egg mass size ranged between 0 and 192 eggs/egg mass, with 91.8% containing <50 eggs. Significantly larger egg masses were found on sweet and black cherry compared with tree-of-heaven, with significantly higher hatch success on black locust. Eggs hatched between May 2 and June 5 and peaked on 18 May 2017. Tree-of-heaven and summer grape were preferred by nymphs and adults, while multiflora rose and black walnut were favored by the first, second, and the fourth instar nymphs, respectively. The first, second, third, fourth instars and adults lasted for 62 (2 May-3 July), 42 (8 June-20 July), 35 (26 June-31 July), 39 (10 July-18 Aug.), and 114 (24 July-15 Nov.) days, with peaks on 25 May, 22 June, 6 July, 31 July, and 22 Aug., respectively. Adult feed for 2 months before laying eggs in early October. Cumulative degree-days were 0-325, 153-652, 340-881, 567-1,020, 738-1,227, and 942-1,795 for the egg, first, second, third, fourth instar, and adult stage, respectively. Oviposition strategies and development patterns were discussed.

Reproductive characteristics of male and female Japanese quails (Coturnix coturnix japonica) fed diets with different levels of crude protein during the growth and production phases

The objective of this study was to evaluate the growth and reproductive performance of male and female Japanese quails fed diets with different levels of crude protein (CP) during the growth (1 to 35 days of age) and production (36 to 96 days) phases. Three hundred one-day-old males, housed in 30 cages (10 birds/cage), and 360 one-day-old females, housed in 10 cages (36 birds/cage), were used in the present study; they were housed as described above until the birds were 35 days of age (growth phase). The treatments tested during this phase included five different levels of dietary CP (18, 20, 22, 24 and 26%), which were reduced by four percentage units for the production phase. During the production phase, the birds were randomly redistributed into 40 laying cages, each with 9 females and 3 males. During all experimental periods, every 3 days, 12 birds of each sex from each CP level were individually weighed, until the birds reached 60 days of age, to estimate the growth parameters using the Gompertz curve. For the production variables, a completely randomized design with five treatments (dietary CP levels) and eight replicates (cages) was used. For the males, there was a linear increase (P<0.05) in the growth maturity rate and a linear reduction (P<0.05) in the maximum growth interval up to the level of 22% CP. A higher weight at growth maturity (P<0.05) was obtained with 18% CP. There was no effect (P>0.05) of CP levels on the semen quality and fertility rate. In females, the highest CP levels (24 and 26%) reduced (P<0.05) the maturity rate and increased (P<0.05) the age of maximum weight gain. The 24% level of CP increased (P<0.05) the weight at maturity, whereas 26% CP reduced (P<0.01) the feed conversion, and the age at first egg, and at 50 and 95% laying; the same CP level increased (P<0.01) the egg mass and egg density. The highest intensity of laying at 47 days of age was obtained (P<0.01) with either 24 or 26% CP. Egg weight was only reduced (P<0.01) when 18% CP was used. The internal quality of the egg was not influenced (P>0.05) by the dietary CP levels. Dietary CP levels influence the overall growth and development of both male and female quails; however, reproductive traits are only affected in females. For both sexes, 26 and 22% CP are recommended during the growth production phases, respectively.

Biology and distribution of Agrilus macer LeConte (Coleoptera: Buprestidae), a species associated with sugarberry (Celtis laevigata Willd.) mortality in the southeastern USA

Agrilus macer is attacking sugarberry trees in the southeastern USA, a region from which few specimens have been previously collected. Despite attacking at high densities, this species appears to be a secondary pest, and there is no evidence it carries harmful fungal pathogens. Because the genus Agrilus Curtis includes significant forest pests, the association of a poorly known species, Agrilus macer LeConte, with unexplained sugarberry (Celtis laevigata Willd.) mortality in the southeastern USA is a cause for alarm. This study sought to investigate the distribution and biology of A. macer and determine whether the species is a primary cause of observed tree mortality. Through a series of studies and literature searches, we documented aspects of A. macer biology and distribution while focusing on egg-laying behavior and searching for fungal pathogens associated with oviposition sites. A. macer appears to be widely distributed throughout the southern USA, but most records are from Texas and Louisiana. Egg mass densities up to 1.2 masses per 10 cm2 (equivalent to ~ 1.9 eggs per cm2) were observed on trunks, branches, and exposed roots of dying C. laevigata trees in our study area, with an average of 16 eggs per mass. Fungi isolated from discolored sapwood around larval galleries did not cause defoliation, dieback, or mortality of sugarberry in inoculation trials. Our findings suggest that A. macer is a secondary pest on sugarberry and does not transmit harmful fungal pathogens.

Population ecology of the snail Melampus bidentatus in changing salt marsh landscapes

We studied the population ecology of the snail Melampus bidentatus in relation to patch composition and landscape structure across several salt marsh systems in Connecticut, USA. These marshes have changed significantly over the past 40–50 years including loss of total area, increased areas of short Spartina alterniflora, and decreased areas and fragmentation of Spartina patens. These changes are consistent with tidal inundation patterns that indicate frequent flooding of high marsh areas. Melampus bidentatus densities were highly variable, both among different salt marsh systems and locations within specific marshes, but were generally similar among short Sp. alterniflora and Sp. patens patches within locations. Densities were lowest where the marsh was regularly inundated at high tide and only remnant Sp. patens patches remained. Almost no snails were found in bare patches. Areas that had large Sp. patens patches adjacent to short Sp. alterniflora supported the highest M. bidentatus densities. Population size-structure varied significantly among patch types, with higher proportions of large individuals in short Sp. alterniflora and hummocked Sp. patens patches than in large and remnant Sp. patens patches. This was likely due to size-selective predation and/or higher snail growth rates due to better food resource conditions in short Sp. alterniflora patches. Egg mass densities and the number of eggs per egg mass were highest in short Sp. alterniflora. Our results indicate that M. bidentatus is resilient to the level and patterns of salt marsh change evident at our study sites. Indeed, snail densities were significantly higher than reported in other field studies, suggesting that increased patch areas of short Sp. alterniflora and associated environmental conditions at our study sites may provide more favorable habitats than previously when marshes were dominated by extensive Sp. patens meadows. However, there may be threshold conditions that could overwhelm the ability of M. bidentatus to maintain itself within salt marsh systems where changes in hydrology, sedimentation and other factors lead to increased numbers of bare patches and ponds and loss of short Sp. alterniflora and Sp. patens. Studies of the responses of resident and transient fauna to salt marsh change are critically needed in order to better understand the implications for salt marsh ecosystem dynamics and services.

Effect of strip-intercropping potato and annual alfalfa on populations of Leptinotarsa decemlineata Say and its predators

ABSTRACTIntercropping systems are practiced to reducing pest density, enhancing predator's diversity and stabling crop yield. We evaluated the effect of strip-intercropping potato and annual alfalfa on populations of Leptinotarsa decemlineata Say, predator's biodiversity and potato yield over two seasons (2014 and 2015). Our results revealed that the densities of egg masses, eggs, larvae and adults of Colorado potato beetle (CPB) were significantly lower in intercrops than in monoculture. The main CPB predators recorded on potato plants (ladybirds and the green lacewing) showed a significant increase in the density at each of the three intercrops than in monoculture. The percentage of dry tubers weight loss was 40.9%–42.6% in monoculture, 16.3%–18.7% in 6P: 2A and <10% in 2P: 2A and 4P: 2A in two studied years. Our results suggest that strip-intercropping potato with annual alfalfa, particularly in 2P: 2A and 4P: 2A patterns may be an effective way in integrated management of CPB for reducing pest density, enhancing the presence of predators in potato fields and improving potato yield.

EFFECT OF CERTAIN WEATHER FACTORS AND SOME NATURAL ENEMIES ON THE POPULATION DENSITY OF THE BOLLWORMS AND COTTON LEAFWORM AT KAFR EL-SHEIKH GOVERNORATE, EGYPT

Experiments were carried out at the Farm of Sakha Agricultural Research Station Kafr El-Sheikh Governorate, during two successive seasons, 2014 and 2015 to evaluate the effect of certain weather factors (temperature, relative humidity and wind speed), and some natural enemies (six insect predators were recorded, Coccinella undecimpunctata L., Scymnus interruptus Goez., Paederus alfierii Koch, Syrphus spp., Orius spp. and Chrysoperlla carnea (Steph.))on the population density of the bollworms larvae (pink bollworm, Pectinophora gossypiella (Saund.) and spiny bollworm, Earias insulana (Boisd.) and the egg-masses of the cotton leafworm, Spodoptera littoralis (Boisd.). The initial occurrence of the pink bollworm larvae on cotton bolls was recorded in the last week of July (26th) during the first season and week early (18th of July) during the second season and exhibited four peaks of population density in every season. Numbers of larvae were highly significant and negative correlated with changes of the temperature (-0.752** and -0.798**) of both seasons, respectively. While, the correlation between numbers of larvae and changes of the relative humidity was insignificantly and negatively (-0.103 and -0.140) in both seasons, respectively. But, the wind speed influenced on the larval occurrence were significant and negative (-0.472*) during the first season, and insignificant and positive (0.020) during the second season. So, the correlation were positive and significant (0.495* and 0.480*) between the density of larvae of pink bollworm and the insect predators during the two seasons, respectively. While, the initial occurrence of the spiny bollworm larvae on cotton bolls was recorded in the 9th and 15th of August during the two successive seasons, respectively, and exhibited three peaks of population density in every season, number of larvae of this insect was highly significant and negative correlated (-0.631** and -0.690**) with changes of the temperature during both seasons, respectively. While, the relationship between the relative humidity and number of the spiny bollworm larvae was negative and insignificant (-0.177) during the first season, but, it was positive and insignificant (0.083) during the second season, while, the wind speed influenced was significant and negative (-0.408*) during the first season, and it was insignificant and negative (-0.173) during the second season, on the larval occurrence of this insect. So, the correlation were positive and significant (0.542* and 0.585*) between density of the spiny bollworm and the insect predators during the two seasons, respectively. The cotton leaf worm egg-masses exhibited three peaks of population density in every season, the effect of temperature on the population density of the cotton leaf worm egg-masses was significant and positive (0.459*) during the first season, and insignificant and positive (0.212) during the second season, while, the effect of the relative humidity on egg-masses of this insect was insignificant and positive (0.347) during the first season, and negative (-0.134) during the second season. So, the effect of wind speed on egg-masses was insignificant and negative (-0.162) during the first season, and positive (0.263) during the second season. While, the correlation were highly significant and positive (0.631** and 0.620**) between the population density of cotton leaf worm egg-masses and the insect predators during the two successive seasons.

Replacement of a dominant viral pathogen by a fungal pathogen does not alter the collapse of a regional forest insect outbreak.

Natural enemies and environmental factors likely both influence the population cycles of many forest-defoliating insect species. Previous work suggests precipitation influences the spatiotemporal patterns of gypsy moth outbreaks in North America, and it has been hypothesized that precipitation could act indirectly through effects on pathogens. We investigated the potential role of climatic and environmental factors in driving pathogen epizootics and parasitism at 57 sites over an area of ≈72,300 km(2) in four US mid-Atlantic states during the final year (2009) of a gypsy moth outbreak. Prior work has largely reported that the Lymantria dispar nucleopolyhedrovirus (LdNPV) was the principal mortality agent responsible for regional collapses of gypsy moth outbreaks. However, in the gypsy moth outbreak-prone US mid-Atlantic region, the fungal pathogen Entomophaga maimaiga has replaced the virus as the dominant source of mortality in dense host populations. The severity of the gypsy moth population crash, measured as the decline in egg mass densities from 2009 to 2010, tended to increase with the prevalence of E. maimaiga and larval parasitoids, but not LdNPV. A significantly negative spatial association was detected between rates of fungal mortality and parasitism, potentially indicating displacement of parasitoids by E. maimaiga. Fungal, viral, and parasitoid mortality agents differed in their associations with local abiotic and biotic conditions, but precipitation significantly influenced both fungal and viral prevalence. This study provides the first spatially robust evidence of the dominance of E. maimaiga during the collapse of a gypsy moth outbreak and highlights the important role played by microclimatic conditions.

Bahasa Indonesia

Asian corn borer, Ostrinia furnacalis Guenée, is known as an important pest of maize, Zea mays L., in both whorl and reproductive stages. Management decisions based on egg-mass density is useful because decision is made before damage occurs. Observation on O. furnacalis egg-mass distribution in maize-field was carried out in Agricultural Training, Research, and Development Station (ATRD) UGM, Yogyakarta. The number of egg-masses laid on each plant surface in maize-field was sampled in reproductive stage of corn at 52 – 58 days after planting. The spatial dispersion was analyzed using the ratio variance-to-mean (σ2/μ = Iδ), Morista’s Index (Iγ), and the negative binomial parameter (κ-value). The results showed that horizontal and vertical distributions were aggregated distributions (σ2 &gt; μ or σ2/μ &gt; 1). In line with the increasing age of plant, the degree of clustering or aggregation likely tended to decline (the κ-value increased, Morisita index decreased) indicating the possible departure from aggregation to randomness (Poison distribution) due to the heterogeneity of the environment, such as microclimate, preferred parts of the plants, and occurrence of natural enemies. The results concluded that the horizontal and vertical distributions of egg-masses of O. furnacalis on corn in generative phase were clustered with the degree of clustering tended to decrease by the increase of age of corn. These findings provide the bases for further study on the ecology and biology of O. furnacalis for management decision-making process.

Seasonal decline in plant defence is associated with relaxed offensive oviposition behaviour in the viburnum leaf beetle Pyrrhalta viburni

1. Plant defence of Viburnum shrubs against oviposition by its specialist herbivore, the viburnum leaf beetle [VLB Pyrrhalta viburni(Paykull)], involves an egg‐crushing wound response in twigs. Although the response is variable among Viburnum species, it can have a strong impact on egg survivorship. Beetles typically aggregate egg masses with conspecifics along infested twigs, forming clusters that can overwhelm the twig response. It was investigated whether twig responses and beetle oviposition behaviour vary seasonally.2. In a field experiment, twig defences decreased towards the end of the VLB oviposition period: wound response of the North American Viburnum dentatum L. and the European V. opulus L. was reduced by 100% and 54%, respectively, in September compared with the July to August period.3. Oviposition trials demonstrated a corresponding behavioural change: VLB females displayed aggregative oviposition in August, but not in September.4. Further tests revealed that late‐season VLB females reverted to aggregative oviposition after being kept on uninfested twigs, whereas females kept on heavily infested twigs did not. This behavioural change suggests that relaxation of aggregative oviposition originates from cues associated with high densities of egg masses.5. Relaxation of aggregative oviposition may be adaptive (and beneficial for invasion) on shrubs with low levels of defences by reducing intra‐specific competition.

Interactions between megaherbivores and microherbivores: elephant browsing reduces host plant quality for caterpillars

Direct effects of herbivory, and indirect effects through induced responses to herbivory, can both influence the susceptibility of plants to subsequent attacks by herbivores. There has, however, been very little research (if any) to investigate how the large‐scale effects of browsing by megaherbivores (&gt;1000 kg body mass) on woody plants might influence the subsequent use of those plants by phytophagous insects. We conducted a field study in Kruger National Park, South Africa, to investigate whether browsing by elephants (Loxodonta africana) on mopane trees (Colophospermum mopane) had any influence on the subsequent selection of those trees by ovipositing mopane moths (Imbrasia belina). Our results showed that, after controlling for differences in canopy volume, the density of egg masses was almost halved in mopane woodlands recovering from severe elephant browsing in the previous season. This is despite the regrowth on heavily browsed trees having lower tannin:protein ratios and longer shoots. Our suggested explanation is that large monophagous caterpillars can only feed in the canopies of the trees in which they hatch and so the quantity of food in each canopy is more important than its quality. There are implications for the sustainable harvesting of mopane caterpillars, which represent an important food resource for rural communities in southern Africa. Future avenues for research include patch selection by large herbivores in response to local nutrient enrichment by frass deposited during caterpillar outbreaks.

Improving Performance of Laying Hens in Hot Regions by Desert Coolers

The efficacy of desert coolers to improve thermal responses and performance of laying hens under heat stress conditions was investigated. Two identical layers houses of deep litter system providing 1600 cm /hen were used. The first house was equipped with a desert cooler while the other was left without 2 control on air temperature (the control treatment). At 32 week of age, 100 hens from 2 commercial lines (Shaver and Hyline) were housed in each house. The average air temperature in the cooled house was 5.4°C lower (p<0.05) than in the control house. Drinking water temperature in the cooled house was 3.4°C lower (p<0.05) than that in the control house. Rectal temperatures of hens in the cooled house were significantly lower than that of the control. Hens housed in the cooled house showed a significan t improvement in feed conversion, significant increase in egg production, egg weight, egg mass, eggshell thickness and eggshell density and significant decrease in unmarketable eggs compared to the control hens. Hyline showed higher (p<0.05) egg production than Shaver when ambient temperature was controlled by the desert cooler. Line had no significant effects on egg weight and egg mass. The net income per hen in the cooled house was US $ 6.80/hen compared to US $ 4.20/hen for the controls, which represented a net gain of US $ 2.60/hen more for the desert cooled hens. Based on these results, the use of desert cooler under hot conditions is efficient and economically feasible.