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Egg Parasitism (egg + parasitism)

Distribution by Scientific Domains

Life Sciences	77%

Selected Abstracts

Influence of non-crop plants on stink bug (Hemiptera: Pentatomidae) and natural enemy abundance in tomatoes

JOURNAL OF APPLIED ENTOMOLOGY, Issue 8 2010
C. G. Pease
Abstract We investigated the effects of weed hosts on stink bug density and damage (Euschistus conspersus Uhler and Thyanta pallidovirens Stal), and a nectar bearing plant on natural enemies of stink bugs in the Sacramento Valley of California. Stink bug density and fruit damage were evaluated in processing tomatoes adjacent to weedy and cultivated borders. The density of E. conspersus was significantly greater in tomatoes adjacent to weedy borders in July but not during August/September. Thyanta pallidovirens was less abundant overall (19%), but was found in significantly greater densities adjacent to cultivated borders in July but not in August/September. Mean percent fruit damage by stink bugs was greater adjacent to the weedy border than the cultivated border, but this difference was not significant. Stink bug egg parasitism and generalist predator density were evaluated in fresh market tomatoes adjacent to a sweet alyssum (Lobularia maritima L.) border and an unplanted control border at three sites. Egg parasitism was significantly greater in the alyssum treatment for the 9,12 September sampling period. Jalysus wickhami VanDuzee (Hemiptera: Berytidae) density was significantly greater in the alyssum treatment in mid-June. No other significant differences in predator populations were detected. Results of these two studies show that habitat manipulations have the potential to reduce densities of E. conspersus in tomato, the first step in developing a farmscape management plan for stink bug control. [source]

Tritrophic interactions and trade-offs in herbivore fecundity on hybridising host plants

ECOLOGICAL ENTOMOLOGY, Issue 3 2004
Maria V. Cattell
Abstract., 1. Interspecific plant hybridisation can have important evolutionary consequences for hybridising plants and for the organisms that they interact with on multiple trophic levels. In this study the effects of plant hybridisation on the abundance of herbivores and on the levels of herbivore parasitism were investigated. 2. Borrichia frutescens, B. arborescens, and their hybrid (B. × cubana) were censused for Asphondylia borrichiae galls and Pissonotus quadripustulatus plant hoppers in the Florida Keys. Levels of egg parasitism were determined by dissecting parental and hybrid stems and galls for herbivore and parasite eggs and larvae. Stem toughness and gall size are plant-mediated modes of protection from parasitism and these were also measured. For gall midges, fly size was measured as an estimate of fecundity. 3. Field censuses indicated that herbivore abundances varied on hybrid hosts relative to parent plant species and that the different herbivore species exhibited different patterns of abundance. Asphondylia borrichiae gall numbers followed the additive pattern of abundance while P. quadripustulatus numbers most closely resembled the dominance pattern. 4. Parasitism of P. quadripustulatus eggs was high on B. frutescens and the hybrids, and low on B. arborescens, which also had significantly tougher stems. Asphondylia borrichiae suffered the highest levels of parasitism on B. frutescens, the host plant which produced the smallest galls. On B. arborescens, which produced the largest galls, levels of A. borrichiae parasitism were lowest. Both parasitism and gall size were intermediate on the hybrid plants. Galls on B. arborescens and hybrid plants produced significantly smaller flies then those from B. frutescens suggesting that, when selecting hosts from among parent species and hybrids, gall flies may face a trade-off between escape from natural enemies and maximising fecundity. [source]

Influence of non-crop plants on stink bug (Hemiptera: Pentatomidae) and natural enemy abundance in tomatoes

Parasitism of cotton leafworm Alabama argillacea eggs by Trichogramma pretiosum in commercial cotton fields

JOURNAL OF APPLIED ENTOMOLOGY, Issue 7 2010
C. S. Bastos
Abstract Release of natural enemies in commercial fields is challenging and has been inconsistent in the results achieved. This work discusses the augmentative releases of Trichogramma pretiosum to control the cotton leafworm (CLW) Alabama argillacea and also examines the parasitoid,host interaction under grower field conditions. The treatments consisted of fields with and without releases of T. pretiosum set up in Primavera do Leste and Campo Verde Counties, MT, Brazil, during three different seasons (2003 and 2004 dry and 2004 regular summer seasons). Trichogramma wasps were weekly released in the treated fields throughout the entire sampling period (14,15 week period) at a rate of 100 000 wasps per hectare. One-way repeated measures analysis of variance was performed for the number of parasitized eggs, followed by a meta-analysis procedure to determine the contribution of T. pretiosum release on overall parasitism. In addition, regression analysis was conducted with each season's data sets to study the relationship of the host density and parasitism response by T. pretiosum. The overall results of Trichogramma augmentative releases did not result in significant increase of CLW egg parasitism beyond the natural parasitism in the areas studied. However, based on Cohen's d effect sizes from the meta-analysis, the parasitism rate was greater in fields under T. pretiosum releases during four out of 15 weeks surveyed. The parasitism of CLW eggs by T. pretiosum exhibited host density-dependence only in one out of three seasons surveyed. These findings are encouraging as they are evidence that T. pretiosum is able to maintain a considerable level of parasitism under commercial field conditions, highlighting their potential value in large-scale commercial areas of cotton as previously found at the small and diverse farming scale. Future studies should address the potential of early-season, low density releases of the parasitoid. [source]

Laboratory and field studies on the integrated pest management of Helicoverpa armigera (Hübner) in cotton, based on pheromone trap catch threshold level

JOURNAL OF APPLIED ENTOMOLOGY, Issue 5-6 2000
G. V. P. Reddy
Results revealed that egg parasitism in the laboratory by Trichogramma chilonis was 75.6%. Among the insecticides tested against T. chilonis and the predator Chrysoperla carnea, nimbecidine (neem product) and dipel resulted in zero mortality, with only a low level of mortality by dimethoate, cypermethrin, fenvalerate, alphamethrin and monocrotophos. Combinations of nimbecidine 2% + NPV at 250 larval equivalents (LE)/ha and dipel 8 l + NPV @250 LE/ha were the most effective treatments against H. armigera. The integrated pest management components (T. chilonis, C. carnea, NPV, nimbecidine, dipel and synthetic chemicals) were imposed at different intervals on the basis of pheromone trap threshold level (7 moths/trap per night) on a consolidated block of 40 ha cotton (MCU-1) fields at two locations, Shankarabanda and Korlagundi. The results demonstrated a significant superiority of the IPM strategy in terms of both cost versus benefit and environmental safety over that used in the farmer's fields where only conventional control methods were followed. [source]

Influence of native ants on arthropod communities in a vineyard

AGRICULTURAL AND FOREST ENTOMOLOGY, Issue 3 2010
Chee-Seng Chong
1Ants can have a range of effects on arthropods in crops, including suppressing herbivores such as caterpillars. However, ants can also increase hemipteran densities while reducing natural enemy numbers. In vineyard ecosystem, the effects of native ants and their interactions with other arthropods are poorly understood. 2An ant-exclusion experiment was designed to test the impact of native ants on both canopy and ground arthropods concurrently. The potential influence of ants on predation and parasitism of light brown apple moth (LBAM) eggs, a grape pest, was also examined. Adult grapevine scale insects and earwigs under bark were counted after a season of ant-exclusion. 3Among 23 ground ant species collected, six were found to forage in the canopy, with two Iridomyrmex species being the most commonly encountered. 4There was no difference in the abundance of most arthropod orders and feeding groups between ant-excluded and control vines, although ground spiders were more abundant under ant-excluded vines, despite increased ground ant foraging pressure. LBAM egg parasitism and predation were low and probably affected by weather and other arthropods. Ant exclusion did not reduce survival of scale insects, although the distribution and abundance of scale insects were negatively associated with earwigs. 5In conclusion, native ants did not consistently suppress arthropod assemblages, including natural enemies, and they did not promote the survival of scale insects. Interactions among native ant species within a vineyard might minimize their effects on other arthropods, although this needs further study. [source]

Geographic variation in winter freezing susceptibility in the eggs of the European pine sawfly (Neodiprion sertifer)

AGRICULTURAL AND FOREST ENTOMOLOGY, Issue 2 2005
T. O. Veteli
Abstract 1,The European pine sawfly, Neodiprion sertifer (Geoffroy) (Hymenoptera, Diprionidae), frequently defoliates Scots pine (Pinus sylvestris L.) forests in northern Europe. It overwinters as an egg. It has been proposed that the high egg mortality caused by low winter temperatures limits the occurrence of outbreaks to the southern part of Fennoscandia. 2,In this study, variation in freezing avoidance by egg supercooling between four Finnish populations (originating between latitudes 60°N and 69°N) of N. sertifer was tested by differential thermal analysis. Offspring of 20 females within each population were selected for the study. The freezing avoidance of parasitized eggs was also examined. 3,The northernmost Inari population was found to be the cold hardiest, and the southernmost (Hanko) was the least hardy population. The within-population variation between females was greatest in the population from Inari, and the next greatest in the one from Hanko. The inland populations in Eastern Finland had the smallest within-population variation in freezing avoidance. 4,The high variation in freezing avoidance of eggs will enable N. sertifer to adapt to the predicted climate change and to spread its distribution northwards. This may also change the risk for outbreaks in this area. Parasitized eggs froze at higher temperature than healthy eggs. This observation indicates that N. sertifer may experience reduced egg parasitism in certain winter climate conditions. [source]

Differences in egg parasitism of Chrysophtharta agricola (Chapuis) (Coleoptera: Chrysomelidae) by Enoggera nassaui Girault (Hymenoptera: Pteromalidae) in relation to host and parasitoid origin

AUSTRALIAN JOURNAL OF ENTOMOLOGY, Issue 3 2002
Helen F Nahrung
Abstract The first instances of egg parasitism of Chrysophtharta agricola, a pest of eucalypt plantations, are recorded. Enoggera nassaui was found parasitising C. agricola egg batches in Tasmania, the Australian Capital Territory (ACT), New South Wales and Victoria: this is the first record of this parasitoid species from Victoria. One instance of Neopolycystus sp. parasitising C. agricola eggs in Victoria was also recorded. Parasitism of egg batches by E. nassaui ranged from 0 to 55% between five geographical populations collected in mainland Australia (n = 45), and from 0 to 2% between two populations collected in Tasmania (n = 300). For mainland sites at which parasitism was recorded, parasitism rates within sites differed significantly from either population in Tasmania. Reciprocal exposure experiments using one Tasmanian (Florentine Valley) and one parasitised mainland (Picadilly Circus, ACT) population were conducted in the laboratory to examine whether these different parasitism rates were attributable to egg or parasitoid origin. Parasitoids from the ACT parasitised C. agricola eggs of both origins more successfully than parasitoids from Tasmania, with up to 65% wasp emergence compared with 33% from Tasmania. Parasitoid origin significantly affected the number of wasps that emerged from exposed batches, but not the total loss from parasitism. [source]