摘要:

Since 1911, over 100 species of exotic organisms have been deliberately introduced for biological control of various pests on Guam. Of these, 27 species were released against seven lepidopterous pests including one butterfly and one skipper. Recently, concern has mounted about the negative effects of these introduced biocontrol agents on nontarget species, particularly endemic island species. Guam may have suffered extinction of as much as 20–25% of its butterfly fauna. To determine the extent of movement and possible impacts of biocontrol agents on nontarget butterflies, mortality factors affecting juvenile stages ofHypolimnas anomala(Wallace) andHypolimnas bolina(L.) were studied. Both species were attacked by the same parasitoids and predators, which included native, accidentally introduced, and deliberately introduced species. Parasitoids killed 2.4% of the eggs ofH. anomala, and ants removed about 25% of the eggs. Parasitization was about 40% inH. bolina, and ants killed about 35% of the eggs. One species introduced for biological control,Trichogramma chilonisIshii, was found parasitizing the eggs, but it caused little mortality. No larval parasites were reared for either species.H. anomalasuffered heavy mortality from a disease. Both species were attacked by ants and two exotic, self-introduced predators. The major pupal parasite wasBrachymeria lasus(Walker), a deliberate biological control introduction.B. lasusparasitized 24.6% of the pupae ofH. bolinaand 2.9% of those ofH. anomala. Ants attacked 17% ofH. anomalapupae and 7% of those ofH. bolina. B. lasus and T. chilonisare polyphagous parasitoids that have the potential to affect a variety of nontarget species. This type of parasitoid, and highly polyphagous predators like ants, should require more intensive evaluation and review for use in classical biological control programs than more specialized species.

DOI:10.1093/ee/22.2.265

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

Normalized yield (i.e., yield with injury divided by yield without injury) of cotton,Gossypium hirsutumL., was observed for various levels of plant injury byHelicoverpa zea(Boddie) orHeliothis virescens(F.) at different plant physiological ages (i.e., stages of plant growth). These data were then used to develop functions describing response surfaces composed of insect injury, cotton yield, and plant physiological age. Normalized yield can be predicted from response surface functions when injury and plant physiological age are known. Plant physiological age was either degree-days, or an index of plant development determined using a mechanistic, physiological cotton plant simulation model. The generalized function (i.e., regression equation) describing response surfaces was In Y =b1ln X +b2X +b3X2+b4X3+b5T +b6T2+b7T3+b8XT, where Y = normalized yield, X = injured reproductive organs, and T = plant physiological age (i.e., as degree-days or plant physiological age index). Regressions were highly significant and fit the data well based on coefficients of multiple correlation, mean square errors, Mallows'Cps, predicted residual error sum of squares, and slopes significantly different from zero for parameters of independent variables. The yield response of cotton to injury changed continuously over physiological age. One response surface function quantified an infinite set of two-dimensional insect injury–plant yield response curves. Different sections of the generalized insect injury–plant yield response curve were observed at different plant physiological ages. Cotton yield was increasingly sensitive to injury from one-third-grown flower bud to first week after anthesis, was decreasingly sensitive to injury from first week after anthesis until 30 d after anthesis, and was unaffected by injury of neonates at 30 d after anthesis. Response surface regression functions were significantly different among cultivar–insect species combinations within degree-days or the plant physiological age index, indicating that cotton responded differently to bollworm and budworm injury and cotton cultivars responded differently to injury. For a given set of economic costs and returns, the economic injury level (ElL) is not static nor a straight line, but is dynamic, varying with plant physiological age and forming a complex continuous curve. Overcompensation increased EILs, steep descents in the response surface resulted in low EILs, and tolerance or inherent impunity rapidly increased EILs.

DOI:10.1093/ee/22.2.273

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

A simulation model (REPO) was developed to predict the rate of resistance development in Colorado potato beetle,Leptinotarsa decemlineata(Say), given various genetic, biological, and management conditions. Values used in exploring variables in the model were chosen to reflect the range of possibilities encountered in field populations of Colorado potato beetle. REPO is different from other resistance management models in that it is temperature-driven, considers age-specific selection, describes the pattern of immigration of colonists, and uses survivorship functions to describe dynamic relationships among genotypes during insecticide selection. The life history of Colorado potato beetle in North Carolina and other areas is presented as a backdrop to model exploration of some of the unique features of this pest that could influence resistance evolution. Foremost among ecological and management factors influencing rate of resistance development were the arrival period of colonizing beetles, timing of insecticide applications, action thresholds, and age-specific selection. Relevance of these findings to management of Colorado potato beetle and future research on this insect is discussed.

DOI:10.1093/ee/22.2.283

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

We field-tested two sticky traps used to monitor populations ofStrobilomyiaspp. developing in the French Alps: a bright yellow horizontal trap and a bright yellow vertical trap with purple stripes. Fluorescent yellow traps captured significantly more flies than nonfluorescent yellow traps. Males ofStrobilomyia melaniaAckland were trapped significantly more often than females of otherStrobilomyiaspecies regardless of sex. Significantly more males were trapped per week when males were removed daily rather than weekly. Spectral patterns of the colors used in this experiment changed only slightly after 1 wk of exposure to sunlight and did not affect the daily captures of flies.

DOI:10.1093/ee/22.2.297

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

Absolute density sampling was conducted to determine population densities ofHypera postica(Gyllenhal) eggs and larvae at two locations in central Oklahoma from 1971 to 1990. For each generation of the weevil, egg deposition began following the return of adults from summer estivation sites during October and November and continued until the following April. Although hatching began as early as December, the appearance of large numbers of larvae coincided with growth of the first alfalfa crop from February to May. Depending upon effects of weather conditions on egg development and survival, the time when larval numbers first exceeded the economic threshold ranged from late February to April. Multivariate discriminant analysis with five variables related to weevil egg numbers and temperature conditions was used in deriving a model for predicting by 15 February whether the economic threshold would be exceeded in late February, early March (1–15), late March (16–31), or April. When tested,>90% of the predictions of the model were correct. This model will provide valuable assistance to growers and consultants in determining when field scouting should be conducted to make decisions regarding sprays for alfalfa weevil control.

DOI:10.1093/ee/22.2.305

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

Potential larval competition betweenAedes albopictus(Skuse) andAedes triseriatus(Say) was examined with replacement series experimental design, an analysis previously used to evaluate competition between plant species. Experimental design was a factorial treatment arrangement with four replications of larval diet (high and low) and species ratio (proportions ofA. triseriatus/A. albopictuslarvae 1:0, 3:1, 1:1, 1:3, and 0:1). Adult emergence, adult biomass, and sex ratio were evaluated. No competitive effects were observed in the high-diet treatments; however, significant competitive relationships were observed for all parameters in the low-diet treatments. Competition was evaluated by replacement diagrams, relative crowding coefficients, and analysis of variance. All techniques indicated thatA. albopictuswas a superior competitor toA. triseriatusunder low diet. The use of the replacement series design was a powerful method for examining competition through a single experiment. The results indicate that replacement series experimental design can be used to characterize competition between animal species, providing that individual animals can be placed in an experimental habitat in appropriate proportions.

DOI:10.1093/ee/22.2.311

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

The mechanisms of resistance ofLeucaena collinsiiRose&Britton against the psyllidHeteropsylla cubanaCrawford were investigated by comparing the plant's response to the psyllid and the psyllid's behavioral and growth responses to the trees, usingLeucaena leucocephala(Lam.) de Wit as the susceptible control. Potted trees in the field were treated with fenvalerate to remove all insects. Four days later, the numbers of adults per shoot and the percentage of trees recolonized were 76–84 and 65% lower, respectively, forL. collinsiicompared withL. leucocephala. The numbers of eggs oviposited onL. collinsiiwere 46 and 63% lower than onL. leucocephalain field and laboratory experiments, respectively. There was also well over 90% reduction in adult eclosion, a smaller adult size and about 67% reduction in nymphal survival onL. collinsiithan onL. leucocephala. Premature leaflet senescence and abscission as well as intraspecific competition for feeding sites onL. collinsiimay have a severe effect on nymphal survival. These results disclose several mechanisms of antixenotic and antibiotic resistance that should be considered in resistance selection and breeding programs.

DOI:10.1093/ee/22.2.319

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

The ability ofNezara viridulaL. nymphs and adults to make up a suitable diet from several poor host plant species was studied. The ability of adult bugs to recover from poor nutrition experienced early in life (nymphal stage or prereproductive adult stage) when fed an optimal food plant was also investigated. Survival and development of nymphs, and reproductive performance of adults fed on a combined diet of poor host plant species, was inferior in comparison with individuals fed an optimal diet. There were indications that adults can partially recover from poor nutrition experienced early in adulthood, but their overall performance was still inferior to bugs fed an optimal diet. The adverse effects of poor nutrition were more dramatic when bugs experienced this condition throughout their nymphal development. It is suggested that, under some environmental conditions, there may be some advantages in periodic host switching by individual bugs, although they are limited in extent; e.g., some adults can survive and still reproduce when fed a combination of poor host plant species. These findings are discussed in relation to the seasonal patterns of abundance and pest stahls ofN. viridulain SE Queensland and its adaptations to its host plants.

DOI:10.1093/ee/22.2.326

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

Protein extracts ofEscherichia coli expressing the toxin gene from Bacillus thuringiensisBerliner were tested for effect on the behavior and development ofLeptinotarsa decemlineataSay using in vitro bioassays. Potato leaf disks coated with protein extracts were used as a diet. Toxicant properties and sublethal effects were scored with no-choice tests, and the relationship between dose of protein extract and larval growth and mortality was defined using regression analysis. Feeding behavior of young larvae was studied with choice tests. No antifeedant effects ofB. thuringiensistoxins were found, even at concentrations that caused mortality or severely inhibited larval growth. The lack of feeding inhibition may limit strategies for producing transgenic potato plants with a low selection pressure against the target insect in the field.

DOI:10.1093/ee/22.2.334

出版商:Oxford University Press    

年代:1993

数据来源: OUP

摘要:

A computer-monitored insect flight mill system is described which allows tethered insects the freedom to take off, fly, and land at will. Take off and landing times, flight duration, distance flown, and average speed are logged automatically. Feeding and oviposition are also possible while the insect is tethered to the device. The mill system has been used under field conditions in India and the Sudan to monitor the flight potential ofHelicoverpa armigera(Hübner) moths. Various methods for monitoring the flight activity of tethered insects and the implications of using flight mills are discussed.

DOI:10.1093/ee/22.2.339

出版商:Oxford University Press    

年代:1993

数据来源: OUP