摘要:

The biology and host specificity ofOxicesta geographicaF. from Romania, Hungary, and Southwestern Russia were studied to evaluate the potential of this moth as a new biological control agent of leafy spurge,Euphorbia esulaL., “complex” in North America. This oligophagous, multivoltine tent caterpillar is common on perennial spurges in southeastern Europe and Asia Minor and prefers dry, open sites. Results of no-choice feeding tests with first instars on 93 plant species and biotypes, distributed in 33 families, show thatO. geographicacompleted its life cycle mainly on plants ofEuphorbia, subgenusEsula, and occasionally fed and developed on species in other subgenera of the genus. Studies of late instars did not show any important extensions of the host range.

DOI:10.1093/ee/23.4.1006

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

A census was taken of a stand of Canada thistle,Cirsium arvense, in northern Utah throughout the growing seasons of 1991 and 1992 to determine the degree to which this weed was attacked by the weevilRhinocyllus conicus, originally introduced to the region to attack musk thistle,Carduus nutans.Overall, the weevil oviposited on 34–37% of Canada thistle flowering stems (both sexes combined); male and female flower heads appeared equally suitable for oviposition and larval maturation. However, relatively few large flower heads (6–10%) with potential to produce seed were oviposited on by the weevil. The seasonal timing of weevil oviposition versus host maturation suggested that low rates of attack derived primarily from few overwintered weevil females persisting long enough into the growing season to oviposit on large flower heads (preferred oviposition sites) as these became available. Field experiments in which the rate of plant maturation was hastened, or in which comparisons were made among plants differing naturally in seasonal timing of development, confirmed that overwintered weevil females oviposited much more heavily on early versus later maturing flower heads. Thus, as has been found for other thistle species, the impact of the weevil on Canada thistle at the study site appears limited by poor synchronization between insect and host life cycles. Nevertheless, field results indicate that considerable numbers of the weevil develop in Canada thistle flower heads at the study site each year, and thus the weed may serve as an important alternate host in maintaining naturalized populations of the insect in northern Utah.

DOI:10.1093/ee/23.4.1013

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

To clarify the interaction among the European corn borer,Ostrinia nubilalis, the parasitic wasp,Macrocentrus grandii, and the entomopathogenNosema pyrausta, we examined behavior and survival in corn stems ofO. nubilalislarvae infected withN. pyraustaand parasitized byM. grandii.Fifty-four percent of heavily infected, parasitizedO. nubilalislarvae emigrated from their tunnels before emergence of parasitoid larvae and did not reestablish on corn plants. One-third as many heavily infected host larvae as noninfected larvae remained in tunnels until parasitoid larval emergence. The tunnels bored by infected, parasitizedO. nubilalislarvae did not differ in length from those of noninfected parasitized larvae, suggesting that emigration behavioral changes occur after feeding. Parasitoid larval and pupal mortalities were greater in infectedO. nubilalishosts than in noninfected hosts. Greater than 46% of heavily infectedM. grandiibroods wandered instead of remaining clustered around host carcasses and pupating. This behavior accounted for almost ≈40%of the observed mortality in infected parasitoids. Wandering was attributed to decreased production of cocoons by hosts, causing parasitoid larvae to search for suitable substrates on which to spin their own cocoons. Percentage emergence ofM. grandiiadults from corn stalks was significantly lower inN. pyrausta-infected treatments, but the sex ratio of the parasitoid was unaffected by the level of host infection. The mean number ofM. grandiiadults per brood was reduced from 39.8 in the noninfected treatment to 10.5 in heavily infected larvae.

DOI:10.1093/ee/23.4.1020

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

The sunlight-UV (SUV) inactivation of field-applied viral and other microbial insecticides has been attributed to a direct effect on DNA or generation of highly reactive radicals, or both. Therefore, it may be possible to inhibit this inactivation by use of antioxidants or oxidative enzymes. Our objective was to determine whether antioxidants and oxidative enzymes would inhibit the UV inactivation ofBaculovirus heliothis, a singly enveloped nucleopolyhedrosis virus (HzSNPV) of larvae of theHelicoverpal Heliothiscomplex. A series of blacklight fluorescent lamps, built into a temperature control cabinet, were used to simulate the ultraviolet-A and ultraviolet-B spectrum of sunlight. Three antioxidants (propyl gallate, ascorbic acid, phenylthiocarbamide) all provided some level of UV protection of polyhedral inclusion bodies (PIB) of HzSNPV. Propyl gallate, however, provided the best protection of HzSNPV (0.2 mg/ml propyl gallate gave 99% UV protection of PIB). Fifty percent UV protection with propyl gallate, ascorbic acid or phenylthiocarbamide was obtained at 0.01 mg/ml, 1.0 mg/ml, or 0.068 mg/ml, respectively. Catalase was the best of three oxidative enzymes tested. The enzyme concentration required to provide 50% UV protection of HzSNPV with either catalase, superoxide dismutase, or peroxidase was 0.4 mg/ml, 2.3 mg/ml, or 3.8 mg/ml, respectively. The increased UV stability provided by an antioxidant or oxidative enzyme supports the hypothesis that reactive radicals, generated by SUV, can cause inactivation of field-applied viral and other microbial insecticides. Although the materials we used increased persistence of HzSNPV, none could be used practically to provide UV protection of commercial microbial insecticides. Others, however, might be used as spray-tank additives, or physically bonded to PIB to provide protection against SUV.

DOI:10.1093/ee/23.4.1025

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

TransgenicPopulusplants (clone NC5339) expressing aBacillus thuringiensisd-endotoxin gene significantly reduced feeding and weight gain by gypsy moth,Lymantria dispar(L.), and the forest tent caterpillar,Malacosoma disstriaHubner. Forest tent caterpillar larvae also experienced significant mortality following exposure to the transgenicd-endotoxin. Gypsy moths were better able to recover after transfer to artificial diet than were forest tent caterpillars. Transgenic leaves deterred feeding by both species in behavioral choice tests. Four additional transformants contained, but did not express thed-endotoxin gene. Results are discussed in terms of efficacy, plant deployment strategies, ecosystem stability, and tree improvement.

DOI:10.1093/ee/23.4.1030

出版商:Oxford University Press    

年代:1994

数据来源: OUP

DOI:10.1093/ee/23.4.1042

出版商:Oxford University Press    

年代:1994

数据来源: OUP