摘要:

Overwintering sites and survival of the carrot weevil,Listronotus oregonensis(LeConte), in various habitats were investigated. Adult weevils overwintered in field borders, but also in the field itself, distributed roughly in proportion to population densities the previous summer. Survival rate was high (70%) through February, and did not differ significantly from that of a laboratory population kept at ca. 20°C, although field soil temperatures were frequently below 0°C Survival in the field decreased markedly in March, demonstrating the importance of duration of cold temperatures. For this reason, damage in the field may be related to time of occurrence of warm weather in the spring. There was no apparent effect of age of adult or habitat (weedy border, unharvested crop, or harvested crop) on survival.

ISSN:1754-5692    

DOI:10.1093/ee/15.1.113

出版商:Oxford University Press    

年代:1986

数据来源: OUP

摘要:

This growth-chamber study was designed to investigate the effect of greenbug,Schizaphis graminum(Rondani), feeding on physiological responses of wheat,Triticum aestivumL., associated with drought stress, to determine how drought stress affects greenbug density, and to determine how drought- and greenbug-resistant cultivars alter responses. The cultivars chosen were ‘Amigo’ (relatively resistant to biotype C greenbugs), ‘Sturdy’ (comparatively drought and greenbug susceptible), and ‘TAM W-101’ (comparatively drought resistant and greenbug susceptible). Greenbugs altered two potentially adaptive responses of wheat to drought; they virtually negated an increase in cell membrane stability associated with wheat conditioned to drought stress, and solute potential was reduced less in greenbug plus drought stress treatments than in drought stress-only treatments; water potential, however, was not altered by greenbug infestations. The lowered turgor pressure that resulted for infested plants suggests that osmotic adjustment (the maintenance of turgor through the accumulation of solutes in plants under drought stress) was also reduced by greenbugs. In addition, greenbug density (number of greenbugs per mg shoot dry weight) was greater on drought-stressed plants. These data provide physical and physiological evidence supporting field observations that greenbug infestations are potentially more damaging when wheat is subjected to drought than when rainfall is sufficient.

ISSN:1754-5692    

DOI:10.1093/ee/15.1.118

出版商:Oxford University Press    

年代:1986

数据来源: OUP

摘要:

Plots of 0.01 ha and 0.04 ha (fixed-radius) and 10-prism and 20-prism basal area factor (BAF) (fixed- and variable-radius) were evaluated in relation to their efficiency for sampling gypsy moth,Lymantria dispar(L.), egg masses (GMEM) in 14 predominantly oak woodlots on the Eastern Shore of Maryland. Relative order of reliability for each sampling method varied with GMEM density. No difference in precision was seen between 10- prism and 20-prism BAF plots; however, the 20 BAF plot required 40% less time to survey. An analysis of cost and precision showed the 0.01-ha plots to be clearly superior to the other sampling methods throughout the range of GMEM densities evaluated. Based on a sample unit size of 0.01 ha, GMEM dispersion patterns were analyzed by Iwao's regression technique. Analysis indicated that egg masses were contagiously distributed, with single egg masses forming the basic component of the population. Parameters for the mean crowding and mean density regression were used to develop research-oriented and pest management-oriented sequential sampling plans with fixed levels of precision.

ISSN:1754-5692    

DOI:10.1093/ee/15.1.122

出版商:Oxford University Press    

年代:1986

数据来源: OUP

摘要:

Glanded and glandless cotyledonary cotton leaves, were used to compare the effects of glandular chemicals (primarily gossypol) on the survival and development ofAlabama argillacea(Hübner), a specialist on Gossypieae, andHeliothis virescens(F.), a polyphagous species.A. argillaceasurvived equally well on either leaf type and the weight of late-larval instars was significantly increased by feeding in glanded leaves. However, survival and pupal weight ofH. virescenswere reduced by this food. The differences in response to glandular chemicals by these two species suggest that changes made in plant chemistry to enhance the resistance of plants against generalist feeders may not lessen, and may in fact increase, the impact of adapted specialists on cotton.

ISSN:1754-5692    

DOI:10.1093/ee/15.1.128

出版商:Oxford University Press    

年代:1986

数据来源: OUP

摘要:

Lygusspp. and their parasites were surveyed on alfalfa, cotton, grain sorghum, guayule, and a number of weed hosts in southern Arizona.Lygus hesperusKnight,L. elisusVan Duzee, andL. desertinusKnight were found at Yuma, while these species andL. lineolaris(Palisot de Beauvais) were found in other areas.L. hesperuswas the predominant species found, although others predominated on individual plant species. The mymaridAnaphes ovijentatus(Crosby&Leonard), a parasite of eggs, was the most common parasite found, with monthly averages of up to 100% parasitization.Leiophron uniformis(Gahan), a braconid parasite of the nymphs, was found in all areas surveyed, but was much less abundant thanA. ovijentatus.The tachinidAlophorellasp. emerged in small numbers from adults collected at Tucson and Benson.

ISSN:1754-5692    

DOI:10.1093/ee/15.1.132

出版商:Oxford University Press    

年代:1986

数据来源: OUP

摘要:

AdultXanthogaleruca luteola(Müller) preference for four elm species was examined in laboratory experiments. The elm species examined were:Ulmus pumilaL.;U. parvifoliaJacq.U. wilsonianaSchneid. 3–14; and ‘Urban’ elm, a hybrid ofU. pumila× (U. hollandica‘Vegita’ ×U. carpinifoliaGleditsch.).X. luteolapreferredU. pumilaand ‘Urban’ elm and these species were the most suitable hosts.U. parvifoliaandU. wilsonianawere found to be nonpreferred and less suitable hosts. No differences in preference were found within species of elms. Significance of these findings forX. luteolapopulation dynamics is discussed.

ISSN:1754-5692    

DOI:10.1093/ee/15.1.143

出版商:Oxford University Press    

年代:1986

数据来源: OUP

摘要:

Horned larks,Eremophila alpestris(L.), and McCown's longspurs,Calcarius mccownii(Lawrence), were collected at intervals from two winter wheat fields in Montana after aerial application of chlorpyrifos to control cutworms. Both bird species had a high (95–100%) incidence of Lepidoptera, mostly pale western cutworms,Agrotis orthogoniaMorrison, in their stomachs at 3 days postspray. Incidence of cutworms and other insects in stomachs of birds from sprayed fields was lower at 9 and 16 days postspray than in control birds, presumably due to insecticide-caused reduction of insects. Effects of birds on population dynamics of insect pests in wheat are unknown, but birds do contribute to cutworm mortality. Predation is one of the limiting factors to cutworm increase and can supplement insecticidal control. Brain cholinesterase activity in horned larks collected from the sprayed fields at 3 and 9 days postspray was significantly lower than in unexposed larks, but at 16 days the difference was not significant. Although nontarget birds clearly were exposed to chlorpyrifos and manifested a sublethal physiological response, toxic effects were lesssevere than those resulting from endrin application for cutworm control in wheat. More study is needed of larger chlorpyrifos-treated fields under a variety of conditions to fully assess effects on nontarget life.

ISSN:1754-5692    

DOI:10.1093/ee/15.1.147

出版商:Oxford University Press    

年代:1986

数据来源: OUP

摘要:

Field trials with four types of pheromone traps and two types of commercial lures were evaluated to develop a population-monitoring technique for spruce bud worm,Choristoneura fumiferana(Clemens). When data were stratified by state or province, mean catch in several treatments (trap model/lure combinations) was significantly correlated with densities of larval stages L3–L4 (generations n and n + 1) and L2. Relationships varied among regions and hosts. There was no significant difference in moth catch between traps within five-trap clusters when traps were spaced 40 m apart. Within-cluster variation in trap catch was high; coefficients of variation averaged 35% for the covered funnel trap/Conrel lure treatment and 49% for the covered funnel trap/Hercon lure treatment. Application of pheromone-baited traps to monitor spruce budworm populations is discussed and recommendations are made to improve the monitoring system.

ISSN:1754-5692    

DOI:10.1093/ee/15.1.152

出版商:Oxford University Press    

年代:1986

数据来源: OUP

摘要:

Two commercial preparations of thuringiensin, the β exotoxin produced by some strains ofBacillus thuringiensisBerliner, were tested for their effect on honey bees(Apis melliferaL.). ABG-6162 (ABG) and SAN410SC72 (SAN) were diluted in 50% sucrose. When bees were fed the toxin solutions throughout their life, only the most dilute preparation of ABG had no significant effect on LT50of replicate cages of bees when compared with untreated controls. All other dilutions of ABG and SAN significantly reduced LT50. A single feeding per bee of a 5 × 10−4dilution resulted in no significant reduction in LT50. for ABG. Higher doses and all doses of SAN caused a significant reduction in LT50. When dilutions in sucrose solutions were sprinkled on bees in cages, only the highest dose of ABG significantly reduced LT50. Lower doses of ABG and all doses of SAN had no significant impact on LT50. Based on low spray volumes and consequent high thuringiensin concentrations, it is possible but unlikely that foraging honey bees could be exposed to doses sufficient to reduce longevity. However, since sprays are water-based, it is unlikely that honey bees would be sufficiently attracted to it to consume a lethal dose. Furthermore, some spray volumes are large enough, and concentrations low enough, that no toxic effect is expected.

ISSN:1754-5692    

DOI:10.1093/ee/15.1.166

出版商:Oxford University Press    

年代:1986

数据来源: OUP

摘要:

Carbaryl, malathion, methomyl, microencapsulated methyl parathion, oxamyl, permethrin, phosalone, and binary mixtures of microencapsulated methyl parathion with all but the first two were sprayed directly on honey bees,Apis melliferaL., in the laboratory in a manner simulating field exposure. Knockdown and mortality were evaluated at periods ranging from 0.25 to 48 h after application. Methomyl and permethrin had the quickest knockdown of insecticides tested. Permethrin had a much lower mortality level than did methomyl, within 1 h of application. Phosalone had the least effect on bees. Within the 1st h of application, knockdown occured in50% knockdown. Mixtures of insecticides with microencapsulated methyl parathion had knockdown and mortality patterns similar to those of the most toxic insecticide in the mixture, but with additional toxicity. Results of this study suggest that oxamyl is highly toxic to bees, whereas it was previously reported as moderately toxic.

ISSN:1754-5692    

DOI:10.1093/ee/15.1.170

出版商:Oxford University Press    

年代:1986

数据来源: OUP