摘要:

We describe a method of quantifying insect paths in the field for use in ecological and behavioral studies. First, we discuss how continuous and curvilinear paths traced by moving insects can be approximated with a series of connected straight lines. Next we describe our procedure for following insects under field conditions and for recording their behaviors (and the timing of behavioral events) with a hand-held TRS-80 computer. We discuss how successive positions of a followed insect can be recorded by triangulation and then translated into spatial coordinates. Finally, we illustrate the method with a study of individual movements in a hilltopping butterfly,Euphydryas edithaBoisduval.

ISSN:1754-5692    

DOI:10.1093/ee/20.4.955

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Discussions and simulation models have been used by others to develop strategies for deploying genes in wheat (Triticum spp.) for resistance to the Hessian fly,Mayetiola destructor(Say). Effects of deploying genes one at a time in sequence and redeploying a gene after a 10-yr absence from the commercial crop in Indiana during 1955–1989 are presented. Three genes,H3, H6, andH5, were deployed in 1955, 1962, and 1971, respectively, andH6was redeployed in 1981. A reduction in infestation levels of Hessian fly occurred for 6–8 yr after each deployment. Redeployment ofH6, after a 10-yr absence in commercial use, was highly effective. Other methods of deploying resistance genes in conjunction with cultural practices should be considered for control of Hessian fly. When considering the pyramiding of genes for resistance, one must evaluate the time required to develop new productive cultivars. Efficient methods to determine that all of the pyramided genes are present in a line are important for the successful use of pyramided genes. Wheat cultivars are seldom grown for more than 8–10 yr, but the same pyramided genes might be used in subsequent cultivars.

ISSN:1754-5692    

DOI:10.1093/ee/20.4.964

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Catastrophe Theory is a branch of mathematics that provides a framework for studying discontinuous phenomena. Application of the cusp catastrophe, a model with two driving or control variables, indicates that rangeland grasshopper population dynamics are catastrophic. Based on bimonthly temperature and precipitation, the cusp catastrophe modeled changes in grasshopper populations dynamics in four ecotopographic regions of Wyoming with an accuracy significantly better than chance. Although there were differences in model performance among regions, the best predictions generally occurred when the changes were large-scale outbreaks (30–45% of the total area of a region) of economic densities (≥9.6 grasshoppers/m2). Because winter weather, particularly in climatically extreme years, is correlated with spring weather, it appears that the climate in December–January has predictive value with regard to population dynamics in the following spring. However, when temperature and precipitation during hatching and early development of grasshoppers (April–May) are used as the control variables, the cusp catastrophe most accurately models the observed population dynamics.

ISSN:1754-5692    

DOI:10.1093/ee/20.4.970

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

The spatial and temporal distribution pattern of apple maggot,Rhagoletis pomonella(Walsh), fly captures was monitored among trees within an unmanaged apple orchard. Each tree within the orchard was monitored weekly for the presence of flies using sticky traps. Fruit maturity was monitored weekly to determine percentage soluble solids. Significantly more apple maggot were captured on trees with mature fruit than on trees with immature fruit. A selective predation model was used to quantify the effect of fruit preference on apple maggot captures. Two hypotheses were evaluated. The first hypothesis was that fly capture among trees is a function of the relative sequence or phenology of fruit maturation (tree category hypothesis). The second hypothesis was that fly capture among trees is a function of apple maturity among trees, regardless of the phenology of fruit maturation (fruit maturity hypothesis). Both models explained the distribution of fly capture among trees early in the growing season, but the fruit maturity hypothesis best explained the entire season. The use of the model for predicting the distribution pattern of apple maggot captures and the optimum placement of traps for apple maggot detection are discussed.

ISSN:1754-5692    

DOI:10.1093/ee/20.4.981

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Four mechanisms within the resource concentration hypothesis influenceOstrinia furnacalis(Guenée) densities. Fewer ovipositing moths were attracted to (1) low density maize (<20,000 plants/ha) and to (2) small patches (<325 m2). (3) In small patches more females oviposited in monocropped than intercropped maize, when offered a choice. Companion crops may interfere with chemical or visual cues emanating from maize. (4) The companion crop may act as a barrier to silk-dispersing first-instar larvae. Plant density and patch size act independently of intercropping, although intercrops are often planted at low maize density. However, the degree of maize borer control from the combined mechanisms is low and intercropping cannot be recommended as a sole means of control. Although important, there was no evidence that intercropping affected natural enemy abundance or that there was any significance to diurnal microclimatic differences of an intercrop. Maize borer behavior in small patches has implications for experimental design of intercropping trials.

ISSN:1754-5692    

DOI:10.1093/ee/20.4.988

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Commercial fields of processing tomatoes located in the Sacramento Valley of California were monitored for eggs of the tomato fruitworm,Helicoverpa zea(Boddie), over a 5-yr period. In general, egg density remained low until near mid-August. During a narrow window of time, egg density increased rapidly across all fields. The first treatable levels ofH. zeaeggs were recorded during this period, or later, for all years. These results better define when to begin sampling processing tomatoes for eggs ofH. zea. Eggs ofH. zeawere found to have an aggregated spatial pattern in tomato fields. A dynamic sequential sampling plan was developed which adjusts the economic threshold according to the level of egg parasitism. When compared with the currently recommended sampling plan, sequential sampling required approximately 60% fewer leaves to reach a management decision.

ISSN:1754-5692    

DOI:10.1093/ee/20.4.1005

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Association of the clover root curculio,Sitona hispidulus(F.), with the alfalfa,Medicago sativaL., rhizosphere remains sketchy. The number of instars ofS. hispidulusthat develop on alfalfa and their feeding behavior was investigated under laboratory conditions. Larvae ofS. hispiduluswere exposed to alfalfa roots grown hydroponically on slant-board cultures. Based on the molting process as evidenced by shed exuvia,S. hispidulusdeveloped through five instars. Feeding of specific instars on alfalfa root components grown in the slant-board culture indicated that first and second instars fed primarily on the root nodules. As larvae grew, feeding shifted to the fibrous and lateral roots. The fifth instars preferred to feed on the lateral roots and the taproot. All instars fed on nodules but the propensity to feed in nodules was associated with the first and second instars ofS. hispidulus.

ISSN:1754-5692    

DOI:10.1093/ee/20.4.1013

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Two moderately resistant varieties (‘MBRV-SWCB’ and ‘P23R’) and one susceptible variety (‘PR7925’) of maize were infested with larvae of the sugarcane borer,Diatraea saccharalis(F.), at fully extended leaf stages 4–5, 6–8, and 9–11 and flowering stage in Mexico during 1987 and 1988. In all varieties, the highest leaf-feeding damage was recorded when plants were infested at the 4–5 leaf stage and damage declined when infestation was done at later stages. Variation in leaf-feeding damage rating was greater when plants were infested at the 4–5 leaf stage. The two resistant varieties had significantly less feeding damage compared with the susceptible variety. This indicates presence of nonpreference or antibiosis or both in two resistant varieties to sugarcane borer larval feeding. Stalk and ear damage in all varieties was highest when plants were infested at 9–11 leaf stage and flowering stage, respectively. Yield of infested treatments compared with that of an uninfested treatment was reduced at all stages in all varieties; greatest reduction occurred when plants were infested at the 4–5 leaf stage. Resistant varieties had less yield reduction compared with the susceptible variety. The results suggest that, for evaluating germplasm for leaf feeding damage, stalk damage, and ear damage resistance, the optimum stages for artificial infestation under conditions in Mexico would be 6–8 leaf stage, 9–11 leaf stage, and flowering stage, respectively.

ISSN:1754-5692    

DOI:10.1093/ee/20.4.1019

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Vials containing founder queens of the red imported fire ant,Solenopsis invictaBuren, were placed under the soil surface at four locations in central Texas; two within the current range ofS. invictaand two outside, to compare founder queen predation mortality and also to document ant predators of the queen. The screen mesh covering vial openings was sufficiently small to prevent queens from escaping but allowed predacious ants as well as other organisms to enter. Queen mortality was compared between treatments and controls and at four locations. Of the four locations studied during 1988, predation by ants had the most pronounced effect on queen survival within the range ofS. invicta. Twelve species of ants that previously have not been recorded as predators ofS. invictafounder queens were observed killing queens during this study. Also, diversity of the ant community was found to be less within the range ofS. invictathan outside the range.

ISSN:1754-5692    

DOI:10.1093/ee/20.4.1024

出版商:Oxford University Press    

年代:1991

数据来源: OUP

摘要:

Two sympatric leafhopper species,Erythroneura aclys(McAtee) andE. bistrata(McAtee), occur together in some Kentucky settings in high numbers on eastern redbud trees,Cercis canadensisL. Seasonal and spatial distributions were examined to determine whether the species segregate within their habitat. Both leafhopper species undergo two generations per year, and population densities peaked within a week of each other in both generations.E. aclyswas the more abundant of the two species. Leafhoppers partially subdivided tree canopies:E. aclysoccurred significantly more frequently in the lower than in the upper canopy.E. bistratashowed less preference for either canopy level, but on average was encountered in greater numbers in the upper canopy. Both species preferred newer leaves along branches, butE. aclysshowed significantly greater preference thanE. bistrata, especially in the lower canopy.E. bistratachanged its resting or feeding position on individual leaves when it was in the presence ofE. aclys. In general, differential distribution among and within trees increased as density increased, but only a change in position byE. bistratawithin leaves whenE. aclyswas present was clearly the result of interspecific interactions.

ISSN:1754-5692    

DOI:10.1093/ee/20.4.1030

出版商:Oxford University Press    

年代:1991

数据来源: OUP