摘要:

The influence of kairomonal baits, containing cucurbitacins, blossom volatiles, and carbaryl, on Diabroticite adult survivorship and trophic interactions with cucurbits was examined. Enrichment of cantaloupes using rubidium (Rb) was developed for monitoring trophic interactions. A soil-soak method was developed to enrich plant Rb concentrations. Beetle uptake of Rb followed a rectangular hyperbola and elimination after transfer to clean plants followed an exponential decay. Models showed beetle uptake occurred within 1 h and the mark is retained up to 2 wk. Naturally occurring endogenous Rb concentrations in beetles varied with species and sex. Baselines were established to allow determination of the incidence and intensity of beetle feeding on Rb-enriched plants. In field cages, kairomonal baits reduced the probability and intensity of feeding on cucurbits byDiabrotica undecimpunctata howardii(Barber) andAcalymma vittata(F.). In one trial, kairomonal baits totally blocked feeding interactions. In field plots, baits also significantly reduced feeding incidence and intensity inD. u. howardiiandD. virgifera virgifera(LeConte), but not inA. vittata.Where the bait reduced feeding, males showed less reduction than females. InD. v. virgifera, there was a higher probability of capturing live males than females regardless of kairomonal treatment. Adult survivorship was reduced by the kairomonal bait in both field and cage experiments. These novel methods allow the monitoring of trophic interactions under field conditions in the presence of behavior-modifying semiochemicals. Hypotheses to explain variation among species and sex and implications of using kairomonal baits to manage vectoring of a pathogen are discussed.

DOI:10.1093/ee/23.5.1138

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Anopheles quadrimaculatusspecies C1 is a member of the recently describedA. quadrimaculatuscomplex and has been collected from temporary pools in intermittently flooded swamps in north Florida. We examined the hypothesis that species C1 uses persistence in the egg stage as a survival strategy. Species C1 larvae appeared in 40 of 153 samples of dry substrate collected from the floor of four intermittently flooded swamps and flooded with distilled water. Cohorts of first-instar species C1 were collected from temporary pools<24 h after the pools formed and at the same time as first instars of the floodwater mosquitoesAedes infirmatusandPsorophora feroxappeared. In the laboratory, eggs of species C1 were successfully hatched after storage for up to 28 d on moist filter paper. Survival of species C1 eggs allows this species to exploit a niche used by floodwater mosquitoes.

DOI:10.1093/ee/23.5.1150

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

In 1987, four gypsy moth,Lymantria dispar, (L.) densities were established in eight 1-ha plots in western Massachusetts, ranging from 50,000 to 1.4 M neonates per hectare. Two tachinid parasitoid species,Compsilura concinnata(Meigen) andParasetigena silvestris(Robineau-Desvoidy), exhibited spatial density-dependent parasistism andC. concinnatawas the major source of gypsy moth mortality. This study investigated whether spatial density-dependent mortality in 1987 translated into temporal density-dependent mortality of experimental gypsy moth populations created the following year (1988).C. concinnatawas responsible for the largest percentage of gypsy moth mortality again in 1988, however, overall mortality caused byC. concinnatain 1988 was considerably less than in 1987. Gypsy moth mortality caused byP. silvestriswas greater in 1988. The killing power of either parasitoid in 1988 were not linearly related to the estimated density of the parasitoids produced in the previous year. We saw no evidence for a between-generation numerical response (1-ha scale) of either the generalist parasitoid,C. concinnata, or the specialist parasitoid,P. silvestris, between 1987 and 1988.

DOI:10.1093/ee/23.5.1155

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

In a Connecticut forest, foraging distances were measured and nests of ants (Hymenoptera: Formicidae) were located by following rewarded individuals back to their nests. Nests were also located by removing all forest litter within an area and counting numbers of ants per nest. Of the three most common species,Formica subsericeaSay foraged further from its nest than did eitherF. neogagatesEmery orAphaenogaster fulvaRoger. A computer-intensive nearest-neighbor analysis showed that nests are distributed without relation to other nests of the same or different species. Also, there was no consistent correlation between a nest's nearest neighbor and the combined size of both nests, but some ants appeared to avoid foraging in the same areas. At baits,F. subsericeawas much more common than would be expected from its population density. The implications these results have for ant effectiveness as biological control agents are discussed.

DOI:10.1093/ee/23.5.1165

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

The foraging behavior of hungry and satiated individuals of three species of polyphagous and predatory carabids was studied by tracking beetles in cereal fields, using a portable harmonic radar system. Fine-scale movement patterns were investigated in both low and high density of the bird cherry-oat aphid,Rhopalosiphum padi(L.). In low aphid density, hungry individuals of the day-activePterostichus cupreusL. switched from directed to random movements (i.e., a correlated random walk), whereas both satiatedP. cupreusand hungry individuals of the night-activeP. melanariusIlliger displayed directed movements only. Conversely, the movement patterns of satiatedP. melanariusand both satiated and hungry individuals of the night-activeP. nigerSchaller could be described as a correlated random walk. In high aphid density, hungry and satiatedP. cupreusdisplayed directed movements. However, hungryP. cupreusexhibited more efficient systematic search activities; foraging on aphids near the base of cereal plants. The movement patterns of both hungry and satiatedP. melanariuscould be described as a correlated random walk related to burrowing into the soil. SatiatedP. nigerdisplayed directed movements but never foraged, whereas hungryP. nigerexhibited a correlated random walk related to near-search activities, foraging on coccinelids near the base of cereal plants. No sex-related difference in maximum sprint speed was detected when the beetles were released on a smooth, regular surface. Conversely, only female carabids were found to alter their speed of movement according to differences in both hunger level and prey (aphid) density in cereal fields. The influence of motivation (hunger level) on movement patterns and foraging behavior exhibited byP. cupreus,P. melanarius, andP. nigerand the associated species-specific responses to differences in aphid density are discussed in relation to energy costs and predation efficiency.

DOI:10.1093/ee/23.5.1171

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Woolly apple aphid,Eriosoma lanigerum(Hausmann), populations were studied in eastern West Virginia from 1985 to 1989. In an unsprayed orchard, peak abundance of arboreal populations was 22–24 colonies per tree in early June each year. Spraying the orchard with a pyrethroid three times during 1989 had little effect on the population behavior, demonstrating the resilience of the woolly apple aphid and its natural enemy guild. Nearly 20% of the aphid colonies in June had syrphid larvae present and parasitism byAphelinus mali(Haldeman) was>50% in July. Age structure of arboreal woolly apple aphid colonies varied through the summer with a significant reduction in first instars in July, signalling a return of aphids to the edaphic from the arboreal environment at that time. Samples of arboreal populations were not useful for predicting year-to-year population abundance or the extent of root infestations in a managed orchard. Microhabitat preference of arboreal colonies during the spring was for wound sites and other protected feeding sites on the tree branches and trunk. Leaf axils were the predominant microhabitat (51% of the colonies observed) from the end of May through August. Cicada oviposition sites were also highly preferred, with one orchard having 98% of the colonies in cicada oviposition scars. Woolly apple aphid colonies were observed more often in wounds and protected sites on branches in sprayed orchards and in high density populations than in unsprayed or low density populations. We suggest that these protected sites act as refugia for woolly apple aphid populations in apple orchards.

DOI:10.1093/ee/23.5.1182

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Predation rates ofHelicoverpa zea(Boddie) eggs on cotton plants were determined by placing 32P-labeled moth eggs on different types of plant structures throughout the vertical strata of cotton plants. There was a slight trend for predation rates to be greater toward the top of the plants. Egg predation rates were higher on mainstem and fruiting branch terminals, and on blooms than on other plant parts. Similar predation rates (=75%) were observed on abaxial and adaxial leaf surfaces. Seasonal predation rates averaged 81.7 and 81.4 in 1982 and 1983, respectively. Rates began high each year (81.8–100%) and slowly decreased toward the end of the growing season when rates ranged from 55 to 80%. Predation by sucking predators ranged from 14.2–37.0%Orius tristicolor(White),O. insidiosus(Say),Geocoris punctipes(Say), andPseudatomoscelis seriatus(Reuter) were the most important. Chewing predators accounted for 0.8–22.9% of the predation.Solenopsis invicta(Buren) was observed removing more eggs from plants than any other predator species. Ground based predators added significantly to egg predation. Mortality rates of eggs dislodged to the soil surface were also investigated. Nearly 90% of eggs placed on the soil surface were predated in<48h. Eggs that escaped predation but that were exposed to high midday soil temperatures (e.g., 45.5°C) died of exposure. Larvae safely eclosed from eggs placed in shaded locations near the plant bases.

DOI:10.1093/ee/23.5.1189

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Sweetpotato whitefly,Bemisia tabaci(Gennadius), has recently become a pest of peanut in the southern United States. Limited observations in grower fields had identified differences in infestation among cultivars. We wished to determine whether selected cultivars grown commercially in this region resisted whitefly infestation and whether parasitism by aphelinid parasitoids differed among cultivars. Five cultivars were evaluated in summer 1992 and six in summer 1993. In 1992, ‘Florunner’ supported the greatest populations of red-eye nymphs and ‘Southern Runner’ supported the lowest populations.Encarsia nigricephalaDozier was the most common parasitoid (53.0% of all parasitoids reared), followed byEncarsia transvena(Timberlake) (25.6%), andEncarsia pergandiellaHoward (18.3%). Parasitism was uniformly high and species composition on the five cultivars did not differ. In 1993, ‘Southern Runner’ supported the greatest populations of all immature whitefly stages except red-eye nymphs. ‘Marc I’ supported the lowest levels of whitefly infestation.E. nigricephalawas extremely abundant in 1993 (85.3% of all parasitoids reared), followed byE. pergandiella(9.8%), andE. transvena (4.7%). Eretmocerusnr.californicuswas found in low numbers in both years. Again, in 1993, parasitism was high on all cultivars (up to 100% by the end of September), and no differences were noted in the parasitoid composition among the six cultivars. Whitefly infestation was light in these noninsecticide-treated peanut plots, most likely because of natural control by native aphelinid parasitoids, and other beneficial insects.

DOI:10.1093/ee/23.5.1203

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Reticulitermes flavipes(Kollar) (third and fourth instar) workers from a laboratory colony were subjected to 0°C for either 10 or 30d after having been exposed to 10°C for varied periods from 0 to 30d. Worker mortality increased with increased exposure to 10°C. The lowest percentage of mortality was observed in workers exposed to 0°C for 10d after 0d of 10°C acclimation. Workers exposed to 0°C for 30d exhibited high mortality rates regardless of the duration of the 10°C acclimation periods. The supercooling point of laboratory reared termite workers generally increased with prolonged exposure to 10°C. Termite workers subjected to 0°e for 10d did not exhibit lower supercooling points following increased acclimation periods at 10°. However, termites subjected to 0° for 30d generally did exhibit decreased supercooling points following increased exposure to acclimation temperatures at 10°C. Lower lethal temperatures were higher than the super cooling points for laboratory workers exposed to 10°C for 0, 1, and 10d and for field collected workers during the months of May to July 1992. However, lower lethal temperatures were lower than supercooling points for laboratory termites exposed to 10° for 20 and 30d and for field collected termites during the months of September to November 1992. These data indicate that 10°C cold acclimation ofR. flavipesdoes not result in lower supercooling points in either laboratory maintained or field collected samples. However, decreased lower lethal temperatures in response to either cooler seasonal temperatures or longer exposure does indicate that a switch from prefreeze mortality to freeze tolerance may be occurring.

DOI:10.1093/ee/23.5.1211

出版商:Oxford University Press    

年代:1994

数据来源: OUP

摘要:

Species of sap beetles present at a central Illinois cornfield—oak woodland habitat were determined by spring to fall collections from can traps baited with fermenting wheat dough and banana.Carpophilus lugubrisMurray was the dominant species.Glischrochilus quadrisignatus(Say) andStelidota geminata(Say) were also collected frequently. Other species collected commonly wereC. antiquusMelsheimer,C. freemaniDobson, andColopterus truncatusRandall, which were generally encountered only in the early spring and late fall. Peak collections ofC. lugubriswere in late April, early June, and throughout the fall. A similar trend was noted forG. quadrisignatus, butS. geminataonly had late spring and fall peaks. The peaks occurred at fairly consistent intervals over all 3yr forG. quadrisignatusandS. geminata, but the spring first generation peak forC. lugubriswas retarded by 3–4 wk during 1988. This change in population distribution might have resulted from the long dry period that occurred during this time.

DOI:10.1093/ee/23.5.1215

出版商:Oxford University Press    

年代:1994

数据来源: OUP