摘要:

The impact of defoliation on gypsy moth,Lymalltria dispar(L.), larval phenology, pupal phenology, pupal sex ratios, and capture of male moths in pheromone traps was determined. Data were collected from 16 plots located in the leading edge area of the gypsy moth infestation in Virginia. A stochastic phenology model was used to describe larval phenology; regression lines were constructed to describe cumulative pupal occurrence and cumulative capture of male moths over time (degree days). Comparison among plots of the stochastic-model parameter sets and degree-day accumulation that describe larval phenology in physiological time indicate that high levels of defoliation did not influence larval development (defoliation of more than ≍70% is considered high). In calendar days, the period required for larval development was reduced in plots with high levels of defoliation. Comparison of the slopes and intercepts of regression lines among plots for cumulative pupal occurrence indicates that pupal phenology was altered significantly in plots with high levels of defc)liation; the sex ratio of pupae was male skewed in these plots. Comparison of the slopes and intercepts of regression lines among plots for cumulative moth capture indicates that capture was not related to defoliation level. Defoliation apparently can have a significant effect on larval phenology (measured in calendar days), pupal phenology, and the sex ratio of pupae, but the effect on these life stages is not reflected in the capture of male moths. Pheromone traps probably draw moths over too large an area and too long a period to reflect the population dynamics of gypsy moth populations in the immediate vicinity of pheromone traps.

ISSN:1754-5692    

DOI:10.1093/ee/21.6.1308

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Overwintering loss of pear psylla,Cacopsylla pyricolaFoerster, in the Yakima area of Washington and the Medford area of Oregon, was estimated as the difference between the peak beat tray count obtained in fall and the peak count obtained the following spring. Thirty five orchards were sampled over 13 yr at Yakima, and 12 orchards were sampled for 10 yr at Medford. Overwintering loss increased linearly with peak fall counts. Loss coefficients were ≥0.90 in three of four regions at Yakima and in all 12 orchards at Medford. Peak spring counts were independent of peak fall counts in three of four regions at Yakima and at 6 of 12 orchards at Medford. At Yakima, peak spring count was positively correlated with November precipitation and negatively correlated with November and January temperature; overwintering loss increased with increasing January temperahue and decreased with increasing November precipitation. At Medford, overwintering loss increased with decreasing fall precipitation but, in contrast to Yakima, increased also with decreasing January temperatures. We suggest that wet auhunns result in higher overwintering success by causing a reduction in dispersal from pear. Spatial autocorrelation showed that peak counts were more similar among neighboring orchards than between distantly separated orchards for two of six analyses in spring and one of six analyses in fall. Counts were less variable in spring than in fall, consistent with the hypothesis that psylla reallocate among orchards between fall and spring. The claim that orchards with intensive pesticide use in some regions have higher fall counts than less intensively managed orchards was tested for Yakima; no differences in counts were noted in commercial versus organic orchards. Initial pesticide applications in spring at a chemically intensive orchard preceded peak spring counts in a neighboring unsprayed orchard by 4–5 d, resulting in an estimated seasonal peak count that was about four psylla per tray lower than what would occur in the absence of pesticides. Julian day of peak spring counts occurred earlier in the wanner regions of the Yakima valley. Variation between regions in timing of spring peaks was eliminated by expressing timing in degree-days (DD); for the Yakima valley, peak counts occurred at ≍80 DD using a lower threshold of 5°C.

ISSN:1754-5692    

DOI:10.1093/ee/21.6.1319

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

The insect prey of the robber flyMegaphorus willistoni(Cole) were sampled in three habitat patches characterized by different plant species and assemblages of potential prey. The prey taken by M.willistonivaried with differences among sites in the relative abundance of Hymenoptera. Predator electivity was consistently positive for largebees, tiphiid wasps, and sphecid wasps and was usually negative or zero for small halictidbees and non-Hymenoptera. The relationship of the results to studies of the foraging behavior of individual robber flies is discussed.

ISSN:1754-5692    

DOI:10.1093/ee/21.6.1333

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Selected biological processes ofLiriomyza trifolii(Burgess) were studied at four constant temperatures (13.9, 20, 25, and 32°C) on tomato foliage in the laboratory. Longevity and oviposition rates of adult leafminer females and developmental rates of eggs, small-sized larvae (>0.15 and<1.5 mm), large larvae (1.5 mm), and combined larval sizes increased linearly with increasing temperature. Fecundity of females was related quadratically to temperature. Lower temperature thresholds were estimated at ≍8.3°C for larvae, 9.5°C for eggs, 12.4°C for oviposition rate, and 1l.8°C for fecundity. The mathematical descriptions provided should aid in the prediction of population dynamics of L.trifoliibased upon scouting for adults and small and large larvae.

ISSN:1754-5692    

DOI:10.1093/ee/21.6.1341

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Maize weevils,Sitophilus zeamaisMotschulsky, were tested in the laboratory using split-arena and olfactometer bioassays to measure the effects of starvation and dehydration on humidity responses and to determine the nature of the humidity response mechanism. Dehydration initially made weevils less hygronegative, but this effect vanished after 24 h. Starvation also made weevils less hygronegative, and this effect persisted for at least 24 h. There was no interaction between these two factors. When weevils were presented humidity alternatives differing only in the magnitude of the lower relative humidity, their response was roughly proportional to the humidity differential, indicating that responses are quantitative rather than qualitative. Olfactometer studies revealed that weevils are capable of detecting and responding to spatial differences in relative humidity; thus, the response mechanism is at least partially tactic in nature. The results as a whole reveal that maize weevils can accurately assess relative humidity and respond accordingly, but the feedback mechanism regulating water balance is rather crude.

ISSN:1754-5692    

DOI:10.1093/ee/21.6.1345

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

A spatial model describing insect population dynamics in a grain bin was developed by coupling a model ofCryptolestes ferrugineus(Stephens) with a twodimensional bin temperature model. In the model, the bin is divided into 16 compartments. The insect model is run separately for each compartment. This allows the insect model to simulate different population growth rates based on each compartment's average daily temperature. Field data for a 351-m3(10,000 bu) bin located in Cloud County, KS, was used to validate the model. The model predicted grain temperatures accurately for each of the nine compartments, except the center top portion of the grain mass. In this region, observed grain temperatures were 8°C higher than predicted during December. This may have been caused by convective air movement. In general, the model accurately predicted insect density for most of the bin compartments. However, the model tended to overestimate insect density in the center of the grain mass during the end of the storage period in December. During this period, actual grain temperatures were still optimal for C.ferrugineusgrowth.Cephalonomia waters toni(Gahan), a common hostspecific parasitoid of C.ferrugineus,may have been responsible for the pest population decrease.

ISSN:1754-5692    

DOI:10.1093/ee/21.6.1351

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

In laboratory studies, adults ofLiriomyza trifolii(Burgess) were impaled by hooked trichomes on bean plants,Phaseolus vulgarisL. The incidence of adult capture was directly related to trichome density, and trichome densities varied with respect to location on a leaf surface, leaf surface (i.e., adaxial or abaxial), leaf size, leaf type (i.e., primary or secondary), and bean cultivar. Reductions in female longevity decrease herbivory by females and may also result in decreased oviposition. These results support the hypotllesis that hooked trichomes are a general plant defense against herbivory by insects and that artificial selection for this characteristic could decrease plant susceptibility to several orders of insects pests.

ISSN:1754-5692    

DOI:10.1093/ee/21.6.1357

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Defensive behavior was investigated in a naturally occurring population ofApis mellifera scutellata(Lepeletier) colonies in the Okavango River Delta, Botswana. In general, colonies exhibited low levels of stinging activity during nest dissection. However, positive associations were observed between defensiveness and increasing colony size (inferred from total comb area) and swarming activity. The lower stinging activity of the smaller colonies and the increased defensiveness of the larger and swarming colonies may have reflected relative levels of investment in colony growth and reproductive potential. Seasonal patterns of colony defensiveness were not associated with fluctuations in resource abundance, although some changes in forage availability may have influenced aggressive behavior. Colony defensiveness was not associated with nest entrance location and orientation; the proportions of comb area devoted to brood rearing, food storage, or the area that was empty, or any of three weather parameters measured.

ISSN:1754-5692    

DOI:10.1093/ee/21.6.1362

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Effects of 17 different plant pollens on the development, survivorship, and reproduction of the predacious miteEuseius tularensis(Congdon) were studied in the laboratory. Mites fed cattail,Typha latifoliaL.; ice plant,Malephora crocea(Jacquin); and five different types of commercially available tree pollens (apple,Malus sylvestrisMiller; pear,Pyrus communisL.; almond,Prunus dulcis[Miller] D. Webb; olive,Olea europaeaL.; and peach,Prunus persica[L.] Batsch) exhibited similar percentage survival of immatures in generation 1 (62.50–87.5%) and similar sex ratios of their progeny (59.48–76.22% female). The developmental times of the first generation from the egg to adult stage ranged from 6.21 to 6.66 d and the percentage survival of immatures of generation 2 ranged from 66.20 to 88.32%. Reproduction (total eggs per female) was greatest for E.tularensisfed apple pollen. Based on life-table analyses of these pollens, apple pollen was found to be the best diet for this predacious mite. Mites fed grass pollens (cultivated and wild annual ryegrass,Lolium multiflorumLamarck; soft chess,Bromus mollisL. var ‘Blando’; California brome,Bromus carinatusHook and Arnott; oat,Avena sativaL. var. ‘California red’; barley,Hordeum vulgareL. var ‘UC476’; rye,Secale cerealeL. var ‘Merced’; meadow barley,Hordeum brachyantherumNevskii; and red fescue,Festuca rubraL. var ‘Malate’) showed 63–97% survival of immatures in generation 1, but survivorship decreased to 44% or less in their progeny. Thus, these grasses did not individually support long-term survival of E.tularensis.The first generation survival (21%) and reproduction (0.5 eggs per female) of the predatory mites fed wheat(Triticum aestivumL.) pollen was significantly lower than all other treatments. This study provided fundamental information for mass rearing ofE. tularensisand to enhance the orchard performance ofE. tularensisas a predator of citrus pests.

ISSN:1754-5692    

DOI:10.1093/ee/21.6.1371

出版商:Oxford University Press    

年代:1992

数据来源: OUP

摘要:

Studies were conducted to improve techniques for the use of elemental marking in dispersal studies of the southern pine beetle,Dendroctonus frontalisZimmermann. Tissues from host loblolly pines,Pinus taedaL., having diameters at breast height ranging from 15 to 46 cm and the emerging D.frontaliswere marked successfully by injection of rubidium (Rb) concentrations based on estimates of bole surface area. A stem-well infusion technique, which is less labor intensive than pressure injections, was found to mark emerging beetles successfully. Use of dimethysulfoxide (DMSO) in RbCI solution did not significantly increase Rb concentration in P.taedaphloem samples or percentage of Rb-marked D.frontalis.Rb was rapidly eliminated by Rb-marked D.frontalisadults when allowed to feed on nonRb-enhanced host tissue, but Rb concentrations remained relatively constant in Rb-marked beetles held without feeding. While this loss of Rb by colonizing D.frontaliswould effect use of the elemental labeling technique for subsequent tracking of reemerging adults, it would be relatively unimportant for typical short duration mark-recapture experiments. Rb-marked D.frontaliswere successfully recaptured in pheromone-baited traps at distances as far as 1 km from the point of emergence. Recaptures in four cardinal directions indicated a random dispersal pattern. Adirect comparison of fluorescent powder and Rb-marking showed both are equally effective. Selection of method will depend on the objectives and experimental design.

ISSN:1754-5692    

DOI:10.1093/ee/21.6.1377

出版商:Oxford University Press    

年代:1992

数据来源: OUP