摘要:

To identify factors affecting the spatial dynamics ofTrichoplusia ni(Hübner) on cabbage, the movements of individual larvae were monitored. Larvae were marked with32p and released individually, one per plant, on cabbage plants in research plots. Their movements were monitored by recording their position on the plant daily, locating them with a Geiger counter. In the same plots, hourly measurements of temperature and relative humidity were recorded in three different parts of the crop canopy. Transition probabilities for the larvae from and to each of five vertical plant strata were modeled as definite integrals of the Beta probability density function (pdf). The shape parameters for these Beta pdf's were modeled as a function of microclimate, and the necessary parameters to do so were estimated by the method of maximum likelihood. This model predicted the data well and was more efficient than logistic regression. The model predicts that under high temperatures and low vapor pressure deficit (vpd), larvae move down to the shaded, cooler, lower parts of the plant; whereas under low temperatures and high vpd, they moved upward toward the economically important wrapper leaves and cabbage heads.

ISSN:1754-5692    

DOI:10.1093/ee/18.2.187

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

That most biological control success stories involve parasitic rather than predatory natural enemies is a well-entrenched myth. In fact, recent analyses have shown that introduced parasitoids and predators have not differed significantly in their rates of establishment or success as agents of biological control. However, it is true that introductions of predators have been attempted much less often than introductions of parasitoids. This may be partly because of controversy over the attributes of the ideal natural enemy. A more basic obstacle has been the lack of a methodology for identifying any but the most prey-specific of predators of target pests. I propose a new methodology, using on-the-spot serological stomach analysis of predators. The feasibility of this approach is illustrated with data from monoclonal antibody-based ELISA assays of predators fed larvae of species of the corn earworm complex.

ISSN:1754-5692    

DOI:10.1093/ee/18.2.195

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

Two-dimensional spectral analysis is used to highlight periodiCities in regular lattice samples of insect spatial distributions. The technique is explained, and simulated distributions are analyzed to show how results are interpreted. Based on analyses of samples at one site, the distributions of gypsy moth larvae are characterized by wavelike periodicities and sometimes by small-scale clumping. The larvae of the gypsy moth predatorCalosoma sycophantaL. exhibit regular, small-scale clumping. AdultC. sycophantadistributions vary between small-scale clumps and large-scale waves, sometimes showing both at once. These analyses are compared with calculations of Lloyd's patchiness index for the same distributions, with generally complementary results. Spectral analysis is a powerful and useful adjunct to other methods of measuring dispersion and should be useful in entomological research.

ISSN:1754-5692    

DOI:10.1093/ee/18.2.201

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

Greenhouse and field studies were conducted to assess the effects of water stress on almond leaf temperatures and Pacific spider mite,Tetranychus pacificusMcGregor, developmental times. Egg-to-egg developmental times on water-stressed almond trees were 11% faster than developmental times on nonstressed trees. Leaf surface temperatures on the stressed trees averaged 2.1°C higher than those on the nonstressed trees. Accumulated degree hours for egg-to-egg development were not significantly different among the mites from the stress and nonstress treatments. Thus, the faster developmental times for the mites on the stressed trees were the result of the higher leaf surface temperatures. Mean daily leaf canopy temperatures from 4-yr-old, water-stressed almond trees were 2.0°C higher than control trees under field conditions. Leaf canopy temperature differences were significantly correlated with differences in predawn leaf water potentials between the water-stressed and control trees. Mature almond trees under an irrigation regime of 55% evapotranspiration (ET) had significantly higher afternoon leaf canopy temperatures than trees under regimes of 85 and 100% ET. Increased leaf surface temperatures in water-stressed almond trees have the potential for accelerating increases in spider mite populations.

ISSN:1754-5692    

DOI:10.1093/ee/18.2.208

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

Diapause in eggs ofChortoicetes terminifera(Walker) is associated with an increase in the temperature threshold for development at the late anatrepsis stage. For most of the year, the threshold for development at all stages of embryonic development is 16°C. but in autumn. development beyond late anatrepsis requires temperatures above about 26°C. When ambient temperatures are below 26°C, embryonic development is arrested and embryos enter diapause. At higher temperatures. some embryos develop but others do not. indicating that there is some variation in the threshold for development. During early winter, the threshold rapidly declines, and embryos resume development when soil temperatures increase above this reduced threshold.

ISSN:1754-5692    

DOI:10.1093/ee/18.2.213

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

Thirteen species from six genera in the family Sesiidae were collected during 1983–1985 in traps baited with single isomers or blends of 2,13 and 3,13 octadecadienyl acetates and alcohols. (E,Z)-2,13 octadecadienyl acetate was shown to be highly attractive toVitacea polistiformis(Harris),Paranthrene asilipennis(Boisduval),P. simulans(Grote), andSynanthedon acerrubri(Engelhardt). Captures of three species were improved by the addition of 2,13 isomers to 3,13 isomers, and the first seasonal plots based on captures in pheromone traps are shown for three species.

ISSN:1754-5692    

DOI:10.1093/ee/18.2.216

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

Eclosion of overwintering eggs of pine needle scale,Chionaspis pinifoliae(Fitch), was modeled from growth chamber fluctuating temperature rearings. A computer model, DEGDAY, was used to determine daily and accumulated degree-day accumulations to hatch. This model and simple regression techniques were used to identify the developmental threshold. Percentage of survivorship ranged from 0 at 9°C to 98 at 18.5°C. At 18.5°C, 136 degree-days accumulated to hatch, and time to 50% hatch was 17.25d. The developmental threshold lies between 10.8 and 11. 8°C.

ISSN:1754-5692    

DOI:10.1093/ee/18.2.223

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

Experimental introductions of the two bark beetlesTomicus piniperdaL. andIps sexdentatusBoerner and inoculations with patches of agar cultures of their associated fungi (respectivelyLeptographium wingfieldiiMorelet andOphiostoma brunneo-ciliatumMath.-K. (Hunt)) were performed and compared in a clone ofPinus pinasterAitone and some forest trees ofPinus sylvestrisL. Results were similar in the two pine species. Tree response to fungal inoculation was characterized by a considerable increase in the concentration of all the phloem monoterpenes. No qualitative differences in the major monoterpenes were noticed between induced resin and preformed resin. For an introduction ofT. piniperda, terpene concentration was always lower than for an inoculation ofL. wingfieldii. After an introduction ofI. sexdentatus, terpene concentration was lower than or equal to that obtained after an inoculation ofO. brunneo-ciliatum. The inoculation of diversified quantities of spores in sterilized water to Scotch pine demonstrated a dose-dependent tree response (expressed as resin concentration in the phloem) to the two species of fungi. The intensity of the response increased to a similar level for the two fungus species. In the case ofO. brunneociliatum, this level was reached for a quantity of spores much lower than in the case ofL. wingfieldii. Consequently, the difference in the intensity of the tree response toT. piniperdaandL. wingfieldiimight be explained by the lack of fungus associated with the attacking insects or by too low a number of spores introduced by the insects in their galleries. In the case ofI. sexdentatusandO. brunneo-ciliatum, the variable response of the tree from one insect to another might depend only on the presence or the absence of a fungus in the insect gallery.

ISSN:1754-5692    

DOI:10.1093/ee/18.2.228

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

Effects of simulated insect damage—artificial defoliation and root damage in combination with two levels of watering—were studied to determine the potential effect on northern red oak seedlings (Quercus rubraL.). Treatments and treatment combinations caused significant differences in stem diameter, percentage of stem dieback, and mortality. Defoliation and a regime of decreased watering seemed to have the greatest effect on seedling growth and mortality. Root injury had no consistent direct effect, but interacted significantly with other factors. Insect damage to foliage and roots, together with water stress, may be a factor in poor survival of oak seedlings under field conditions.

ISSN:1754-5692    

DOI:10.1093/ee/18.2.235

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

The within-plant distributions ofNabis americoferus(Carayon),N. roseipennisReuter, andN. rufusculusReuter differ in soybean.N. americoferusadults are located in the upper canopy, whereas adults of the other two species are located lower in the plant canopy. Early-instar nymphs of all three species are vertically separated from their respective adult stages. Nabids were observed to feed on a wide variety of arthropods including pest, beneficial, and innocuous species. The seasonal abundance of nymphalN. roseipennisand the within-plant overlap of its distribution with early instars of the green cloverworm suggested that it may be an effective predator on this pest species.N. roseipennisnymphs were successful in reducing numbers of green cloverworm larvae in the field in the presence of other predators and alternative prey under minimally modified conditions. Starting densities of 20–25 third instars per 0.9-m plot resulted in up to 50% reduction in subsequent green cloverworm populations.

ISSN:1754-5692    

DOI:10.1093/ee/18.2.240

出版商:Oxford University Press    

年代:1989

数据来源: OUP