摘要:

In 1980 and 1982, the temporal pattern of Colorado potato beetle,Leptinotarsa decemlineata(Say), damage to individual field-grown potato plants was manipulated by five schedules of insecticide application. The insecticide applications resulted in plants that sustained either minimum damage, damage during the vegetative phase, damage during the tuber-bulking phase, or damage during the entire season (maximum damage). Plants were harvested weekly, and polynomial growth curves were fit to the data. The only treatments that significantly affected the plant growth curves were maximum damage and damage during the tuber-bulking phase. Damage during the vegetative phase delayed the occurrence of maximum haulm and tuber growth rates, whereas damage during the tuber-bulking phase permanently reduced these growth rates. This indicates that plants damaged before the initiation of tubers were able to recover from beetle damage, but plants damaged after tuber initiation were not. Plants receiving maximum damage or damage during the tuber-bulking phase appeared to have reduced tuber and total relative growth rates, indicating a decrease in the efficiency of dry matter assimilation. An important factor behind the changing temporal sensitivity of potato growth to beetle damage appears to be the dramatic difference in leaf area ratio between plants in the vegetative phase and plants in the tuber-bulking phase. Plants in the vegetative phase have approximately 200 cm2of leaf area to support each gram of dry plant tissue; plants in the tuber-bulking phase have only 50 cm2of leaf area per gram of dry weight. Loss of leaf area caused by Colorado potato beetle during the tuber-bulking phase should have a greater relative effect on assimilation than proportionately equal reductions in leaf area during the vegetative phase.

ISSN:1754-5692    

DOI:10.1093/ee/18.5.854

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

Insect management tactics can be divided into three groups according to the influence of insect movement on their evaluation: (1) the use of insecticides and antibiotic host plant characters directed against immatures, (2) the use of trap crop, trap out, adulticides, and antixenotic host plant characters directed against mobile adults and augmentative biological control relying on mobile control agents, and (3) wild host management and the use of autocidal genetic controls applied on an area-wide basis. A simulation model of insect movement is subjected to a sensitivity analysis based on average parameter values derived from the literature. It is used to explore the process of reinvasion of an area in which a pest population has been suppressed. It is estimated that suppression ofHeliothis virescens(F.) over an area 25 km in diameter would be necessary to prevent substantial infiltration into the treated area by the wild population within two generations. Given such potentially large treatment areas, eight experimental designs that reduce the size and number of areas required to test the efficacy of area-wide control tactics experimentally are explored. The best designs require two smaller areas for 6 yr or two larger areas for 2 yr. The latter requires extensive sampling effort because it depends on measuring spatial gradients of insect density

ISSN:1754-5692    

DOI:10.1093/ee/18.5.868

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

The abundance ofLyonetia speculellaClemens larvae on each tree of a 1.25- ha apple orchard, planted in 1986, was determined monthly from June to September 1986 and May to September 1987. In both years, the abundance ofL. speculellawas low initially, increased in early summer, remained constant through midsummer, and increased again at the end of the summer.L. speculellaabundance per tree was aggregated, but the distribution of infested trees was initially random, then regular for the remainder of each year. The initial increase in abundance was caused by an increase in the percentage of the trees infested and the late summer increase by an increase in aggregation on infested trees. There were differences in distribution of mines between ‘Northern Spy’ and ‘Red Delicious’ because of phenological and growth habit differences between the two cultivars. An application of oxamyl in 1986 temporarily altered the spatial distribution ofL. speculella, increasing the aggregation and decreasing the percentage of the trees infested for the sample following oxamyl application. A graph of the relationship between sample size and sampling precision is provided to estimate required sample size for future studies. Random, systematic, random cluster, and systematic cluster sampling designs were all equally effective in simulated sampling from the field data

ISSN:1754-5692    

DOI:10.1093/ee/18.5.875

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

The fall armyworm,Spodoptera frugiperda(J. E. Smith), oviposited on plants in all phenological stages (presquaring, squaring, early bloom, full bloom, mature boll, and open boll) of cotton,Gossypium hirsutumL., studied in field cages. Studies of within-plant distribution of egg masses indicated that most (>84.5%) fall armyworm oviposition occurred in the middle to lower portions of the plant. Most (92.4%) of the egg masses were found on the under surface of leaves. More egg masses were deposited on leaves emerging directly from the main stem than on leaves emerging from branch nodes. In general, the highest number of egg masses was located near the main stem of the plant.

ISSN:1754-5692    

DOI:10.1093/ee/18.5.881

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

Effects of the cotton allelochemical, gossypol, on the development and survival ofCampoletis sonorensis(Cameron) were studied inHeliothis virescens(F.) larvae exposed for different lengths of time and dose to the chemical. We used three feeding methods: exposure of the host to gossypol from neonate stage onward, from 24 h before parasitization, and 24 h after parasitization. A gossypol concentration of 0.013% (wt gossypol/fresh wt diet) from the neonate stage onward positively affected the growth of the endoparasitoid, probably due to the stimulated growth ofH. virescens. However, this dose of gossypol did not induce significant positive parasitoid growth when fed to the host after parasitism. When the gossypol dose before parasitism was increased to 0.1% and above, the growth and weight of the adult parasitoid were significantly reduced. Although the weights of the parasitoids were affected,C. sonorensiswere capable of developing from hosts exposed to a dose that precluded development ofHeliothisto the adult stage. Exposure ofHeliothisto 0.4% doses and higher before parasitism resulted in host death, which led to parasitoid mortality. Time to cocoon formation and time to adult parasitoid emergence increased significantly at the dose of 0.2% and above. Gossypol at doses of 0.013–0.4% in the diet ofH. virescensdid not show any significant effect on longevity ofC. sonorensisadults.

ISSN:1754-5692    

DOI:10.1093/ee/18.5.886

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

Laboratory and greenhouse studies examined the effects of road dust on predation by the western predatory mite,Typhlodromus(=Galandromus)occidentalis(Nesbitt), on the Pacific spider mite,Tetranychus pacificusMcGregor. Significantly fewer Pacific spider mites were found on bean plants and almond trees with western predatory mites regardless of the presence or absence of dust. A detrimental effect of dust was not evident on populations of western predatory mites. The effect of dust on populations of Pacific spider mites was not conclusive because high and low populations were associated with the presence of dust. In addition to dust and predators, we examined the effect of almond tree water stress on predation. Water stress did not have any significant effects on either population, however the accumulated degree hour difference between stressed and nonstressed trees was low. These studies suggest that road dust does not influence predation by western predatory mites on Pacific spider mites.

ISSN:1754-5692    

DOI:10.1093/ee/18.5.892

出版商:Oxford University Press    

年代:1989

数据来源: OUP

摘要:

Interactions between larvae of the banded cucumber beetle (Diabrotica balteataLeConte), a resistant cultivar (‘Regal’), a susceptible sweet potato clone (SC-1149-19), and a nematode arthropod parasite,Heterorhabditis heliothidis(Khan, Brooks, and Hirschman 1976) Poinar, Thomas, and Hess 1977, South Carolina strain, were evaluated. Plant resistance in the cultivar Regal was active against younger larvae. Reduced adult weights and fewer emerging adults were observed when second instars were exposed to the parasite on sweet potato tissue, and the eclosion period was longer for second instars and reduced for third instars. Exposure to the resistant cultivar reduced the eclosion period of second instars as compared with larvae exposed to the susceptible clone, whereas no differences were observed among plant entries for third instars. When second instars were exposed to the parasite, the eclosion period was reduced and no differences were noted for third instars. The duration of the eclosion period was negatively correlated with adult weight.

ISSN:1754-5692    

DOI:10.1093/ee/18.5.897

出版商:Oxford University Press    

年代:1989

数据来源: OUP