摘要:

A study was undertaken to determine species composition and seasonal abundance of ground-dwelling insects associated with European corn borer (ECB),Ostrinia nubilalis(Hübner), adult action sites and to determine impact of adult ECB control on nontarget insects in these sites. A total of 24,497 ground-dwelling insects was collected during the 2-yr study. Coleoptera, Orthoptera, and Homoptera accounted for 98% of the total insect fauna. Three predator species were abundant in ECB action sites:Evarthrus alteransCasey,Pterostichus chalcites(Say), andHarpalus pennsylvanicusDeGeer. Carbaryl (2.26 kg [AI]/ha) or fenvalerate (0.1 kg [AI]/ha) applied for adult ECB control had minimal impact on the ground-dwelling insect community. Predator populations were not affected. Role of action sites as a source of predators for Iowa cornfields is also discussed.

ISSN:0046-225X    

DOI:10.1093/ee/16.1.231

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Corn earworm (CEW),Heliothis zea(Boddie), third filial egg and larval populations were monitored in field trials during 1980–82 in eastern North Carolina to investigate the effects of soybean planting date, cultivar, phenological stage, and degree of canopy development on CEW oviposition and survival. In 1982, soybeans were sampled every 3–4 d during the entire CEW F3generation. This allowed for calculation of total within-generation production of eggs, egg parasitism, and stage-specific mortality. Planting date and phenological stage were the most important factors affecting CEW oviposition and survival. Late-planted soybeans had more eggs and higher insect survival than did early-planted soybeans, and treatments beyond the pod-set stage received few eggs. The highest correlations were found between the number of eggs and the number of plant terminals (r= 0.7) and flowers (r= 0.79). Greatest CEW mortality occurred between the egg stage and the third instar. Total incidence of natural enemies was higher in early-planted soybeans.

ISSN:0046-225X    

DOI:10.1093/ee/16.1.237

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

A prediction of forest insect defoliator climatic release hypotheses is that there will be a consistent association between outbreaks and weather favorable to fitness. However, such predictions are difficult to test. Simplifying assumptions regarding population processes, definition and delineation of outbreaks, and the nature of climatic variation are usually required. To determine if there was a relationship between saddled prominent,Heterocampa guttivitta(Walker), outbreaks and moisture condition, we grouped infestations into outbreaks based on correlation of drought between climatic regions and overall spatial and temporal pattern of infestations. We then developed parametric tests using these outbreaks as independent observations. No consistent relationship between drought as indicated by the Palmer hydrological drought severity index and outbreaks was found. Implications of our procedure are discussed in terms of other studies involving climatic release hypotheses.

ISSN:0046-225X    

DOI:10.1093/ee/16.1.246

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Effects of potato leafhopper,Empoasca fabae(Harris), feeding were coupled to a simple potato growth model that accumulates and partitions dry matter into leaves, stems, roots, and tubers. Feeding effects of leafhopper on potato were modeled in two ways: as a temporary and reversible reduction in the plant's potential net crop growth rate, and as leaf area lost to hopperburn. Daily reductions in potential net crop growth rate were determined by an exponential relationship of leafhopper feeding activity, which was defined as number of nymphs per 30 midplant leaves multiplied by daily degree-day increment. Rate of hopperburn development was determined from a modified logistic equation. Values for the model's parameters were derived with data from 8 or 13 sequential, within-season harvests of plant dry matter and counts of leafhopper nymphs from infested and uninfested field plots collected over 2 yr. Partitioning responses of the modeled crop were similar to those observed for field-grown plants. Model output was also verified against nymphal counts, hopperburn readings, and final yields from an independent field experiment, which resulted in a one-to-one correspondence between predicted and final yields. Computer simulations with nymph infestations at different times of the season indicated that reductions in final tuber yield were differentially effected by leafhopper feeding at different stages of growth.

ISSN:0046-225X    

DOI:10.1093/ee/16.1.250

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Sampling Malayan black bugs,Scotinophara coarctata(F.), in rice was conducted on the island of Palawan, the Philippines, using fluorescent-street-light traps, Petromax gas-lantern traps, and visual counts in the field. Peak catches in light traps occurred around the time of the full moon, especially during mid-August 1984, mid-April to mid-May, and June 1985. However, we found no relationship between densities ofS. coarctatain light traps and in the field. Population sampling revealed that data fromS. coarctatafit a negative binomial distribution, with a clumping coefficient ofk= 0.50. A sequential sampling plan was developed and compared with intensive sampling using visual counts of bugs on individual hills of rice. Using sequential sampling, 44–56% fewer samples were needed to arrive at the same decision obtained by intensive sampling. Over 90% agreement between intensive sampling and sequential sampling was found.

ISSN:0046-225X    

DOI:10.1093/ee/16.1.259

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Effect of thePhylloxera notabilisPergande gall was assessed on leaf chlorophyll, leaf nutrient status, and leaf gas exchange of nursery pecan,Carya illinoensis(Wangenh.) C. Koch, ‘Stuart’. Gall tissue was significantly different from ungalled tissue in every nutrient investigated. Galls contained 60% N, 50% Ca, and 50% Al, but 260% K, 150% P, and 200% Na of leaf tissue from uninfested (control) leaflets. Analysis of concentric rings of tissue revealed that chlorophyll and all macronutrients except P were altered in leaf tissue 0–1.5 cm away from a gall compared with control leaflets. Net CO2assimilation rate of infested tissue was reduced by an average of 27%, which was equivalent to almost 4-fold the percentage of gall area occurring in the field of measurement. Significant reductions in leaf conductance and transpiration also occurred over leaf tissue containing a gall. Cumulative gall cross-sectional area was negatively correlated with net CO2assimilation rate. Thus, not only did theP. notabilisgall divert resources away from normal metabolic function, but it also interfered with the nutrient status and photosynthetic capacity of adjacent leaf tissue.

ISSN:0046-225X    

DOI:10.1093/ee/16.1.264

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

The squash bug (SB),Anasa tristisDeGeer, completes 1.5 generations per yr in northeastern Kansas. Overwintered adults mate and oviposit on cucurbitaceous host plants from early June to mid-August. Most eggs are deposited from June to early July when female survivorship is highest, but some oviposition occurs through mid-August. First-generation adults begin to emerge between the 1st and 3rd wk of July. Oviposition commences 7–10 d after emergence. Females that emerge before late July avoid diapause and produce a second generation. Thereafter the incidence of diapause increases progressively, reaching 100% in first- and second-generation females that emerge in early September. Diapausing females do not mate or reproduce until the following spring. SB males also appear to undergo diapause but, unlike females, they overwinter with mature reproductive organs. The primary expression of male diapause is suppressed reproductive behavior. Reproductive periods of overwintered and first summer-generation adults overlap. The extent of this overlap depends in part on spring temperature conditions that influence field entry by overwintered adults; the oviposition schedule; and development of first-generation progeny. During cool springs, a large proportion of first-generation SB emerge late in the season and enter diapause. In these years, smaller, less-damaging, populations occur.

ISSN:0046-225X    

DOI:10.1093/ee/16.1.269

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Effects of stand density and late-season defoliation by Mexican bean beetles,Epilachna varivestisMulsant, on three yield components of beans were estimated from field studies conducted during 1983 and 1984 in four fields of pinto beans in northeastern Colorado. Number of beans per plant, mean weight of a bean, and mean weight of beans per plant were calculated for 100 samples per field, and regressed against three independent variables: plant density, percentage of defoliation, and density × defoliation interaction. Results of the analyses showed that plant density negatively affected number of beans per plant and weight of beans per plant, but not average weight of a bean. Responses were not linear; slope decreased at higher densities. Defoliation negatively affected all three yield variables. Average weight of a bean was linearly related to defoliation. Number of beans per plant and weight of beans per plant showed linear responses above a threshold level of defoliation. A piecewise regression model indicated that yields were not affected by defoliation until levels reached approximately 19% foliage loss. Laboratory consumption studies were conducted to determine age-specific damage potential for Mexican bean beetles and two occasional defoliators of pinto beans, saltmarsh caterpillars,Estigmene acrea(Drury), and yellow woollybears,Spilosoma virginica(F.). Insect consumption potentials and field studies of yield responses to defoliation were used to estimate threshold densities.

ISSN:0046-225X    

DOI:10.1093/ee/16.1.274

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Larvae ofAnopheles punctipennis(Say),Culex territansWalker,Aedes atlanticusDyar&Knab, andPsorophora ferox(von Humboldt) were collected and 13 water-chemistry variables were measured at permanent and semipermanent pools in Duplin County, N.C., during 1982 and 1983. Stepwise logistic regression was used to identify water-chemistry variables associated with habitats and to predict the occurrence of each species. Models based on pH and concentrations of Cl, K, and Na ions gave reasonable predictions of occurrence.

ISSN:0046-225X    

DOI:10.1093/ee/16.1.281

出版商:Oxford University Press    

年代:1987

数据来源: OUP

摘要:

Pulvinariella mesembryanthemi(Vallot) andPulvinaria delottoiGill are closely related soft scales recently introduced to California, where they attack aizoaceous ground covers. Populations of both species were cultured onCarpobrotus edulis(L.) ×aequalateris(Haw.) under greenhouse conditions to determine their responses to various fertilizer formulations and concentrations and five water regimes. We measured scale growth, survivorship, ovisac size, fecundity, and developmental time for each treatment population. There were no differences in population responses ofP. delottoito any water or fertilizer regime. Although all fertilizer treatments increased growth rate ofP. mesembryanthemi, we found no significant correlation between amount or form of nitrogen addition and survivorship, ovisac size, or fecundity. Survivorship was similar amongP. mesembryanthemipopulations treated with different water regimes. However, as watering frequency increased,P. mesembryanthemigrew faster, ovisacs were larger, fecundity was greater, and developmental time was shorter.

ISSN:0046-225X    

DOI:10.1093/ee/16.1.286

出版商:Oxford University Press    

年代:1987

数据来源: OUP