摘要:

Arthropod predation on small (second instar) velvetbean caterpillar,Anticarsia gemmatalisHübner, in Florida soybeans,Glycine max(L.), by a complex of arthropod predators was measured using cage exclusion techniques. Average per capita rates of predation remained relatively constant during two seasons. Relative contributions of the species composition of predator complexes, predator number, small velvetbean caterpillar number, temperature, and soybean leaf area to predation dynamics are described. The searching universe of predators in soybeans was influenced by the dynamics of soybean leaf area. Compensation for leaf area changes by predators searching more area is suggested as an important factor influencing predation on small velvetbean caterpillar in soybeans.

ISSN:1754-5692    

DOI:10.1093/ee/17.5.821

出版商:Oxford University Press    

年代:1988

数据来源: OUP

摘要:

Rate of development of the immigrant azalea lace bug,Stephanitis pyrioides(Scott), reared on hybrid evergreen azalea, was measured at three constant temperatures. Egg development across temperatures was nonlinear and ranged from a mean of 11.6 d at 31.7°C to 23 d at 20.6°C. Stadial development rate between instars for both sexes was similar at each temperature. Development of instars across temperature was nonlinear. Third instars required the minimum time for development; this was half the time required for fifth instars, which required the longest time. Adults are nondiapausing, and males lived longer than females when paired independent of temperature. Single males and females lived longer at 20.6°C than single and paired cohorts at 26.1 and 31.7°C. Single males lived as long as 246 d and females 253 d at 20.6°C. Fecundity and average oviposition rate varied nonlinearly with temperature. Presence of the male was found to affect oviposition rate. Postoviposition longevity for females is reported. Overwintered eggs hatch earlier than reported previously, and four generations were determined in Maryland with adults present in early December. The immigrant mirid predator ofStephanitislace bugs,Stethoconus japonicusSchumacher, was discovered during the study.

ISSN:1754-5692    

DOI:10.1093/ee/17.5.827

出版商:Oxford University Press    

年代:1988

数据来源: OUP

摘要:

Bacteria in the guts of southern corn rootworms,Diabrotica undecimpunctata howardiBarber, feeding on artificial diet (AD larvae) and on corn roots (CR larvae) were studied. Species composition and abundance of gut-inhabiting bacteria differed between AD larvae and CR larvae. The total bacterial population in AD larvae was about 100 times less than those in CR larvae. The majority of bacterial species found in the gut of CR larvae were glucose fermenters, whereas the major bacteria found in AD larvae were fluorescent pseudomonads.Enterobacter cloacaewas predominant among glucose-fermenting bacteria in CR larvae.Pseudomonas putida, P. fluorescens, andAgrobacteriumsp. were major bacteria in the glucose nonfermenting bacteria group in CR larvae and AD larvae. The numbers of fluorescentPseudomonasspp. andAgrobacteriumsp. found in CR larvae were positively correlated with their population on corn roots.

ISSN:1754-5692    

DOI:10.1093/ee/17.5.832

出版商:Oxford University Press    

年代:1988

数据来源: OUP

摘要:

The effectiveness of endemic predators and parasitoids as biological control agents of the greenbug,Schizaphis graminum(Rondani), was experimentally evaluated during 1985 and 1986 in Kansas winter wheat,Triticum aestivum, and grain sorghum,Sorghum bicolor.Mechanical exclusion was used as the experimental method of evaluation. The coccinellidsColeomegilla maculata lengiTimberlake,Hippodamia convergensGuèrin, andScymnusspp. were the predominant predators of greenbugs in sorghum and comprised 89% of the predator population.Lysiphlebus testaceipes(Cresson) was the most abundant primary parasitoid in sorghum. The natural enemy complex was able to suppress experimental greenbug densities at all stages of sorghum growth from 3-leaf through the boot stage. The impact ofL., testaceipeson greenbugs was sporadic between locations. In winter wheat,H. convergenswas the most abundant natural enemy and significantly suppressed greenbug densities. Natural enemies, primarily coccinellids, consistently reduced experimental greenbug populations in winter wheat and grain sorghum.

ISSN:1754-5692    

DOI:10.1093/ee/17.5.836

出版商:Oxford University Press    

年代:1988

数据来源: OUP

摘要:

Dispersal of the leafhopper vector of X-disease,Paraphlepsius irroratus(Say) within and into peach and cherry orchards was monitored by a mark, release, and recapture experiment. Field-collected adults were marked using fluorescent dyes and released at locations in and outside of two orchard sites. The marking method did not significantly affect leafhopper flight activity or survival. Dispersal was monitored using yellow sticky board traps for 21 d following each release, and the data were fitted to equations. The overall leafhopper recapture rate within 60 m was 2.35%. Dispersal rate for the first and second generations averaged 2.9 and 3.8 m/d. Wind was the major factor influencing leafhopper dispersal direction, as mean dispersal direction correlated significantly with mean wind direction (r= 0.94,P≤ 0.05). Temperature affected leafhopper activity; this was particularly apparent with second-generation adults active at temperatures approximately 11°C less than first-generation adults. There was no significant difference in the overall dispersal behavior between first and second generations. Implications of this movement to the spread of X-disease are discussed.

ISSN:1754-5692    

DOI:10.1093/ee/17.5.842

出版商:Oxford University Press    

年代:1988

数据来源: OUP

摘要:

Native boll weevils,Anthonomus grandisBoheman, were compared to two laboratory-reared strains, NEVIE (reared for 20 generations) and CAST (reared for>400 generations) in terms of number of flights, resting time before flight (preflight), flight distance, flight duration, and flight speed. Native weevils did not differ significantly (P<0.05) from the laboratory-reared strains in total number of flights and the resting time before a given flight. Overall mean number of flights and resting time before a given flight were 7.7 ± 0.9 and 20.6 ± 1.1 min, respectively, ±SD. However, native weevils had significantly (P3 times higher flight durations, and only 1.1 times higher flight speeds for their first flight than for the remaining five flights. Native females tended to fly farther and longer than their laboratory-reared counterparts.

ISSN:1754-5692    

DOI:10.1093/ee/17.5.852

出版商:Oxford University Press    

年代:1988

数据来源: OUP

摘要:

The frit fly (FF),Oscinella frit(L.), is a pest of golf course and home lawn turfgrasses. Adult occurrence was monitored with a sweep net and a modified unit area sweep net. There are three and a partial fourth generations per year in northern Ohio (Wooster). Adult peak densities occurred during mid-May, late June, late July-early August, and mid-September in 1984. FF adult peaks were about 2 wk earlier in 1985. There was a slight male bias in sex ratios within sampling nets because of sampling technique and FF behavior. Parous females were determined by examining ovarian morphology. Parasitic nematodes were found within FF abdomens. Five of eight FF adult occurrence periods indicated major ovipositional activity when 40% of adults occurred (approximate time of control treatment). The best linear regression models for predicting 40% adult occurrence were a base temperature of 0°C and a 1 March starting date. Degree-day prediction methods may be more reliable for targeting dates to time control programs than calendar dates.

ISSN:1754-5692    

DOI:10.1093/ee/17.5.855

出版商:Oxford University Press    

年代:1988

数据来源: OUP

摘要:

Cohorts of mating pairs of newly-emerged first-generationLeptinotarsa decemlineata(Say) adults were established each week on potato foliage to examine seasonal changes in reproductive and diapause activity and to determine when diapause induction occurred in the field in western Massachusetts. The percentage of newly emerged females that oviposited before entering the soil was much higher in the 25 July cohort (81.8%) than in the 1 August cohort (8.3%), indicating that diapause induction occurred by early August in this region. Population data supported this finding. Differences in within-season population dynamics over a 6-yr period (1981–1986) were evaluated with respect to the role of timing of arrival of colonizing adults and diapause induction. Because oviposition consistently dropped off by mid-August due to diapause induction, the extent of second-generation populations was most influenced by the timing of oviposition by first-generation females. Substantial differences in the abundance of second-generation populations relative to that of first-generation resulted from differences in time of colonization by overwintered adults and subsequent emergence of first-generation adults. A temperature-dependent phenological model corroborated the importance of diapause and time of colonization in the phenology and population dynamics of this insect. Implications for pest management are discussed.

ISSN:1754-5692    

DOI:10.1093/ee/17.5.863

出版商:Oxford University Press    

年代:1988

数据来源: OUP

摘要:

Five techniques were evaluated for sampling efficiency for leafhopper nymphs and adults in bermudagrass,Cynodon dactylon(L.). The D-Vac insect collector was selected as the best sampling technique because it provided greater density estimates of nymphs and adults with less relative variation (SEM/$\bar x$) (100) than sweep-net, drop trap, pan-shake, and cut-and-bag techniques. Iwao's regression method and Taylor's power law were used to describe the dispersion patterns of adults ofCarneocephala flaviceps(Riley),Endria inimica(Say),Exitianus exitiosus(Uhler),Graminella nigrifrons(Forbes),Graminella sonora(Ball),Planicephalus flavocostatus(Van Duzee),polyamia weedi(Van Duzee),Psammotettix lividellus(Zetterstedt),Stirellus bicolor(Van Duzee), and total adults. Dispersion patterns of nymphs ofC. flavicceps, E. inimica, E. exitiosus, Graminellaspp. plusP. lividellus,P. weedi, and total nymphs also were quantified. Both dispersion analyses found that nymph and adult populations of all leafhopper taxa were aggregated. The results of Taylor's analysis were used to calculate the minimal mean density that can be estimated for a given sample size and precision level for each leafhopper taxon. The uses of these data in selecting an optimal sample size for a fixed-sample-size program are discussed.

ISSN:1754-5692    

DOI:10.1093/ee/17.5.872

出版商:Oxford University Press    

年代:1988

数据来源: OUP

摘要:

Dynamics of the asparagus aphid,Brachycorynella asparagi(Mordvilko), were studied in two mature asparagus fields and one immature field for a minimum of two seasons. To minimize disturbance to the asparagus, no harvesting, spraying, or cultivation was done. Numbers ofB. asparagiwere low early in the spring and increased to a peak in late June or July or in September to early October. No midseason peak was observed. Fields with an early summer peak had a midsummer low point and usually a late summer peak. Decline of aphid numbers in the fall coincided with egg laying that started during the last week of September when day length was about 12 h. Production of winged aphids and parasitism byDiaeretiella rapae(McIntosh) were density-dependent on some plots. These mortality factors undercompensated for changes in aphid density and failed to keep aphid numbers at acceptable levels. No consistent, significant correlations between temperature or rainfall and aphid numbers were found. Egg hatch occurred shortly after the first asparagus spears emerged in the spring. Predicted time of egg hatch based on degree days was within 1 d of observed hatch. Growth of asparagus plants during a growing season had a weak, inverse relationship to aphid numbers.

ISSN:1754-5692    

DOI:10.1093/ee/17.5.878

出版商:Oxford University Press    

年代:1988

数据来源: OUP