摘要:

In 1986, B. Dennis and coworkers formulated a model describing the temperature-dependent and stochastic character of insect development in field populations. This paper presents three additional statistical inference techniques to be used in conjunction with the model. We derive a confidence interval forpi(t), the proportion of the population in development stageiat timet;confidence intervals for the times at which intermediate stage proportions peak; and a test for detecting outlying observations. Examples of each of these techniques are presented using data from the rangeland grasshopper,Ageneotettix deorum(Scudder).

ISSN:1754-5692    

DOI:10.1093/ee/17.5.887

出版商:Oxford University Press    

年代:1988

数据来源: OUP

摘要:

The effectiveness of the exotic South American hymenopterous parasitoidEpidinocarsis lopezi(De Santis) in controlling the cassava mealybug (CM),Phenacoccus manihotiMatile-Ferrero, in southwestern Nigeria, was assessed using emergence samples. Ten infested cassava tips were collected from each of 679 fields during four surveys over an area of 200,000 km2in the 2 yr following establishment of the parasitoid. These samples were used to determine frequency and abundance of this and other insects associated with the CM. Survey results suggest that CM infestation levels as measured by frequency of plants showing CM damage symptoms declined as a result of the parasitoid's activity from 88% at the end of the first dry season (March 1983) to 23% in the same period the following year.E. lopezinumbers per field also declined during the same period, but parasitoid densities per infested cassava tip in both years remained the same. A sharp fall in numbers of indigenous polyphagous coccinellids on cassava, particularly ofHyperaspisspp. and to a lesser extent ofExochomussp., was also associated with decline in CM infestation levels. By contrast, the infested tip densities of the cecidomyiidDicrodiplosis manihotiHarris, which is specific on CM, were not affected. Other indigenous primary parasitoids of the genusAnagyruswere rare. Ten species of native hyperparasitoids were common fromE. lopezi; most common wereProchiloneurusspp. andChartocerusspp. AsE. lopezidensities declined, percent hyperparasitism dropped significantly from 43.8% in March 1983 to 30.7% in March 1984, and from 35.7% in December 1983 to 17.5% in December 1984. In the last two surveys, CM densities, as determined from dissected cassava tips, were low throughout southwestern Nigeria. It is concluded thatE. lopeziis responsible for declines in CM densities and damage symptoms, for reduction of coccinellid abundance via competition for a common food source, and that hyperparasitism does not preventE. lopezifrom being an efficient parasitoid.

ISSN:1754-5692    

DOI:10.1093/ee/17.5.894

出版商:Oxford University Press    

年代:1988

数据来源: OUP

摘要:

Emergence of boll weevils from overwintering habitat was variable among years and among fields within a year. Use of heat units to predict emergence was no more accurate than use of Julian dates. Emergence curves with confidence limits were constructed to show the variability in emergence that could be expected at any time during the emergence period, and to predict future emergence.

ISSN:1754-5692    

DOI:10.1093/ee/17.5.903

出版商:Oxford University Press    

年代:1988

数据来源: OUP

摘要:

Field studies were conducted in 1983 and 1984 to determine the optimal timing of 2,4-D ((2,4-dichlorophenoxy) acetic acid) applications for compatibility with two seed head flies,Urophora affinisFrauenfeld andU. quadrifasciata(Meigen), introduced for control of spotted knapweed,Centaurea maculosaLamarck, in Montana. Application of 2,4-D at the spring rosette stage had no effect on the adult emergence of either fly species in either year. Application of 2,4-D at the flower-bud and flowering stages had no effect on the emergence ofU. quadrifasciatabut significantly reduced the June emergence ofU. affinisduring both years except for the 1984 application at the flowering stage. Integration of the two fly species and the herbicide, 2,4-D, at the rate of 2.25 kg (AI)/ha, for the control of spotted knapweed is possible if the 2,4-D is applied during the spring rosette stage in May.

ISSN:1754-5692    

DOI:10.1093/ee/17.5.911

出版商:Oxford University Press    

年代:1988

数据来源: OUP