摘要:

The practice of quantitatively sampling within-tree populations ofDendroctonus frontaliswas investigated by comparing the relationships between sampling intensity, informational content of samples, and precision in estimation.Random and stratified random sampling plans were compared and contrasted to selective or purposeful sampling using the tree geometry model-probability density function (TG-PDF) estimation procedure. The random techniques required large quantities of data and were therefore less suitable than the TG-PDF procedure. The latter procedure incorporates knowledge of the vertical distribution of theD. frontalislife stages and therefore required much less data for a given level of precision.The TG-PDF procedure was evaluated on the basis of precision obtained in using the technique on different numbers of sample levels and the position of the sample levels. Precision as judged by the refined standard deviation of the estimate σRincreased as the number of levels sampled increased. For a given number of levels, the refined σR, which associates covariables with the sample levels, always produced a better estimate than the basic standard deviation σBwhich assumed equal information from each sample level. Positioning of sample levels along the infested bole influenced the precision obtained. Dispersing the sample levels over the infested bole while avoiding the extremes generally resulted in better precision for each life stage. The precision in estimation was best where the informational content C of the individual levels was similar.The optimal location for sample levels varied with the life stage being sampled. Generally 2 or 3 levels provided an adequate estimate for most sampling requirements. The emerging adult life stage was the most variable and therefore the more difficult and costly to sample.

ISSN:1754-5692    

DOI:10.1093/ee/6.5.607

出版商:Oxford University Press    

年代:1977

数据来源: OUP

摘要:

Bioassay techniques were employed to determine the persistence ofBeauveria bassiana(Bals.) Vuill.,Nomuraea rileyi(Farlow) Sampson, andNosema necatrix(Kramer) on soybean foliage. One-half of the original activity of each pathogen was lost between 5 and 10 days postapplication. The average % mortality ofSpodoptera frugiperda(J. E. Smith) larvae resulting from exposure to the foliage treated withB. bassianaranged from 83.2% on the day of application to no deaths 10 days later. The average % mortality caused byN. rileyidecreased from 98.4% to 10.4% over the same period, while the average % infection ofHeliothis zea(Boddie) larvae caused byN. necatrixranged from 91.2% on the day of application to 14.4% on the 10th postapplication day. The effects of precipitation, relative humidity, and direct solar radiation are possible reasons for the observed decreases in pathogen activity.

ISSN:1754-5692    

DOI:10.1093/ee/6.5.616

出版商:Oxford University Press    

年代:1977

数据来源: OUP

摘要:

Seasonal population changes in chironomid fauna of an urban concrete-lined flood control channel system were studied from Aug., 1974–Sept., 1976. Benthic samples from 9 stations along a 20-km stretch of the channel system were collected biweekly and air and water temperatures and rainfall were also recorded.Midge larvae of 7 genera were taken.Cricotopusspp.,Dicrotendipessp., andChironomusspp., in that order, were of quantitative importance; the other 4 genera collectively formed 0–7% of the total monthly-collected larvae.Cricotopusspp. were present year-round, forming>86% of the total midges collected and 65–99% of the monthly totals.Dicrotendipessp. (densest May–Nov.) were also present throughout the year, but their monthly populations ranged from<1–34% of the total.Chironomusspp. occurred from July–Nov., their density reaching up to 28% of the total midges taken then.The numerical increase in midges during the spring and summer coincided with warmer air and water during these periods. Two to 3 cm or more of rainfall in the area in a 24-h period drastically reduced larval populations, but within 2–4 wk, after a period of rainfall, they greatly increased.

ISSN:1754-5692    

DOI:10.1093/ee/6.5.619

出版商:Oxford University Press    

年代:1977

数据来源: OUP

摘要:

Fecundity of tussock moth populations varied among plots after the 1st yr (1972) of conspicuous tree defoliation and declined sharply after a 2nd yr (1973) of defoliation. Degree of defoliation in the 1st yr had no significant effect on egg production, although fewest eggs per mass were produced in the most severely defoliated areas. Severe tree defoliation in the 1st yr significantly affected quality of the filial generation. Field populations that had not already collapsed naturally had a 30% drop in fecundity after the 2nd yr of defoliation. The conclusion is that fecundity was influenced by many factors, food-related and otherwise, in the outbreak. Tree defoliation had its greatest effect at exceptionally high population densities when the favored current needles were destroyed early in the summer, placing surviving larvae under a food stress for much of their development.

ISSN:1754-5692    

DOI:10.1093/ee/6.5.623

出版商:Oxford University Press    

年代:1977

数据来源: OUP

摘要:

Heliothis zea(Boddie) pupae were tested for overwinter survival in alfalfa, cotton, and native grasslands. Survival was high in all areas until midwinter, then dropped off sharply. Less than 0.5% of the pupae survived in alfalfa and native grasslands and none survived in cotton fields. Plowing cotton fields destroyed the pupae quickly. Emergence from natural populations was also low, with less than 200/acre surviving.

ISSN:1754-5692    

DOI:10.1093/ee/6.5.627

出版商:Oxford University Press    

年代:1977

数据来源: OUP

摘要:

Laboratory experiments were conducted using a variety of photoperiod and temperature conditions to determine the mode of overwintering exhibited byTrichogramma nubilaleErtle and Davis. The results of these tests show thatT. nubilaleprobably overwinters by hibernation in host eggs. In addition, it was determined that overwintering success is optimal for those parasites which developed to the pupal stage In eggs of the European corn borer,Ostrinia nubilalis(Hübner).

ISSN:1754-5692    

DOI:10.1093/ee/6.5.629

出版商:Oxford University Press    

年代:1977

数据来源: OUP

摘要:

We describe a rapid and efficient technique for extracting from soil samples immature bean leaf beetles (BLB),Cerotoma trifurcata(Forster), other than small first instars. The percent recovery did not differ between 2 soil types and differed only slightly with larval size. Recovery from samples stored at 12°C (one layer deep to avoid crushing) was about 90% after one week but then declined rapidly. Some extracted larvae survived to maturity, suggesting that this method could be used to extract some species which cannot be identified as larvae. Other samples were frozen, killing the larvae, but giving a recovery rate of about 89% after 18 days. In field samples, 92.3% of the BLBs were found within 7.6 cm of the soil surface. Immature BLBs were most abundant in 5.1×5.1-cm samples centered on the row, but also occurred in samples of the same size contiguous to the center sample on either side of the row.

ISSN:1754-5692    

DOI:10.1093/ee/6.5.633

出版商:Oxford University Press    

年代:1977

数据来源: OUP

摘要:

Distribution patterns of foraging honey bees among 5 fields (2 onion, 2 safflower, and one carrot) were determined by a magnetic recapture system for 404 hives located at 14 apiaries. Of 5000 tagged and released bees, 3770 (75.4%) were recovered. Nectar and pollen loads of foragers were analyzed. Distribution patterns for foraging bees indicated competition effects and adjustment of foraging range.The relative attraction of the different crops was carrots, safflower, and onions.Adaptation and habituation of potential forager recruits to common food sources may enhance recruitment to new sources.

ISSN:1754-5692    

DOI:10.1093/ee/6.5.637

出版商:Oxford University Press    

年代:1977

数据来源: OUP

摘要:

Oviposition by a strain of the Indian meal moth,Plodia interpunctella(Hübner), and by 2 strains of the almond moth,Ephestia cautella(Walker) was usually stimulated by the presence of moth rearing medium, peanuts, or dates and was influenced by the type of food. Moths taken from a specific food source laid most eggs. TheP. interpunctellaoriginated from peanuts, one strain of theE. cautellaoriginated from peanuts, and the other from dates. The possibility that the 2 strains ofE. cautellaare sibling species is discussed.

ISSN:1754-5692    

DOI:10.1093/ee/6.5.641

出版商:Oxford University Press    

年代:1977

数据来源: OUP

摘要:

The abundance of house dust mites,Dermatophagoidesspp., as influenced by environmental conditions in human dwellings, was investigated in southern California. Significant positive correlation was found between mite numbers and house dust load. A significantly reduced amount of dust and number of mites occurred on mattresses fully encased with plastic sheeting as compared to those unencased. Noncarpeted floors under beds yielded a significantly lower quantity of dust and mites than those carpeted. Amount of dust and mite abundance on floors under beds was noted to depend on frequency and extent of vacuuming by residents. Significantly fewer mite numbers occurred on unencased new mattresses than unencased older ones. No significant positive correlation was noted for dust load and mite numbers as related to house age, nor was significant positive correlation noted for mattress age as compared to house age.

ISSN:1754-5692    

DOI:10.1093/ee/6.5.643

出版商:Oxford University Press    

年代:1977

数据来源: OUP