摘要:

Sterile flies from a prospective mass-production strain of the screwworm,Cochliomyia hominivorax(Coquerel), were tested in the field on two occasions between August and November 1981 in the Pacific coastal plain of Chiapas, Mexico. In Test I, flies were released over a 30-by-120-km area where all nine sentinel sheep sampling sites were located 5 to 23 km, including 5 sites<10 km, from the nearest perimeter. The maximum egg mass sterility rate (25%) was obtained by the third of 6 weeks of sterile fly releases. In Test II, flies were released over a 40-by-80-km area where all eight sentinel sheep pens were located 18.5 to 34.5 km from the nearest perimeter. For all pens, the maximum egg mass sterility rate (38%)was obtained by the fourth week. Egg mass sterility rates at sites considered well-insulated from the perimeter were statistically higher than sterility rates at sites considered poorly insulated. In Test II, distance from the sentinel sheep sampling sites to the nearest perimeter of the fly release area and egg mass sterility rate were positively correlated, and a maximum sterility rate of 60% was recorded. This relationship was attributed, at least in part, to the movement of native screwworm females into the test area from untreated areas.

ISSN:0046-225X    

DOI:10.1093/ee/14.2.101

出版商:Oxford University Press    

年代:1985

数据来源: OUP

摘要:

The location and aggregation of gypsy moth egg masses in a population near New Paltz, N.Y., were monitored yearly during the period from 1971 to 1981. The population went from a peak in 1971, through a trough between 1974 and 1977, to another peak in 1981. Warm, dry conditions during May and June were associated with population increases, while cooler and wetter conditions were associated with decreases. During the years of greater abundance the egg mass density (no. per ha bark) varied with the abundance of xeric soils, xeric indicator tree species, and the preferred food plants. During the trough, however, the density of egg masses on vegetation was unrelated to woodland type. The ratio of egg masses found on human-built structures to those on vegetation varied inversely with the total egg mass count. During the trough and nontrough periods the density of egg masses on structures in a woodland depended on both the amount and types of structures present. Egg mass aggregation was determined at the following levels: microsite, individual plant, species, and landscape (woodland). In all cases aggregation was greatest during the trough. After the trough, landscape scale aggregation decreased sharply. By 1980 it attained a level similar to that of 1981 when the egg mass density was two orders of magnitude greater. The possible meanings of these changes in egg mass location and aggregation are explored in terms of gypsy moth survival strategies.

ISSN:0046-225X    

DOI:10.1093/ee/14.2.106

出版商:Oxford University Press    

年代:1985

数据来源: OUP

摘要:

Trichogramma pretiosumRiley andT. exiguumPinto and Platner were compared in a temperature study at five constant temperatures of 15, 20, 25, 30, and 35°C. Developmental time of both parasite species in host (Heliothis virescens[F.]) eggs decreased with increases in temperature.T. exiguumdeveloped faster thanT. pretiosumat 25 and 30°C, but not at 20°C.T. pretiosumcompleted development at 35°C, butT. exiguumdid not. Additionally,T. pretiosumfemales lived longer thanT. exiguumfemales at 20 and 25°C; longevity decreased for both species with increase in temperature. Females outnumbered males at all temperatures. There was no significant difference between species in number of females or in number of parasites completing development per host egg.

ISSN:0046-225X    

DOI:10.1093/ee/14.2.118

出版商:Oxford University Press    

年代:1985

数据来源: OUP

摘要:

Populations of the blackmargined pecan aphid,Monellia caryella(Fitch), were studied in the field, using sleeve cages to manipulate aphid populations and their natural enemies. Each cage enclosed 10 compound pecan leaves.M. caryellapopulations were observed to increase rapidly within closed cages from 1 aphid per leaf to 50 aphids per leaf at any time throughout the summer. Opening sleeve cages to allow natural enemies access to the increasing aphid populations always resulted in the decline of aphid numbers compared to their activity in adjacent closed cages. Release of 1 chrysopid or 1 coccinellid larvae per 10 leaves when aphid populations were increasing in closed cages always resulted in the prevention of an aphid outbreak. Laboratory feeding studies of selected chrysopid and coccinellid predators showed average feeding rates of between 25 and 60 aphids per day. Results indicate that natural enemies, particularly predators, play an important role in maintainingM. caryellapopulations at low levels in the field.

ISSN:0046-225X    

DOI:10.1093/ee/14.2.122

出版商:Oxford University Press    

年代:1985

数据来源: OUP

摘要:

Overwintered boll weevils,Anthonomus grandisBoheman, were caged on various food sources to determine their longevity after emergence from winter habitat. Weevils caged on a combination of nonfruiting-fruiting cotton survived longer than those confined on nonfruiting cotton, a wild feeding host (Hymenopappus flavescensGray), and those held without food. Only weevils feeding on fruiting cotton exhibited a high percentage of survival beyond 20 days. The relatively short life span of overwintered weevils not having access to fruiting cotton supports the concept of delayed uniform cotton planting as a cultural management technique.

ISSN:0046-225X    

DOI:10.1093/ee/14.2.127

出版商:Oxford University Press    

年代:1985

数据来源: OUP

摘要:

Sex pheromone traps for the yellowheaded spruce sawfly,Pikonema alaskensis(Rohwer), and its ichneumonid parasitoid,Syndipnus rubiginosusWalley, were placed in white spruce,Picea glauca(Moench) Voss, plantations in north central Minnesota. The objective was to study the relationship between catches of the sawfly and its parasitoid and subsequent sawfly-caused defoliation. A significant linear relation was obtained when catches of both the sawfly and parasitoid were included in the model. The best-fit model was log(I) = 1.36 − 0.17 log(S) − 0.25 log(P) + 0.13 log(S·P) − 0.3 log(Ht), whereIis a trend index calculated usingI=N(t)/N(t-1),Nis amount of defoliation during yeart, Sis sawfly catch,Pis parasitoid catch,S·Pis the interaction between the two, andHtis tree height. Pheromone trap surveys of a host and parasitoid may provide information of the extent on natural control of the pest.

ISSN:0046-225X    

DOI:10.1093/ee/14.2.131

出版商:Oxford University Press    

年代:1985

数据来源: OUP

摘要:

Herbivorous and carnivorous feeding byGeocoris punctipes(Say) on nectaried and nectariless cotton with and withoutHeliothis virescens(F.) eggs was measured using the radionuclides of carbon (14C) and phosphorus (32P). Leaf material ingested byC. punctipeswas measured as percentage of leaf sample disintegrations per min and was significantly greater for insects on nectaried cotton without eggs (12.08%) than on plants in the other treatments. Plant feeding was not significantly different on nectaried cotton with eggs (3.34%), nectariless cotton with eggs (1.97%), and nectariless cotton without eggs (0.35%).G. punctipesegg ingestion was not significantly different on the nectaried or nectariless cottons.

ISSN:0046-225X    

DOI:10.1093/ee/14.2.134

出版商:Oxford University Press    

年代:1985

数据来源: OUP

摘要:

The hypothesis that larvae of the western corn rootworm (WCR) are competitively superior to those of the northern corn rootworm (NCR) was tested under greenhouse conditions. Potted corn seedlings were inoculated with various numbers of embryonated eggs of each species to determine if the WCR would affect the survivorship or the spatial distribution of the NCR. The WCR reduced the survivorship and affected the spatial distribution of the NCR within the root system, whereas the NCR did not affect the WCR.

ISSN:0046-225X    

DOI:10.1093/ee/14.2.138

出版商:Oxford University Press    

年代:1985

数据来源: OUP

摘要:

Five groups of final-instar nymphs ofEpitheca cynosuraSay, collected from October 1978 until March 1979, were maintained until emergence at experimental temperatures of 15, 20, 25, and 30°C and at natural photoperiods plus 15-min increments every 5 days. Pre-emergent development proceeded most rapidly at experimental temperatures of 20 and 25°C. The data, demonstrating that the most rapid physiological development of final-instar nymphs in nature occurred during the coldest winter months, strongly suggest a synchronizing effect on development caused by the changing sign of the photoperiod at the winter solstice.

ISSN:0046-225X    

DOI:10.1093/ee/14.2.142

出版商:Oxford University Press    

年代:1985

数据来源: OUP

摘要:

Adult chinch bugs,Blissus leucopterus leucopterus(Say), were inoculated with dried conidia ofBeauveria bassiana(Bals.) Vuill. and incubated in growth chambers with various host plants, liquid diet, or water. Results from these bioassays showed that mortality in the populations that had fed on sorghum and corn were reduced when compared with insects bioassayed on other food sources. More importantly, fungal presence and development in the cadavers of insects fed on sorghum and corn was significantly reduced when compared to the populations fed on other host plants, artificial diet, or water. These results indicate the presence of a plant produced fungal inhibitor fortuitously protecting the insect feeding upon it.

ISSN:0046-225X    

DOI:10.1093/ee/14.2.146

出版商:Oxford University Press    

年代:1985

数据来源: OUP