摘要:

A relative sampling method for second flight adult European corn borer,Ostrinia nubilalis(Hübner), was used to predict egg mass levels within hybrid seed cornfields (Zea maysL.). An aluminum bar (1 m) was swept through adult aggregation areas of giant and green foxtail grass (Setariaspp.) and adults were counted as they flushed from the grass. Numbers of scouted egg masses in the field were regressed onto numbers of flushed adults during early to late silking stages of corn. Egg masses were dependent on the number of European corn borer adults in aggregation areas (example: predicted 0.5 egg masses per corn plant with an average of 52 moths flushed from 10 m2grass at 5% silking or an average of 66 moths flushed from 10 m2grass at 80% silking). This relationship between flushed adults and egg masses can be used to determine the need and timing of field scouting by consultants or seed companies for second-generation egg masses in the Corn Belt.

DOI:10.1093/ee/19.4.1081

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

Survival of larvae of the diamondback moth,Plutella xylostella(L.) was reduced on several genotypes of cabbage from the breeding program at Geneva, N.Y. Polar fractions of ethanol extracts of partially resistant lines 2535 and 2503, when incorporated into diet, reduced survival ofP. xylostellalarvae by 14.9 and 19.0%, respectively. Whether this effect was due to reduced feeding or postingestive toxicity was not determined. Although survival on glossy-leafed line 2518 was very low in the field and larvae on this line failed to form visible feeding mines during the first 72 h after egg hatch, extracts from 2518 had no activity. Survival of larvae confined on leaf disks of 2518 in the laboratory was much greater (80% of controls) than it was on whole plants in the field (0.36% of controls). In the field, neonateP. xylostelladispersed two to three times more rapidly on the leaves of 2518 than on other lines. Resistance toP. xylostellain the lines investigated was therefore due to at least two mechanisms, (1) antibiosis or nonpreference due to extractable compounds present in normal bloom resistant cabbage genotypes, 2503 and 2535, and (2) possible nonpreference for glossy-leafed 2518 by neonate larvae, as suggested by the greater dispersal rates of neonates on these plants. Survival is relatively high on 2518 in leaf disk bioassays in the laboratory, suggesting that nonpreference in combination with environmental stresses to larvae in the field may produceP. xylostellaresistance in the glossy 2518.

DOI:10.1093/ee/19.4.1086

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

A study was conducted to investigate whether pH values of selected maize,Zea mays(L.), tissues could serve as useful screening criteria for resistance to whorl leaf feeding and stalk tunneling by the European corn borer,Ostrinia nubilalis(Hübner). Inbred line CI31A displayed the highest whorl leaf pH and had the least leaf feeding. Over all six maize genotypes, however, only a low level of correlation (P<0.05,r= −0.35) between whorl leaf pH and whorl leaf feeding was observed. Similarly, in a study of four inbred lines, correlations of leaf sheath and stalk pith pH with amount of stalk tunneling were inconsistent and of low magnitude. When whorl leaf, leaf sheath, and stalk pith pH were determined in four cycles of selection of a maize population which had undergone recurrent selection for resistance to both generations of European corn borer, no significant relationships between pH and cycle of selection were observed. Measurement of pH of these plant parts apparently would not be a useful technique to select genotypes resistant to European corn borer.

DOI:10.1093/ee/19.4.1091

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

Pholetesor ornigis(Weed) is capable of parasitizing tissue-feeding larvae (fourth and fifth instars) as well as sap-feeding larvae (first, second, and third instars) ofPhyllonorycter blancardella(F). In no-choice tests, similar numbers of offspring were produced on first-fourth instars hut fewer on fifth instars. In choice testsP. ornigisproduced similar numbers of offspring on first, second, and third instars, but fewer on fourth instars and none on fifth instars. In the field primarily sap-feeding larvae were available during the first threeP. ornigisflight periods. However, tissue feeders were predominant during the partial fourth-generation flight period.

DOI:10.1093/ee/19.4.1097

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

This study was undertaken to measure destruction and feeding by two species of grasshoppers,Camnula pellucida(Scudder) andMelanoplus sanguinipes(F.), common on fescue prairie, in relation to forage preferences, stubble height, and leaf water content.C. pellucidashowed no significant preferences, whereasM. sanguinipespreferred rough fescue (Festuca scabrella Torrey).M. sanguinipesdisplayed greater preference for higher leaf water content than didC. pellucida. The presence of stubble restricted feeding of both grasshopper species, butM. sanguinipeswas less inhibited. The inhibition by stubble was related directly to its density (grams per cubic centimeter) and, therefore, inversely to its height. The significance of these aspects of feeding behavior in relation to grassland condition is discussed.

DOI:10.1093/ee/19.4.1103

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

Late fall and midwinter disking of piles of cotton bolls that contained diapausingBracon mellitorSay were investigated as methods to increase overwintering survival and to delay spring emergence. In one year, disking in early December significantly increased survival of females; but in the second year disking did not influence survival. Spring emergence was completed in April and was not affected by December or February disking treatments. In another study, winter survival was increased and spring emergence was delayed by holding bolls in complete darkness at about 10°C. The parasitoids were held under these conditions for 6 mo, and then they were exposed to long daylengths (>13.5 h) and warm ambient temperatures in an outdoor insectary. Emergence began in late June and winter survival was 51.9% compared with 3.7% survival and emergence in April from bolls left on the soil surface.

DOI:10.1093/ee/19.4.1110

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

Five baculovirus strains were introduced in 1984–1985 into virus-free island populations ofOryctes rhinoceros(L.) in the Maldives, either singly or in combination. Pest populations were monitored by palm damage surveys for up to 4 yr on 22 islands, some of them deliberately untreated. The method used allowed estimates from a single survey of the number of beetle attacks during each of 18 mo (3rd–20th month before the survey date). Such surveys gave continuous records forO. rhinocerosattacks during 1983–1987. Most islands where the virus was released showed a highly significant reduction in palm damage. The prerelease pest density on a given island influenced the efficacy of the virus introduction. Adjustments were made for this effect when the performances of the different virus strains were compared. Strain X2B gave consistently better reduction in pest populations and more virus-infected beetles compared with strain V2/3B; the remaining strains gave intermediate control. These results agreed with earlier laboratory tests, in which the virulence of both strains was compared by infectingO. rhinoceroslarvae. Two islands where three strains were released simultaneously also experienced a high damage reduction; here, X2B predominated eventually over strains V2/3B and S2A.

DOI:10.1093/ee/19.4.1115

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

Laboratory-reared adults of the tachinid parasitoid,Archytas marmoratusTownsend, were released and evaluated against larvae ofHeliothis zea(Boddie) in whorl stage corn during 1986–1988. Resulting rates of parasitism byA. marmoratusonH. zealarvae occurring at 0.3, 0.5, and 1.0 per row-m were 58.3, 44.2, and 52.8%, respectively, when about 340 females/ha were released, and 45.9, 38.2, and 32.1%, respectively, when about 170 females/ha were released. In both studies, no significant differences (P>0.05) in rates of parasitism were found between host densities. The number ofH. zealarvae parasitized byA. marmoratusincreased linearly over the range of host densities studied. This suggests that per capita mortality is density-independent and, therefore, should not increase or decrease as host density is varied within the range of early season populations.A. marmoratusfemales appeared to disperse predominately into the prevailing wind. Rates ofA. marmoratusparasitism were significantly higher (P<0.05) on fourth and fifth instars than on third instars. Approximately 370 and 860 femaleA. marmoratus/ha would be needed to yield 50 and 80% parasitism of fourth and fifth instars ofH. zea, respectively, in 9–14-leaf stage dent corn. Data suggest thatA. marmoratusfemales are highly efficient in finding larvae ofH. zeain whorl stage corn, and that rates of parasitism observed in the relatively small release areas are likely far lower than could be expected from sustained releases throughout large corn ecosystems wherein the effects of predominately unilateral movement from release areas would be minimized. With the development of economical methods of mass propagation,A. marmoratuslikely could play a major role in the safe, efficient, and selective management of the early season populations ofH. zeain whorl stage corn.

DOI:10.1093/ee/19.4.1122

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

The longevity of two primary aphid parasitoids,Aphidius liriodendriiLiu andTrioxys curvicaudus(MacKauer), was severely reduced when they were exposed in the laboratory to a malathion bait spray used to eradicate the Mediterranean fruit fly,Ceratitis capitata(Wiedemann). The longevity of several hyperparasites ofA. liriodendriiandT. curvicaudusalso was reduced. Oviposition ofA. liriodendriiwas severely reduced on plants that received field applications of malathion bait spray. The parasitoids appeared neither attracted to nor repelled by the malathion bait. Pesticide contact occurred during apparently random searching by the parasitoids. AsT. curvicaudusis reportedly responsible for the biological control of its aphid host,Eucallipterus tiliae(L.), malathion bait sprays used for Mediterranean fruit fly control may cause an increase in aphid populations by reducing the effectiveness of primary parasitoids.

DOI:10.1093/ee/19.4.1130

出版商:Oxford University Press    

年代:1990

数据来源: OUP

摘要:

Heliothis zea(Boddie) larvae and eggs were collected from soybean fields in five Virginia counties during 1987 and six counties in 1988.Microplitis croceipes(Cresson) was the predominant parasitoid associated withH. zealarvae throughout the study. GreaterH. zealarval density and rates of parasitism were observed in fields planted after 10 June than in fields that were planted earlier. High levels of parasitism occurred only in fields where the presence ofM. croceipescoincided with first appearance of host larvae. Most parasitoids emerged fromH. zealarvae collected as third or fourth instars. No parasitoids emerged fromH. zealarvae sampled from field corn, suggesting thatM. croceipespopulations in soybeans do not originate fromH. zeahosts in corn fields. Despite warm holding temperature, 14% of theM. croceipesprepupae collected in 1987 entered diapause in the laboratory and emerged in August the following year. This is evidence for the hypothesis thatM. croceipesoverwinter in soybean fields and emerge in summer to coincide with first presence ofH. zealarvae. Less than 4% of collectedH. zeaeggs were parasitized by Trichogrammatidae in Eastern Shore counties. However, high levelsof egg parasitism,>90% on some sample dates, occurred in fields in the Northern Neck.

DOI:10.1093/ee/19.4.1135

出版商:Oxford University Press    

年代:1990

数据来源: OUP