摘要:

Influence of corn plant densities (37,000, 54,600, and 71,300 plants/ha), time of day, and plant growth stage on adult western (WCR) (Diabrotica virgifera virgiferaLeConte) and northern (NCR) (D. barheriSmith&Lawrence) corn rootworm population estimates was studied in eastern Nebraska during 1981 and 1982. Populations of both NCR and WCR adults were affected by plant density. Smaller populations of beetles were present in low plant density plantings. Adjusting beetle counts (whole-plant and ear zone) for plant density resulted in better estimates of the beetle population. Beetle counts for both species were significantly correlated with the actual beetle population. However, there were higher correlations between beetle counts and actual beetle population when counts were adjusted for plant density and expressed on an area basis. WCR beetle counts adjusted for plant density were highly and significantly correlated with number of eggs laid. With only one exception, NCR beetle counts adjusted for plant population were also highly correlated with number of eggs laid. Unadjusted counts were not significantly correlated with egg numbers.

ISSN:0046-225X    

DOI:10.1093/ee/14.6.701

出版商:Oxford University Press    

年代:1985

数据来源: OUP

摘要:

Addition of p-aminobenzoic acid, inositol, thiamine, nicotinic acid, or choline chloride did not provide significant UV protection for gypsy moth,Lymantria dispar(L.), nucleopolyhedrosis virus (NPV), while the addition of pantothenic acid, pyridoxine, folic acid, and riboflavin protected NPV. Pantothenic acid and pyridoxine (at 1%) increased UV protection significantly by factors of 1.88 and 2.08, respectively, which resulted in 52–57% of original activity remaining. Folic acid (93% original virus activity remaining [OAR]) and riboflavin (94% OAR) were superior protectants, and enhanced UV tolerance by 3.3- and 3.4-fold, respectively. Riboflavin provided little protection at 0.10%, some protection at 0.25%, and significant protection at 0.50 and 1.00%. The effect was concentration-dependent, and 1.00% riboflavin preserved 80% of original viral activity. Even at 0.10% concentration, folic acid enhanced UV persistence, and 87% of original activity remained with addition of 1.00% folic acid. Folic acid is a substituted pteridine, with both p-aminobenzoic acid and glutamic acid in the side chain. A pterin, xanthopterin, was almost as effective as folic acid, and 89% of the folic acid activity could be accounted for by the pterin alone. However, both p-aminobenzoic acid and glutamic acid (at 1.00%) were ineffective, either alone or in combination.

ISSN:0046-225X    

DOI:10.1093/ee/14.6.705

出版商:Oxford University Press    

年代:1985

数据来源: OUP

摘要:

Functional relationships ofLygus lineolaris(Palisot de Beauvois) and selected predator densities estimated with sweep net, drop cloth, whole-plant-bag samples (WPBS), and visual search were determined in early to mid-season cotton. Slopes of relative as a function of absolute densities were not different between years for most taxa. When compared against absolute density estimates (WPBS or visual search) drop-cloth estimates were generally more precise and captured a larger percentage of arthropods than 10-sweep samples of the sweep net. With few exceptions (notablyGeocorisspp. nymphs) the proportion of the absolute density estimated by drop-cloth or sweep-net samples was low (ca. 10–30%). Reasonably precise relationships (R2>0.50) of relative over absolute density were obtained for nymphs ofGeocorisspp.,L. lineolaris, andOriusspp.;Oriusspp. adults; and spiders. Relationships using total predator counts generally had greater precision than those using individual species and stages. Adults ofGeocorisspp., Coccinellidae, and possiblyL. lineolaris, however, were not estimated with precision by drop-cloth or sweep-net samples.

ISSN:0046-225X    

DOI:10.1093/ee/14.6.709

出版商:Oxford University Press    

年代:1985

数据来源: OUP

摘要:

Larvae of the Mexicanbean beetle,Epilachna varivestisMulsant, grew larger when fed on soybean foliage fumigated for 24 h with SO, at concentrations of 131 to 1,834μg m−3than when fed on nonfumigated leaves. Relative weight gain was not linear against SO2concentration in the range sampled; it was greatest when leaves were fumigated with ca. 786μg m−3and less pronounced at either higher or lower concentrations. Smaller relative weight gains, also having a maximum at a concentration of approximately 786μg m−3, were found when larvae were reared on foliage allowed 24 h in which to recover from fumigation. No effect on growth was observed when plants were fumigated with 65μg m−3, indicating a threshold for effect between 65 and 131μg m−3under the conditions of these tests. Change in the plant induced by fumigation, as indicated by growth response of the insects, was rapid, occurring in less than 6 h when plants were fumigated at a concentration of 1,310μg m−3; recovery of the plant from an exposure was slow relative to response time.

ISSN:0046-225X    

DOI:10.1093/ee/14.6.718

出版商:Oxford University Press    

年代:1985

数据来源: OUP

摘要:

Naturally occurring insect populations were studied in a commercial warehouse containing farmers stock peanuts. Precision of four different sampling/analysis methods, the temporal and spatial distribution patterns ofPlodia interpunctella(Hübner) andCadra cautella(Walker), and interactions between these moth species and the parasiteBracon hebetorSay were determined. Averaging two sampling units, each 21.6 cm square and 10.2 cm deep, Yielded more precise data than taking one sampling unit 30.5 cm square and 10.2 cm deep; each technique involved the same total volume of peanuts. Moth populations had contagious distribution patterns and were more abundant on the side than the top (horizontal) surface of the peanut stack.B. hebetorappeared to greatly suppress moth populations, but not before peanuts were damaged.

ISSN:0046-225X    

DOI:10.1093/ee/14.6.722

出版商:Oxford University Press    

年代:1985

数据来源: OUP

摘要:

Olfactory, aggregatory, and feeding responses of normal (untreated) laboratory stocks of Mediterranean fruit fly (medfly),Ceratitis capitata(Wiedemann), and of Caribbean fruit fly (caribfly).Anastrepha suspensa(Loew), were compared to those of flies irradiated (10 had in air) 2 days before eclosion. Females of both species consumed greater quantities of protein hydrolysate solutions, entered protein hydrolysate-baited olfactory traps, and aggregated on agar plates containing protein hydrolysate in greater numbers than males of the same age and condition. However, male medflies consumed more sucrose than did females of the same age and condition. In the medfly, irradiation resulted in reduced olfactory response, reduced total food intake by flies of both sexes, and a significant reduction in aggregation on and intake of protein hydrolysate by females and of sugar consumption by males. In the irradiated caribfly, there was a significant reduction in olfactory response of females to yeast hydrolysate. In both sexes, aggregation on and consumption of yeast hydrolysate were reduced. Effects of irradiation on feeding behavior are discussed in relation to the biology of the flies and their control by the sterile insect release method.

ISSN:0046-225X    

DOI:10.1093/ee/14.6.726

出版商:Oxford University Press    

年代:1985

数据来源: OUP

摘要:

Population dynamics and biological control of the citrus thrips,Scirtothrips citri(Moulton), was studied over a 3-year peiod on ‘Washington’ navel orange, ‘Lisbon’ lemon, and ‘Marsh’ grapefruit near Corona (Riverside County), Calif. The native phytoseiid predator,Euseius hibisci(Chant), was excluded from experimental plots in citrus groves by spraying a residue of malathion on plot trees and those surrounding the plots. Subsequent mass release of this predator into these plots suppressed the citrus thrips below economic levels. In plots that had been sprayed with malathion, the disappearance of the insecticide from the leaves was monitored. The leaf residues did not stimulate fecundity of the citrus thrips by early summer. Early spring populations of>0.50E. hibisciper leaf on inland valley citrus groves of southern California responded numerically and functionally to second- and third-generation increases ofS. citri. These responses byE. hibiscioccurred before citrus thrips could irreparably damage the rind of fruit of ≤4 cm diameter. Field trials on lemon were designed to assess the effect of five citrus pesticides on the Corona Foothill strain ofE. hibisci. Dimethoate, methomyl, and parathion were extremely toxic toE. hibisci; residual toxicity of chlorobenzilate and carbaryl to the predator 26 days posttreatment was comparable to the water control.

ISSN:0046-225X    

DOI:10.1093/ee/14.6.733

出版商:Oxford University Press    

年代:1985

数据来源: OUP

摘要:

The tea scale,Fiorinia theaeGreen, is a serious pest of camellias and hollies in the United States and many other parts of the world. In 1976, an attempt was made to introduce its natural enemies from India into Florida. As a consequence, an aphelinid,Aphytis theae(Cameron), was released at several locations in Gainesville. Though flourishing during spring, summer, and fall, it failed to survive the winters of north-central Florida, despite repeated colonizations during 1978 and 1979. Data taken from September 1977 to August 1978 were used to construct a life table and survivorship curve of tea scale. During that period, the population trend index was 0.98, indicating a slight decline in the tea scale population. Analysis of the life table revealed that the most important mortality factor was dispersion loss of crawlers. The second most important factor was action of natural enemies on nymphs. A measure of the degree to which the trend of corresponding points on theKcurve and those of theKcurves conform is proposed as an objective method of identifying and quantifying key factors.

ISSN:0046-225X    

DOI:10.1093/ee/14.6.742

出版商:Oxford University Press    

年代:1985

数据来源: OUP

摘要:

Shoreline mud in two southern California dairy ponds was subjected to three shading treatments: deep shade, partial shade (screen), and full exposure to the sun. Shading panels were positioned above the mud after sunset, and surface mud temperatures and samples were taken from just below the waterline the following day at 0700, 1000, 1300, 1600, and 1900 hours. Invertebrates were extracted by direct MgSO, flotation, and data from the five sampling days were analyzed.Culicoides variipennis(Coquilleu) larvae were the most prevalent insects recovered. No correlations ofC. variipenniswith Chironomidae, Corixidae, predatory Hydrophilidae, or Tabanidae larvae were detected. Numbers of all fourC. variipennislarval instars were significantly lower in all shading treatments at 0700 hours, and were highest at 1300 and 1600 hours. There was no interaction between time of sampling and degree of shading. The highest numbers of all larval instars were found in open mud, followed by partial shade and deep shade. Later instars were found in markedly lower numbers in deeply shaded mud, while numbers of first instars in deep shade were not significantly less than in the other shading treatments. Factors influencing larva movement are discussed.

ISSN:0046-225X    

DOI:10.1093/ee/14.6.749

出版商:Oxford University Press    

年代:1985

数据来源: OUP

摘要:

We performed laboratory tests to examine effects of different densities ofPulvinariella mesembryanthemi(Vallot) on population growth, development, survivorship, and reproduction. We also measured survivorship and growth of its ice plant host,Carpobrotus edulis×aqualateris(Aizoaceae), supporting various scale densities. Scale body size and fecundity were inversely related to density, indicating intraspecific competition; both scale and host-plant survivorship were strongly density-dependent. Scale mortality at high densities was attributed to limited settling sites, honeydew fouling, physical crowding, and death of host plants and plant parts supporting scales. On dying plant tissues, scales reproduced prematurely and produced fewer offspring. Plant growth was negatively correlated with scale densities, and at high scale densities plants stopped production of new leaves and shoots, reducing the resource base for subsequent generations of scale.

ISSN:0046-225X    

DOI:10.1093/ee/14.6.755

出版商:Oxford University Press    

年代:1985

数据来源: OUP