Showing papers on "Aphididae published in 1979"

The biology and pest status of cereal aphids (Hemiptera: Aphididae) in Europe: a review

Abstract: The biology and pest status of the common species of Sitobion, Metopolophium and Rhopalosiphum found on wheat, barley and oat crops in Europe is critically reviewed. After preliminary sections on species and sampling, the factors that induce the production of the different morphs of cereal aphids are considered. Basic life-cycles are described and the importance of migration and dispersal considered. Host-plant preferences, survival and reproduction on different Gramineae, and feeding site preferences are considered, particularly in relation to the type and amount Of damage caused by the aphids. The effects of constant temperatures on the biology of some species have been investigated, but little is known about the effects of weather in the field. There have been few quantitative studies on the effects of natural enemies on cereal aphids, but the evidence suggests that they may be important in reducing their numbers. Side-effects of pesticides and fertilisers on aphids are also discussed. Aphids may reduce grain yield and quality. Direct damage may result from reductions.

Feeding and multiplication of three cereal aphid species and their effect on yield of winter wheat

Abstract: Sitobion avenae F. multiplies at a higher rate on winter wheat than Rhopalosiphum padi L. and Metopolophium dirhodum Wlk. Unlike the other two species S. avenae prefers the ear, where it multiplies twice as quickly as on the flag leaf. Infestation of the ear rather than of the leaves leads to reduction of the average grain weight. These results suggest that S. avenae is the most injurious. In 3 field trials with this aphid fungal growth on honeydew caused about half of the damage. After correction for the fungus effect, the loss in yield caused by S. avenae feeding on the ear did not differ much from that calculated from its energy budget. Therefore, it is concluded that stylet insertion and saliva injection have no important influence on the growth of grains. From results with long living and highly productive crops it seems that honeydew can cause a more serious loss in yield if the crop does not prematurely ripen under the influence of various other yield-reducing factors.

Behavioural and physiological adaptations of pea aphids (homoptera: aphididae) to high ground temperatures and predator disturbance

Abstract: Pea aphids can avoid ladybug predators by dropping from the food plant when disturbed. Once off the plant the aphid must find another food plant. If temperatures on the ground are high, the aphid may die before finding a new food plant. In Kamloops, B.C., summers are hot and dry, compared with Vancouver where the climate is warm and moist. Pea aphids from Kamloops generally exhibit back-up behaviour and rarely drop from the plant when approached by a ladybug. By contrast, Vancouver pea aphids readily drop from the plant when disturbed by a predator. Adult aphids from Kamloops are more tolerant of heat under moist conditions at 37.5 °C than Vancouver adults but under dry conditions and at 42 °C, both groups have similar survival times. First instars of both aphid biotypes die sooner at high temperatures than adults. Mortality of aphids on the ground is sufficiently high to select against dropping behaviour as a first line defense against predators in areas with hot, dry climates.

The effect of superparasitism by Aphidius smithi (Hymenoptera: Aphidiidae) on the food budget of the pea aphid, Acyrthosiphon pisum (Homoptera: Aphididae)

Abstract: Parasitism by Aphidius smithi affected the food budget of its host, Acyrthosiphon pisum, fed on a synthetic diet. During the embryonic stage of the parasite, the weight-specific rates of feeding, food assimilation, and growth were less in parasitized aphids than in controls. In the presence of a developing parasite larva, aphids ingested more food but assimilated it less efficiently; they achieved the same or a higher relative growth rate than nonparasitized aphids as a result of having either a higher feeding rate or a higher efficiency of incorporation of assimilated food, or both. Honeydew excretion was up to 129% higher in aphids containing a parasite larva. Parasitism by A. smithi did not obviate host feeding and capacity for growth until host size was sufficient for the successful development of the parasite larva.It is suggested that the nutritional requirements of the parasite larva differ from those of the aphid. Thus parasitism affects the homeostatic regulation of aphid feeding and food assimil...

Temperature-dependent model for predicting field populations of green peach aphid, myzus persicae (homoptera: Aphididae)

Abstract: A temperature-dependent model for predicting green peach aphid population development in potato fields was devised and tested. A laboratory estimate of generation time was utilized to derive expected generation number from field accumulated degree days (1975–77). Different aphid populations were produced in replicated field plots (1975–77) with various application rates of the systemic insecticide, aldicarb. Density data from these plots were regressed on the expected number of generations to derive prediction equations. These equations were coupled in a Fortran computer program with a degree day algorithm. Weather forecasts, therefore, provide input for future aphid population predictions. The model is being used to evaluate various control strategies and to decide on spray dates from weather forecasts.

Diel Activity of Green Peach Aphid Predators as Indexed by Sticky Traps

Abstract: The diel activity of the predaceous natural enemies of the green peach aphid (GPA), Myzus persicae (Sulzer) (Homoptera: Aphididae) occurring on field potato plants was investigated to quantify time of day effects on sampling. Diel activity was determined by recording from 0900–2030 hours the predator density on 44 sticky traps placed within and on the borders of the field. Coccinellid adults were the most abundant GPA predators collected, and Hippodamia convergens Guerin-Meneville (Coleoptera: Coccinellidae) was the most numerous species caught. Analysis of time of day counts indicated that the 1300–1700 hour sample period contained the largest diel means for H. convergens adults, Coleomegilla maculata (DeGeer) (Coleoptera: Coccinellidae) adults, and Coccinella transversoguttata richardsoni Brown (Coleoptera: Coccinellidae) adults. Chrysopids were common late in the season. Ninety-five % of the chrysopids collected were Chrysopa carnea Stephens (Neuroptera: Chrysopidae). The 2030–0900 hour sample period contained the largest diet means for C. carnea .

Effect of the pea aphid, acyrthosiphon pisum (homoptera: aphididae), on cold-hardiness of alfalfa

Abstract: The pea aphid, Acyrthosiphon pisum (Harris), infests alfalfa in southern Alberta and is known to reduce yield and quality of the crop (Harper 1972). From the literature on the pea aphid, recently reviewed by Harper et al. (1978), there do not appear to be any publications on the effect of the pea aphid on cold-hardiness of alfalfa or other host crops. Harper and Lilly (1966), however, found that some aphid-infested plants that were clipped in late fall did not survive the winter. We have observed that numbers of pea aphids often reach high levels on alfalfa in Alberta late in the growing season.

Paralysis by the hymenopteran parasite, aphelinus asychis, as a mortality factor of two aphid species.

Abstract: Paralysis by the hymenopteran parasite, Aphelinus asychis, as a mortality factor of two aphid species. The aphid parasite Aphelinus asychis (Walker) (Hymenoptera: ~phelinidae), when reared on the pea aphid, Acyrthosiphon pisum (~arris) or the potato aphid, Macrosiphum euphorbiae (Thomas) (Homoptera: Aphididae), contributes to host mortality in three different ways: by internal parasitism as a larva and by paralyzing and feeding on hosts as an adult female. The relative importance of any one cause of host mortality varies with the physiological condition of the parasite and the weight/size of the host, or both. After female Aphelinus had been deprived of hosts for 24 h they preferentially laid eggs into pea aphids weighing 0.06 mg or less by dry weight (or potato aphids weighing 0.07 mg or less), larval parasitism being the chief cause of host mortality. Paralysis was the chief cause of mortality of older (and larger) aphids. For deprivation times ranging between 1 h and 37 h, host mortality due to paralysis increased with increase in deprivation time whereas mortality due to larval parasitism decreased. For deprivation times of up to 13 h, paralysis accounted for about 6% and 9% mortality of first-and second-instar pea aphids, respectively. For deprivation times between 1 3 h and 25 h, mortality increased to 85% in first-instars and to 70% in second-instars of pea aphid; aphid mortality remained unchanged for deprivation times longer than 25 h, averaging 75% and 65%