Aphis Pomi DeGeer Research Articles

Natural Enemies and Their Effects on Apple Aphid, Aphis pomi DeGeer (Homoptera: Aphididae), Colonies on Young Apple Trees in Central Washington

Thirty-nine predators and two parasitoids were found attacking apple aphid, Aphis pomi DeGeer, in north-central Washington. Exclusion-cage experiments were conducted to determine the effectiveness of natural enemies. Early-spring control depended on aphidiid parasitoids which killed but failed to complete development in A. pomi . Poor synchrony between A. pomi and its major predators in most years resulted in a month-long “predator gap” allowing rapid aphid colony growth in June. Ground faunal predators including Forficulidae, Nabidae, Lygaeidae, and Phalangiidae helped to slow aphid population growth during this period. Terminal bud set usually occurred in July on mature trees, greatly reducing aphid populations, but young trees sometimes continued growing, allowing buildup of large aphid populations. These were preyed upon by large numbers of Coccinellidae, Chrysopidae, Miridae, Syrphidae, and Chamaemyiidae, which provided control of varying effectiveness. Important sources of effective apple aphid predators were peach orchards, riparian trees and shrubs, some urban ornamental plants, and weeds. Sage-chaparral and pear orchard habitats produced primarily ineffective apple aphid predators. Field feeding trials in single-leaf cages were used to estimate feeding rates of most of the predators.

Sampling Schemes for Estimating Populations of the Apple Aphid, Aphis pomi (Homoptera: Aphididae), on Apple 1

Various sampling schemes were evaluated for estimating the population size of the apple aphid, Aphis pomi DeGeer, on an apple tree. More aphids were found to inhabit the actively growing shoots in the top of the tree canopy than the bottom. An average of 90% of the total aphid population occurred on the first six leaves at the top of the tree, whereas the first four leaves contained 90% of the aphids at the bottom for all sampling dates. The method of counting the number of aphids on the most infested leaf provided the most accurate assessment of aphid density, but it required the most effort. Counting only the number of infested leaves per shoot resulted in a decrease in accuracy, but also a 4- to 8-fold decrease in the time required to sample. Reliable estimates of the aphid population over an entire tree can be made from sampling only those areas of the tree reachable from the ground. Sample size estimates are presented on the number of shoots and trees to sample, as well as an estimate of precision.

Control of Insects and Mites on Fruit Trees by Trunk Injections

In greenhouse tests with the two-spotted spider mite, Tetranychus telarius (L.), the antibiotics cytovirin, cycloheximide, and streptovitacin A were effective when injected into peach seedling stems and sprayed on leaves. Cyclohcximidc was not effective when sprayed on trunks and limbs of peach seedlings or applied in bands of paste on limbs of mature apple trees. Trunk injections and foliar sprays of cycloheximide were effective also against peach silver mite, Aculus cornutus (Banks). Solutions of such water-soluble compounds as trichlorfon and methyl demeton moved rapidly to leaves of pear and cherry trees and gave good control of two-spotted spider mite. Water-insoluble compounds moved to leaves of cherry trees when injected in trunks in emulsions and in solution in dimethyl sulfoxide and some other solvents. Many solvents and solutions were phytotoxic at dosages used and caused considerable streaking or uneven distribution in different tree limbs owing to a much more rapid longitudinal than cross movement of materials from the injection site. Distribution was not improved when solutions were injected into a large tree root. Good control of pear psylla, Psylla pyricola Forster, was obtained in biotests of adults on pear leaves 2 weeks after trees were injected with Bidrin® (3-hydroxy-N,N-dimethyl- cis -croton-arnide dimethyl phosphate) and Bayer 47043 (O,O-dimethyl-S- (N,N'-dimethylmalonicamide) thiophosphate). Trunk injections of dimethoate emulsions and some water solutions of other compounds gave control of the green peach aphid, Myzus persicae (Sulzer), the apple aphid, Aphis pomi DeGeer, and the woolly apple aphid, Eriosoma lanigerum (Hausmann).

Persistence of Erwinia amylovora in the Apple Aphid (Aphis pomi DeGeer), a Probable Vector

INSECTS of the family Aphidae and particularly the apple aphid, Aphis pomi DeGeer, have long been suspect as significant vectors of the phytobacterial pathogen Erwinia amylovora (Burrill) Winslow et al., 1920. That these insects could artificially transmit the fireblight bacterium and establish progressive infections in apple and pear tissue was demonstrated by Stewart1, Stewart and Leonard2, and Merrill3.

Effects of Some Antibiotics on Three Aphid Species

A number of antibiotics, including some known to be toxic to and to suppress egg laying in orchard mites, were tested as sprays at different concentrations for toxicity and sterilizing effects on the green peach aphid, Myzus persicae (Sulzer), the apple aphid, Aphis pomi DeGeer, and the pea aphid, Macrosiphum pisi (Harris). In tests on the green peach aphid, cytovirin (from Streptomyces sp.), cycloheximide (3-[2-(3,5-dimethyl-2-oxycyclohexyl)-2-hydroxyethyl]glutarimide), streptovitacin A (3-[2-hydroxy-2-(5-hydroxy-3,5-dimethyl-2-oxocyclohexyl) ethyl] glutarimide), antimycin A (7-hexyl-3-(2-hydroxy-3-foramidobenzamido)-4,9-dimethyl-1,5-dioxa-2,6-dioxo-8-(iso-valeroyloxy) cyclononane), and hygromycin B (from Streptomyces hygroscopicus (Jansen) Waksman & Henrici) were definitely insecticidal. The other compounds were only slightly toxic or had no effect. Plssible sterilant effects of the more active antibiotics were not shown because of their toxicity and those with lower or no toxicity did not show any marked sterilant effects although the number of progeny was generally less than in the untreated control. Similar effects of some of these antibiotics were shown in tests on the apple aphid and the pea aphid.

Some Eggs of Insects That Change Color during Incubation

When the chorion is opaque the original deposition color of the egg usually remains unchanged during incubation. Many examples of these occur among the Orthoptera, Coleoptera, Hemiptera, Homoptera and Lepidoptera, but there are some exceptions to this generalization such as the exposed overwintering eggs of many Aphididae (Homoptera) which are black or a very deep brown. At deposition time they may be cream colored, green or a light brown. For example the eggs of the apple grain aphid, Rhopalosiphum fitchii (Sanderson) and the apple aphid, Aphis pomi DeGeer, on twigs of apple trees are green when deposited, while the eggs (3)2 of Longistigma caryae (Harris) on twigs of sycamore (plane) trees are light brown. A few days to several weeks after deposition these colors change to black or near black. The pigment in these eggs is located in the tough, membranous chorion which is completely covered with a thin, transparent, adhesive coat secreted by the female when the egg is deposited. Upon exposure to air it hardens and glues the egg to the twig or leaf. It also serves as an insulation against evaporation of the embryonic fluid. Among some species the external adhesive covering is very sticky and dries slowly. This is the case with the eggs of Longistigma caryae (Harris). It is not unusual to find eggs of this species covered with numerous grey or brown dust particles, especially if the host plant is adjacent to a dusty field or road.

Some Studies on the Influence of Environmental Factors on the Hatching of the Eggs of Aphis Avenæ Fabricius and Aphis Pomi DeGeer.*

The eggs of Aphis avenue Fabricius1 and Aphis pomi DeGeer have two distinct layers in the egg shell (Figures 1 to 4). The outer layer, when the eggs are first deposited, is transparent, soft and glutinous, but it soon hardens upon exposure to weather conditions and becomes semi-transparent, toughened, dry and decidedly impervious to water. The inner layer is a soft, elastic, black membrane and decidedly pervious to water. The outer layer usually splits (Figures 2 and 3) along the dorso-mesal line a number of days before the nymph emerges. The above structure and splitting of the outer layer is also characteristic of the eggs of other species of plant lice; a species of Lachnus, which deposits its eggs on the needles of whitepine, another aphid which deposits its eggs about the buds of weeping willow and at least one species of aphid which deposits its eggs in ant nests. I am indebted to Mr. J. L. King for furnishing me with eggs from an ant nest.

Studies on the Morphology and Susceptibility of the Eggs of Aphis Avenæ Fab., Aphis Pomidegeer, and Aphis Sorbi Kalt.

Journal Article Studies on the Morphology and Susceptibility of the Eggs of Aphis Avenæ Fab., Aphis Pomidegeer, and Aphis Sorbi Kalt. Get access Alvah Peterson, Ph. D Alvah Peterson, Ph. D Assistant Entomologist, New Jersey Agricultural Experiment Station Search for other works by this author on: Oxford Academic PubMed Google Scholar Journal of Economic Entomology, Volume 10, Issue 6, 1 December 1917, Pages 556–560, https://doi.org/10.1093/jee/10.6.556 Published: 01 December 1917