Wooly Apple Aphids

Homoptera: Aphididae, the Wooly Apple Aphid (Eriosoma lanigerum (Hausmann)) is a small pest that is present in
almost all areas of apple production. This pest has a piercing-sucking mode of feeding, attacking roots and tender
branches. The main food source is the sap of the tree; however, the juices from leaves are also consumed. These
pests are small (less than "), pear shaped, soft bodied, and visible to the naked eye. The color of this insect depends
on the host plant, the apple aphids are generally red, and commonly called rosy aphids. The particular aphid I have
chosen has a wooly covering on its body. Many of the characteristics of the wooly aphid are common to all aphids.
All aphids have a pair of tuber structures protruding out their backs, these are called cornicles. These cornicles are
what distinguish these pests as aphids (source1).
In general the adult aphids are wingless, most species experience a winged stage of growth. The aphid can produce
many generations in a season and often reproduce asexually. There are three stages in the life cycle: egg, nymphs,
and adult (see fig. #1).
Eggs over winter on ground debris and crevices on the tree (source2). Each adult can produce a hundred offspring;
therefore populations can explode in a short time. These large numbers of aphids gather in "communities" and tend
to stay in one place or migrate together (source 5).
The damage done by aphids is minimal when populations are small. Larger populations of the pest bring more
severe damage. The damage on roots include galls and swelling, dead tissue, and stunted sucker growth (See fig. #).
The damage to the upper plant is on both the leaves and plant tissues. Leaves are curled, yellow, and distorted. The
young shoots are destroyed and galled, and have a fungus that accompanies the honeydew excreted by the aphid
(See fig. #). Seedlings can also be completely killed by the aphid. Some aphids have been known to inject toxins,
damaging or stunting growth. The biggest damage is economical. The aphid is hard to wash off of produce, aphid
infested plants are usually not accepted by the retailers in the market place (source 1).
The first step to control the aphid is to identify, monitor, and record pest populations. Monitoring allows you to
begin control methods before leaves curl. Curled leaves provide the aphids with protection from the control method,
either biological or chemical (source1).
Biological Control
Biological control can be one of the easiest and more effective methods of removing the pest. There are a few
parasitic insects that reduce the population without damaging the crop. Aphelinus mali is a small wasp that lays eggs
inside the aphids (see fig. #). The eggs hatch, internally digest the insect, leaving a dried "mummy" behind (source
4) (See fig. #). These insects do not appear until the aphid population is quite high; introducing them into the site
when aphids are first observed will reduce the chance of a population increase. The Diaeretiella rapae is another
parasitic killer of aphids. The Aphelinid is a third parasite egg layer. One problem with this type of control is that the
parasites are prone to common insecticides. If organic gardening is used and the orchard is isolated, this may be one
of the best control methods. This form of control would seem to be the most effective, when all factors of cost,
availability, and ease of use are taken into account!
Predator insects are another type of good biological control. Lady beetle is the most commonly known predator
insect. The introduction of the beetles can be effective, however they may leave the area before they kill the pest.
Lacewing Fly larvae also kill the aphids quite well. Both of these can be released as eggs and increase the
effectiveness of its control because initial feeding are done in the area of infestation. One consideration in regards to
predators is ants. Some ant species protect aphids and "milk" the honeydew. These ants need to be controlled; they
will protect their food source and kill or scare off aphid predators. Predators are a cheap method of control, though
less effective than parasitic killers. When this control is coupled with parasitic methods the failure rate is very