PEST
 
   NAME
     Woolly Aphid
     Eriosoma lanigerum
 
   ORDER
     Hemiptera
 
   FAMILY
     Aphididae

Description of the Pest
Females are 2mm long, globular, purplish brown insects that are covered in woolly white wax threads and greyish powder that is secreted from there bodies.  Adults are almost exclusively females, some of which may be winged and produce about 100 brown flat larvae. Nymphs are smaller than adults and pale in colour. Woolly aphids are sap sucking insects that produce honeydew, encouraging sooty mold.

Appearance and Distribution of the Pest
This insect is found through the world and is primarily found on apple trees. It is first seen on the new woody growth where the bark is thin, buds or in wounds in the bark, forming colonies. Nymphs are distributed by wind or on clothing and infested plant material.

Life Cycle
This insect has a Hemimetabolous life cycle, ie. When the immature nymphs resemble the adults.
The species reproduces asexually; 2-20 live female nymphs are produced daily. Some sexual forms produce eggs, which seldom hatch. Many generations appear each year. The immature form overwinters on the roots or near the ground on the trunk of the host.

Period of Activity
During winter (and during periods of unusually high temperatures), most activity is below-ground, or in sheltering cracks in the lower trunks of host plants. Otherwise, the aphids are most active through Spring and Summer, especially during humid conditions.

Damage Caused
Larvae suck sap on lateral growth, shallow roots and trunks of apples, where the wood is thin or has been broken as a result of injury (including old feeding sites). Feeding sites may become gnarled and trunks & roots disfigured; buds are destroyed and the overall vigour of the plant is reduced with less new growth. Excreted honeydew produces sooty mould, to which the waxy threads adhere; this interferes with photosynthesis, weakening the plant. Heavy infestations cause fruit to fall prematurely.

Susceptible Plants
Apple trees are the main host of this insect and are more susceptible when in poor health, this leads to low quality fruit and an overall loss of vigour.  Ornamentals such as Crab-apples, Cotoneasters, Hawthorns are also attacked.

Cultural Control
It is very difficult to eradicate this pest but numbers can be kept down to a non-problem level. Infested parts may be removed; however, reinfestation is likely due to migration of larvae from infested roots. Note that some host species have resistant rootstocks and are preferred plantings. When mowing or wiper-snippering around susceptible plants take care not to damage the bark on the trunk. Bark eating animals such as cattle, sheep or wallabies should be kept away from the plants. Other preventive measures include pruning during summer when the wounds heal quickly and all wounds should be painted with a antifungal sealant.

Biological Control
Ladybirds, lacewing lava, syphid fly and parasitic wasps generally keep the aphid in check if the plants are not sprayed.  

Chemical Control
Winter oil may reduce some over-wintering larvae populations. Insecticides, if used, will also destroy the parasitic wasp, which is an introduced and effective predator.
Note
Always read the label for registration details and direction of use prior to application of any chemicals.