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FactSheet
ECI-NRSP-GEF Extension FactSheet on Woolly Apple Aphid in Tehsil Murree
Woolly apple aphid Eriosoma lanigerum is one of the important pests attacking apple trees in Tehsil Murree. It may be found either in commercial orchards or in home plantings. To monitor the infestation, pruning cuts and water sprouts should be examined in late-spring and every few weeks throughout the summer for the presence of new colonies of woolly apple aphid.
Damage
Woolly apple aphid is both an indirect and direct pest of apple that weakens the tree by its feeding on bark and roots, which reduces tree health, prevents wounds from healing and transmits perennial apple canker disease. Colonies of woolly apple aphid are formed at wound sites on trunks, limbs and twigs where they feed on tender bark. As populations grow, aphids can be found around the axils of leaves on water sprouts or on terminal shoots. Swollen galls form on stems where aphids have fed. The foliage turns yellowish on infested branches.
Life Cycle
Woolly apple aphid usually overwinters in the nymphal stages underground on apple tree roots. Nymphs and adults may be able to survive above ground in sheltered crevices of the bark during winters. In the spring, wingless females give birth to live nymphs. The first-stage nymphs are called crawlers because they are the most active of the four nymph stages. Crawlers allow colonies to disperse from roots to above-ground parts of the tree. Crawlers can be carried by the wind, birds or other insects from tree to tree within an orchard or nursery. Crawlers also move downward to infest the roots. Once aphids complete four nymph stages, they reach the adult stage. Woolly apple aphid reproduces without mating during the spring and summer; female aphids give birth to large numbers of nymphs. Winged adult females are produced when colonies become crowded. There are several generations per year.
Natural Control
The small parasitic wasp known as Aphelinus mali attack the aphids by laying their eggs in aphids by stinging with their egg-laying organ. The wasp egg hatches within the aphid and the young wasp larva consumes the aphid. Parasitized aphids turn brown or black. In time, the wasp larvae emerge as adults from the aphids leaving behind empty aphid skins. These skins, called "aphid mummies," can be found attached to leaves. A. mali is highly susceptible to insecticides. It can reduce woolly apple aphid populations in abandoned orchards where insecticides are not used, but usually cannot survive in commercial orchards where insecticides are used, particularly pyrethroids or carbamates.
The redistribution of parasitized aphids (mummies) from orchards where their population is high to orchards where their population is low can give effective control of the pest. The same training is being provided to the
Master Trainers selected from Community Organizations (COs) established by National Rural Support Programme (NRSP) in Tehsil Murree.
Cultural Control
ü Resistant varieties need to be identified and must be planted to prevent underground infestations. The Malling-Merton (MM) rootstock series provide resistance to woolly apple aphid attack. Some apple varieties such as Northern Spy are resistant to this pest. There may also be several local resistant varieties in Tehsil Murree that need to be identified.
ü Careful pruning can be used as a cultural method to provide clean cuts with limited sites for woolly apple aphid infestations and also to remove its colonies.
ü Root suckers and water sprouts may be removed that help in effective control of Woolly apple aphid.
ü Another cultural technique which may influence woolly apple aphid populations, is tree nutrition. Many aphid species are known to reproduce more rapidly as nitrogen levels increase in the host plant, including that caused by added nitrogenous fertilizers. Therefore, nitrogenous fertilizers may be avoided.
Chemical Control
An insecticide can only be applied as a last resort. The judicious use of following insecticides are recommended:
ü Pirimor
ü Insecticidal soap
ü Diazinon
Eco-Conservation Initiatives
299, Street-64, I-8/3 (GPO Box 2888), Islamabad-44000, Pakistan
Tel: +92-51-4446362, 4443461, Fax: +92-51-4443461, e-mail:
NRSP Field Unit Danna, Post Office Lower Topa
Tehsil Murree, Tel: 0320-4267513
Sponsored by: UNDP/GEF – Small Grants Programme, Islamabad