WOOLY APPLE APHID
WOOLY APPLE APHIDS are type of sucking pests that live on apple tree and its roots fed by the tree sap. They can be generally seen on the branches of the apple trees, pruned wounds, and cracks on the barks of the apple tree. They can be easily identified as it produces a wax white covering like cotton or wool. The insects can be seen by blowing off the wax, which are deep red or purplish in color. The adults have wings and they moves to different tree locations where they lay eggs. They have pointed needle like parts which helps them in sucking the tree sap. They also make their diet from buds, leaves and roots of the plants.
- ‘WOOLY WAX’ seen on old prune cuts in spring but by mid-summer they are seen on the young shoots.
- In autumn season branches can be seen covered with white wooly material.
- The shoots which are affected usually develop pump near the buds. These shoots can be easily found during pruning. These swellings often develop cracks during extreme frost conditions and put an invitation to other fungal diseases like apple canker.
- The underground colonies found during ploughing the tree basin. This results in stunned growth and can even cause the death of the plant.
The white wooly colonies are found on the branches, such as current season’s growth, unprotected pruned wounds, water sprouts or cankers. Besides this its main attack is on the roots of the apple tree. If populations are high, honeydew and sooty mold will also be problems, and aphids may enter the calyx end of fruit. Severe root infestations can result in poor growth or kill young trees but usually cause little damage to mature fruit trees. It sucks the sap resulting in reduced growth and is found as pump or swollen type structure on the affected part.
It is very easy to find the colonies of wooly apple aphid. On small trees with small infestations it is possible to control by scrubbing the aphid with the help of brush. This should be done in the beginning of the summer. Keep the health of the tree in good condition. Wooly apple aphid has many natural enemies which help to keep in check but they are not so effective. The natural enemies include ladybirds, lacewings and Aphelinus Mali. If Aphelinus Mali is found, it can be encouraged by limiting the use of pesticides. A. Mali has been successfully introduced to many apple growing areas of the world and is providing adequate control to wooly apple aphid. Chemical control can be done by spraying thoroughly with thiachloprid or thiamethoxam or carbosulfan or chlorpyrifos. Because the woolly apple aphids are somewhat protected by their waxy covering, regular spray programs may not provide adequate control. High volume applications of recommended insecticides may be necessary to penetrate the wax. So it is recommended to spray in the early season when the wax layer is too thin. Soil drenching of the insecticides may help in curing the root infestation. To avoid infestation on pruned wounds, chaubatia paste should be applied on the wounds.
SUSCEPTIBILITY OF APPLE ROOTSTOCK TO WOOLY APPLE APHID
The Malling-Merton rootstock series was developed to provide resistance to wooly apple aphid. The table below lists the susceptibility of various clonal rootstocks to the wooly apple aphid.
- M.26———–VERY SUSCEPTIBLE—-SEMI-DWARF
Wooly apple aphids overwinters on its hosts plants as immature nymphs that hide in cracks in the bark or in the crevices of the trees. The waxy material of the wooly apple aphid can not be seen during the winter months. It produces its coating during summer season. In early spring they can be seen on old pruning cuts or other places of the trunk as they become active. So now they start sucking the sap from the bark of the tree and starts secreting the ‘waxy wool’. During late summer these aphids get transferred to younger shoots. At this time the infestation reaches to its peak. In late summer, winged forms of the aphid develop and these will fly off in search of new host plants.