Conifers are a tree that bears cones and evergreen needlelike or scalelike leaves. If you have conifer trees you may have to worry about Adelgids, which are are aphid-like insects that suck the sap from conifers.
Adelgids can cause distortion of shoots, affecting the appearance of trees. Yellow, winged adults leave galls in late summer and lay eggs on host plants. The nymphs soon hatch and overwinter close to buds. In spring these nymphs feed on plant sap but do not cause galls, maturing into light green wingless females. These females lay eggs covered in white waxy threads. The nymphs hatching from these eggs induce the galls when they feed at the base of needles. The galls contain numerous chambers within which groups of pale orange nymphs develop.
Adelgids only lay eggs, and never give birth to live nymphs as aphids do. Adelgids are covered with dense woolly wax. A complete adelgid life cycle lasts two years.
Adelgid nymphs are known as sistentes, and the overwintering sistentes are called neosistens.
Rain can kill adelgids by dislodging eggs and sistentes from trees.
So now that you know a bit more about adelgids, let’s discuss the reason why you’re probably reading this:
How do I get rid of adelgids?
The damage adelgids cause is often minor and can usually be tolerated, however, if you wish to remove adelgids from your plants, here are a few suggestions.
Adelgids can be difficult to kill with insecticides as they’re protected by waxy secretions. In addition it’s only feasible to treat adelgids on trees that are small enough to be sprayed thoroughly. It’s quite difficult to deal with infestations on very tall trees.
The following insecticide information is from the RHS
The College of Agriculture, Food and Environment offers some clever ideas for controlling and eliminating adelgids including:
Spraying foliage with insecticidal soap or horticultural oil at the proper times during the HWA life cycle.
Using a systemic insecticide that moves with the tree sap and is consumed by the adelgids as they feed.
There are three main methods for introducing insecticides including trunk injection. soil injection and soil drenching.
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