Sprucelarch adelgid Adelges viridis

This relative of the aphid may cause serious damage on spruce grown for Christmas trees.

Damage. Although nursery trees less than four years of age are rarely badly damaged, early infestation in the young plant may result in serious damage as it gets older. In June-September the adults move to larch, acquire woolly white hairs and may cause defoliation of the leaves.

Life cycle. The green female adult develops from overwintering nymphs on spruce, and in May (year 1) lays about 50 eggs on the dwarf shoots. The emerging nymphs, injecting poisons into the shoots, cause abnormal growth into pineapple galls, which spoil the tree's appearance. After a further year (year 2) on this host, the female adelges returns to the spruce, where it lives for another year (year 3) before the gall-inducing stages are produced.

Spread is by flighted females.

Control. In Christmas tree production, the adelges may be controlled by sprays of deltamethrin in May, when the gall-inducing nymphs are developing.

Adelges Viridis

Figure 14.10 Adultglasshousewhitefly, actual size is about 1 mm long

Figure 14.10 Adultglasshousewhitefly, actual size is about 1 mm long

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