Anthonomus pomorum

Scientific Name Anthonomus pomorum
Common Names English: Apple blossom weevil; German: Apfelblütenstecher; Spanish: Gorgojo del manzano; French: Anthonome du pommier; Italian: Antonomo del melo
Description The adult beetle is 3.5 - 5 mm (0.14 - 0.19 inch) long, brown, and coated all over with fine gray scales. It has a very long rostrum of about 1/3 the body length.

Biology

Damage

In early spring, the female deposits one egg into each of up to about 100 still mostly green flower buds. The oviposition sites are visible as little holes, which often exude a small amount of brownish liquid. After 4-14 days, the larvae hatch and start feeding on the immature reproductive organs and the inner surfaces of the petals. Thus the blossom is destroyed and fails to open. Instead, the petals become brown and dry, which looks at first glance similar to frost damage. They form a typical, small hollow ball. Inside, without building a cocoon, the larva develops for about 2-3 weeks, after which time it pupates. Ca. 10 days later, mostly in May/June, the adult beetle emerges.
The adults feed on the undersides of leaves and sometimes on fruits, where they cause small lesions. The damage they cause is, however, of little economic importance.
When A. pomorum occurs only at low densities, it is not usually a great problem. In years with abundant blossom, the loss in terms of number of fruits is often compensated for by an increase in their weight, as the weevil only has a „thinning“ effect. The population can, however, build up over several years, so the damage can be serious, especially in years in which there are fewer flower buds. Trees near to woods or abandoned orchards are particularly at risk.

Lifecycle

A. pomorum has one generation per year. It overwinters as the adult under the bark of trees or in other sheltered places, preferably in leaf litter.
Convenient hiding-places are rare in modern apple orchards, so the beetles often migrate into adjacent woods for hibernation. They become active again in the spring and colonize the apple trees when mean temperatures during the daytime rise above 9-10°C (48.2 - 50°F).
In order to achieve sexual maturity, they have to feed externally on buds for 10-14 days, after which they mate. The female starts laying eggs 2-3 days later.
In order to achieve sexual maturity, they have to feed externally on buds for 10-14 days, after which they mate. 2-3 days later the female starts laying eggs.
When the adult has emerged from the pupa, it will feed for some weeks until late summer. Then it seeks a place for hibernation, where it stays in diapause until the following spring.

Occurrence

Additional Crop Information

Apple and pear.

Agricultural Importance

The apple blossom weevil is found in all parts of Europe and those regions of North Africa and Asia where apples are grown.
The amount of damage varies greatly between years and sites. It can be negligible in one year and considerable in another, depending on the weather, and particularly, on the abundance of blossoms.
While this insect is certainly no longer as great a threat as it was considered to be several decades ago, it has gained significance again in some regions during the last twenty years.

Control

Integrated Crop Management

In order to decide in time whether an insecticide application is indicated, careful monitoring of this pest is important. The most-used method is limb jarring; recent research suggests, however, that the results gained by using shelter traps are more reliable.

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