Wasps and hornets attack colonies for bees and for stores. Pressure rises in late summer — precisely when the flow ends and colonies are preparing for winter.

Why late summer

In that period wasp nests are at their largest and their own food source disappears. At the same time bee colonies are rearing winter bees and less able to defend the hive.

The damage

• Bees taken at the entrance
• Stores robbed
• Weak colonies entered and emptied
• The colony stops flying under sustained pressure

That last point is the greatest harm. A colony that no longer forages brings in nothing, even if only a few bees were actually caught.

Invasive hornets

Where invasive species have established, the problem is of a different order. They hover in front of the entrance and hold the colony in that suppressed state.

Western honey bees show little of the defensive balling behaviour of Apis cerana, which is one reason they are so vulnerable.

Measures

• Reduce the entrance to a few bees wide; the area to defend shrinks
• Keep colonies strong; a strong colony defends itself
• Unite weak colonies
• Keep the apiary clean; spilt honey and extraction waste attract wasps
• Close the hive of a dead colony immediately
• Locate and report nests of invasive species

About traps

Traps baited with sugar are not selective. They catch honey bees, bumblebees and beneficial insects alongside the target.

They are no substitute for reducing the entrance. Targeted trapping near a known nest in spring can have value, but broad deployment does more harm than good.

Reporting

Invasive hornets are notifiable in many countries. Photograph, record the location and date, and inform the competent authority.

Finding and destroying nests is work for equipped personnel, not for the beekeeper.

Perspective

Except where invasive species are established, wasps rank low among the causes of colony loss. Check Varroa, nutrition and wintering first.