Why Are Wasps Attacking My Plums?

By late summer, wasps switch from protein-based foods to sweet, sugary ones, and ripening plums are one of their favourite targets. A plum tree near ripeness in August can attract dozens of wasps simultaneously, each hollowing out fruit from the outside or entering through cracks. Understanding why wasp activity peaks in late summer and what practical steps can reduce the damage helps protect the most valuable part of your harvest.

Why late summer brings the worst wasp pressure

Wasps are social insects whose colonies peak in size in August, creating large numbers of workers at exactly the time they have lost access to their usual larval food supply. The colony's own brood is winding down, so workers no longer receive the protein feedback they need and switch entirely to sweet food sources. Fermented, overripe or cracked fruit releases volatile compounds that attract wasps from considerable distances. The peak problem period is typically late July through early September.

Harvest at the right time — the most effective defence

The most practical way to reduce wasp damage is to harvest plums as soon as they reach full ripeness, before they begin to overripen and ferment on the tree. Check the tree daily during the harvest window — a ripe plum lifts away from the spur with barely any pressure. Leaving plums beyond full ripeness for the sake of convenience means presenting wasps with progressively more attractive targets. Slightly underripe plums can be harvested and left to ripen indoors in small batches.

Remove windfalls and damaged fruit immediately

Fallen, fermenting plums on the ground are the single biggest wasp attractor under the tree. Clear windfalls daily during harvest season — they do not need to be composted immediately, but they should be moved away from the tree. Similarly, remove any plums on the tree that are already damaged or have been penetrated — leaving them attracts more wasps to the tree.

Wasp traps — limited effectiveness

Commercial wasp traps or homemade bottles baited with sweet liquid can catch individual wasps but make little dent in the overall population arriving at the tree. They are more useful as a monitoring tool than a control measure. Do not place traps in the tree itself — they can attract as many wasps as they catch in the immediate vicinity.

Fine mesh netting

For a small or fan-trained tree, draping fine insect mesh over the tree as the fruit approaches ripeness is the most reliable physical barrier against wasps, and also excludes birds. Ensure the mesh does not rest directly on the fruit and remove it for hand-picking.