PESKY PAPER WASPS
I get a few of these wasp nests on my bromeliads. Is there any way to stop them?
M. Bell, Warkworth Answer
This is the early nest-building stage of one of the Asian or Chinese paper wasps, which are now widespread throughout warm parts of the country. They thrive in hot, dry conditions and can give you a nasty sting if threatened (or disturbed while you’re gardening, peacefully unaware of their presence – which I know from experience).
Pregnant queen paper wasps overwinter in dry nooks and crannies on trees, between pieces of timber in the wood shed, among rocks or such like. In spring, queens become active and chew wood fibres from old wood to form papier-mâché to build the first cells of their nest hanging in a suitable sheltered spot, such as under the leaves of your bromeliads. Into each cell she lays an egg, then gets on with building more cells and laying more eggs. She feeds the larvae a variety of things, including pollen, nectar, honeydew, some vegetable matter and even insects, but they also have a liking for fresh caterpillar meat, so they help control caterpillar pests. But they can also decimate populations of monarch caterpillars in summer and monarch numbers are in decline worldwide, so we need to do what we can to provide them with safe gardens where they can live and breed.
I’ve tried many ways to kill off paper wasp nests and find the safest, most effective solution is to wait until late in the evening when the wasps are all in the nest, each with its head stuck up into a cell and its rear end sticking out. Use a can of normal household fly spray and spray upwards, quickly covering the whole nest and the rear ends of all the wasps with spray. Some wasps will drop out, so back off, go inside and have a cup of tea and don’t return until the next day. If you did a good job, the nest will be empty and dead wasps will be lying around. Pull the nest off the plant, drop it to the ground and congratulate yourself on a job well done.