A prolonged spell of hot weather has led to an explosion in wasp numbers with experts reporting finding nests bigger than basketballs.

After last year’s wet summer and a damp start to 2013, the stinging insects have been thriving in near constant sunshine and are expected to still be present in large numbers until late October.

Although an increase in wasps is bad news for picnics, their return could be a boost for gardeners as they feed on caterpillars and other pests.

Richard Harvey, founder of East Anglian Pest Control, said: “They didn’t come out as early as they normally do, then the queens came out and they started getting established. They are about six to eight weeks late but now they are out and around with a vengeance. Last year we had practically zero call outs, the year prior to that was one of our best year and we saw record number of calls. Now this year has really picked up we are seeing all types of call outs, to domestic and commercial properties.”

He added: “The wasp nests we have done, about 60% or 70% of them are bigger than a basketball. They are getting larger and larger and this will carry on, I anticipate it will go through to the end of October, because the nests are so big.”

Julian Roughton, chief executive of Suffolk Wildlife Trust, said there appeared to be more wasps and nests around. He added: “The superb weather has helped butterflies, dragonflies and, for a lot of people, less desirable things like wasps. The nests have now built up and they are becoming much more active.”