The decline in the number of oak processionary caterpillars observed may be because the insects can spend a year, possibly even longer, underground. Researchers have recently seen an unexpected number of butterflies crawling out of the ground. This makes combating the plague more difficult, and nuisance may be greater, writes Nature Today†
A researcher from Kennisplatform Processierups saw this week that both males and females emerge that had burrowed into a test set-up last year. In other places, caterpillars have been observed that, with a short interruption above ground, have even been underground twice a year.
The fact that caterpillars remain in an extended diapause, a kind of hibernation, for a year or even longer, may explain why the Knowledge Platform caught 40% fewer butterflies in the caterpillar peak year 2019 than in 2018. The large number of caterpillars meant a further increase. of the number of butterflies expected.
Researchers wonder when these ‘disappeared’ caterpillars will reappear and whether they will emerge from the ground as caterpillars or butterflies. “It will be exciting to see how many butterflies will be caught in placed traps in the coming months,” they say.
The behavior of the caterpillars can possibly cause more nuisance. Where the caterpillars have been hiding in recent years, it’s also unclear how many have burrowed into the ground. Underground caterpillars are hard to fight and ‘control of pest pressure becomes a lot more complicated’, according to Nature Today† It could happen that suddenly a large group of caterpillars goes above ground again, or that an unexpectedly large group of butterflies comes up to lay eggs, and then things are serious.
itchy hairs
The caterpillar lives in oak trees in summer and thrives best in warm weather. The animal has hairs and these can cause itching, breathing problems and complaints to the eyes. In 2019, the caterpillar caused a lot of nuisance and the fighters could barely handle the work.
In the past two years, the nuisance was not too bad. This was due to the relatively low temperatures in the spring. The caterpillar was seen in 17 percent of the nearly 110,000 monitored trees last year.
Free unlimited access to Showbytes? Which can!
Log in or create an account and never miss a thing from the stars.