Friday, 2 November 2012

Very small red dots

Panonychus ulmi (Dept Agriculture UK)

This is the European red spider mite (Panonychus ulmi), ("ácaro vermelho europeu"), but it has emigrated. It is now found all over the world, where it is something of a nuisance. It feeds on plants, and unlike many invertebrates, it`s not fussy. Add a very high reproductive rate and you have a pest.

In Brazil it is mainly found in the south, where like many European migrants it finds the climate more congenial.  There it is a major pest of apples, pears, peaches and vines, overwintering as eggs on the tree trunks.  In the spring the eggs hatch and nymphs  start crawling over the plant. Now, these mites are very very small, about 0.7 mm, so you wouldn´t think it would matter much, but there are a LOT of mites. Each female only lives about 2-3 weeks, but can lay up to 50 eggs. Gradually the leaves become spotted, then bronzed and they fall off. Infested flowers often produce no fruit.

Incidentally, mites are NOT insects, they´ve got eight legs and they are distantly related to spiders. Including the ability to spin webs.
 Neoseiulus californicus

The main predators of mites are other mites, predatory mites.  Since 1992 hundreds of thousands of Neoseiulus californicus have been reared in huge plastic greenhouses in Brazil and released into orchards. They don´t eat all the mites, which is a good thing as then they themselves would starve. They just kill enough to leave the tress healthy. With luck you get a balance.

1 comment:

Anonymous said...

Even mites prefer the south!!! Heating no more!!!