Magazine - The Couch Mite

By Jerry Spencer in Consultancy on 15th Nov 2009 11:40

The couch mite (Eriophyes cynodoniensis) can be a serious pest wherever couch is grown. It does not attack other turfgrasses. It is an eriophyid or gall mite, being extremely small, yellowish-white, somewhat worm-like in shape, and have two pairs of forward-facing legs.

Females lay round, transparent eggs singly or in groups between the grass stem and blade sheath. A 10-20X hand lens or microscope is needed to find the mites - they cannot be seen with the naked eye contrary what some people will tell you!

The mites are active usually during late spring and summer. One generation (from egg to adult) may take 7-10 days, so many generations occur each year. Most of their life is spent hidden within the leaf sheath. Nearly 100-200 mites of all stages (eggs, immatures, and adults) can occur under just one leaf. They cannot survive on couch seeds. As a general guide control is warranted if the grass has 4-8 stunted tufts per 100cm2

Cultural Control
Keeping the turfgrass healthy and growing vigorously may help the plants tolerate or outgrow an infestation. However, to manage small infestations, reduce the use of nitrogen fertilizers, and dispose of all clippings. Water thoroughly for several days afterwards to minimize turf stress. This may slow down mite development and remove a large portion of the population.

Recently registration was given to an abamectin (Group 6) based miticide. The active ingredient, which occurs naturally, is derived from the soil micro-organism, Streptomyces avermitilis. This miticide has both contact and translaminar activity. “Translaminar” is a term that refers to products that can penetrate the leaf tissue and form a reservoir of active ingredients within the leaf, such as the spongy mesophyll and palisade parenchyma cells. Mites, feed on the leaves and may ingest enough active ingredient to kill themselves, even after spray residues have dried.

This may provide up to 28 days of residual activity being active on the mobile life stages of mites but having no activity on eggs. It is slow acting (so don’t expect immediate results) with mortality being high within 24 to 48 hours, and any treated mites are immobilized after exposure. Bearing this in mind after the first application a second may well be required 5-7 days later.

In the US It is recommended that abamectin not be applied more than twice in sequence.

Jerry Spencer

Endeavour Turf Products Pty Ltd

Tel: 0439 019 050 Fax: 03 8555 0642 E-mail: jerry.spencer@etpturf.com.au web: www.etpturf.com.au

Read more articles in Consultancy, by Jerry Spencer or from November 2009.