Global Plant Protection News

There has never been a better time to implement integrated pest management (IPM)) for spider mites in almonds, according to entomology farm advisor David Haviland, University of California Cooperative Extension, Kern County.

A bevy of new reduced-risk, selective miticides have come on the market in recent years, and UC researchers have developed presence-absence monitoring thresholds to help almond growers understand exactly when they need to pull the trigger on treatment.

Haviland told a packed house at The Almond Conference last December that these new products have different modes of action, are easy on beneficial insects, and all are effective in the control of spider mites.

Despite this fact, pesticide use reports in recent years show a distinct trend toward preventive, prophylactic mite treatments in almonds. Perhaps growers are piggybacking onto early-season applications for other pests, or perhaps they are trying to stay ahead of mites to prevent flare-ups later in the season.

But Haviland said growers who spray at the first sign of mites might, in fact, be setting themselves up for problems later.

Food source

It is important for some mites to be present in the orchard early season to provide a food source for beneficials including six-spotted thrips, which, if allowed to thrive in the orchard, are an excellent natural biological control for spider mites. Allowing biocontrol organisms to get established, in fact, can reduce the risk of spider mite explosions later in the season.

Products containing abamectin, while inexpensive and effective on mites, are also known to kill six-spotted thrips and should be used cautiously if this predator is present in the orchard. In addition, pyrethroids and other broad-spectrum insecticides should be avoided until hull split unless they are absolutely necessary for leaffooted bug or other sporadic pests when no alternatives exist.