Raisin moth
Raisin moth

Raisin moths, a rather nondescript gray-brown moth that feeds on grapes, has been on the rise in organically managed Central Valley raisin vineyards during the past 10 years.

Kent Daane, a University of California Cooperative Extension entomologist, led a group that examined moth populations in both organic and conventional vineyards, according to a news blog.

They wanted to identify possible practices that contributed to increased raisin moth densities.

Pheromone trap catches during the 2013 spring and summer were prevalent across numerous vineyards, regardless of management practices. But overall seasonal damage was low.

The primary different between sites with raisin moth damage and those without was well-time insecticide sprays.

One challenge for organic producers may be the availability of approved insecticides that have a long enough residual to control the larvae.

Raisin moths had long been considered just a pest of stored raisins, either infesting raisins as they dried on trays in the field or after they were picked up and stored.

More recently, they've also become pests of fresh grapes in the field. The damage appears similar to that of omnivorous leafroller.

Grapes are infested when they begin to soften, especially when rotten or premature raisins are nearby.

You can hear more about Daane's work by attending the San Joaqin Valley Grape Symposium, Jan. 7, in Eaton, Calif.

For more information, including the agenda, or to register, visit https://ucanr.edu.

Read more about the raisin moth by clicking in the Raisin Production Manual.