Chemical control options reviewed Wintertime is vacation time for San Joaquin Valley farmers, who either head for the coast or the mountains for a little R&R after spending their spring and summer in the fields.

One of their pest nemesis, cotton aphid, also takes a vacation each winter, only to return during growing season to cause costly problems. While farmers often know where they want to go for vacation, they heretofore have been unsure where the cotton aphid spends its winter.

University of California entomologist Larry Godfrey has found where the aphids like to take a break from munching on cotton They like pomegranates for overwintering, a crop that is becoming more widespread on the West Side of the Valley where most of the valley's cotton is produced.

"We have found both adult aphids and aphid eggs on pomegranates," Godfrey told producers at the recent cotton field day at the West Side Research and Extension Center, Five Points, Calif.

Pomegranate, however, is not the aphid's only host. It also spends the winter on winter annual weeds, added Godfrey. Growers knew that, but most were not aware of the pomegranate host.

Not dormant sprayed One reason the aphids can overwinter on pomegranates is that pomegranates is one tree crop where producers do not typically apply a winter dormant spray. Almonds, which are more widely planted than pomegranates on the West Side of the San Joaquin Valley where cotton also is grown, typically are treated for overwintering OLR.

Unfortunately, cotton producers cannot get rid of the pomegranates, therefore, they must learn to control them. Fortunately, said Godfrey, there is chemistry effective against the aphid.

Fulfill, is an anti-feeding compound currently registered for use on vegetables, that may be available soon for cotton. "It works well," said Godfrey, adding that the old standby Furadan continues to be a good control compound as does Lorsban. Vydate, an insecticide more noted for control of lygus, has also proven to be effective against aphids in Godfrey's trials.

Aphid populations were high this past season, reaching 200 to 300 aphids per leaf in some locations, said Godfrey.

Some of this population could be caused by high nitrogen levels, specifically petiole nitrogen. Godfrey has found that when petiole N is high, aphids develop faster and have more offspring.

On the other hand, potassium may have the potential to reduce the effect of high nitrogen on the aphids, he added.