Soft approach is effective in control of many pests

University of California researchers have developed and tested a low impact peach insect pest control program that leaves enough beneficials in the orchard that it is rarely necessary to treat for mites.

This program has come together at the right time, both because there is evidence that the Oriental fruit moth is developing resistance and because peach growers in the San Joaquin Valley face close scrutiny by water quality regulators.

The soft program for peach pest control includes pheromone mating disruption, beneficial insect attraction, careful monitoring and the application of softer insecticides when needed. When practiced for years, this approach has reduced populations of peach pests to negligible levels.

"Our Oriental fruit moth problem has been reduced in the IPM trials to the point that we can't find enough larvae to see if they have been parasitized. Oriental fruit moth has been managed very well," said Walt Bentley, UC Cooperation Extension integrated pest management entomologist.

The IPM program begins with pheromone mating disruption to reduce moth pest populations. In the San Joaquin Valley, Bentley recommends putting up 150 to 180 Isomate TT pheromone hangers per acre in the spring. The program calls for monitoring for San Jose scale, Oriental fruit moth and using a delta pheromone trap to monitor four different moth species.

One difficulty with the Oriental fruit moth traps is that the bait evaporates within two weeks, and within just one week in the summer in the San Joaquin Valley.

"So far they haven't been able to integrate a dry bait with the pheromone," Bentley said. Manufacturers and researchers continue to work on coming up with a user-friendlier trap.

In numerous trials, Bentley has found that timing has a very important impact on the effectiveness of softer materials like Success, Intrepid and Altacor.

"There is a significant amount of missing the timing on applications of materials for both Oriental fruit moth and peach twig borer. That timing is important to the effectiveness of the applications, and being ahead is better than being behind," Bentley said. "Work on making the timing closer and you'll do better with the material."

UCCE farm advisors in areas where peach twig borer and Oriental fruit moth are important pests regularly post degree-day information to help growers time their applications.

Another key element in the IPM program is planting sunflowers as part of an Oriental fruit moth control strategy. The sunflowers attract both sunflower moths, which are not a pest in peaches, and parasites that feed on the sunflower moths until Oriental fruit moths show up.

"We started planting sunflowers and we are finding both sunflower moths and the parasite that goes to both the sunflower moth and Oriental fruit moth," he said.

Researchers are also finding both the sunflower moth and the parasite on native sunflowers. The flowers bring back beneficial insect populations that have been reduced by the use of broad-spectrum materials. The effectiveness of these beneficials is variable, but at times they are potent.

"There's a reservoir of the parasites out there if we can stay away from broad-spectrum materials. I've seen 90 percent control of Oriental fruit moth with these parasites, but I've also seen 30 percent control," Bentley said.

On the whole, however, when the low impact IPM program is implemented for a few years it results in very good control of Oriental fruit moth.

The materials used in the IPM program are more expensive than the widely used pyrethroids, but the softer materials usually solve the problem of water quality regulations. And some of the higher cost of the softer materials can be recouped in reduced costs for mite control.

"Nothing is going to match the price of pyrethroids, but if we lay off the pyrethroids we won't have to spray for mites. I think a lot of you could push the envelope a little more on not putting on a miticide," Bentley said.

He said he is finding unusually low levels of predatory mites in many orchards and suspects the cause of this problem is miticide applications. Bentley suggested easing into this part of the program by trying the no-miticide approach in a small area of the orchard to see how it works.

"I would treat for mites if I were using pyrethroids. There's a comfort zone behind not spraying a miticide and you have to feel that comfort. I wouldn't push it if I were using a pyrethroid during the growing season, but if you're using materials that don't flare mites, try it on an acre or maybe three rows," Bentley said.

Roger Duncan, UCCE farm advisor in Stanislaus County, agreed that miticides are frequently not necessary.

"I think a lot of orchards can do without a miticide, and if mites show up you can knock them back with potassium nitrate," he said.

He also said that pest resistance could make the IPM program an attractive alternative for many growers.

"I think we're seeing more and more Oriental fruit moth resistance to pyrethroids. We're finding more and more Oriental fruit moth in late harvest varieties," Duncan said.

He invited growers with this problem in their late harvest peach varieties to do a trial of the alternative treatments.

The brown marmorated stinkbug could be the next invasive pest to cause problems for peach growers.

"This is giving them fits in Pennsylvania, and they've found it in Oregon. It has also been found in Los Angeles, but nowhere in California north of the Tehachapis. You don't want this if you're a winegrape, peach or pear grower. It will decimate the fruit," Bentley said.

If a grower finds something unfamiliar in a trap, Bentley advises taking the trap to the county UCCE office.

Details and the latest information on the entire tree fruit IPM program are available on the Internet (www2.uckac.edu/treefruitipm/). The program is also summarized in the UC publication Seasonal Guide to Environmentally Responsible Pest Management Practices in Peaches and Nectarines.

(Bob Johnson is a reporter in Magalia. He may be contacted at bjohn11135@aol.com.)