San Jose Scale Problem for Peach Producers

Clint Thompson Alabama, Georgia, North Carolina, Peaches, Pests, South Carolina, Top Posts

Photo from Brett Blaauw/University of Georgia/Shows San Jose scale crawlers.

By Clint Thompson

Brett Blaauw, University of Georgia assistant professor in the Department of Entomology, says the time is now to treat San Jose scale crawlers which are peaking in peach orchards.

“Right around late June, early July and then again in August, we see these real high populations of their larvae, the crawlers. Crawlers are also susceptible to insecticides. They do not have that waxy coating yet. They’re the mobile stage of the scale. They’re leaving their mothers and searching for another part of the plant to settle down and start to feed. These crawlers have a few days of vulnerability so we can also try to time our insect sprays to target those scale crawlers,” Blaauw said.

He said in his blog that he expected this week to see a peak in crawler activity. South Carolina producers should expect to see crawler activity in the next week or two.

What is San Jose Scale?

San Jose scale is a tiny insect that has a waxy coating. It covers and protects the whole body of the insect. It protects them from the environment. It protects them from other insects that would eat them. And unfortunately, it protects them from insecticides. Once these insects create their waxy covering, they are hard to kill, according to Blaauw.

They also reproduce at an extremely high rate. It does not take long for a minimal problem to balloon to a major concern for peach producers.

“Females can produce hundreds of offspring. Just from one female, she can produce almost 300 offspring. Of those 300 offspring, if they’re female, can go on to have 300 more offspring. The population can get quickly out of hand,” Blaauw said. “When you have thousands of these little insects feeding on the branch of a peach tree, it can quickly kill or reduce the vigor of that branch. If the problem goes untreated, you lose branches, and then you lose limbs and eventually you lose whole trees.”

Another Management Option?

Blaauw said another management option is to apply two dormant sprays of horticultural oil. It is best to spray once the trees are dormant and then before bloom next growing season. The high-volume sprays will suffocate the San Jose scale.

“That usually works pretty well and significantly reduces the scale population. But even when the growers are doing that, we’re seeing the numbers skyrocket about now. I can go out there and monitor almost any time of the season and find San Jose scale in the trees,” Blaauw said.

The San Jose scale can be traced back to the 1800s. With modern insecticides, the scale was not a problem in the 1900s. But it has come back with a vengeance in the 2000. It thrives in Georgia’s warm summers and winters and can be active all year long.

Another issue is that complicates farmers’ management options is that the scale may not impact the whole orchard. It could be clustered in one area or part of the orchard. It can be hard to manage if a grower has many acres of peach trees.