When you’re growing 3,200 acres of pecans, you don’t do things on a small scale — and that includes controlling insects.
For more than 20 years, orchard managers at Stahmann Farms, San Miguel, N.M., have been using lady beetles and lacewings to control both yellow and black-margined pecan aphids.
This biocontrol program is much less expensive than using insecticides, says Sally Stahmann, and these natural predators eliminate the possibility of the aphids becoming resistant to an insecticide.
Stahmann, who supervises the company’s production operations, is a granddaughter of Deane Stahmann, Sr., who is credited with starting New Mexico’s pecan industry in 1932 when he planted the Mesilla Valley’s first pecan trees.
Today, Stahmann Farms, which grows, processes, packages and sells pecans, is the country’s largest pecan producer owned by a woman.
THeir main varieties are Western Schley, Bradley and Wichita. About half of the trees are 80-years-old; the rest are 30 years younger. Most are planted on a 30 x 30-foot spacing (48 trees per acre). All are hedged about every four years to a height of 33 feet and a width of 10 feet from the center of the tree.
To establish a self-sustaining biocontrol program to control aphids, new supplies of the beneficial insects were released each summer for a number of years. Lady beetles were distributed at the rate of one gallon per acre. Sometimes, lacewings were introduced by placing cards of insect eggs in the trees; other times, eggs were mixed with corn meal and spread over the orchards by airplane.
No new lacewings have been introduced into the orchards since the late 1990s, Stahmann says. The last release of lady beetles was four years ago. “Now, the populations of both species are holding their own,” she says.
“We still get some yellow and black-margined aphids in our trees. But, with the beneficial insects feeding on them, the aphid numbers crash in about a month or less and cause few problems for us.”
However, she reports, a chlorpyrifos insecticide is sprayed on trees, when needed, to keep black pecan aphids in check.
“We haven’t found an insect that we can use to control that species of aphid,” Stahmann says. “But, to minimize the amount of insecticide used, we spray every other tree row instead of all the trees. We’ve been doing this for more than 20 years, and it’s worked really well. Because we spray very little, we haven’t seen any major impact on the beneficial insects.”
This year, Stahmann Farms’ biocontrol program was aided by unusually hot weather in early June, which helped limit development of the yellow aphids.
“Temperatures were over 100 degrees just when the aphids were expected to peak, and we had good rainfall in mid summer to wash off their honeydew,” Stahmann says. “Keeping the leaves clean and free of honeydew allows them to work more efficiently.”
Meanwhile, the trees are going into the fall in good condition. “They’re healthy, and it looks like they’ll produce more nuts than normal for an off-year like this one,” she says.