Issue link: http://read.dmtmag.com/i/56260
Pest Management Biocontrol is FRAGILE T he arrival of the brown marmorated stinkbug in the eastern United States has upset efforts by growers to effectively use biological agents to control second- ary pests. It has also stalled efforts toward developing more ecologically based integrated pest man- agement practices using mating disruption and more pest-selective insecticides. These would conserve biolog- ical control agents and help achieve biological control of primary pests such as codling moth and oriental fruit moth. Biocontrol—the control of pests by their natural ene- Invasive stinkbug further upsets already delicately balanced IPM systems. mies—has always been fragile whenever pesticides are used, Dr. David Biddinger, an entomolo- gist at the Pennsylvania State University Tree Fruit Research and Extension Center in Biglerville, explained during the Great Lakes Fruit, Vegetable, and Farm Market Expo in Michigan in December. Most pests develop resistance to pesti- by Richard Lehnert cides much more quickly than the natural enemies, he said. Even well-intended actions, such as phasing out older neuro- toxic pesticides under the Food Quality Protection Act of 1996 and the introduc- tion of more than 20 safer pesticides in the last 15 years, could upset the balance. Fruit growers were adapting to setbacks caused by the new pesticides and the new rules, and were moving towards enhancing the role of biological control when the stinkbug came along and set them back again. Biddinger's advice to growers facing the stinkbug: Do the best you can until better methods come along. Preserve IPM tools that have been effective in the past, but watch out for possible side effects in the next few years from using broad-spectrum insecticides to control the brown marmorated stinkbug. One of these effects could be a reduction in beneficial biological control agents and outbreaks of secondary pests like mites, woolly apple aphids, scale, leafminers, and leafrollers. "We have already seen a move away from pheromone mating disruption, which was an effective nonpesticide alternative for controlling important pests like codling moth," he said. Some history Biddinger traced the history of IPM programs that were developed beginning in the 1960s. "Experience in many crops has shown that if pesticides are used without considera- tion of the natural enemy complex, the management system shifts to a 'pesticide tread- mill' syndrome where pesticides are used for dealing not only with the initial pests, but also with the secondary pests whose natural enemies are destroyed," he said. This occurred in many apple orchards, where organophosphate and carbamate insecticides, with their broad-spectrum activity, were the main insecticides of choice directed mainly at codling moth. Fortunately, a few—but only a few—beneficial mites and insects became resistant to these insecticides. These included some predatory mites, the lady beetle Stethorus punc- tum, and the woolly apple aphid parasitic wasp, Aphelinus mali.These developed resist- ance to organophosphates and were incorporated as key components in apple IPM programs, Biddinger said. They learned to live with materials like Guthion (azinphos- methyl), Lorsban (chlorpyriphos), and Sevin (carbaryl), allowing growers to use them 10 MARCH 1, 2012 GOOD FRUIT GROWER These four creatures have survived pesticide treatments to become the most important biocontrol agents in eastern apple orchards. There are two species of predatory mites (top and bottom pictures); the "mite destroyer" ladybeetle Stethorus punctum (second photo); and the woolly apple aphid parasitic wasp, Aphelinus mali. www.goodfruit.com