Controlling apple and peach pests without OPs
Researchers found that reduced-risk chemicals are not necessarily soft on beneficials.
Results from a reduced-risk pest management research trial in eastern states show that high-quality tree fruit can be grown without organophosphates, but growers can expect higher costs and more troublesome secondary pests when using the newer and more selective chemicals.
The four-year project, funded by the U.S. Department of Agriculture’s Risk Avoidance and Mitigation Program, evaluated reduced-risk pest management practices for peaches and apples in seven eastern states to develop strategies that reduce worker exposure to and residues from broad-spectrum organophosphate and carbamate insecticides.
Scientists from New Jersey, Michigan, New York, and Pennsylvania shared project results and observations during tree fruit grower talks in Grand Rapids, Michigan.
Reduced-risk and pheromone mating disruption management programs were tested in orchard plots of five acres or larger. Blocks with similar orchard characteristics were treated with the grower’s standard pest management practices and used to compare fruit quality, economics, and such.
The same sites were studied each year in order to compare results from different growing seasons. Integrated pest management strategies were based on site-specific sampling protocols, local pest complexes, selective insecticides and acaricides, pheromone mating disruption, conserving natural enemies, and cultural practices.
Pest consultants played a key role in the research, assisting growers in monitoring and ensuring that insecticides were applied when necessary. In areas where the numbers of private consultants were insufficient, extension personnel performed such services.
Michigan State University entomologist Dr. Larry Gut said that the impetus in Michigan to evaluate reduced-risk practices stems from pesticide regulatory changes and a growing resistance of codling moth to organophosphate chemicals. Nine apple and six peach orchards in five different production areas in Michigan participated in the RAMP project.
“Management of tree fruit pests using reduced-risk practices is possible,” Gut said. In Michigan, reduced-risk chemicals provided good control of obliquebanded leafroller, apple maggot, and plum curculio, with pheromone mating disruption and granulosis virus providing good control of codling moth.
But shortcomings from the reduced-risk pest programs were evident in several areas.
Natural enemies: “We were hoping you’d get help from natural enemies,” Gut told the grower audience. “But we didn’t see an increase in the natural enemies in the reduced-risk plots. We think a lot of the reduced-risk chemicals are not completely reduced-risk to natural enemies. They are more selective, but not completely reduced-risk.”
Researchers found a range of survival rates for beneficial insects—from 20 percent to 90 percent—when several of the new reduced-risk materials were used.
Management: Intensive management and expertise are needed to implement the programs, he noted. “It will be hard to find the expertise that’s needed.”
Secondary pests: Growers will have to be alert for secondary pests. San Jose scale was a pest that crept up in the reduced-risk blocks, causing significant damage in some peach orchard blocks during the last year of the project. No damage from San Jose scale was found in the conventional blocks.
Economics: Pest control practices in the reduced-risk blocks cost more, averaging up to three times more in apple blocks and up to 5.5 times more in the peach blocks. Costs are based on materials only.
Shifting risk: Because of the high costs, new pest management programs shift the risk to growers, Gut said. “We’ve moved the risk away from the environment, workers, and consumers, and put a very great risk on to growers. Growers are going to have to learn how to work with these new risks.”
He encouraged orchardists to explore using USDA Environmental Quality Incentive Program funds to help pay for scouting, pheromone dispensers, and other costs associated with shifting from standard pesticide programs to reduced-risk programs.
Dr. Arthur Agnello, entomologist at the New York State Agricultural Experiment Station in Geneva, reported that 17 apple orchards from major production regions in New York were part of their study.
In general, he found little difference in the percent of fruit insect damage between the reduced risk, pheromone, and standard programs during the four years. Internal worm damage was minimal, and damage from lepidopterous pests, which was noted in 2002, was greatly reduced in the subsequent three years.
Populations of the secondary pests plum curculio and tarnished plant bug fluctuated each year, but control of obliquebanded leafroller was disappointing, Agnello said. “The first few years, population numbers were down low, a mean average of 1 percent at harvest, which in New York, are very good numbers. But when we withheld an overwintering spray in 2005, the numbers popped back up.”
Mite population trends were similar in the blocks, but were accomplished in the reduced-risk blocks without using preventative ovicides.
Agnello, too, was surprised by the effect on natural enemies. “We rarely had more natural enemies in the RAMP orchards compared to conventional orchards,” he said. “RAMP practices are not necessarily kinder to beneficials than conventional practices.”
Average costs for materials used in the reduced-risk orchards did come down by the fourth year because 15 of the 17 orchards did not use pheromone mating disruption, which is relatively expensive. Other tactics implemented instead included border sprays for plum curculio and apple maggot, and omitting pink-bud sprays or petal-fall sprays for secondary pests in low-pressure blocks. However, the average costs of $163 per acre for reduced-risk and $149 per acre for conventional were for materials only and did not include time and labor for monitoring and scouting.
“We did achieve general stabilization of mite populations, and we had low populations of indirect pests,” he said. “But the five most troublesome pests—obliquebanded leafroller, tarnish plant bug, oriental fruit moth, and San Jose scale—were always there.
“My biggest concerns from the project are the inability to achieve sustained suppression of obliquebanded leafroller and the difficulty of controlling secondary pests,” he concluded, adding that the lack of additional beneficials and the excessive costs associated with reduced-risk practices are also troubling.
Dr. Peter Shearer, associate extension entomology specialist at Rutgers, the State University of New Jersey, explained that pest control in peaches is more challenging than in other commodities like apples because uses of several key organophosphate pesticides have been cancelled, are scheduled for cancellation, or are restricted.
Data shows that the reduced-risk tactics for managing key peach pests are effective, he said, “as long as we have the tools and persistence to monitor regularly.”
As in New York and Michigan, they saw no major increases in biological control or natural enemies in the reduced-risk blocks compared to standard pesticide treatments.
Controlling plum curculio with pyrethroids was not effective in the first year. However, control was effective once they received an Emergency Use Permit for Avaunt and used two sprays of Avaunt and one application of Actara.
The organophosphate replacement Actara and new chemistry of Avaunt did “wonders” in controlling plum curculio, he added.
For San Jose scale, control was effective from using a prebloom oil spray, combined with an in-season application of Esteem or Centaur. “But the one in-season spray is very expensive, representing half to one-third of the growers’ entire insecticide bill.”
Mating disruption was effective for oriental fruit moth, peach tree borer, and lesser peach tree borer, and helped reduce worker exposure by eliminating trunk spraying in the fall. The new chemicals controlled leafrollers and Japanese beetles, but there were problems in the grower trials with stinkbugs. Pyrethroids used to control stinkbugs can disrupt integrated mite control and cause scale problems.
His research group saw no real difference in fruit quality at harvest between the two pest control programs, although the reduced-risk treatments in New Jersey peach blocks were 2 to 2.7 times more expensive than conventionally managed blocks.
The research project also demonstrated the importance of good weed management in helping reduce some pest pressures.
Shearer worries about the limited number of new products registered for peaches and that pests are developing resistance to the new insecticides. “Many of the new products have similar chemistries. Resistance management will be very difficult because there are a limited number of products growers can use to rotate chemistries.”
RAMP researchers will be working with growers this year to develop new pest control guidelines and help them implement aspects of the program to make it more affordable.