- By Mary and Bill Weaver
Pennsylvania Correspondents
A recent meeting of a group of such scientists, “where we just sat and brainstormed for two days,” was attended by Larry Hull of Penn State University. The meeting’s agenda was to lay the foundation for a transitional strategy of lessening dependence on OP insecticides, according to Hull.
“OP risks and concerns are not going away,” he asserted. “Agriculture must be proactive and develop strategies reflecting the needs of the growers. We must show EPA what agriculture can do to reduce and eliminate use, risks, and residues of the OPs. Otherwise the EPA and environmental groups will be dictating what growers must do.”
“We considered first and foremost the welfare of the growers,” continued Hull. Scientists looked to identify gaps, pest by pest, in different regions of the country, in order to make a “to do” list of needed research, regulatory action and educational programs.
“We looked at alternative chemicals to the OPs, both those presently available and those in the pipeline,” continued Hull. They began with the OP “drivers,” the pests that necessitate the greatest use of the OPs: the apple maggot, the codling moth, the oriental fruit moth, and plum curculio.
For example, to control plum curculio at the period of petal fall, several non-OPs are already available including esfenvalerate, permethrin and Surround (kaolin clay). No non-chemical controls are available. And several new chemicals are in the pipeline including thiomethoxenam, which will be registered soon and indoxcarb, which should be registered this year, according to Hull.
For the codling moth, a number of non-OPs are already available. “Carbaryl has some activity - not great; Lannate is pretty good; the pyrethroids can make a contribution - Confirm has some activity; and Surround.” Mating disruption can also be used, and in the pipeline are methoxyfenozide, to be called Intrepid, and Thioclopid, which is also very effective, Hull said.
For the oriental fruit moth, the same materials can be used as for the codling moth.
“As we get to the apple maggot,” said Hull, “it gets a little more dicey.” Available non-OPs include carbaryl and the pyrethroids, “But any time you’re talking about these chemicals, you’ve got major mite problems.” SpinTor (spinosad) and Surround are also available, and have some activity, “but must be applied quite frequently.” For non-chemical apple maggot controls, we can do mass trapping. In the pipeline are indoxacarb, Attract and Kill.
For the leafrollers, said Hull, “I think we’re in pretty good shape because they’ve developed resistance to all the OPs anyway. We do have some excellent non-OPs: BT, Lannate, SpinTor, and Confirm. These are labeled. There are no non-chemical controls for leafrollers now available, but there are some in the pipeline that are quite effective,” Hull said.
Where do we stand now? Fruit growers have lost PennCap M. Guthion (azinphos methyl) “which has been sprayed across the country on a high percentage of apple acreage,” has been restricted in use. New regulations restrict application rates to 4 1/2 pounds of active ingredient per acre per season, but growers are already within the new limits.
Most growers are spraying less than a pound of active ingredient (a.i.) per acre, and in Pennsylvania, typically only a quarter of a pound of a.i. per acre is used because of growers’ effective use of integrated pest management (IPM).
Phosmet is under review now, and chlorpyrophos is too. On both, Hull said, “We may know something by summer.”
Several new technologies, including mating disruption, mass trapping, and biocontrol agents could help with the possible loss of OPs. “To use these new technologies,” asserted Hull, “growers are really going to have to climb the staircase of IPM, and practice it more intensively. They’ll need to understand the biology and behavior of the pests and their natural enemies. They’ll need to spend more time monitoring and determining the pest injury/yield relationship, asking ‘How many pests can I allow in my orchard?’
“There’s a concern that significant problems with oriental fruit moth are developing in the mid-Atlantic area, and that with our chief pests, we may have some problems,” said Hull.
The new pesticides will be much more physiologically selective than the OPs, which kill pests and their natural enemies. The new “soft “ chemicals are soft on a lot of the natural enemies. “With broad spectrum OPs, we used the machine gun approach,” said Hull, “controlling everything in the orchard. We’re going down now to pistols and rifles.”
Soft chemicals now registered include BT, Confirm 2F, SpinTor, Esteem (which just got registered for pears and apples,) and mating disruption products: Isomate M l00, Isomate C for codling moth, and Isomate P for peach tree borer.
“With broad spectrum chemicals,” said Hull, “growers typically used one chemical per tank, unless maybe they added Provado for aphids or a miticide. This year and beyond, if we lose the OPs, growers will be using mixtures galore - a real cocktail in the spray tank.
“Because the new chemistries are so selective, you’ll maybe need to put four things in the tank at one time. And new products are never cheaper than the ones they replace. Also, with the “soft” chemicals, the margin of error will be much lower, and coverage and timing will be much more critical.”
New mating disruption technologies are available, and are continuing to evolve. These include sprayable pheromones that you can put in your tank with your fungicides and spray on the trees; microsprayers, which use adapted fuel injectors from Ford Motor Co. to mist pheromones in the air at preset intervals; and Puffers, “that I call spitters,” said Hull “They spit pheromone on the tree on a set schedule.”
In Attract and Kill, companies are baiting plastic apples with attractant to lure the apple maggot fly, which will then be killed by the insecticidal coating. Pheromones can also be applied with a grease gun. An insecticide is in the grease that kills attracted insects.
“I think computers will be required equipment for fruit growers in the future,” said Hull, “for environmental monitoring, for decision support, for the wealth of information that’s on the Internet, and for email communication with specialists and other growers.”
For the future, growers really have to pay attention to the FQPA process. “Communicate with the EPA, USDA and legislators,” said Hull. “After all, azinphos methyl made it through.”
“I’m not sure what will happen with FQPA,” concluded Hull, “especially as they start lumping all the chemistries together. But somehow, we have to keep some of the OPs around.”
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