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Over the past several years, progress towards registration of new agricultural chemicals has slowed substantially as the focus of the EPA has shifted toward careful consideration of label changes for organophosphates as dictated by the FQPA. With uncertainty surrounding the continued practical use of some common chemicals, many companies have placed an emphasis on development of materials that may stand as new-generation substitutes for some of the flexible uses of Ops. In the past year, several new chemicals (some with very new chemistries and modes of action) and a few older materials have made strides toward registration for use on tree fruit in Massachusetts.
Esteem (pyriproxyfen) received full federal registration for use on apples and pears in the fall of 1999. This material is classified as an insect growth regulator, and is only known to be effective as an egg-growth suppressant. It has been labeled for use on cotton for a number of years (under the trade name Knack) and is now labeled on apples and pears for use against codling moth, leafroller, aphids, San Jose scale, and leafminer –– data from recent use under a Section 18 permit in Washington and Oregon suggest that it is most effective against scale insects. Although this material has demonstrated translaminar foliar residula activity, efficacy against leafminer is not fully established, and it is not yet clear whether it will impact development of early- to mid-instar larvae as well as eggs, which is critical in a scouting-based LM management program. Cost may be somewhat prohibitive to trial use; early estimates indicate that label-rate use will run roughly $75 per acre.
After many years of regional trials, Confirm (tebufenozide) received both federal labeling and state approval for use on pome fruit for the 2000 season. This material is labeled against a wide range of lepidopteran pests (including codling moth, leafroller, lesser appleworm, and green fruitworm), and works by inducing premature molting of developing leps –– killing the target pest but few nontarget individuals. As is the case with many new-generation insecticides, this material is most effective when consumed by the target insect, so thorough coverage is necessary for consistent pest control.
Danitol (fenpropathrin), classified as a Type I and Type II synthetic pyrethroid, received full federal registration for use on apples, pears, and grapes a month ago, though state approval is still pending. Like most pyrethroids, Danitol offers broad-spectrum arthropod control, and is labeled for use pre-bloom, post-bloom, or late season (with a 14 day preharvest interval). Interestingly, this material is labeled for use against European red mites and two-spotted spider mites, though it is also known to kill most beneficials in the bargain. It is likely that this material will be of most value as a prebloom treatment or for use in areas with OP resistance problems. No more than 2 applications per season are recommended, and resistance development is a major concern. It is a fairly inexpensive material, costing $12-15 at the labeled rate of -16 oz. per acre.
Surround (kaolin clay) Crop Protectant represents a new technology for use in apple orchards: particle barrier film. A sprayed application of the clay (at 25 lbs. per 100 gallons) dries to form a thin, white particle residue on fruit and foliage, barring tissues from a wide range of insect and disease pests, enhancing growth, and protecting fruit and foliage from heat stress. Although this material is labeled as a nearly all-encompassing season-long crop protector, it has not yet demonstrated effectiveness against aphids, San Jose scale, or mites. However, Surround may offer a potential leap forward for nonlethal control of many other apple pests, notably apple maggot, plum curculio, codling moth, leafrollers, leafhoppers, and thrips. In addition, this material was recently listed by the Organic Materials Review Institute as acceptable for use in organic production. That said, this technology will undergo some broader trials in Massachusetts this season to more fully understand its potential for use in IPM programs.
Pending Registration of New Materials
There are several materials that have been in the product development and registration pipeline for many years that will remain there for the foreseeable future. For example, Comply (fenozycarb) was initially developed as a growth regulator with a scope of activity similar to Confirm (above). However, in 1999 it was classified as a carbamate, and has encountered consistent registration hurdles since. According to the manufacturer, it is unlikely that this material will be registered for use on apple anytime soon.
Last year, it appeared that Pennstyl (cyhexatin –– formerly sold as Plictran) was being placed on the EPA fast track toward registration as a resistance management tool for control of European red mites on apple. This material received a Section 18 emergency registration for use on hops in Washington and Oregon in 1999, and it appears that the registration emphasis will be on hops and small fruit in 2000 and 2001. Use on pome fruit will not be considered for registration until 2002.
FQPA Restrictions on Current Insecticides
Certainly a great majority of the chemical registration debate in 1999 revolved around continued use of Guthion and other Ops on tree fruit. When the dust had settled (if it has indeed settled), the principal label change on Guthion was a reduction in total amount of product allowed per acre per season from 12 lbs. to 9 lbs. and an increase in preharvest interval to 14 days (21 days if the final application = 16 oz. (a.i.) per acre or more). The reentry interval was increased to 14 days as well (from the previous 48-72 hour interval) for certain activities, such as hand thinning, propping, and pruning. For scouting, mowing, and other less contact-intensive activities, the REI remains at 48 hours. However, the situation surrounding continued practical use of Guthion and a few other major chemicals is consistently evolving.
Methyl parathion. Under FQPA, this chemical is no longer allowed for orchard use. According to Glen Morin of New England Fruit Consultants, the following is the situation on several other currently-labeled insecticides as of February 21, 2000.
Phosmet. Phosmet (Imidan) has reached a critical point in the review process. EPA''s revised risk assessment was released and a technical briefing was held in Pasco, WA on February 10. This event officially began the 60-day public comment period for submitting risk mitigation proposals. The revised risk assessment indicated that acute dietary risk was not an issue as phosmet accounted for an average of only 5% of the ""risk cup"" for all sub-groups. EPA also indicated that exposure to handlers (mixer/loader/applicators) could be satisfactorily managed with increased personal protective equipment (PPE) and engineering controls such as closed loading systems and enclosed cabs.
However, EPA did voice concern for post-application workers who may contact residues after applications have been made. Current information indicates that, depending on the rate used, acceptable margins of exposure may not be met until 37-52 days after application. Re-entry intervals of this magnitude would virtually eliminate phosmet as a pest management option for many crops. The registrant and other meeting participants raised objections to some of the assumptions EPA used to compile the worker exposure assessment and presented information as to how the assessment could be further refined during the risk mitigation phase.
Occupational exposure is regulated under FIFRA (Federal Insecticide, Fungicide and Rodenticide Act), not FQPA. As such, EPA is obligated to consider the benefits of a particular material when assessing its risk. Attendees reiterated to the EPA panel the importance of phosmet in existing IPM programs, its relatively low acute toxicity, its low impact on many beneficial species, the lack of viable alternative pest management options and the uncertain effects of potential replacement products on the crop ecosystems for consideration in determining the REI. EPA should release their risk management recommendations by late May to early June.
Dimethoate. Dimethoate (Cygon) is currently in Phase 5 of the review process since the release of the revised risk assessment and technical briefing in mid December. As with methyl parathion, this material has not been an important tool for producers in the Northeast but according to USDA surveys, dimethoate is applied to 35% of the total U.S. apple acreage and is labeled for approximately 40 other food crops.
Despite its widespread usage, EPA is not concerned with aggregate risk from diet or drinking water. Worker exposure and ecological issues seem to be their main concern. The registrants, U.S. Apple Association, and EPA are currently discussing methods to reduce this risk in tree fruits by utilizing increased PPE, decreasing the maximum seasonal rates per acre and lengthening re-entry intervals for high-contact activities such as hand thinning, summer pruning and harvesting.
Chlorpyrifos. Chlorpyrifos (Lorsban) is somewhat in limbo in Phase 4 of the review process. The public comment period following the preliminary risk assessment ended December 27 and EPA is currently reviewing any new information that may have been put forth in preparation for releasing their revised risk assessment. No date has yet been set for the technical briefing. After that event, there will be another 60-day public comment period and then EPA will have up to 60 additional days to compile the final risk mitigation proposal.
Healthy Fruit is written by Dan Cooley, Ron Prokopy, Starker Wright, Wes Autio, and Duane Greene except where other contributors are noted. Publication is funded in part by the UMass Extension Agroecology Program, grower subscriptions, and the University of Massachusetts IPM Program. A text version can be e-mailed to you if you contact Doreen York. Please cite this source if reprinting information.
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