Critical uses and needs

Due to rapid urbanization in the Eastern Panhandle of West Virginia, an increasing number of commercial orchards are being abandoned, with trees left standing until the land is developed. These abandoned orchards support significant pest populations which often invade adjacent commercial orchards, resulting in more complex and costly management programs.

Specific uses for various insecticides and acaricides are listed below, along with alternative management strategies. Although there are alternatives available for some of the traditional organophosphate uses, they are typically more costly or are disruptive to mite management programs because of toxicity to predators. In addition, some of these products are quite new, and additional experience is needed before they can be considered as suitable alternatives.

Organophosphates

Azinphosmethyl: The most important use of this material has been for the control of redbanded leafroller at 7-15 days after full bloom (DAFB), plum curculio (7-30 DAFB), and codling moth (15-45 DAFB and 75+ DAFB). This material has a good fit in an IPM program because it is well tolerated by Stethorus punctum (Leconte), a ladybird beetle predator of European red mite. Although more expensive, IPM alternatives such as BT exist for the control of redbanded leafroller in the early postbloom period. The only present, non-OP alternative for plum curculio control are pyrethroids, which because of toxicity to predators would destroy an IPM mite management program and necessitate the use of acaricides. Since this strategy would likely lead to increased mite resistance to acaricides, maintaining use of this OP at this stage is an important resistance management tool. The use of this OP against the second generation of codling moth (75+ DAFB) would also control apple maggot, which is believed to be a major reason for the lack of apple maggot establishment in commercial orchards in West Virginia, especially in those that are adjacent to abandoned orchards. The only present, non-OP registered alternative for codling moth control are pyrethroids which would be detrimental to an IPM program. Tebufenozide, an IGR used under a Section 18 Emergency Exemption for tufted apple bud moth control since 1996, is also effective against codling moth, but would not control apple maggot. Mating disruption of codling moth has not been successful in the East.

Phosmet: This material has the same usage pattern against the same pest spectrum as azinphosmethyl, but has received little use because it has a shorter residual and is a little more expensive.

Methyl parathion: The most important use of this product is for the control of tufted apple bud moth, variegated leafroller and San Jose scale crawlers (30-60 DAFB and 90+ DAFB). It also fits well in an IPM program due to mite predator tolerance. Effective alternatives for leafroller control include tebufenozide and spinosad, however these products do not control San Jose scale crawlers. The only non-OP alternative with some efficacy in the control of San Jose scale crawlers is imidacloprid. Therefore, having an OP for this use would be a good resistance management strategy. Use of methyl parathion at 90+ DAFB would also control apple maggot (not controlled by above alternatives), which is another factor that has prevented the establishment of this insect in commercial orchards in West Virginia. This product also replaces azinphosmethyl in some orchards for codling moth control due to its lower cost. Although effective against plum curculio, use of this product at petal fall is not recommended because of its hazard to bees.

Chlorpyrifos: The most important use of this product (wettable powder formulation) is for the control of dogwood borer in burr knots (15-30 DAFB and 75-90 DAFB) and San Jose scale crawlers (30-60 DAFB and 90+ DAFB). There are currently no effective alternatives for dogwood borer control. Imidacloprid is the only non-OP alternative with some efficacy against San Jose scale crawlers. Therefore, maintaining chlorpyrifos for this use would be a good resistance management tool. The liquid formulation of chlorpyrifos has a little use for the control of rosy apple aphid and overwintering San Jose scale during the delayed dormant period. The low usage is primarily due to the cheaper cost of esfenvalerate, which is an effective alternative at this stage for rosy apple aphid control. Chlorpyrifos serves as a good resistance management alternative to esfenvalerate for rosy apple aphid control.

Dimethoate: The major use of this product is for the control of rosy apple aphid during the late prebloom and petal fall period, and for the control of white apple leafhopper at petal fall. This material has a fair fit in an IPM program, with toxicity ranging from low to high depending upon the predator species. Endosulfan is an effective alternative that is slightly less toxic to predators, but is more expensive. Esfenvalerate, while an effective alternative, is highly toxic to predators and would be disruptive to mite management. Substitution of this product would necessitate additional acaricide use for mite control and increase the likelihood of mite resistance to existing acaricides. Imidacloprid is a very effective alternative at petal fall, but is not registered for use during the prebloom period.

Carbamates

Methomyl: This product is primarily used in a tank mix (at reduced rates) with an OP insecticide (usually methyl parathion at reduced rates) for the control of tufted apple bud moth and variegated leafroller (30-60 DAFB and 90+ DAFB). This use also provides fair to good control of spirea aphids, second generation spotted tentiform leafminer and second generation white apple leafhopper. This product has moderate toxicity to predators at reduced rates, and generally does not have a good fit in an IPM program. Imidacloprid is a good alternative, although more expensive, for aphid, leafminer and leafhopper control. Tebufenozide, available under a Section 18 Emergency Exemption since 1996, is a good alternative for leafrollers. Spinosad, registered in 1998, is a good alternative for both leafrollers and leafminer.

Oxamyl: This product has minimal use for the control of spotted tentiform leafminer and European red mite. It has moderate to high toxicity to predators and does not have a good fit in an IPM program. Imidacloprid is a good alternative for spotted tentiform leafminer control, and there are more effective acaricides for mite control. Oxamyl has recently had some use as a fruit thinning agent during the early postbloom period. Carbaryl, another carbamate, is an alternative for this use.

Formetanate hydrochloride: This product has received limited use in recent years for the control of European red mite, and occasionally for white apple leafhopper control at petal fall. It is generally of moderate toxicity to predators and has only a fair fit in an IPM program. Although efficacy against European red mites has declined recently, this product is still a useful resistance managment tool for alternation with other summer acaricides.

Carbaryl: The major use of this product is as a fruit thinning agent in the early postbloom period. Because of its moderate to high toxicity to predators it does not have a good fit in an IPM program. The XLR PLUS formulation is somewhat safer to predators than wettable powder formulations. When used as a thinning agent this product also provides control of white apple leafhopper. Oxamyl, another carbamate, is an alternative for fruit thinning.

Miscellaneous insecticides and acaricides

Endosulfan: This product has minimal use for the control of rosy apple aphid during the prebloom period. It has low to moderate toxicity to predators and has a fairly good fit in an IPM program. Dimethoate is an effective alternative that receives more use because it is less expensive, even though it is slightly more toxic to predators. This is a good resistance management tool for the organophosphates as it is the only chlorinated hydrocarbon used on apple.

Esfenvalerate: This product is the most widely applied insecticide on apple during the green tip to tight cluster period, primarily for the control of rosy apple aphid. Although this material is moderately to highly toxic to predators, this effect is reduced by making the application as close to green tip as possible. Delaying the application can be disruptive to an IPM program and necessitate the use of acaricides for mite management.

Imidacloprid: The use of this product is increasing as it is very effective against aphids, white apple leafhopper and spotted tentiform leafminer during the postbloom period. It has a low to moderate toxicity to predators and generally has a good fit in an IPM program. It is a good resistance management tool for rotation with OP and carbamate insecticides, and is of low mammalian toxicity.

Petroleum distillate: This product is applied during the green tip to tight cluster stage primarily for the control of overwintering eggs of European red mite, and in some cases for overwintering San Jose scale control. It has low toxicity to predators and good fit in an IPM program. It is a good resistance management tool because pests have not developed resistance to its physical mode of action.

Clofentezine: This material is an ovicide, applied no later than tight cluster, for the control of overwintering eggs of European red mite. It has low toxicity to predators and a good fit in an IPM program. Use has been very limited in West Virginia because of cost, narrow spectrum of activity (only effective against mites), and the product must be applied on a preventive basis before the potential severity of a mite problem is known. It is a good resistance management tool to rotate with materials for postbloom mite control.

Hexythiazox: This material is an ovicide, applied no later than the pink stage, for the control of overwintering eggs of European red mite. It has low toxicity to predators and a good fit in an IPM program. Use has been very limited in West Virginia because of cost, narrow spectrum of activity (only effective against mites), and the product must be applied on a preventive basis before the potential severity of a mite problem is known. It is a good resistance management tool to rotate with materials for postbloom mite control.

Abamectin: This product is increasing in use during the early postbloom period for the control of European red mite and spotted tentiform leafminer, with suppression of white apple leafhopper. Toxicity to predators is moderate from spray contact, but low from contact with residues which makes this product a generally good fit with an IPM program. This material is a good resistance management tool for rotation with other acaricides of different chemistry.

Pyridaben: This product is the most recently registered acaricide that is receiving increased use for the management of summer populations of European red mite. Toxicity to predators is moderate, but can be reduced by lowering the application rate while still maintaining effective mite control in an IPM program. This is the most effective acaricide for summer use and a good tool for rotation with other mite management products.

Tebufenozide: This insect growth regulator has been used since 1996 under a Section 18 Emergency Exemption for the control of tufted apple bud moth. It has low toxicity to predators and good fit in an IPM program. Resistance of this insect to OP and carbamate insecticides necessitated the request for use of this product under an Emergency Exemption.