Jay W. Chapin, Extension Entomologist
Use Situation: The major use on soybean is methyl parathion for the control of stink bugs (Nezarra viridula) and velvetbean caterpillar (Anticarsia gemmatalis).
1. 120,000 acre treatments are required annually for stink bug control.
2. Satisfactory stink bug control can be achieved with high rates of pyrethroid insecticides rather than methyl parathion. However, the cost differential is approximately $3 per acre. Therefore, the annual loss from cancellation of methyl parathion is $360,000 (120,000 x $ 3.00).
3. The increased use of pyrethroids on soybean would significantly increase the risk of developing bollworm (Helicoverpa zea) resistance on this and other major crops such as cotton. While no one can calculate precisely the economic risk of contributing to bollworm resistance, the consequences would be very serious. It would be most imprudent, and contrary to the basic tenets of integrated pest management to increase reliance on a single chemical mode of action.
Conclusion: Methyl parathion use on soybean is based on well-researched economic thresholds. Cancellation of this use would result in direct economic loss to the producer and increased risk of pyrethroid resistance in key economic pests.
Use Situation: The major uses on peanut are:
1. Chlorpyrifos (Lorsban, etc.) for control of lesser cornstalk borer (Elasmopalpus lignosellus) and other members of the soil pest complex (southern corn rootworm, Diabrotica undecimpunctata and wireworms, Conoderus spp.).
2. Aldicarb (Temik), phorate (Thimet) and acephate (Orthene) for control of thrips ( Frankliniella fusca) and suppression of the tomato spotted wilt virus.
1. There are currently no alternatives to chlorpyrifos for lesser cornstalk borer control.
2. A lesser cornstalk borer outbreak occurs every 3 years and causes severe loss (600 lb per acre = $200 per acre) on half of the S.C. acreage. Therefore the annual loss is $462,000 ($200 x 7,000 ac x .33 yrs = $462,000).
3. Treatment costs $25/ac (material and application). Therefore, the net annual loss from cancellation of chlorpyrifos is estimated at $404,250 ($462,000 - $ 57,750 treatment cost ($25 x 7,000 ac x .33 yrs).
4. Research has shown that in addition to causing direct loss, the lesser cornstalk borer is a primary factor in the transmission of aflatoxin to peanut pods. Increased levels of this potent carcinogen would pose a significant health risk to the consumer.
5. Repeated, preventative foliar sprays of the only registered pyrethroid (cyhalothrin) could potentially be used as an alternative for preventing direct thrips injury at approximately the same cost. However, this increased reliance on pyrethroid chemistry would pose significant risk in developing resistance.
6. In addition, it has not been demonstrated that cyhalothrin is as efficacious in suppressing tomato spotted wilt virus (TSWV) as phorate. Therefore, we assume an annual loss of $390,000 (13,000 ac x 100 lb/ac x $ 0.3/lb = $390,000) due to reduced TSWV efficacy. This may prove to be a very conservative estimate for an emerging problem in S. C. since losses of over $500 /ac were documented in some fields in 1998.
1. Chlorpyrifos is a vital component of the peanut pest management program, with use based on economic thresholds. There are no control alternatives and cancellation of this product would result in significant economic loss and unwarranted health risk to the consumer.
2. Temik and Thimet use could be replaced by pyrethroids, but at significant risk of economic loss and increased pesticide resistance.
Use Situation: The major uses on wheat are disulfoton (Di-Syston) and phorate (Thimet) for control of Hessian fly.
1. Host plant resistance is an effective alternative on 70% of S.C. acreage. However, approximately 90,000 acres has biotype L Hessian fly which can't be controlled with currently available host plant resistance.
2. One-third of this area (30,000 ac) will have economic infestation of Hessian fly which would justify treatment. Hessian fly causes loss of $450,000 (5 bu/ac x $3/bu x 30,000 ac).
3. Treatment costs $5 per acre. Therefore the annual loss calculation is $300,000 ($450,000 - $150,000 treatment cost ($5 x 30,000 ac).
Conclusion: Disulfoton and phorate are currently used only in high risk situations as the only chemical components of an integrated management approach to Hessian fly. Cancellation would weaken this responsible, integrated approach and expose some S.C. wheat growers to significant economic loss.
Mitchell Roof, Extension Entomologist & Cotton IPM Specialist
The loss of organophosphates and carbamates on cotton. Would pose several problems. The pests on cotton and their individual controls represent an interrelated management scenario. Some minor pests are minor because controls applied to other pests keep them in check as well. Temik, a carbamate, is used at planting on 90+% of the South Carolina cotton acreage and controls nematodes, but also controls thrips at about 5 pounds per acre. Replacement of this material alone would require multiple materials. Their application would require multiple applications because one, Telone, has a long waiting period that would not allow a one pass application. Lorsban (chlorpyrifos), which is used for beet armyworm control, as well as cutworms (only material), and aphids and mites, simply would have no replacement if other OPs are lost as well. Stinkbug control has become important since the boll weevil eradication program has largely eliminated that insect from South Carolina, and with the advent of Bt cotton. We would be left with no reliable materials if we lose dicrotphos and methyl parathion. Replacement materials for bollworm control and control of other caterpillars include Bacillus thuringiensis, but this must be applied early. Larvin (B1, B2 grouping), is also slated for loss and this further reduces options for bollworm control. While aphids are not currently much of a problem on cotton, the loss of early season materials could lead to aphid problems, but the five currently recommended organophosphates would also be gone, leaving no products for their control. An increase in aphid problems and mites is anticipated with the use of pyrethroids.
Another big problem is pesticide resistance management. We are now fighting resistance in the tobacco budworm to pyrethroids. Current resistance management in cotton calls for avoiding pyrethroid applications before July 1, and using biological insecticides (Bacillus thuringiensis) with an ovicide, as Bt does not kill eggs. Three of the four ovicides are OPs or are on the B1, B2 list.
The boll weevil eradication program relies entirely on malathion. Losing malathion would have a big impact on that program. Other materials have too many downsides, including aggravating aphid and mite problems, and being hard on beneficials.
Comments by John Mueller, Extension Plant Pathologist
Regarding the loss of OPs and carbamates for nematode control on cotton, 50% of S.C. cotton acreage is above the nematode threshold level. If OPs and carbamates are lost, alternative products would increase production cost by 2/3 or more. Cotton losses would rise from 5% to 10%, due to nematodes. There would need to be increased applications of more than one replacement pesticide per desired control strategy would result in less control, i.e., it will take two or more pesticides in more than one application to control the nematodes on thrips (thrip control is a benefit of OPs applications for nematodes). The replacement pesticide, Telone, has 7-10 day waiting period which does not allow "one pass" application strategy used by 50% of those cotton growers who must treat for nematodes.