Information Requests Monitoring System

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Request ID: 169
Request From: Steve Toth
Date Requested: Feb 22, 2007
Request: Note the following information request from Wilfred Burr, USDA OPMP regarding methomyl (Lannate) and thiodicarb on sweet corn and head lettuce. Please circulate among the specialists in your respective states and territories and submit any responses to the Southern Region IPM Center's Information Requests Monitoring System by Wednesday, March 7, 2007. Thanks. Steve Toth ------------------------------------------------------- Pesticide Information Request Active Ingredients: Methomyl (Lannate) and Thiodicarb Crops/Target sites: Sweet corn (especially in FL) and head lettuce (especially in CA). EPA is also interested in other sections of the country where these crops are grown and these active ingredients are used. Questions: 1. For head lettuce and sweet corn, if these two active ingredients are used: a. what are the typical use rates for each crop, b. what are the typical number of applications per crop, and c. what is the timing of the applications 2. Would these two chemicals be applied to the same crop during the same growing season? a. if yes, would the rates be any different than reported above. b. how often might the two be applied during the same growing season to the same crop Please Respond to: Colwell Cook at cook.colwell@epa.gov Wilfred Burr at wilfred.burr@ars.usda.gov Deadline: March 7, 2007 Background Information: These questions arose during the carbamate cumulative risk assessment conducted by the Environmental Fate and Effects Division (EFED) at EPA. The concerns involve drinking water. Apparently thiodicarb breaks down into 2 molecules of methomyl and this is complicating the risk analysis as both products can be used on the same crops; head lettuce and sweet corn being of the most concern.

Responses
Responder: Charles Luper
State: OK
Date Requested: Feb 23, 2007
Response: Dr Edelsons reponse is listed below. No significant quantities of commercial lettuce grown in our state so for sweet corn: Questions: 1. For head lettuce and sweet corn, if these two active ingredients are used: a. what are the typical use rates for each crop, MAXIMUM LABEL USE RATE b. what are the typical number of applications per crop, and 0 TO 1 c. what is the timing of the applications SEEDLING STAGE 2. Would these two chemicals be applied to the same crop during the same growing season? NO a. if yes, would the rates be any different than reported above. b. how often might the two be applied during the same growing season to the same crop NA Jonathan Edelson

Responder: Noel Troxclair
State: TX
Date Requested: Feb 26, 2007
Response: Hi Steve, There hasn't been much commercial sweet corn production in the Winter Garden of Texas for several years (2002-2003 ?) but methomyl was used heavily at that time. Spraying started at initiation of silking and continued, daily, for two to two and a half weeks, with methomyl being alternated with a pyrethroid. At that time, a typical rotation was methomyl and esfenvaelrate or lambda-cyhalothrin. Today, where sweet corn is grown in Texas, spinosad or methoxyfenozide often is worked into the mix, but methomyl might still be used as much as (or maybe more than) anything else. Part of the issue for Texas growers is the occurrence of resistance (documented) to pyrethroids in H. zea populations. To my knowledge, thiodicarb is hardly/not used in sweet corn production, in Texas. We grow some lettuce in the Winter Garden, but not any head lettuce, as far as I know. Please contact me if you need additional information regarding this response. Sincerely, Noel Troxclair

Responder: Mark Mossler
State: PR
Date Requested: Mar 02, 2007
Not Important/Relevant to my state(s)
Response:

Responder: Mark Mossler
State: VI
Date Requested: Mar 02, 2007
Response: Response from the VI is that their lettuce and sweet corn growers are organic to service the high-end tourist resorts in the area.

Responder: Mark Mossler
State: FL
Date Requested: Mar 02, 2007
Response: In checking with the two main head lettuce growers in FL (approx. 6,000 acres) neither thiodicarb or methomyl are used. However, both of these materials are used widely in FL sweet corn production. Based on conversations with sweet corn growers, NASS statistics, and the FL crop profile for sweet corn, the following reflects use of these materials in Florida. For methomyl, historical data (1992 through 2004) reflects use on between 80 and 100 percent of the crop. The use rate has ranged between 0.28 and 0.33 lb ai/A and the number of applications has ranged between 6 and 14 per crop, and these are dictated by larval stage and density at the whorl stage. For thiodicarb, historical data (1992 through 2004) reflects use on between 55 and 80 percent of the crop. The use rate has ranged between 0.39 and 0.52 lb ai/A and the number of applications has ranged between 3 and 7 per crop, and as this compound provides more residual control of fall armyworm that methomyl, its application is governed on population level and rate of plant growth. Growers are aware that the active ingredient in these two pesticides is largely the same, and indicated that they do not tank mix the two. While they may be applied to the same crop, it would not be as a tank mix. Some growers do not use thiodicarb as they have witnessed more dermatitis with this material in comparison to methomyl.

Responder: Holly Gatton
State: VA
Date Requested: Mar 07, 2007
Response: We conducted an email survey of Extension agents to obtain their feedback on the use of methomyl (Lannate) and thidiocarb (Larvin) on sweet corn and lettuce. All of the agents who responded indicated that they recommend using either methomyl or thidiocarb at their book rates (e.g., 1.5 pints LV Lannate), but not together. They are unaware of any growers using both pesticides concurrently on either crop. One agent said that his largest sweet corn grower has used Lannate in the past, but not since synthetic pyrethroids arrived on the market. He has never used Lannate and Larvin together, but would consider it in the future if pyrethroid resistance becomes an issue. Another agent said that both chemicals could be used on the same crop in the same year, but that methomyl is typically only used as a last resort spray. He also mentioned that spraying begins just prior to silking and continues for 2 to 3 weeks at weekly intervals. Methomyl is applied 1 or 2 times, while thidiocarb may be applied more often. A third agent said that sweet corn growers in his district have used methomyl extensively in the past, but thidiocarb use is uncommon. Finally, one agent weighed in and said his growers typically use pyrethroids in sweet corn for earworm control, but thidiocarb could be beneficial in the event of pyrethroid resistance. He does not want to lose either product because “they are valuable to our ag. industry in many other crops.”

Responder: Alan Morgan
State: LA
Date Requested: Mar 07, 2007
Response: Lannate LV-(29% Methomyl) Lettuce- Alfalfa Looper--3/4-3 pts/A Thrips, Aphids, Beet armyworm, Cabbage looper, Corn Earworm, Aster leafhopper- 1 1/2- 3 pts/A. Varigated Cutworm- 1 1/2 pt/A Last application-Days to Harvest- 3/4-1 1/2 pt- 7d Over 1 1/2 pt-10d Note- Lettuce-head varieties- Do not apply more than 24 pints of LANNATE LV/acre/crop; Do not make more than 5 applications/crop; minimum interval between treatments is 2 days. Sweet Corn- earworm- whorl as needed- 1-1 1/2 pts/A Fall armyworm, armyworm, earworm, European corn borer, corn rootworm, flea beetles, picnic beetles, aphids- 3/4- 1 1/2 pt/A. Varigated cutworm, beet armyworm- 1 1/2 pt/A. Last application/days to harvest- 0 ears, 3 forage, 21 stover. Note- Do not apply more than 21 pints of Lannate LV/acre/crop, Do not make more than 28 applications/crop; minimum interval between treatments is 1 day. Lannate SP (90% Methomyl, 10% inert ingredients)- Lettuce-(head and leaf varieties) Thrips,aphids, beet armyworm, cabbage looper, corn earworm, aster leafhopper- 1/2- 1 lb/A. - varigated cutworm- 1/2 lb/A Last Application-Days to Harvest- 1/4- 1/2 lb- 7d Over 1/2 lb- 10d Note: Lettuce (head varieties)- Do not apply more than 7.2 a.i./A/crop; Do not make more than 15 applications/crop. Sweet Corn Earworm- Whorl as needed- 1/3-1/2 lb/A Fall armyworm, armyworm, earworm, European corn borer, corn rootworm, flea beetle, picnic beetles,aphids- 1/4-1/2 lb/A Varigated cutworm, beet armyworm- 1/2 lb/A Last application/ Days to Harvest- 0 Ears- 3 Forage- 21 Fodder. Note- Certain hybrid varieties of sweet corn are susceptible to methomyl injury. Treat a small area to determine crop safety before full scale spraying. Do not apply more than 6.3 a.i./acre/crop; Do not make more than 28 applications/ crop. Alan Morgan, Ph.D. Associate Professor Department of Entomology Orleans/Jefferson Parish Chair 404 Life Sciences Building Louisiana State University Baton Rouge, LA 70803 Telephone: 225-578-2368 E-mail: AMorgan@agcenter.lsu.edu

Responder: Ples Spradley
State: AR
Date Requested: Mar 09, 2007
Not Important/Relevant to my state(s)
Response:

Responder: Paul Guillebeau
State: GA
Date Requested: Mar 14, 2007
Response: Georgia does not grow lettuce. On sweet corn, I would say Lannate is used somewhat extensively and Larvin probably has minor use. Lannate is used if Fall Armyworm are a problem and if pyrethroid resistance is suspected in the Corn Earworm. The pyrethroid resistance question is new and could change the use pattern considerably (pyrethroids make up the majority of sprays on sweet corn). Lannate is probably applied at the 0.45 lb AI rate most of the time. In the spring crop, almost all of the applications will be during silking (last three weeks of the crop). In the summer and fall crops, applications can be made throughout the season. The Spring crop can be treated from 5 to 20 times depending on the pest pressure, etc. Most of these will be pyrethroid applications. I would estimate Lannate to be applied 2 to 4 times in the Spring. The fall crop is much more likley to have FAW in it and it can be a season long problem. The fall crop can probably be sprayed anywhere from 15 to 30+ times, but I would estimate an average around 20. Half of these may be Lannate because of FAW. As I said, this may change if pyrethroid resistance becomes a bigger problem (this would increase use of Lannate). On the other hand, we are likley to see some reduction in Lannate use (particularly during whorl stage) as more efficacious insecticides for FAW are registered on sweet corn.

Responder: Henry Fadamiro
State: AL
Date Requested: Mar 14, 2007
Not Important/Relevant to my state(s)
Response:

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