Pesticide Note

North Carolina Cooperative Extension Service
North Carolina State University



Pesticide Note Number 6
ENT/pia-6
February 1996

Insect Management by North Carolina Potato Growers in 1994




Stephen J. Toth, Jr., Extension Pesticide Impact Assessment Specialist

Kenneth A. Sorensen, Extension Vegetable Entomology Specialist


Caution!
The information and recommendations in this Note were developed for North Carolina and may not apply in other areas.




Introduction

The commercial production of potatoes in North Carolina is mostly concentrated in nine counties in the coastal region of the state (Sanders et al. 1995). Most of the crop is planted in March and harvested in June and July. Atlantic and Superior are the primary varieties of potato grown in North Carolina. Approximately sixty-five percent of the crop is sold for processing into potato chips, with the remaining sold for fresh market. In 1994, 3,186,000 cwt. of potatoes were produced on 18,400 acres in North Carolina (Watson 1995). The value of the potatoes produced in the state in 1994 was estimated at $23.5 million.

Pest problems confronting potato growers in North Carolina include weeds, nematodes, plant diseases and insects. Growers in the state employ a variety of chemical and nonchemical pest management practices to manage pests. Insect pests of economic concern in North Carolina are Colorado potato beetles, European corn borers, aphids, blister beetles, flea beetles, leafhoppers and wireworms.

A mail survey of potato growers in fourteen counties in North Carolina was conducted in the winter of 1995 to determine the pest management practices used by the growers on the 1994 crop. Insect management practices used by survey respondents in 1994 are compared to results from a similar grower survey conducted for the 1989 potato crop (Toth et al. 1993).


Survey Method

Ninety-five potato growers in Beaufort, Camden, Carteret, Chowan, Currituck, Henderson, Hyde, Johnston, Lenoir, Pamlico, Pasquotank, Sampson, Tyrrell and Washington Counties (Fig. 1) were surveyed by mail in January and February 1995, following methods described by Christenson (1975) and Dillman (1978). All commercial potato growers in these counties who were included on mailing lists provided by the respective county extension centers and the North Carolina Potato Association were surveyed.

Figure 1

Fig. 1. North Carolina counties (hatched) participating in mail survey of potato growers. Hatching denotes counties in which potato growers were surveyed.

On January 31, a sixteen page survey questionnaire accompanied by a cover letter and pre-stamped return envelope was mailed to each potato grower from their respective county extension centers. On February 7, a postcard was sent to each grower as a reminder to complete and return the questionnaire. Finally, on February 21, another letter, questionnaire and pre-stamped return envelope was sent to those growers not responding to previous correspondences. Information contained in the survey questionnaires returned by potato growers was compiled and analyzed in the Department of Entomology at North Carolina State University.


Results and Discussion

Potato Production. Sixty-four (67%) of the 95 potato producers surveyed responded. A total of 52 respondents planted 14,156.65 acres of potatoes in 1994, while the remaining respondents did not produce a potato crop. Potato growers responding to the survey harvested 13,938.35 acres of potatoes in 1994. The average yield of those growers returning questionnaires was 199.24 cwt. per acre. Approximately 18,400 acres of potatoes were harvested in North Carolina in 1994 (Watson 1995). The statewide average yield of potatoes in 1994 was 173 cwt. per acre.

Colorado Potato Beetles. The Colorado potato beetle is the most important insect pest on potatoes in North Carolina. Adult feeding on potato plant foliage is seldom damaging; however, larvae can cause extensive defoliation resulting in significant yield losses.

Asana XL was the primary insecticide used for Colorado potato beetle management on potatoes in 1994. Potato growers treated 72% of the acreage with Asana XL (Fig. 2). Furadan and Thimet were used by growers in 1994 on 26 and 24% of the acreage, respectively. Other insecticides used in 1994 include Monitor, M-Trak, Ambush, Vydate, Pounce and Guthion. Higher percentages of the potato acreage were treated with Asana XL, Monitor, M-Trak and Vydate in 1994 than in 1989. Furadan, Thimet, Ambush, Pounce and Guthion were applied to more acreage in 1989.

Figure 2

Fig. 2. Insecticides applied to manage Colorado potato beetles on potatoes in North Carolina. Bars indicate the percentage of potato acreage treated in 1994 (dark) and 1989 (hatched) (Toth et al. 1993) with the respective insecticides.

Seventy percent of the potato growers surveyed felt that Colorado potato beetles in their potato crop had developed resistance to insecticides in 1994; up from 58% in 1989. Thirty percent of potato growers claimed that Furadan was no longer effective against Colorado potato beetles in 1989, while 10 to 25% of growers reported Sevin, Pydrin and Guthion as ineffective (Fig. 3). In 1994, Sevin and Furadan were considered no longer effective on Colorado potato beetles by over 40% of growers. Between 10 and 25% of growers reported beetle resistance to Guthion, Thiodan, Asana XL, Monitor, Ambush, Thimet and Vydate in 1994.

Figure 3

Fig. 3. Insecticides no longer effective against Colorado potato beetles according to North Carolina potato growers. Bars indicate the percentage of potato growers who found the insecticides ineffective in 1994 (dark) and 1989 (hatched) (Toth et al. 1993).

European Corn Borers. The European corn borer is a common stem-boring pest of potatoes in eastern North Carolina. This insect continues to cause concern among growers of fresh market potatoes. Monitor, Furadan and Asana XL were used by potato growers on 27, 24 and 17% of the acreage, respectively, to manage European corn borers in 1994 (Fig. 4). Growers also used Ambush and Guthion for the management of this pest. Compared to 1989, the percentage of potato acreage treated with Monitor and Asana XL was significantly higher in 1994, whereas the percentage of acres treated with Furadan, Ambush and Guthion was lower. Pydrin and Pounce were no longer used by potato growers for European corn borers in 1994.

Figure 4

Fig. 4. Insecticides applied to manage European corn borers on potatoes in North Carolina. Bars indicate the percentage of potato acreage treated in 1994 (dark) and 1989 (hatched) (Toth et al. 1993) with the respective insecticides.

Other Insect Pests. Wireworms (i.e., corn wireworms, tobacco wireworms and southern potato wireworms) may attack seed pieces at planting or tubers late in the season. Their damage can result in reduced plant stands or rejection of loads of potatoes by processors. Aphids (potato, green peach and other species) are sporadic pests of potatoes. Aphid feeding causes little damage in potatoes; however, the spread of plant viruses by aphid vectors can be of some concern to growers. Flea beetles and leafhoppers are minor pests of potatoes and are usually addressed through management techniques used for the major insect pests.

The use of Thimet, Di-Syston and Vydate for the management of foliar-feeding insects and wireworms on potatoes has increased since 1989 (Fig. 5). Potato growers treated about 40% of their acreage in 1994 with Thimet. Problems with wireworms have been responsible for the use of granular soil insecticides. Some early season management of insects is also obtained through the application of soil insecticides to potato fields.

Figure 5

Fig. 5. Insecticides applied to manage aphids, flea beetles, leafhoppers and wireworms on potatoes in North Carolina. Bars indicate the percentage of potato acreage treated in 1994 (dark) and 1989 (hatched) (Toth et al. 1993) with the respective insecticides.

Nonchemical Pest Management Practices. Potato growers were asked to indicate on the survey questionnaire the nonchemical pest management practices they used in 1994. Seventy-six percent of the growers responded that they, a family member and/or an employee scouted their potato fields for weeds, insects or plant diseases (Fig. 6). Nearly 39% reported that a professional scout or consultant performed this service. One grower indicated that a county extension agent scouted his potatoes. Similarly, 76% of potato growers reported that they, a family member or employee scouted their potatoes in 1989, while 24% used a professional scout. Slightly less than 2% of potato growers did not have their potato fields scouted for weeds, insects or plant diseases in 1989.

Approximately 86% of potato growers indicated that they rotated the fields on which they planted potatoes as a means of pest management in 1994, up from 74% in 1989 (Fig.6). Corn and soybeans were the predominant crops rotated with potatoes in 1989 and 1994. Seventy-four percent of potato growers applied different insecticides to reduce Colorado potato beetle resistance in 1994; 85% of growers claimed to use this practice in 1989. A Colorado potato beetle resistance monitoring kit developed in the Department of Entomology at North Carolina State University was used by 28% of growers in 1994, compared to 16% of growers in 1989.

Figure 6

Fig. 6. Pest management practices used by potato growers in North Carolina. Bars indicate the percentage of potato growers using the respective pest management practices in 1994 (dark) and 1989 (hatched) (Toth et al. 1993).


Literature Cited

Christenson, J. A. 1975. A procedure for conducting mail surveys with the general public. J. Community Development Society 6(1): 135-146.

Dillman, D. A. 1978. Mail and Telephone Surveys: The Total Design Method. John Wiley and Sons, New York. 325 pp.

Sanders, D. C., W. W. Collins, and R. D. Schiavone. 1995. Potato varieties. Horticulture Information Leaflet No. 22-B (revised). North Carolina Cooperative Extension Service, Raleigh. 4 pp.

Toth, S. J., Jr., H. E. Duncan, D. W. Monks, K. A. Sorensen, and L. G. Wilson. 1993. Potato Pest Management 1989: A Survey of Pesticide Use and Other Pest Management Practices by North Carolina Potato Producers. AG-497. North Carolina Cooperative Extension Service, Raleigh. 20 pp.

Watson, D. D., ed. 1995. 1995 North Carolina Agricultural Statistics. Publication No. 180. Agricultural Statistics Division, North Carolina Department of Agriculture, Raleigh, NC. 132 pp.


Acknowledgments

The following county extension directors and agents in North Carolina are acknowledged for their valuable participation in the mail survey of potato growers: Henry C. Riddick (Beaufort County), Freddie E. O'Neal (Camden County), A. Ray Harris (Carteret County), John Michael Williams (Chowan County), Marjorie J. Rayburn (Chowan County), Alton E. Wood, Jr. (Currituck County), Marvin A. Owings, Jr. (Henderson County), Malcolm O. Gibbs, Jr. (Hyde County), Cindy Flinn (Johnston County), W. R. Jester III (Lenoir County), Richard F. May (Pamlico County), Thomas M. Campbell (Pasquotank County), Allan C. Thornton (Sampson County), Kevin E. Johnson (Tyrrell County) and Frank C. Winslow (Washington County). Also acknowledged are the following extension specialists for their help in planning the survey and designing the survey questionnaire: Marc A. Cubeta (Plant Pathology), Harry E. Duncan (Plant Pathology), David W. Monks (Horticultural Science) and Douglas C. Sanders (Horticultural Science). Appreciation is extended to the North Carolina Potato Association for providing mailing lists of growers. Rebecca Osborne is recognized for preparation of grower survey materials and entry and compilation of survey data. This research was supported by the National Agricultural Pesticide Impact Assessment Program, Extension Service, United States Department of Agriculture under project 94-EPIX-1-0174.




Published by North Carolina Cooperative Extension Service

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Web page last modified on August 14, 1996 by Stephen J. Toth, Jr.