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C.O.R.N Newsletter 2009-15
     May 26, 2009 - June 2, 2009


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Potato Leafhopper in Alfalfa
by Ron Hammond, Andy Michel, Bruce Eisley

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We have begun finding potato leafhoppers in alfalfa in the state, and thus, growers should plan on scouting the regrowth for the leafhopper as soon as alfalfa reaches sufficient height for sweep-net sampling. Sampling is done using a sweep net and taking 10 samples throughout the field. Each sample should consist of 10 sweeps with the net. Count all potato leafhopper adults and nymphs, though over the coming weeks, mostly adults will be seen. When the average number of leafhoppers in a single sample (10 sweeps) is equal to or greater than the average height of the alfalfa stand, insecticide treatment is warranted for varieties not resistant to the potato leafhopper. For example, if the alfalfa is 6 inches tall and the average number of leafhoppers per 10-sweep sample is 6 or higher, insecticide treatment is warranted. If the average is lower, the grower should re-sample in a few days to check for populations above threshold.

For potato leafhopper-resistant varieties of alfalfa, the economic threshold established from research is three leafhoppers per inch of growth (30 leafhoppers for 10” tall alfalfa, for example). If the resistant alfalfa is a new planting this spring, growers might want to use thresholds meant for regular alfalfa, at least during the very first growth from seeding. Resistance improves as the seedling stand develops. After the first cutting of the stand, the threshold for a highly resistant variety can be increased to 3 times the normal level for susceptible varieties.

A new fact sheet on potato leafhopper with a lot more information is available at http://ohioline.osu.edu/ent-fact/pdf/0033.pdf . A list of insecticides labeled for leafhopper is at http://entomology.osu.edu/ag/images/aiplh.pdf . As we mentioned last week, it would also be worthwhile to keep an eye out for alfalfa weevil larvae that might be limiting alfalfa regrowth. Weevil larvae are quite common in many fields that are being cut. Although weevil injury to regrowth is rare, it does require mentioning at this time.

Readers can subscribe electronically to this newsletter by signing up at http://agcrops.osu.edu/services/email.html. E-mail labarge.1@osu.edu if you have problems subscribing or no longer wish to receive this newsletter.

C.O.R.N. is a summary of crop observations, related information, and appropriate recommendations for Ohio Crop Producers and Industry. C.O.R.N. is produced by the Ohio State University Extension Agronomy Team, State Specialists at The Ohio State University and Ohio Agricultural Research and Development Center. C.O.R.N. Questions are directed to State Specialists, Extension Associates, and Agents associated with Ohio State University Extension and the Ohio Agricultural Research and Development Center at The Ohio State University.


Information presented above and where trade names are used, they are supplied with the understanding that no discrimination is intended and no endorsement by Ohio State University Extension is implied. Although every attempt is made to produce information that is complete, timely, and accurate, the pesticide user bears responsibility of consulting the pesticide label and adhering to those directions.

All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.

Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Keith L. Smith, Director, Ohio State University Extension.

TDD # 1 (800) 589-8292 (Ohio only) or (614) 292-1868

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