Extension/Research Information

2001 Ohio Forage Performance Trials

Ohio State University Extension
Ohio Agricultural Research and Development Center
The Ohio State University

Horticulture and Crop Science
Series 195
December 2001

Performance of Potato Leafhopper Resistant Alfalfa Varieties

    The potato leafhopper (PLH) is usually the most damaging insect pest of alfalfa in Ohio. Beginning in 1997, commercial varieties with improved resistance to this pest have been sold. The largest gains in resistance have been achieved using germplasm with erect glandular hairs on the stems and leaves. These varieties show resistance through reduced survival of adults and nymphs feeding on the foliage, and by reduced egg laying and feeding preference of adults. 

    Tables 10 - 15 summarize results from trials seeded at N. Baltimore, S. Charleston, Wooster, and Jackson to evaluate performance of the new glandular-haired alfalfa varieties. First harvest yields were reduced in those trials by alfalfa weevil damage (no insecticide was applied to control infestations except in the 2000 trial at South Charleston). All varieties suffered damage by the alfalfa weevil. The results demonstrate that the PLH-resistant varieties are not resistant to alfalfa weevil, and will need to be treated with insecticides when weevil populations exceed action thresholds. The weevil damage in those trials contributed to the lower overall yield for the year, compared with the standard insecticide-treated trials. Yield differences among the susceptible check variety (5454 a standard, non-glandular-haired variety) and glandular-haired varieties were relatively small this season in trials seeded before 2000 (Tables 10-13). In contrast, the PLH-resistant varieties had higher yields than susceptible entries (5454, Vernal, 54V54) in the 2000 and 2001 seeded trials at S. Charleston (Tables 14-15), where PLH populations were very high.

     Seeding year alfalfa is very susceptible to PLH. Although the glandular-hair resistance trait can dramatically reduce this damage, yield reductions still occur in the resistant varieties when PLH infestations are high. Based on our observations and data collected to date, we recommend that PLH resistant varieties be carefully scouted during the establishment year, and insecticide applied if PLH populations exceed the normal action threshold, especially during the very first growth cycle. In established stands, insecticide treatment may also be warranted if PLH populations are very high (especially if populations approach twice the normal threshold).

     For more information on potato leafhopper management and control, see Ohio State University Extension Fact Sheet FC-ENT-31 (Insect Pest Management on Alfalfa) and FC-ENT-33 (Potato Leafhopper on Alfalfa). These are available through county Ohio State University Extension offices or through Ohioline on the Internet at (http://ohioline.osu.edu/ent-fact/).

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