Issue No. 10, Article 3/June 11, 2010
Potato Leafhoppers Can be Found Statewide
Producers are encouraged to scout their alfalfa stands for potato leafhoppers. On June 4, crop systems extension educator Jim Morrison examined two alfalfa fields in Winnebago County and found low numbers of potato leafhoppers. In the first field (plants 16 inches tall), he took 40 sweeps (four sets of 10) and found two potato leafhoppers. In the second field (plants 10 to 12 inches tall), he found only one potato leafhopper in 40 sweeps.
Although the numbers Jim provided are well below economic levels, his observations confirm that at this point in the season, this migratory insect pest of alfalfa is most likely present in fields throughout much of the state. So far I've not received any reports of potato leafhoppers at densities exceeding the economic threshold. For alfalfa taller than 12 inches, two leafhoppers per sweep is considered the economic threshold, so in the first field Jim sampled, about 80 leafhoppers in 40 sweeps would have been required before management options should be considered.
Potato leafhopper adult (Courtesy of Matt Montgomery).
For more information on the life cycle, scouting procedures, and management options for potato leafhoppers, please go to ipm.illinois.edu/fieldcrops/insects/potato_leafhopper. The University of Nebraska has also published management guidelines for potato leafhoppers based on the height of the alfalfa, the value of hay (per ton), and the cost of the insecticide application: elkhorn.unl.edu/epublic/pages/publicationD.jsp?publicationId=559. If anyone begins to find economic densities of this important insect pest of alfalfa this season, let me know so I can share your observations with readers of the Bulletin.--Mike Gray