May 20, 2016How to manage beet leafhoppers
There were a lot more beet leafhoppers (BLHs) on our yellow sticky traps this week. They were found on traps at 42 of the 53 potato fields we monitored this week (79%). The counts ranged from 0-49 BLH per trap, and averaged 3.2 per trap. The traps near Mattawa had more BLHs compared to other areas in the Basin. We expect to see the number of BLHs in many areas of the Columbia Basin continue to increase over the next several weeks, with peak populations in June. So far, the results are similar to those of the past two seasons (see the graph below). BLH counts are not as large as they were in 2013.
BLH populations are usually larger in some parts of the Basin than others. We suggest you pay particular attention to locations where the catch rates of BLHs are increasing rapidly each week; i.e. trapping locations that start with < 5 BLH per card in early to mid May and then increase to 15 > 30 > 50+ BLH per card per week in the later weeks of May and in June. Other trap sites begin the season with 0-5 BLH per card in early May, but will go on to collect only 10-15 BLHs total for the entire season. These locations are not likely to have significant problems with purple top disease. Purple top disease is caused by the beet leafhopper transmitted virescence agent (BLTVA) spread by BLH.
Potato growers are not the only vegetable producers in the Columbia Basin that need to worry about BLHs. The same insect can also spread BLTVA and/or the the beet curly top virus (BCTV) to crops like beans, peppers, tomatoes, eggplant, radish, melons and squash, carrots and coriander, sugar beets, and more.
Insecticides for controlling BLH are usually applied in May and June to potato fields that have significant numbers of BLH. In some areas, controls may be warranted in July if BLH continue to be found in large numbers. Foliar insecticides with long residual activity (10-14 days) are probably the best choice, because they can provide almost a month of control with two applications. Insecticides with short residual activity are not recommended because they require multiple applications to maintain control and are probably not cost-effective. Residual activity may vary depending on the amount of product used and the method of application.
Systemic insecticides applied at planting may provide some early season control of BLH, but results from trials and observations in the field have been inconsistent. Results may vary depending on the product used, application rate, insect pressure, and amount of residual insecticide in the plant at the time of infestation. Systemic insecticides have been quite effective for early-season control of BLH on sugar beets, perhaps because sugar beet is a preferred host of BLHs and they stay in the crop long enough to ingest a lethal dose.
Do not apply Assail, Actara, Endigo, Brigadier, Belay, Admire Pro, or Leverage if you applied a systemic neonicotinoid at planting including Admire Pro, Belay, Platinum, or Cruiser. It is important that these products are used wisely, or we will end up with insect resistance to neonicotinoids. Neonicotinoid resistant Colorado potato beetles, aphids, and psyllids have become a problem in other parts of the country due to repeated use. Let’s not make the same mistake here.
Use pesticides with care. Apply them only to plant sites listed on the label. When mixing and applying pesticides, follow all label precautions to protect yourself and others around you. It is a violation of the law to disregard label directions.
The IPM Guidelines for Insects and Mites in Idaho, Oregon and Washington Potatoes includes a lot of information about cultural and chemical controls for beet leafhoppers in potatoes.
The 2016 PNW Insect Management Handbook also includes detailed information on managing this pest in potato (and in other vegetable crops too).
– Carrie H. Wohleb, Washington State University
Source: Washington State University Extension