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Potatoes at WSU

2014 Potato Insect Pest Survey for the Columbia Basin of Washington

Aphids, Leafhoppers, Tuberworm, and Psyllids

The insect pest survey provides the potato industry with current information about the size and location of important insect pest populations in the Columbia Basin.







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Beet leafhoppers are important pests because they transmit BLTVA, a phytoplasma that causes purple top disease in potatoes. Research indicates that about 35% of the BLH in the Columbia Basin are infected with BLTVA. In the Columbia Basin, the first spring generation of BLH usually migrates towards potato fields in late May and early June, with a peak flight in late June. Yellow sticky traps placed near potato fields are one way to monitor BLH. Information about setting up traps and identifying BLH can be found in the article, Beet Leafhopper Monitoring with Yellow Sticky Cards. Treatment thresholds based on BLH numbers on traps have not been established, but we know that the risk of infection increases as BLH populations become large. If the numbers on traps build up to 40 or more BLH per week, then it is probably time to be concerned. A typical weekly catch during peak BLH activity is 100.

Eliminating weed hosts (wild mustards, Russian thistle, kochia) in areas surrounding potato fields is an important cultural management approach for BLH. Potato growers may also select cultivars that are less susceptible to purple top (Ranger, Umatilla, and Norkotah are considered highly susceptible; Russet Burbank is susceptible; and Alturas and Shepody are moderately susceptible). A number of insecticides are labeled for use on potatoes to control leafhoppers. Systemic at-planting insecticides, especially those with longer residual activity applied at the maximum allowed rate, have been shown to provide some early season control of BLH. Results may vary depending on the product used, application rate, soil and environmental conditions, and insect pressure. Foliar insecticides may also be used to control BLH. These are usually applied in May, June, and sometimes July. Insecticides with long residual activity (10-14 days) are best. Remember to always read and follow instructions on the pesticide label, and don’t apply the insecticides below labeled rates. For more information about managing BLH, visit IPM Guidelines for Insects and Mites in ID, OR, and WA Potatoes and the PNW Insect Management Handbook.


Potato psyllids are important pests mostly because they can transmit a bacterium (Candidatus Liberibacter solanacearum) to potatoes that causes zebra chip disease (ZC). This disease reduces both yield and tuber quality and has lead to serious economic losses in some regions. ZC was first detected in potato fields in the Columbia Basin in 2011.

Yellow sticky cards are recommended for detecting psyllid migration into an area. The cards should be placed inside the field, very near the field edge, and right above the canopy. We recommend using the AlphaScents brand sticky cards, because they are stickier than most sticky cards and hold up under irrigation. It is best to have at least four yellow sticky cards around the field, and more is better. For more information about trapping psyllids, read Psyllid Monitoring with Yellow Sticky Cards”. Other life stages of the psyllid can be found by collecting several leaves (mid-plant) from the outside rows of the field, and then scanning the underside (with a hand-lens) for the tiny nymphs and eggs.

It is not possible to stop psyllids from migrating into potato fields, but it is possible to prevent potato psyllid populations from establishing once they have landed.  Population establishment is defined as potato psyllids successfully laying eggs that lead to development of a nymphal population. Psyllid control programs should be in place prior to population establishment. One way to manage psyllids is to start with a neonicotinoid insecticide at planting, followed by foliar insecticide applications. Neonicotinoids applied at planting appear to provide 80-90 days of residual control of psyllids. It is recommended that no more than 80% of fields on a farm be treated with Group 4 neonicotinoids at planting. If only foliar insecticides are used, then it is recommended that applications begin upon first detection of potato psyllids in your area. Potato psyllid trapping information for the Columbia Basin of WA is available via emailed pest alerts each week (contact to sign up for emails).  For more information about psyllids, including insect identification, monitoring, and control recommendations, read IPM Guidelines for Insects and Mites in ID, OR and WA Potatoes.


Aphids are important pests because they transmit several important potato viruses, especially potato leafroll virus (PLRV) and potato virus Y (PVY). Green peach aphids are the most important vector of PLRV, which has caused substantial yield and tuber quality losses in the Columbia Basin. PLRV causes net necrosis in some cultivars, an unacceptable tuber defect in processing potatoes. PVY can also result in significant yield losses, and some strains of the virus cause tuber defects. The tuber necrotic strains of PVY are becoming more prevalent in the PNW. The first step in preventing the spread of potato viruses is to plant certified seed potatoes with very low incidence of PVY and PLRV.

Potato growers should monitor fields for aphids at least once a week, because early recognition and control of aphids is the next-best tactic in limiting spread of potato viruses, especially PLRV. Current recommendations are to treat long-season storage potatoes as soon as wingless aphids are detected. Low tolerances have been established because even a low incidence of seed borne PVY and PLRV can spread rapidly if aphids go unchecked.


Potato tuberworm (PTW) was first recognized as an important pest of potatoes in the southern Columbia Basin in 2003. PTW larvae feed on tubers causing damage that renders them unmarketable. Potato growers with fields south of Connell, WA are recommended to pay close attention to regional trapping data, and should deploy pheromone traps. Infestations of PTW are highly localized, and it is risky to conclude too much from traps that may be several miles away. Information about setting up traps and identifying PTW moths can be found in the article, Tuberworm Monitoring with Pheromone Traps. Trap counts from mid-season to harvest are particularly important to watch. Pre-harvest control measures may be warranted in fields where PTW moths in pheromone traps are found to be increasing every week, especially in August-October.


This project is sponsored by the Washington State Potato Commission.

Potatoes at WSU, PO Box 646414, Washington State University, Pullman WA 99164-6414, 509-335-9502
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