2013 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.
INSECT MONITORING REPORTS
Report for June 14, 2013
Beet leafhoppers were found at 95% of our trapping sites across the Columbia Basin this week. The traps in the northwest part of the Columbia Basin (Mattawa, Royal City, George) continue to have the largest BLH counts; the counts in these areas were as large as 151 BLH per trap and averaged 54 BLH per trap. The BLH counts in the central areas (Franklin County) are climbing; the counts were as large as 126 BLH per trap and averaged 31 BLH per trap. Go to the pest data mapping section below to see all of the BLH trap counts for this week. These counts are much larger than we were seeing at this time in 2012 and 2011.
Beet leafhoppers are important pests because they transmit BLTVA, a phytoplasma that causes purple top disease in potatoes. 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 preferred. If you apply a non-systemic insecticide, it may be necessary to shorten the application interval during periods of rapid plant growth to ensure adequate plant coverage. Remember to always read and follow instructions on the pesticide label. 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.
This week we did not find potato psyllids on any of our yellow sticky cards deployed in potato fields across the Columbia Basin. However, we found an adult potato psyllid in our sentinel potato plot near Pasco. We found it using the method we use to sample aphids, i.e. by shaking plants over a small bucket. So far, none of the potato psyllids that have been submitted for testing this spring have come back positive for Lso, the bacterium that causes zebra chip. Last week we identified a potato psyllid on a sticky card in a potato field east of Bruce, WA. We thought it might have migrated from a wetland area about 1 mile downwind from the field. Potato psyllids are known to overwinter on bittersweet nightshade, which is often found growing under trees in wet areas. So, we went hunting for psyllids this week in the wetland. It was not difficult to find them. We found several patches of bittersweet nightshade, and found a lot of potato psyllid eggs and nymphs on the leaves. Most of the potato psyllids that we have found in potato fields this spring can be linked to a nearby wetland area harboring bittersweet nightshade. Of course, these areas are very common throughout the Columbia Basin. Although potato psyllids have been shown to overwinter in the Pacific Northwest on bittersweet nightshade, more research is needed to confirm whether they can harbor the bacterium. The insect is also known to overwinter in California, Texas, and Mexico and then migrate northward in the spring and summer.
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, and occurred again in 2012. Yellow sticky cards are recommended for detecting psyllid migration into an area. The cards should be placed inside the field, near the field edge, and just above the canopy level. It is best to have five or more yellow sticky cards around the field. Another method for sampling adult psyllids is to use an inverted leaf blower with a mesh net secured to the end of the cylinder (see photo on the sidebar). This method is better for detecting low population densities than the sticky cards. Operate the machine (in vacuum mode) above the potato plants for at least 5 minutes, 5-10 feet from the edge of the field, and then carefully remove the net from the end of the cylinder. It helps to transfer the insects from the net to a plastic bag that you can seal, and then look for the tiny winged adults. If you place the bag in the freezer for a while, you can slow the buzzing insects down which will make it easier to scan the bag. Other life stages of the psyllid may be found by collecting several leaves (mid-plant) from the outer rows of the field, and then scanning the underside (with a hand-lens) for the tiny nymphs and eggs. It is also recommended to scout for psyllids in cull piles and volunteer potatoes. For more information about psyllids, including insect identification, monitoring, and control recommendations, read Biology and Management of Potato Psyllid in Pacific Northwest Potatoes and Potato Psyllid Vector of Zebra Chip Disease in the Pacific Northwest.
Potato growers should be monitoring fields for aphids. This week we found a small number of aphids in 22% of the fields we are monitoring. Most of the fields with aphids are in the lower Columbia Basin (south of Othello). Of these aphids, most are winged, migratory types. There are, however, a few wingless green peach aphids beginning to establish themselves in potato fields; they averaged about 0.2 aphids per plant, which is a very small population density that may be overlooked without close inspection.
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 cause tuber defects. Potato growers should monitor fields for aphids at least once a week, because early recognition and control of aphids is the best tactic in limiting spread of potato viruses. 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.
Moths were found at six locations this week in the lower Columbia Basin of Washington. It is too early in the season to warrant control measures.
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.
Big-eyed bugs were found in 75% of the potato fields we monitored this week. These are good insects to have in the fields, because they are voracious predators that have been observed to eat more than 20 aphids in a day. Unfortunately, they can be very susceptible to certain insecticides, especially the broad-spectrum insecticides. Dr. Bill Snyder, WSU Entomologist, has found that big-eyed bugs can be 6 xs more abundant in fields sprayed with selective insecticides compared to fields treated with broad-spectrum insecticides.
Previous 2013 reports - click here
Pest Data Mapping
Click on the map to view insect population data (http://www.nwpotatoresearch.com/IPM-Home.cfm).
- 2012 IPM Guidelines for Insects and Mites in ID, OR, and WA Potatoes
Authored by PNW entomologists, this report is a set of recommendations as to how to best manage potato insect pests.
- PNW Insect Management Handbook
This handbook is a tool for making decisions regarding the management of important insect pests in the PNW. For information about potato pests, select the Chapter: Irish Potatoes.
- Northwest Potato Research: Integrated Pest Management
Find information about insect pests, insect-transmitted diseases, and beneficial insects. View regional pest data mapping from this website.
- Beet Leafhopper Monitoring with Yellow Sticky Cards
This article explains how to deploy yellow sticky card traps for monitoring beet leafhoppers. It also provides information about correctly identifying beet leafhoppers, as there are many look-alike leafhoppers in the Columbia Basin.
- Biology and Management of Potato Psyllid in Pacific Northwest Potatoes
This article by A. Schreiber, A. Jensen, and S. Rondon includes information about zebra chip disease, explains how to identify potato psyllids, and provides options for controlling psyllids.
- Biology and Management of the Potato Tuberworm in the PNW
This PNW Extension publication is an excellent resource for potato tuberworm information.
- Potato Psyllid Vector of Zebra Chip Disease in the PNW
This OSU Extension publication provides extensive information about the biology, ecology and management of potato psyllid in the PNW.
- Recognizing Potato Psyllid Adults
- Psyllid Monitoring with Yellow Sticky Cards
This article explains how to set up sticky traps for monitoring potato psyllids. It also explains how to identify them correctly, as there are several psyllid species they can be confused with.
- Tuberworm Monitoring with Pheromone Traps
This article explains how to set up traps for monitoring tuberworm moths, and how to identify them correctly.
- University of California IPM Pest Management Guidelines – Potatoes
- Northwest Potato Research - WA, OR, ID Potato Commissions
- 2012 Potato Insect Pest Survey Results
Detailed weekly reports from the 2012 growing season, and the 2012 Annual Report.
- 2011 Potato Insect Pest Survey Results
Detailed weekly reports from the 2011 growing season, and the 2011 Annual Report.
- 2010 Potato Insect Pest Survey Results
Detailed weekly reports from the 2010 growing season, and the 2010 Annual Report.
- 2009 Potato Insect Pest Survey Results
Detailed weekly reports from the 2009 growing season, and the 2009 Annual Report.
This project is sponsored by the Washington State Potato Commission.
Pest alerts via email!
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The Washington State Potato Commission is offering free supplies to Washington growers for trapping leafhoppers and tuberworm moths. To receive supplies for trapping these insects, simply call the commission office (509) 765-8845 or send an e-mail to firstname.lastname@example.org
|Potato tuberworm moth|
|Green peach aphid|
|Psyllid sampling with a leaf blower/vacuum|
For more information about the potato insect pest survey contact: