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2010 Potato Insect Pest Survey for the Columbia Basin of Washington

Aphids, Tuberworm, and Leafhoppers

The insect pest survey provides the potato industry with current information about the size and whereabouts of important insect pest populations in the Columbia Basin. The project targets three key insect pests: beet leafhopper, potato tuberworm, and green peach aphid.


2010 Annual Report (Part 1)

Note: Click on graphs to view larger images

Survey Routes

Survey routes were established in the “North Basin” (areas including Moses Lake, Warden, Othello, and Connell), “Mattawa”, “West Basin” (areas including Quincy, George, and Ephrata), and “South Basin” (areas including Burbank, Pasco, Eltopia, and Basin City).  Thirty-six potato fields were selected along these routes (Figure 1).

Figure 1
Fig. 1

Insect Monitoring Methods

Beet leafhoppers and potato tuberworm moths were trapped using methods established in earlier survey work by Dr. Andrew Jensen and his collaborators. Beet leafhoppers were trapped using 4” x 6” yellow sticky cards mounted on stakes about 3” above the soil surface. Tuberworm moths were trapped using a pheromone lure on a sticky liner inside a Trece delta trap suspended 12” from the ground. Aphids were monitored by sampling potato plants, using the same method used by Dr. Keith Pike in his regional aphid surveys, i.e. potato plants were vigorously shaken over a collection bucket slipped under the foliage. Observations of lygus bugs, thrips, Colorado potato beetles, spider mites, and beneficial insects collected in plant samples were also recorded.

Beet Leafhopper

General Population Trends

Several years of beet leafhopper (BLH) trapping data helps us to understand population trends in the Columbia Basin. Figure 2 shows the weekly beet leafhopper trap counts averaged over four years (from 2007 to 2010) for different parts of the Basin. On average, beet leafhoppers show up near potato fields in mid-late May.  Beet leafhopper numbers increase rapidly between May and June, and the largest populations occur between late June and early August. The numbers usually drop off in August, with the smallest populations occurring in September. They then pick up again in October, but by then we are not too concerned about beet leafhoppers in potato fields.

Figure 2: Click to view larger image

The area surrounding Mattawa, WA tends to be a hot spot for beet leafhoppers, and maintains the largest populations in the Basin through most of the season. Beet leafhoppers show up early in Mattawa compared to other parts of the Basin, usually in early-mid May. The largest beet leafhopper populations in Mattawa occur between May and early August, and the populations tend to remain high through that period, and then drop off. The North Basin tends to maintain the smallest populations of beet leafhoppers in the Basin through most of the season. Beet leafhoppers usually show up in the North Basin between late May and early June, which is a little later than other parts of the Basin. The largest populations in the North Basin usually occur in early July. In the South Basin, beet leafhopper numbers tend peak early, around late June, and then drop off for most of the remainder of the season. In the West Basin, beet leafhopper populations tend to build more gradually, peak around late July or early August, and then drop off.

2010 Population Trends

Figure 3 shows the average weekly beet leafhopper trap counts for each of the routes in 2010; it illustrates the relative size of beet leafhopper populations in different parts of the Basin in 2010.

Figure 3: Click to view larger image

North Basin

Figure 4 shows the average weekly beet leafhopper trap counts for North Basin routes 2007- 2010, and the four-year average. The beet leafhopper catch in the North Basin for 2010 was similar to the four-year average most weeks of the season. In 2010, average trap counts in the North Basin peaked at 11.6 BLH per card the week of July 28th. The highest number of beet leafhoppers found on a card in the North Basin in 2010 was (70) the week of August 3rd on a trap near Connell. Only 29% of the traps in the North had counts higher than 40 BLH per card in the 2010 season, and 36% of traps never had counts higher than 10 BLH per card. We ran out of our usual yellow sticky cards for the North Basin route in October, and had to try a different brand. Unfortunately, the new brand of cards did not work well, so the October data was not usable.

Figure 4: Click to view larger image

Mattawa 

Figure 5 shows the average weekly beet leafhopper trap counts for the Mattawa routes in 2007, 2008, and 2010 (we did not have any Mattawa traps in 2009), and the three-year average. Beet leafhoppers showed up in our traps earlier in Mattawa in 2010 than they did in 2007 and 2008. The beet leafhopper population in Mattawa in 2010 was quite large in early and mid-May. The 2010 data indicate a sharp drop in the catch rate for late May and moderate counts for June, but these numbers may not reflect the true population, because significant amounts of rain in the last week of May and the first weeks of June made the sticky cards less effective, i.e. less sticky. In 2010, average trap counts in Mattawa peaked at 134.7 BLH per card the week of May 15th. The highest number of beet leafhoppers found on a card in Mattawa in 2010 was (388) the week of May 15th.

Figure 5: Click to view larger image

West Basin 

Figure 6 shows the average beet leafhopper trap counts for West Basin routes 2007-2010, and the four-year average. The average beet leafhopper catch in the West Basin for 2010 was smaller compared to the four-year average during the first two months of the season, but some of the low counts may have been due to the rains.  The 2010 counts were higher compared to the four-year average from mid-July to the end of the season. In 2010, average trap counts in the West Basin peaked at 33.7 BLH per card the week of July 27th. The highest number of beet leafhoppers trapped on a card in the West Basin in 2010 was (115) the week of August 3rd on a trap near Quincy. Two of the West Basin traps had counts higher than 100 BLH per card in the 2010 season, and 63% of the traps had counts higher than 40 BLH per card in the season.

Figure 6: Click to view larger image

South Basin 

Figure 7 shows the average weekly beet leafhopper trap counts for South Basin routes 2007-2010, and the four-year average. The beet leafhopper populations in the South Basin in 2010 appeared to get off to a slow start, but some of this was probably due to the late May and early June rains. The beet leafhopper counts in the South Basin for 2010 were smaller compared to the four-year averages through much of the season. In 2010, average trap counts in the South Basin peaked at 17.4 BLH per card the week of June 29th. The highest number of beet leafhoppers trapped on a card in the South Basin in 2010 was (93) the week of June 29th on a trap near Pasco. Only 33% of the traps had counts higher than 40 BLH per card in the 2010 season, but none of the traps had counts less than 10 BLH per card in the season.

Figure 7: Click to view larger image

RECOMMENDATIONS

In the weekly survey reports potato field managers were encouraged to monitor beet leafhopper populations closely in May-July. Studies by Munyaneza et. al (2008) suggest that this is the time when potato plants are most susceptible to purple top, an important disease transmitted by beet leafhoppers that can result in significant yield losses. We also recommended that potato growers deploy their own traps to monitor beet leafhoppers, because the populations can be spotty. The more traps near a field, the more likely that an infestation will be detected. Unfortunately, treatment thresholds based on trap counts have not been established, but we know that the risk of infection increases as beet leafhopper populations become large.  Traps should be checked regularly. If the numbers on traps build to 40-100 BLH per week, then it is probably time to be concerned. Growers were recommended to read the chapter, “Management of Leafhoppers and BLTVA” in the on-line publication,Integrated Pest Management Guidelines for Insects and Mites in ID, OR, and WA Potatoes. This chapter contains general information about beet leafhoppers, and includes information about trapping beet leafhoppers and managing them in the field with cultural controls and insecticides. Several foliar insecticides are available to control leafhoppers. In the Columbia Basin, these insecticides are usually applied in May, June, and/or July to target beet leafhopper and limit the spread of purple top.

Next » Potato tuberworm


This project is sponsored by the Washington State Potato Commission.

 

Beet leafhopper (photo by Andy Jensen, WA State Potato Commission)
Beet leafhopper
Potato tuberworm moth (photo by Andy Jensen, WA State Potato Commission)
Potato tuberworm moth
Green peach aphid (photo by Andy Jensen, WA State Potato Commission)
Green peach aphid
Potato aphid (photo by Andy Jensen, WA State Potato Commission)
Potato aphid
 

For more information about the potato insect pest survey contact:

Carrie H. Wohleb, Ph.D.
Extension Educator
Potatoes and Vegetable Crops
WSU Grant-Adams Area
35 C Street NW
Courthouse, PO Box 37
Ephrata, WA 98823
509.754.2011 ext. 413
509.754.0163 Fax

cwohleb@wsu.edu


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