As we prepare to wrap up the month of July, Washington State University is warning potato growers that pest populations continue to increase.

 

WSU says it has confirmed Late Blight in a field outside of Eltopia.  The strain was identified as US-23, which infects both potatoes and tomatoes.  This strain is susceptible to metalaxyl/mefenoxam (Ridomil).  This is in addition to cases of Late Blight north of Pasco earlier this month.

 

Fields in the area should be treated with a fungicide every seven days.  Other potato fields across the Columbia Basin should be treated on a ten to 14 day schedule.  If you come across Late Blight as you scout your fields, please contact WSU Extension.

  • Rachel Bomberger, WSU Plant Pest Diagnostic Clinic, rachel.bomberger@wsu.edu(509) 335-3292.
  • Carrie Wohleb, WSU Extension Grant-Adams Counties, cwohleb@wsu.edu, (509) 707-3510.
  • Tim Waters, WSU Extension Franklin-Benton Counties, twaters@wsu.edu, (509) 545-3511.
  • Matthew Blua, Washington State Potato Commission, mblua@potatoes.com, (509) 765-3680.
  • Gary Grove, WSU Prosser Irrigated Agriculture R&E Center, grove@wsu.edu, (509) 786-9283.

 

WSU also reported potato psyllids on nearly a quarter of the fields they are monitoring.  School officials added they are also finding them on a few sticky cards deployed by area crop consultants.  Potato psyllids are slowly moving into fields

 

Lygus bugs were discovered in 100% of the monitored fields, with an average sample of 1.2 lygus per plant.  The field with the largest numbers of lygus bugs had six per plant.

 

Beet leafhoppers (BLH) were found on 96% of our traps around potato fields this week; same as last week.  They are everywhere, but the numbers are low for the most part.  The sticky cards with BLH averaged 7 per card, which was similar to last week.  The numbers have been decreasing since then end of June.  There are two locations that have maintained some high to very high beet leafhopper numbers for most of the season, southeast of Ephrata and north of Pasco.

 

Aphids were found in 56% of the fields we monitored this week; fewer than last week.  The field with the largest number of aphids had 0.9 aphids per plant.  All of the fields had low to moderate numbers of aphids, i.e. less than 1 per plant.

 

If you have a story idea for the Washington Ag Network, call (509) 547-1618, or e-mail gvaagen@cherrycreekradio.com

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