Thursday, July 25, 2013

Here's the catch for the Trapping Period ending July 21*.

Green peach aphids (GPA) have been recovered in several traps this week; traps in Forest River (ND) and Crookston, Perham and Staples (MN) all recovered GPA.  Green peach aphid is perhaps the most efficient vector of PVY.  Its appearance is further indication aggressive scouting and management are a good idea this season.  Soybean aphid (SBA) also continues to make its presence known this week; the traps at Walhalla and Linton II (ND) and Gully and Crookston (MN) all recovered SBA this past week.  While not as effective a vector of PVY as is
green peach aphid, soybean aphids are probably the second most important vector in the disease epidemic because their dispersal events involve very high numbers of the aphid.  We can expect increased movement of soybean aphids over the next 2 weeks, reports from Bruce Potter at the SW Resarch & Outreach Center indicate soybean aphids there are developing wings and this indicates an impending dispersal event.  Southerly winds will bring increasing numbers of soybean aphids into the Red River Valley from southern locations.

Trap catches are variable this week at different locations with some trap locations recovering increased numbers and others recovering lower numbers of aphids.  Vector species persist, and non-vector species continue to be recovered, indicating aphid movement is occurring. For the species captured at each location, see the weekly and cumulative tables below.  For a quick glance at the seasonal pattern of vector capture, see the bar graphs near the bottom of the page.

Scouting & treating aphids in potatoes:

  • select leaves from the lower to mid canopy.  Lower, older leaves will have more established colonies and aphids prefer the balance of nutrients found here; aphids are rarely found on leaves in the upper canopy.
  • avoid leaves on the ground or in contact with the soil.
  • in seed potatoes there is only a threshold for PLRV (10 aphids/100 leaves), reactive application of standard broad-spectrum insecticides are not an effective control for PVY (by the time the aphid has been exposed and dies, it can have moved PVY inoculum into and, more importantly, within the field.
  • the use of feeding suppressing insecticides, such as Fulfill (Syngenta Crop Protection)  or Beleaf (FMC Corp.) and refined crop oils, such as Aphoil and JMS Stylet Oil, at or prior to field colonization by aphids may reduce the transmission of PVY within fields.
  • in table stock potatoes, a treatment threshold of 30 aphids /100 leaves should deter yield loss due to aphid feeding
Always read the label!!
*Traps are generally changed at the end of the week and the contents sent to us at the NWROC Entomology lab in Crookston.  It takes approx. 1 week to sort and identify the trap contents.  Because trap counts were late this week due to field work, we included all trap catches received up until Wed July 21.  Therefore some trap reports represent >7 day trapping period.  

Weekly Trap Catch

Cumulative Seasonal Catch