Thursday, July 18, 2013

Fri., July 17, 2013

Here's the catch for the Trapping Period ending July 12*.

Aphid catches in many locations took a very large jump this week.  At least one site reported Green Peach Aphids and 3 locations reported Soybean aphids. This is developing into a potentially high aphid year; the appearance of the two most important vectors of PVY is concerning.  While the seasonal timing for the movement of aphid vectors into potato fields is well within the expected time frame, many fields throughout the region were planted late, and so the plants are younger than they ordinarily would be at this time.  The younger the plant is when it contracts the virus, the greater the concentration of virus will develop in the plant by the end of the season.  This means later flights of aphids (esp. late season soybean aphids) entering seed potato fields will have more inoculum to move around the current aphids are not prevented from entering fields and probing plants now.  Aggressive and vigilant scouting is recommended, the application of crop oils, if not already begun, should start now.  If aphids are already in fields, the use of the anti-feedant insecticides, Fulfill or Beleaf can be applied to prevent some transmission and within-field movement of PVY.

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.  

Weekly Trap Catch

Cumulative Seasonal Catch