Friday, September 9, 2016

Trap Catches Identified to Sept 09.


Only 4 traps reporting again this week, Erskine, Hoople, Lake of the Woods and Tappen.  There were no aphid vectors in any of them.  Consequently, the PVY Vector Risk Index Values have not changed from last week.  The number of mosquitoes in the traps was a bit depressing, even for someone living in northern Minnesota!

Most fields are done, so I suspect there isn't much green left out there.  In case there are a few fields left with live vines....

Scouting for 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 insecticides an effective control for PVY.
- The use of feeding suppressing insecticides, such as pymetrozine (Fulfill®) or flonicamid (Beleaf®) 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. Some other insecticides, such as clothianidin (Belay®), imidacloprid (Admire Pro® or Provado®), and spirotetramat (Movento®), have also been demonstrated to reduce the transmission of PVY.
- In table stock potatoes, a treatment threshold of 30 aphids /100 leaves should deter yield loss due to aphid feeding.

The PVY Vector Risk Index
Not all species of aphid are equally efficient at transmitting PVY, some are better than others (green peach being the most efficient vector of PVY).  So, the total number of aphids in a trap don't necessarily reflect just how much vector pressure there is at that location. The PVY Vector Risk Index compares aphid numbers, incorporating their relative vector efficiency compared to the Queen of PVY vectors (green peach aphid!).  Using averaged reference comparisons from the literature, we multiply the number of each aphid species captured by it's efficiency compared to Green Peach Aphid to more accurately depict risk posed by the species being trapped.  We then sum the totals.  The PVY-VRI values are presented on the tables below but also on maps comparing current cumulative risk to the total risk from the sample sites of last year (to compare with your local winter grow out results).  Click on the map for full sized image.

The First map represents the current cumulative PVY Vector Risk Index values up to Sept 09, 2016.  The Second represents the cumulative seasonal PVY Vector Risk Index values from 2015.

 Aphid Alert Trap Catch Identified Sept 05-09

Seasonal Aphid Trap Catches to Sept 09, 2016