Trap Catches to July 05 - July12, 2024.
With 10 traps reporting, we have seen an increase in per trap capture numbers. That said, our regional populations remain low and are tracking behind 2023. Temperatures are rising and aphid reproduction is responding. Remember, aphids, at this time of year are all female. And they give birth to live offspring, the maturation rate of which increases with temperature, until the temperatures reach an upper threshold. Meaning aphid populations can increase rather rapidly at this time of year. So, as the summer warms up, we're going to see increasing aphid populations and we expect to see increasing vector movement.
We're also starting to see some important vectors, including one capture of Green Peach Aphid. This is not surprising given our weather systems. Green Peach Aphid, the most efficient vector of PVY, does not over winter here but in states to the south. Our populations in the Red River Valley of MN & ND are re-established annually by individuals that catch a ride on low-level jet streams. This is often the case when we're getting storms from the south. Populations become established in the region, populations rise and move between potential crop hosts. With rates of population growth responding to rising temperature, vector numbers usually increase.
So... Keep on scouting!
Scouting for aphids in potatoes:
- Select leaves from the lower to mid canopy. Start at the edge of the field.
- 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 Risk Index 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 its 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).
Scouting for aphids in potatoes:
- Select leaves from the lower to mid canopy. Start at the edge of the field.
- 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.
Click on any image below for full-scale version.
Cumulative PVY Vector Risk Index to 7/12/2024
Cumulative PVY Vector Risk Index to 7/14/2023 for ComparisonAphid Species Capture and PVY Vector Risk Index for the week ending 7/12/2024
Cumulative Aphid Species Capture and PVY Vector Risk Index to 7/12/2024
