Trap Catches Identified to August 09, 2019

Greetings

Sorry this is late getting out this week, I was on a road trip collecting Colorado Potato Beetles for resistance bioassays and didn't get back till late last night.  If I'd known what was waiting in the trap samples, I might have stayed on the road...

Aphid numbers took a big jump this week, with some important vector species (including Green Peach Aphid) making appearances.  The cumulative seasonal catch increased by almost 50% with just last week's catch (our total vectors captured was 214 last week, in the past week, traps captured a total of 197 vector species across the region).  The Vector Risk numbers rose accordingly, doubling over last week.  Especially with the first seasonal appearance of Green Peach Aphid, the most efficient vector of PVY.  

Green Peach aphid was recovered at 4 locations in northwest/west central MN (Gully, Humboldt, Lake of the Woods and Sabin).  Potato aphid, another important vector species that colonizes potatoes, also saw increases and distribution. 

Most vector species were recovered in increased numbers at many locations, but the crown for numbers this week again goes to English Grain Aphid, which was recovered at most trap sites.  The other small grain aphids, Corn Leaf and Bird-Cherry Oat aphids, also increased in numbers and locations being trapped.  This increase in cereal aphids at this point in the season is due to the rapid senescence of grain fields and is an important factor in the late season transmission of PVY in seed potatoes in MN & ND.  Soybean aphids have started to be more widely recovered, but in limited numbers.  Thistle, Buckthorn and Cotton/Melon aphids also seem to be on the wing and turned up in numbers at several locations.

Bottom line - aphids are flying, the late summer dispersal events have started and scouting and weekly oil treatments are strongly recommended.  Some early fields may be nearing vine kill - this may well be a season where early vine kill may decrease PVY infection in seed potato fields.

Aphid Fact of the Week -  Maturation is occurring in crops other than cereals, and aphids will be sensing a decreasing food quality there as well.  Aphids in these crops will also eventually be developing a winged generation which will disperse to find better food sources.  Many of these species will be non-colonizing species in potato and will work their way through fields, probing and testing plants as potential hosts.  In this way, an increased movement of PVY can occur.  The later development of aphids in the northern plains is evident by the seasonal flight dynamics monitored by the Aphid Alert trapping network.  Our peak flights tend to be in late July to early August (a benefit of living in the home of the Polar Vortex?).  Weekly trap catches are available on the archived Aphid Alert Blogs, going back to 2012 on this site.    

As always, keep on scouting!

Click on any image below for full-scale version.

Cumulative PVY Vector Risk Index to August 09, 2019.

Cumulative PVY Vector Risk Index for 2018 (for comparison)

Aphid Species Capture and PVY Vector Risk Index for Aug 02-09, 2019

Cumulative Aphid Species Capture and PVY Vector Risk Index to Aug 02-09, 2019