We are approaching 1993 rainfall amounts https://swroc.cfans.umn.edu/weather/graphs We need some dry weather.
Corn rootworms – Adults (still mostly males) are beginning to emerge at the UM SWROC near Lamberton, MN.
Did flooded soils counter the effects of a mild winter on corn rootworm populations? While it is too early to know, early hopes of drowning larvae may have been overly optimistic. I looked at non-Bt continuous corn at the SWROC that, like much corn this year, had spent too much time in flooded or saturated soils and was yellow and stunted. Western corn rootworm larvae had significantly damaged many of these roots. The roots on nodes 5 and 6 were destroyed and node 7 had not yet formed.
It will pay to get a handle on beetle populations to make economically sound management decisions in 2025.
The SWROC black light trap captured the first western bean cutworm of the season. We would need much larger captures to signal a potential outbreak.
Soybean aphid – Based on the calendar and soybean growth stage, it is time for soybean aphid populations to increase rapidly. They are on plants they were able to establish earlier. Aphid populations on R3-R4 soybeans at the SWROC have increased, and while average aphids/plant numbers are still low, a high percentage of plants are infested. Bob Koch has reported similar observations at Rosemount, MN. Later-planted beans have also been colonized over the past week.
Based on observations over a few years, aphid populations increase until late R4-early R5 stage soybeans. As terminal vegetative growth ceases, large numbers of winged aphids are produced and leave these plants for other areas. Populations may remain collapsed, or they may rebound later in R5-R6 stage soybeans.
We are entering a period of cooler, drier weather that will favor aphid reproduction. Don’t ignore them as the season progresses.
First-generation bean leaf beetle adults are beginning to emerge here.
Soybean disease issues continue to develop. I am seeing an unusual amount of Phytophthora this season. I anticipate white mold, brown stem rot, and SDS issues to show up later this season, particularly SDS if it were to turn hot and dry. I am starting to see some new areas of off-colored soybeans developing in some of the fields along my commute to the SWROC. I will try to get more than a windshield diagnosis soon to determine if the symptoms are truly a disease or a result of a recent kamikaze weed control attempt.
Waterhemp escapes are starting to reach above the soybean canopy. Other than pre-emerge performance, it has been a generally tough year for weed control.
Potato leafhopper should be a focus when scouting alfalfa and edible beans now. New seeding alfalfa is particularly vulnerable to potato leafhopper.
Happy Trails!
Bruce