SW MN IPM Stuff 2020 Issue 7

Volume 23 number 7

6/11/2020

This newsletter and the advice herein are free. You usually get what you pay for.

This newsletter is also available in a print-friendly pdf format at: PDF icon SW MN IPM Stuff 2020-07

Greetings,

For the most part, the crop in SW Minnesota, and much of Minnesota, still looks pretty good, so far. 

In-person meetings are expected to be restricted for some time because of Covid-19 virus precautions. I’ll try to do more videos on scouting and research plot treatments.

Crop Weather

Rainfall, air and soil temperatures, degree-days, soil moistures, and other current and historical weather data for the University of Minnesota Southwest Research and Outreach Center (SWROC), a little spot about two miles west of Lamberton, MN, can be found at SWROC Weather.   

Since the last issue, hail has caused problems for crops, particularly soybeans in scattered areas of SC and SW MN.

Problematic and more widespread have been the number of windy days limiting opportunities for post-emerge herbicide application. Fields without an effective pre-emerge herbicide have been easy to spot this spring. On June 10, while driving through Watonwan County, I watched the wind convincing some real estate to change hands.

The night of June 9-10, the SWROC was part of a small area of SW Minnesota that received heavy rainfall (2.25”). This was from the system that moved out of the Rockies to the SW. The eastern portion of Minnesota received rainfall from the tropical storm out of the Gulf. Both of these systems could have transported insects and fungal spores. While most of the area saw some rain, pockets of southern MN saw little or none.

Things that go bump in the night 

The larvae from black cutworm moth flights into Minnesota are feeding on leaves with those from the earliest flights large enough to cut corn. The larvae from the earliest flight should begin pupating by June 15 while the mid-May flights will continue to feed until June 21 or a bit later. Do not ignore scouting later planted soybeans and sweetcorn for these later flights. Migrating moths made it as far north as Crookston this past weekend.

Corn

hop vine borer

Early-planted corn in the Lamberton area is 7-collars and rows are starting to close. While this larger corn is now safe from cutworms, the growing points are above the ground and it is more vulnerable to hail damage. 

Ryan Bode reported that hop vine borer have moved from grasses to corn. The larvae damage and kill corn by tunneling into the growing point of corn from below ground. 

Certain fields tend to have recurring problems from this insect near field edges or where grassy weeds occur.

Multivoltine European corn borer flight is on in Southern Minnesota (https://www.vegedge.umn.edu/moth-data/ecb-info ). Captures have been low. Over the next week, scouting of the tallest non Bt fields should be underway in southern MN (https://www.vegedge.umn.edu/ecbddmulti).

I’ll try to get some info on scouting and management tips out within the next day or two.

Soybean

Early planted soybeans are V2-V3. Expect to see IDC and soybean cyst nematode symptoms soon. 

On June 3rd, considerable angst was created when the U.S. court of appeals for the 9th Circuit vacated the registration for the XtendiMax, Engenia, and FeXapan dicamba formulations. Subsequent Minnesota Department of Agriculture and EPA decisions should help reduce the impact of this decision for this season.

Soybean gall midge adults have begun emerging to our south. We expect to see emergence in Minnesota soon. For more information see: Soybean gall midge-Spring 2020 update. During the growing season you can find updates on emergence and management at the soybean gall midge alert network.

Soybean aphids were found June 3 on soybean at the SWROC and at Rosemount on June 9. Populations are still very low. High winds and heavy rains can cause mortality to aphids on small soybeans. Hailstones are particularly lethal.

I would appreciate hearing when you first find aphids on soybean in your area.

Alfalfa

Alfalfa weevil cocoonsFigure 3. Alfalfa weevil cocoons on the ground beneath alfalfa

1st to 3rd instar alfalfa weevil larvae are active in southern MN now. Matt Bruyette sent a picture of an alfalfa weevil cocoon so development is quite spread out. A considerable number of fields in central and western MN were treated with insecticide for alfalfa weevils.

Potato leafhoppers arrived at the SWROC. Over 2 adults/sweep were found where alfalfa was sheltered from wind. 

If you need to treat a field for potato leafhoppers and have already treated for alfalfa weevil, switch insecticide group! Watch for resurgence of pea aphids after insecticide applications.

Wheat, Oats, Rye, Barley

Early spring wheat varieties are starting to head. 

Bird-cherry oat and English grain aphids are present in low numbers in SWROC winter wheat and cereal rye. For those of you scouting spring grains – scout for aphids before heading. At this time, I am still seeing little disease in spring wheat. 

Fungicides 

The following information is provided courtesy of Xianming Chen, USDA-ARS Research Plant Pathologist at Washington State University.

In the recent days, I have got several e-mails and phone calls about the latest stage for applying fungicides. Attached is a list of fungicides for managing foliar wheat diseases (including stripe rust) with harvest restrictions. These fungicides can be grouped based on their latest stage or days before harvest for application:

1) Fungicides that can be used up to Flowering (Feekes 10.5)

Aproach SC       6.0 - 12.0 fl oz/A

Headline SC       6.0 – 9.0 fl oz/A 

Delaro 325 SC              8.0 fl oz/A

Nexicor EC        7.0 – 13.0 fl oz/A

Preemptor SC     4.0 – 6.0 fl oz/A

Priaxor                4.0 – 8.0 fl oz/A

Stratego YLD     4.0 fl oz/A

2) Fungicides that can be used up to Flowering completed; kernel watery ripe (Feekes 10.5.4)
Tilt 3.6 EC            4.0 fl oz/A
Miravis Ace SE     13.7 fl oz/A
Quilt Xcel 2.2 SE  10.5 – 14 fl oz/A
Trivapro SE           9.4 – 13.7 fl oz/A
Topguard EQ        4.0 – 7.0 fl oz/A

3) Fungicides that can be used up to 45 days before harvest
Aproach Prima SC  3.4 – 6.8 fl oz/A

4) Fungicides that can be used up to 40 days before harvest
Preemptor SC  4.0 – 6.0 fl oz/A

5) Fungicides that can be used up to 35 days before harvest
Absolute Maxx SC  5.0 fl oz/A
Delaro 325 SC         8.0 fl oz/A
Stratego YLD          4.0 fl oz/A

6) Fungicides that can be used up to 30 days before harvest
Caramba              0.75 SL   10.0 – 17.0
Folicur 3.6 F        4.0 fl oz/A
Proline 480 SC    5.0 – 5.7 fl oz/A
Prosaro 421 SC   6.5 – 8.2 fl oz/A
Topguard EQ      4.0 – 7.0 fl oz/A 

For the fungicides listed in two categories of latest application (such as Delaro 325 SC, Preemptor SC, Stratego YLD, and Topguard EQ), the one that comes first should be considered as the restriction. Some of the above listed fungicides, such as Folicur, Tilt, and Quilt Xcel, there are different commercial names, check the active ingredients. Folicur contains 38.7% Tebuiconazole. Tilt contains 41.8% Propiconazole. Quilt Xcel contains 11.7% Propiconazole and 13.5% Azoxystrobin.

Check fungicide labels for both the latest use and the total amount for a crop season.

The North Central Regional Committee on Management of Small Grain Diseases (NCERA-184) has developed a table listing the fungicide efficacy for control of certain wheat diseases.

Happy trails, 

Bruce Potter