SW MN IPM STUFF 2018 Issue 3

Volume 21 number 3

5/17/2018

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

A printer-friendly pdf version of this newsletter is available to download here: SW MN IPM Stuff 2018-03

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 http://swroc.cfans.umn.edu/weather.  

Areas that received the heavy mid-April snow have had issues with poor soil condition all spring, melting snow left soils dense and compacted. To add to spring difficulties, the southern tier of counties, and area near and south of I-90 in particular, has received more than adequate rainfall.

Things that go bump in the night

The appearance of insects, like planting progress and many other things, has been slow this spring.

We continue to pick up a few true armyworm moths in the SWROC black light trap but not at a level causing concern. This could change if we get a large migration of moths from the south as the spring progresses.

May beetles (a.k.a June beetles or June bugs) have started to show up. The larvae are the true white grubs, which have a 3-year life cycle in the soil. Populations of second year grubs were abundant in several WC MN soybean fields last year. I did not observe any first year larvae or pupae in the few fields I looked at last September. This could mean problems seen in 2017 might not repeat in 2018.

Some things to consider right about now

Alfalfa

alfalfa weevil adultFigure 1. Alfalfa weevil adult. The adults overwinter and depending on the biotype lay most or all or their eggs in alfalfa stems in the spring.

Alfalfa weevils have started to move into alfalfa to feed and lay eggs. Some minor feeding can be observed in SWROC alfalfa stands. Watch the resultant larval populations as the 1st cutting matures and in 2nd cutting regrowth. There will be more on alfalfa weevil scouting in next issue. In the meantime, there are a couple crude, in need of an update, videos on alfalfa scouting here: https://www.extension.umn.edu/agriculture/forages/pest/#insect

Currently, there is a much smaller weevil present in SWROC alfalfa as well. This weevil lacks the long, Jimmy Durante-like proboscis (the younger readers may need Google’s assistance for this adjective) of the alfalfa weevil. These appear to be one of the broad nosed weevils, Sitona sp. These small weevils are unlikely to pose the same level of economic threat to alfalfa as the alfalfa weevil. I’ll collect a few and see if I can get an ID when, and if, things slow down this spring.

broad nosed weevil, likely a Sitona speciesFigure 2. Likely a Sitona species, a broad nosed weevil. Members of this genus include clover weevil, alfalfa curculio, pea leaf weevil and others.

Pea aphid and tarnished plant bugs have been at low populations. I have not picked up any potato leafhoppers in the sweep net yet this spring.

Small grains

There are not many fields out there, but any winter wheat and rye grown for grain should be scouted for cereal aphids. Bird cherry oat aphid, English grain aphid, corn leaf aphid and greenbug all migrate on winds from the south. As small grains reach the three-leaf stage or so, they also may be colonized and scouted. It’s been quiet so far. 

Corn

Scouting should begin as soon as stands can be rowed. Winter rye can increase the risk from true armyworm. The later the termination with respect to corn planting, the greater the chance for a migrant moth flight to find the field and lay eggs. When the rye is killed, hungry larvae move to corn. A similar situation can occur in cornfields with dense, grassy weed stands killed post-emerge. There really isn’t much of an excuse for dense, grassy weeds in modern, conventionally farmed corn. Anyhow… a sweep net is your friend for detecting armyworm and other pest problems in corn planted into cover crops.

Black cutworm can also be attracted to weeds or living cover crops present early in the season. Watch corn seedlings for leaf feeding and cutting. Unlike the grass feeding armyworm and cereal aphids, black cutworms will feed on grass crops, such as corn, and on broadleaf crops including sugarbeets and soybean. This has been an active year for black cutworm particularly into the SW corner of MN and along the Interstate 90 corridor. The two previous weeks have seen moth captures in multiple pheromone traps at concerning levels.

Information on black cutworm trap captures and predictions of when and where cutting is most likely to occur can be found in weekly reports at MN Cooperative Black Cutworm Reporting Network. The most recent projections are available at 2018 Black cutworm trapping network report #4. Larvae should be hatching and leaf feeding in corn and weeds should be visible soon. 

Pay particular attention to cutworms when scouting corn and other crops this year. Scouting tips, cutworm ID (important with cutworms in corn) and management advice can be found in the magnum opus black cutworm facts.

Soybeans

As with all crops, scouting for crusting and other emergence issues, stand-reducing early-season disease and insects, and pre-emerge herbicide success is better done sooner than later. The earlier problems are found the better the success with rotary hoe, crop protection chemical or, if worse comes to worst, replanting.

Yes, this has been an uncooperative spring for many of us. Pushing tillage and planting in wet soils, clay loams in particular, can lead to season-long problems. Emergence, plant disease management and weed control all can suffer. If you work and plant soils wet, you often end up hoping that either: a) It keeps raining for a while so emergence and root system development can occur or b) You know where a rotary hoe can be found and you have the time to use it. 

Remember that adobe bricks are made from clay, organic matter (straw, etc.). These are the same components of many western Minnesota high organic matter clay loams. The other requirements in the manufacture of adobe is heat and pressure.  A hot, sunny and windy day will supply the baking power. You can supply the pressure when you compact wet soils.  

Sometimes you need to push things and hope for the best to get a crop planted. We are not to that point yet, particularly with the soybean crop. If you need confirmation, see the Seth Naeve Crop News Soybeans and the Spring of 2018....

By the way, sign up for MN Crop News if you have not already. Be careful out there!

Happy trails,

Bruce