SW MN IPM Stuff 2016 Issue 1

Volume 19, Issue 1 - April 5, 2016.

This newsletter is available in a print-friendly pdf format: SW MN IPM STUFF 2016-01

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

This is the first newsletter of the 2016 growing season. Emily Neperman at the U of MN Southwest Research and Outreach Center has made some formatting changes to the web version this newsletter to make it easier to view on your mobile device at your convenience. However, in the interest of safety, do not read these while driving, simultaneously walking and chewing gum, or any other activities requiring concentration.

Crop weather

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

There is a chance that some insects that have broken hibernation were hurt by the cold (24F) temperature on the night of April 3-4. Unfortunately, most common insect crop pests had not become active, were still sheltered under plant residue in the soil, or are still wintering in warmer climes.

Winter grain seedings and alfalfa for the most part look very good. They might have been slightly nipped by the freeze but should be fine. We’ve had enough moisture and warm temperatures for emergence of giant ragweed and common lambsquarters to begin; they should be fine too. A spring tillage pass can help thin the stand of early germinating weeds and this might be considered when deciding which fields to plant first.

Some small grains have been planted, but soil conditions have not been fit to go in many areas. Depending on the precipitation forecast for the remainder of the week, fieldwork activities could increase later this week. Soil moisture is not excessive, but we need some warmer weather to get soils fit to work. 

As the crop insurance go-date approaches, remember that it is still early!

IPM 2016 01a

I am not a tillage expert, but I think this field needs to dry a bit more.

There are always a few folks that scratch around on the early side, some are just impatient, some treat it as a personal challenge and some enjoy torturing nervous, impatient neighbors.

Someone once told me about a guy that ran his corn planter through a small field very early one spring. It was the cause of great consternation to others farming in the neighborhood. A few weeks later, he put some seed in the planter and planted the field for real.

Crop pest reminders for 2016

Some growers are planting less acres of Bt to reduce input costs. There are a few insect problems that might need special attention if you are scouting or managing fields without Bt. These include corn rootworm, European corn borer and black cutworm.

Corn rootworms

After the tough winter of 2013-14, populations of western corn rootworms have been low. This past mild winter should have been easy on the survival of western corn rootworm eggs. In Minnesota, I'd be concerned about western corn rootworms only in corn following cornfields. Some percentage of these fields may need neither a Bt-rootworm trait pyramid or at-plant insecticide. To know which fields are at risk required scouting corn for rootworm beetles last August.

Northern corn rootworms are a more winter-hardy species. A portion of the northern corn rootworm population displays the extended diapause trait, where eggs delay hatch for a year and cause problems in a corn/soybean rotation. During 2016, there were a few fields without Bt-rootworm traits that saw northern corn rootworm extended diapause problems. Many rotated cornfields may have little risk of extended diapause, but again, to know just which fields those are, would have required scouting in 2014.

European corn borer 

Since the introduction of Bt corn hybrids, populations of this insect have been very low. This can change if non-Bt acreages increase. We will be using a network of black light traps to monitoring MN corn borer flights. We are trying to increase the number of traps operating across MN to help with predictive capabilities. Scouting and timely insecticide applications can minimize losses where corn borer populations are higher.

Black cutworm

We once again have a good crew of cooperators monitoring the migration of black cutworm moths into Minnesota. 

Early this spring, weather systems were not been favorable for bringing cutworms into MN. A pheromone trap in Swift County had 8 black cutworm moths the morning of the March 28th and a trapper in Nobles County found two moths on April 1st. The Swift County trap is significant and will be a date to start calculating degree days to predict potential cutting.

Cutworms are attracted to un-worked fields, particularly with winter annual or early germinating spring weeds. There are several reasons that black cutworm are a cause of concern this spring. Most 2016 corn ground has not yet been worked and spring annual weeds have started emerging. A new wild card could be those fields planted to cover crops surviving the winter. These also could be attractive sites for black cutworm egg-laying. For example, in 2014, some fields where corn was planted into winter rye cover crops saw black cutworm problems.

While delayed spring tillage and planting may help with reducing early emerging weed populations, it has the opposite effect on attractiveness to migrant black cutworm moths. Yes, this presents a pest management dilemma.

Some of the above-ground Bt traits provide control of black cutworm. Growers that have planted hybrids without Bt should pay particular attention to black cutworms when scouting this spring. There is a bit of uplifting news. Bt hybrids or insurance insecticide are not needed for black cutworms. Yield loss from black cutworm can be avoided by careful scouting and timely rescue insecticide application.

This spring, pheromone trap capture data, estimated dates of for first cutting of corn plants and other black cutworm information can be found at the MN cooperative black cutworm reporting network.

Seed corn maggot

When livestock manure is spread or large amounts of green plant material are incorporated, the decaying organic material will be attractive to egg-laying seed corn maggot flies. Corn, soybean and other crop seeds can be damaged by the larvae. High populations of maggots can overwhelm neonicitinoid seed treatments.

Avoid timing your planting close to the incorporation of manures, particularly when adults are active. Fortunately for corn and soybean growers, the timing of seedcorn maggot populations can be predicted based on degree-day models. UW Extension Ag weather estimates will show when flies are expected to be active. I am concerned that incorporation of some cover crops may be attractive to egg-laying seed corn maggot flies. Use caution when planting into fields with livestock and green manures.

Goss's blight and wilt

As always, the environment will play a major role in determining the severity of this disease in 2016. The presence of the bacteria inoculum on corn residue, wet weather, injury to corn tissue (hail for example) and susceptible hybrids combine to favor this corn disease. Resistant hybrids are a management tool but there are no post-emerge treatments that are effective in controlling this disease.

 Typically, rotated corn in fields where tillage has been done are at a lesser risk from infection. If you used corn stover bedding from a Goss's blight infected field and spread it on a field to be planted to corn in 2016, you may be spreading the bacterial inoculum.  Plant a hybrid with good Goss's resistance.

The next issue of SW MN IPM stuff will present my predictions on soybean pests. They have to be better than my NCAA basketball bracket. I had no teams left by the sweet 16.

Other newsletters

I don't often repost articles from newsletters that you should already be subscribed to. If you are involved in MN agriculture, you might want to be subscribed to the University of Minnesota Extension Crop News Blog. Recent articles include changes to fertilizer recommendations and nitrogen fertilizer.

You can view previous MN Crop News articles. There is a signup button at the upper left for email announcements of new issues or you can send an email to bonga028@umn.edu. Put subscribe in the subject line.

Happy trails,

Bruce Potter

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