SW MN IPM STUFF 2017 Issue 2

05/05/2017

This newsletter is also available in a print-friendly pdf format: SW MN IPM Stuff 2017-02

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

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.

Some of the other University of Minnesota ROCs also keep up on crop weather and growing conditions. You can obtain these weather at:

There are several other sites that are useful for weather and climate. These include:

The spring started off well in SW Minnesota and most of the area’s few spring seeded small grains went in in mid-April and are looking good now.

As I write this, the sun is shining but only small percentage of corn has gone in. The early-planted corn is emerging well with some coleoptile tips a little dinged up from the 28°F low temps on April 27th and 28th and 2.5” of snow on May 1st. Corn planted on April 28th, just before things went bad weather-wise, have sprouted and look okay so far.

The alfalfa in the area has had a bit of a tough go this spring, successfully tolerating being nipped by cold temperatures for a second time. Warm weather will help bring the 1st crop along.

It is still early but insect populations are generally low around here. Either many had broken hibernation and been caught in the two bouts of frigid weather or the winter was not as mild for our resident insects as it was for us. We are not capturing moths in the black light trap - perhaps due to cool night temperatures. Yes, I checked and it is plugged in and the light is working.

Unlike some states to our east, we have had few migrant black cutworms. The low-level jet streams that many insects migrate on have been tracking south and east of MN. Be cautious in assuming insect problems in your fields are similar to other areas. We have had one significant black cutworm moth flight that arrived on April 15th in Brown County. The cutworms that will hatch from eggs laid by these moths are projected to be large enough to cut corn by May 21st. We update black cutworm information weekly at: MN cooperative black cutworm reporting network.

lady bug on cornThis spring, other insects are also at levels much lower than we typically see. I have only a single male red admiral hanging around my house. I hope he has some red and black winged companions migrate in soon.

Aster leafhoppers are present at low numbers in winter wheat and rye plots but potato leafhoppers have not yet arrived in alfalfa where very low numbers of tarnished plant bugs and a small population of pea aphids tracked by pink-spotted and seven–spotted lady beetles.

A few alfalfa caterpillar have survived and the butterflies are about but this spring, I am only seeing the pale yellow –white morphs instead of the more typical bright yellow color form.

Since some corn is now emerging, I reckoned it was time to dust of the following early season scouting article

SCOUTING EARLY SEASON STAND PROBLEMS IN CORN

Evaluating corn stands or lack thereof, is an important task early in the growing season. Stand counts can be effectively combined with other early season scouting tasks. The following hints may provide some help in detecting and determining the cause of stand losses.

SCOUT EARLY: Corn should be scouted soon after emergence to determine if an acceptable stand is present and to detect potential problems, such as cutworms, in time to take action. Once corn can be rowed, scouting should begin in earnest. When an unacceptably low corn population occurs, the earlier a replant decision can be reached the better. If all goes well, you won’t need these but in case you need to determine if replanting is economically justified, refer to Manage corn planting decisions to optimize yield and economic return and Corn field guide evaluating crop damage replant options and other University of Minnesota Extension corn planting information publications for information.

CHECK THE WHOLE FIELD: Check corn populations throughout the field. Problems tend to develop in portions of the field that are farthest away from the field approach or road. Before entering the field, look over the entire field for areas that appear different. Check them when scouting. Scout the field with an adequate scouting method (X or M patterns work well). Make a close examination of plant population in several areas throughout the field. Only large-scale disasters can be detected at 55 mph. Determining the cause of missing corn plants often requires detective work.

LOOK FOR PATTERNS: Is the problem throughout the field? Is there a pattern to the missing corn? Are individual rows missing or emerging erratically? In areas without corn, determine if seed was planted. In spite of modern electronics, areas of a field can mysteriously be planted without seed. Check planting depth. Counting rows can determine which planter row(s) was malfunctioning. Poor stand or seedling vigor can sometimes also be traced to compaction and other field preparation problems. Patterns relating to wheels or tillage equipment will be visible. Misapplication of herbicide, herbicide carryover, and excessive N or K fertilizer in contact with the seed provide identifiable symptoms. These symptoms can often be related to soil type and soil moisture.

Stand losses caused by insects and plant disease don’t follow straight lines and damage is usually not throughout the entire field. Localized or spotty areas of the field being affected provide a clue that a stand problem is disease or insect related. Examine entire plants as well as the appearance and location of problem areas in the field before drawing conclusions. Corn seed is treated with a combination of several fungicides and insecticides, they do not, however, make your germinating corn seed and seedlings invincible.

WEATHER AND FIELD HISTORY: Several fungi, including Pythium and Fusarium in particular can cause pre-emergence and post-emergence “damping-off” of corn. A rotted, discolored or water-soaked appearance of the seed or portions of the seedling indicates the presence of a pathogen. Corn seedling diseases are often associated with cold wet soils such as low areas. Disease can be secondary to damage caused by other factors.

Damage from several insects tends to be worse when cool, wet soil conditions slow corn germination and emergence. Field history can provide clues to the species causing stand reduction. For example, if a poor stand is associated with heavy manure application or other high organic matter conditions, suspect seed corn maggot. A recent history of sod implicates wireworms or white grubs.

Several species of cutworm attack Minnesota corn. Unlike the insect and disease problems previously mentioned, cutworm damage can be controlled effectively with insecticide rescue treatments. Early detection is important. Look for leaf feeding. Most species will feed on leaves before they are large enough to cut plants. Knowing which species is present, the stage of cutworm and corn development, and amount of damage will help determine if an insecticide treatment is necessary.

SEED PROBLEMS: Modern seed corn has often has better early season vigor than its predecessors do. Infrequently, however, seed lots have problems with poor germination and emergence. Poor seed should be suspected only if planting, insect and disease problems have been eliminated.

Consider the nature of the problem if the remaining stand dictates replanting. For example, a seed treatment may be appropriate when planting back into an insect problem. Keep record of where the loss occurred as problems can repeat themselves in future years.

There are many additional factors that can cause poor corn stands and a combination of factors often occurs. Fortunately, things usually go well. Good Scouting and...

Happy trails,

Bruce Potter