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IPM Stuff Newsletters: Issue
1 - February 18, 2009 IPM Stuff Classics Corn
Planting Depth - 3/5/99 SWROC Pages: Home Page Other Cropping Newsletters: Minnesota Crop eNews - Regional Newsletters Minnesota Fruit and Vegetable IPM News The Bulletin - Other States IPM Newsletters
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Integrated Pest Management Newsletters and Information IPM Stuff Print this newsletter using Acrobat Reader Table of Contents:
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Crop WeatherKeep up to date on all the crop weather details during the growing season at the SWROC's weather page.
As an oversimplified and extremely generalized statement, dry years are insect problem years and wet years are disease years. Temperature helps determine which species thrive.
It is dry but we still have adequate subsoil moisture in most cases. The long-term average May rainfall at the Southwest Research and Outreach Center (SWROC) is 3.32 inches and for 2009 we are at 1.63 inches. This is not all bad; it has encouraged good early season root development and minimized seedling disease issues on corn and soybeans and leaf disease on small grains.
Yes, it has been windy this spring. Evidently, piles of corn residue in ditches and fields to the north of 2008 corn fields were, in some cases, capable of spontaneous combustion. A fair number of corn stalk bales were made this spring. This residue movement is an example of chaos theory for those of you who roll your soybean ground. The high winds also moved a lot of soil were there was no residue. The winds did not do all that much for insect migration. The lack of thunderstorms and associated low-level jet stream activity has minimized the migration of problems into SW Minnesota from the south. Light trap captures of black cutworm and true armyworm have been low. Very few painted lady butterflies (thistle caterpillar) have been observed so far this spring.
The spring has been slightly cooler than average as reflected in degree day (DD) accumulations; 318 DD base 50F compared to 348 DD historical average. Out of sync with low temperatures; a field cricket was chirping outside my window tonight. This is the earliest in the year I can remember hearing one. Perhaps, it was escaped pet food.
There is a good looking corn crop in much of the area. The earliest planted corn on the SWROC (April 22) is at 3 collars in a heavy residue corn on corn situation. There are producer fields out there further along.
April planted soybeans are V1 or first trifoliate opened. Most soybeans are looking good as well unless they were planted late and shallow and where low moisture is causing slow and uneven emergence.
Winter rye headed last week and early winter wheat varieties are starting to head now. Spring wheat, planted in a timely fashion is jointed. The winter and spring wheat crops look very good but will need some moisture soon. Due to dry weather, foliar diseases are at very low levels on wheat including winter wheat. I have not observed any leaf rust to this point. Based on current disease levels at Lamberton, a single fungicide application for Fusarium head blight (scab) on spring wheat should be all that is needed. Wheat planted after corn is at particular risk. Dry conditions during flowering will minimize risk from this disease. Information on making a scab treatment decision can be found at http://www.wheatscab.psu.edu/.
A Weed Species Shift?I don't often get too deeply involved in weed control topics, preferring to be confused and humbled by organisms with a nervous system. However, a recently emerging weed threat has the potential to impact much more than crop yield through competition. I am referring to the tremendous levels of volunteer corn in some fields. Much of this volunteer corn is glyphosate tolerant. Dry topsoil conditions this year will mean continued emergence with later rains and complicate already difficult control.
Why am I concerned about volunteer corn surviving in corn and soybean crops? Simply, you are in effect losing crop rotation for corn. In soybeans, preliminary data from a study funded by the Minnesota Corn Research and Promotion Council indicates volunteer corn plants serve as sites for corn rootworm egg laying and damage to subsequent corn crops. The potential for volunteer corn produced from glyphosate tolerant/ rootworm Bt hybrids to express the corn rootworm protein at low levels means volunteers can create major resistance management issues. I would suspect corn pathogen populations can be affected by these volunteers as well.
Pay attention to volunteer corn in soybean. Obviously, glyphosate will not control the tolerant volunteers. More than one application of a grass herbicide may be needed.
In corn on corn situation, I am not optimistic enough to believe everyone planned for this problem and selected hybrids appropriately. As a practical matter, I am not sure this can be done effectively. Row cultivation can clean out between rows. Yes, I did use the C word. Volunteers in the row are not going anywhere. On the bright side, later emerging volunteer plants will be less competitive.
Herbicide resistant weedsThe Minnesota Soybean Research and Promotion Council are funding a project on glyphosate resistant weeds. Later this season, I will provide information on submitting seed samples from suspected glyphosate weeds in Southwest Minnesota
The status of crop pestsThis has been a remarkably uneventful crop pest year to this point.
Winter kill hurt some fields but most look very good. We had few potato leafhoppers in sweep net samples today. We had at least one weather system that allowed a few to arrive from the Gulf coast. Scout for these insects in second and third cuttings with sweep nets.
In alfalfa, near a grove, we picked up some unusual looper caterpillars. They were fall cankerworm larvae (the eggs are laid in fall) falling from nearby trees on silk threads. I doubt that these are a threat to alfalfa but I received a call about these insects defoliating a grove west of here.
Alfalfa weevil larvae are present now. The larvae are mostly small 1st and 2nd instars. We are seeing minor pinhole feeding at this point and larval levels are unexciting this point. Watch for slow re-growth with dry conditions and alfalfa weevil in any heavily weevil infested fields.
Cutworm observations, for the most part, have been dingy cutworm which is not a major threat to corn. I have received few calls on wireworm and white grub infestations. European corn borer moths have started to fly. Two (2) females have been captured at the Fulda location and none at Lamberton. I am not expecting big things from this insect this year.
Bean leaf beetle feeding is present but minor in the early planted soybeans I have looked at.
Soybean aphid (some things never change)As predictably as the swallows returning to Capistrano, the lilacs flower, the 1st generation corn borer moth flight coincides with the blooming of peonies, and the political ads take over the airwaves every other fall; the season's soybean aphid insecticide marketing plans are unveiled.
I am not in the business of policing crop pest management philosophies. I would simply like to point out that things that sound to be too good to be true usually are. There is a large amount of data generated over the past few years indicating soybean aphid insecticide treatments applied at a 250 aphid/plant economic threshold (ET) provide the least yield and economic risks.
Calendar based insurance timings can coincide with the ET and work out. There is, however, much data demonstrating yield risk with the insurance approach.
The cool, dry weather, if it continues, could favor soybean aphid populations. I have not observed any in the field as of yet and 2009 could end up as a low aphid year. Last summer, some soybean growers and their advisors experienced frustration and in some cases yield loss from poorly timed insecticide applications. Repeating ones mistakes is a sign of a learning disability or worse. Being as predictable as any marketing group, I enclose the following opinion piece written by several U of M types last summer.
Insurance insecticide treatments for soybean aphids - Why we are concerned about this management strategy.Everyone dreads another pesticide trip across the field. You may be planning or have been encouraged to apply an insecticide with an upcoming glyphosate application, without regard for aphid populations in the field. While this strategy may occasionally work out, there are several potential problems that can arise from this strategy.
You are responsible for managing your crop for a profit. There is nothing illegal about applying an insecticide labeled for soybean when aphid populations are below threshold. However, insecticide applications do have consequences in the environment. We wish only to point out that there are potential short and long term risks when insecticide applications are made without regard to pest populations. Respectfully,
Department of Entomology |
