The month of June soon will be history. In Iowa the prospect of a trend line corn crop is still a possibility. In other parts of the Midwest that does not sound likely in many states as conditions during planting were too wet and/or too cold and planting into less than ideal soil conditions was the reality. Everything that seemed to go right last year seems to have detoured off course this year. For the soybean crop the hurdles again are planting too late or having conditions not conducive to getting a good stand. I have only had a good look at the crops in five states. A colleague who has been in every state from Colorado to Minnesota, and the Dakotas through to Ohio said many acres he has seen were having major problems.
How about these cool temperatures? Just when we were tired of temps in the mid 90s we are back in the 50s and jacket weather at night. A few observant crops people are comparing crop growth versus calendar date and GDU accumulations across different years. A number of them are noting that given the number of heat units that have accumulated the corn plants seem to be behind. What I have noticed in recent years is that the plant leaves often feel cool beginning about 7 p.m. even though air temps are still in the mid 70s.
Every June cropping season is packed with a long list of tasks that need to be completed. This year everyone’s schedules seem to be even more compacted. First it was to get all post-emerge or post plant residual herbicides applied. As soon as that was done it was any post grass herbicides needed to be applied. Then without any break it was time to apply any post emerge grass or broadleaf post-plant products while the weeds were in the 0 to 4-inch stage. That was been a priority of the last week. Many growers are checking for the degree of control or escapes in their fields. Anything less than satisfactory means it is time to move to plan B and figure out which products may still offer control while meeting label requirements.
In many fields it is still too early to judge which post emerge broadleaf soybean herbicides worked and which ones did not. It takes time and effort to visit each soybean field and do a thorough evaluation of the efficacy of each. In recent seasons after the waterhemp escapes become visible we recognize that looking for any 1-inch tall waterhemp is time consuming but needs to be done. The next step in those cases is developing a rescue plan that works. This year that might be which fields should receive another dose of amide chemistry along with any PPO to extend residual control. It is an extra cost in a low budget year, but one that might be needed. Remember that we are approaching the July 1 cutoff date for several of the PPO products.
The weeds that I am seeing that are surviving in many fields are waterhemp, marestail, giant ragweed, Kochia, hemp, and lambsquarters. Any escapes can be the result of poor application timing, not enough penetration by the spray, lack of surfactants in the mix, a degree of tolerance by the weed population, or possibly greater tolerance of the weed to the spray mix. In today’s weed science there are a very small number of actual new products.
Rainfall and hail
Depending on location of the scattered rainfall the June rainfall amounts range from .3 to over 4 inches. There are fields that are showing leaf curling and moisture stress and more rain will be needed. We saw in 2016 that moisture arriving by July 10 can save a corn crop that has been severely stresses. Many prediction centers are forecasting a major front moving in later this week. As of Monday morning lots of showers are marching across southern Iowa.
In the last few weeks the major thermals caused many tall thunderstorm clouds to form causing lots of hail damage. Those events continued through last week leaving a number of growers and crop adjustors to scout and assess the damage. Early damage to corn typically looks bad but recovery is usually good as the new leaves emerging cover it up. With soybeans there are still replant situations occurring.
One of the factors to consider in corn is that tissue damage can predispose the plants to later bacterial disease problems. There have been cases where farmers who supply minerals and growth promoting compounds have seen their plants recover quicker and more completely after such hail. In soybeans damage assessments need to include determining the percent of plants having deep enough bruising that the plants will topple over as the seed weight gets greater.
Corn root worm and corn borers
Growers and crop scouts are seeing root worms beginning to feed on corn root systems now and lowering both the root size and root branching. Early in the season the roots can form new feeder roots root to replace those lost earlier. This regrowth of roots is more likely to disappear as the plant size increases.
Research was done at several levels to see if applying certain insecticides via Y-drops protected the roots. If rainfall around .5 to 1 inch arrived to move the materials into the feeding zone control was good. There is also a Neem oil compound which has been used foliarly with good results, though its actions were slower and more avoidance.
2017 was predicted to be a peak corn borer year based on their five year cycle history. Remember than the upper Midwest normally expects the first brood in the June 15 to 25 time period. The second brood typically emerges and begins laying eggs in the July 20 thru Aug 10 time period. With the first brood damage is seen as feeding on the tender unfurling leaves emerging from the whorl. Scout for this feeding and be observant of the brownish moths flying during the late evening hours along grassy ditches. If your windshields get very smeary from insect impacts it is typically from the egg laden females.
The plant tissue labs have been receiving many samples from growers the last few weeks, but not enough to suggest that every field is getting tested. The analytical results from those we have sent in are indicating shortages of Bo, Mn, Zn, Cu and Mo are very common. Each of those are minerals important to plant health or nitrogen fixation. There are now many companies formulating and marketing such mixes.
In the past seasons about this time there is announcement by extension pathologists that they have found the disease caused by Clavibacter bacteria. This happened two weeks ago in Nebraska. I began seeing the caramel colored lesions on corn plants late last week in fields that had received enough rain to allow the bacteria to form their brown slime. This means that the plugging of the vascular tissue is beginning. In areas with lots of late planted corn acres the potential for major yield losses from plants that will have their fill period cut short growers had best be aware of this finding. Any rookies scouting for this symptomology might want to order their immunoassay strip kits from Ag Diagnostics out of Elkhart, IND soon, as in last week.
At this point the lesions are small, but they are like a small fire in the attic. We hope to explore further the use of thermal imaging cameras to detect the disease appearing or moving into corn fields. This has been the case with an aerial pilot in Northwest Iowa who has such equipment. Be sure to scout your fields looking at the leaves sloughing off near ground level for the brown, slimy mottling.
In case you have not been following the situation in northern Minnesota and North Dakota, the sugar beet growers in 2016 found out what complete resistance to the strobe fungicides looked and acted like. Growers who applied six to eight doses saw no control of Cercospora leaf disease. Previously they were spending roughly $30 per acre for disease control. This year they are told to expect to spend $100 to 120 per acre on a crop that many have been losing money on. We feel a better approach than going down another dead end path is to boost plant nutritional levels and increase plant defense response by foliar applications of products from Redox Chemical Company which are often silicon based. The latest research findings from Brazil suggest this approach has value.
Bob Streit is an independent crop consultant and columnist for Farm News. He can be reached at (515) 709-0143 or www.CentralIowaAg.com.
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