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Crop watch

By Staff | Jul 16, 2019

The 4th of July holiday period is behind us now. In central Iowa we followed up a 3-inch rainfall week with a 4-inch precipitation week. The combination of heat and moisture has been great for the crops and just what the crop doctors ordered. The muggy nature to each day makes a person wish for one of those days in the low 70s.

There are lots of climate predictions floating around these days, and most are saying that we can expect bursts of heat through July with more than adequate rainfall, then cooling off in August.

The question then is how cool and what sort of conditions and heat units will follow in September and October?

Across the entire Midwest several factors were in play to entice farmers to keep planting corn weeks after the normal drop dead date. The number of fields that held V1 to V2 corn on June 21-23rd across the entire Midwest was both amazing and scary. Will those fields make black layer before the first frosts and the 28 degree freeze date? That is the big question that will determine the success or failure of the 2019 corn crop in many states.

Field scouting and recommendations

After the late, wet fall of 2018 when most combines made seriously deep tracks in many fields and wet conditions prevented any deep tillage to be performed, we were all hoping for a dry spring where we would not have to risk doing more damage to the soil again. That didn’t work out. Now after most areas had quite a few sizeable rains that packed the soils even harder, an apparent cause of some of the poor growth in a number of corn fields is leaning to compaction and low oxygen levels.

Returning to row crop cultivating these stunted fields is not what growers would like to hear, but making a cultivation pass with a ‘Hiniker type’ wide sweep cultivator may turn a number of those problem fields around. The ground is very hard and compacted. This is where the no-till and cover crop fields shine as to much improved rainfall infiltration, with ‘coffee grounds’ texture, and much improved root growth. Inspect your fields by taking a spade to dig the roots, crumble the soil and examine the roots for length and direction of growth.

Fast growth

After seeing such rapid growth in the corn plants during June of 2018 and seeing how the crop caught up in development once the conditions improved, we knew it could repeat the performance. Many growers have three different maturity in corn crops, we are now seeing the April planted corn starting to push out tassels or being one to two weeks from doing so. The middle planting is V6-8 and the last is in the V2-3 stage. With cool weather the pace of growth in corn is two leaves per week. With temps in the mid 80s the pace is 2.5 per week.

It appears the 110 RM hybrids are forming 18 total leaves while the 105 RM ones are forming 16. To tabulate your corn’s schedule for the expected black layer and safe from frost date simply count leaf No. 5, which is the first leaf that stays attached to the stalk, and each higher up. Pull the tassel out and divide by 2 or 2.5 to get to tasselling. Then add 60 days to figure the black layer date.

A few areas have had significant winds, enough to cause lodging and some snappage. Rapid top growth often comes at the risk of not forming an expansive root system. With the often saturated topsoil and the shallow rooting of this year’s crop, strong winds could cause a high amount of root lodging. If the corn blows down prior to tasselling and rights itself, yields are not severely affected. If the corn has to regrow brace roots after silking it can affect yields dramatically.

Judging the corn and bean crops

The really good corn and bean fields are few and far between. They have improved as the corn got taller as the waterholes are hidden from view. Beans have finally begun to grow. The main yield risks to corn planted late are the reduction in GDUs and hours of heat with the grain fill occurring in Sept. and Oct.

Late planted soybeans form few podded nodes and branches. On a whole we have never seen a slower developing bean crop. Most knowledgeable people believe NASS yield projections are still too high and do not figure on an early frost. History suggests the risk is real.

Replacement nitrogen

Losing spring applied N appears to be very common to operators who did not use any products to stabilize their nitrogen. There are now many patented and unpatented products such as humates, sugars, molasses, calcium, ATS, N-serve, Instinct, Nutri-Sphere and so on that are available. Maintaining a high level of soil biological activity will do the same as the N can be stored in the microbial bodies. This method is attracting more interest after researchers found that plants are capable of directly uptaking amino acid able through the roots. There are also a number of newer products that have been introduced the last two seasons with a few more due to be commercialized. Study each as using one could be important to your profitability.

Weed control in soybeans

Sisyphus was the ancient Greek mythological person, who being vain, was sentenced to rolling a boulder up a hill. It constantly slipped from his grasp, thus he repeatedly had to start over. Welcome to weed control in soybeans 2019.

Luckily many of the pre-emerge herbicide mixtures have given good early residual control. But those waterhemp keep emerging. Those escapes that have slipped through are best controlled when they are less than 4-inches tall.

Reducing the burn to both weeds and crop plants is ideal as the crops don’t have to recover and the AI can get into the weed rather than fall on the ground as the leaves abscise. The use of Flexstar by the late planting farmers on the small beans was not an option as July 1st arrived too early.

Disease concerns

Hot and humid weather turns most corn fields into an incubation chamber, ripe for fungal and bacterial diseases. Once the plants reach VT when energy is diverted to reproductive activities the immune function in micro-nutrient deficient plants is not as strong and fungal infections occur. Then is when you need to be scouting your corn fields for any tell tale lesions.

In the past two weeks in chest high corn, I have been seeing lots of the caramel colored lesions in the lowest above ground node. This indicates that a vascular system plugging bacteria is and will be reproducing through the rest of the season. I will post a short PPT on our website that tells the story so you can view the strip test kits that can be used to identify the symptoms and remediative actions.

No-till fields with lots of residue will become good hosts for GLS if high temps are the rule. South winds could bring in rust spores so common or southern rusts will be here either warm or cool temps are the rule. News on Tar Spot has been quiet, but in states such as Wisconsin through Ohio the scouts remain vigilant and hope to detect it and then implement control measures if needed.

One leaf disease, Bacterial Leaf Streak/Stripe, is expected to make its return in an area from Ohio to Nebraska. Though it was not identified and written about until two years ago, it is believed to have been here for about five years. We were seeing the leaf blemishes that did not match any other diseases but did not know what to call it. It is a Gram negative Xanthomonas vasicola, meaning it has no cell wall, so no official patented product will control it. There is a product used already in greenhouses, developed by a PhD biochemist from Utah that looks good against it.

Insect news

There are a few insects making their appearance. The first of these, now making a big splash on many varieties of plants, are the Japanese beetles. They are feeding on many trees, berries, flowers and veggies. Hero from FMC was the best hard product to use on them.

The Soybean midge gall has now been documented in an area from Obrien to Cass Counties. The small flies will be flying around looking to lay eggs in or on the soybean stems. The jury is still out on what product (s) may work on them while providing enough residual to last thru late August.

Western Bean Cutworm moths have been picked up in light traps. They seem to have reached their peak about ten years ago and they declined in numbers. A few states in the eastern Cornbelt have been sustaining economically damaging populations since then. A few states, as in Nebraska, publish their black light trapping as officials know this insect is capable of causing serious damage.

So the main focus in the next week will be to get the weeds controlled in the beans and any late season N applied. Late planted beans need a mix applied to speed up their growth and development. Begin scouting V10 corn for those browning lesions, and if they are present figure out how to control it. The big rains that show up on radar to our west in the evening are dissipating and never arrive. For now that is a positive.

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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