Be on the Lookout for "Rootless Corn"
The recent hot, dry weather combined with poor root development in corn planted in relatively dry, compacted soils may be setting the stage for rootless corn problems.
Rootless corn problems are widespread in parts of Iowa and Illinois. Rootless corn (or "rootless corn syndrome") occurs when there is limited or no nodal root development. Plants exhibiting rootless corn symptoms are often leaning or lodged. Affected corn plants may only be anchored in the soil by seminal roots or by a single nodal root. This condition is generally observed in plants from about the three leaf stage to the eight leaf stage of development.
The problem often becomes evident when corn is subjected to strong winds, which result in plants falling over because there is a limited number or no nodal roots supporting them. The force of strong winds can also break off nodal roots and inhibit establishment of a permanent root system. Leaning and lodged plants (sometimes referred to as "floppy corn" – see Figure 1) may also be wilted. When affected plants are examined, the nodal roots appear stubby, blunt, and unanchored to the soil.
Rootless corn problems are usually caused by weather related conditions that coincide with development of the permanent (or nodal) root system and various environmental factors. These include shallow plantings, hot, dry surface soils, compacted soils, and loose or cloddy soil conditions. Excessive rainfall and shallow plantings may cause erosion and soil removal around the crown region that can result in rootless corn.
“High crown syndrome” has been associated with rootless corn problems (http://bulletin.ipm.illinois.edu/article.php?id=1650). One of the causes of high-crown syndrome is subsidence of the soil due to rainfall after planting, when planting occurs in dry soils fluffed by tillage. If the planting furrow opens as soils dry after planting (this is most common in no-till), coleoptile growth stops and the crown can be set near the seed, essentially placing the seed and seedling above the soil (Nafziger, 2012).
The nodal roots develop above the seed and comprise the permanent root system of corn. The nodal roots, not the seminal roots (associated with the seed), are important in providing the water and the mineral nutrients that the corn plant needs for normal growth and development. If corn seed is planted 11/2 to 2 inches deep, then the nodal (or crown) roots begin develop at about 3/4 inches below the soil surface. However, if seed are planted shallower (1 inch or less), then the nodal roots may form near or at the surface where they are more exposed to fluctuations in soil moisture and temperature. Nodal root growth is very sensitive to high temperatures (w/ root growth slowing or stopping at soil temperatures exceeding 86 degree F ). When unshaded surface soil temperatures reach the mid 90's or higher on hot days, the nodal root growth of shallow planted corn may stop. Plants are forced to rely on the seed root system or limited nodal root growth until more favorable temperatures and moisture conditions allow nodal root growth to resume.
Certain types of herbicide injury (e.g. 2,4-D, Banvel) and insect feeding (e.g. corn rootworm) may also cause lodging to occur in corn plants during vegetative development. Generally they are not the major causes of the rootless corn problems. However, there may be situations where insect feeding and/or herbicides may be a contributing factor.
Can rootless corn recover? Yes, after plants lodge, adequate rainfall will promote crown root development and plants can recover. Cultivation to throw soil around exposed roots may aid the corn's recovery. Of course, this is difficult to do in a no-till situation or when the soil is hard and dry. Since affected corn is likely to be vulnerable to potential lodging problems at maturity, it should be harvested as soon as grain moisture conditions permit.
Nafziger, E.. 2012. Root Problems in Corn Plants.The Bulletin, Univ. of Illinois. http://bulletin.ipm.illinois.edu/article.php?id=1650 [URL accessed May 2012].
Nielsen, R.L.. 2012. Hot & Dry; More of the Same Not Good for Corn Yield.Corny News Network, Purdue Univ.
Start Sampling for Potato Leafhoppers in Alfalfa
Although a few weeks early this year, we are entering that time period when potato leafhoppers are being collected and thus, might become a concern in alfalfa. Growers should begin scouting for the leafhopper when alfalfa regrowth reaches sufficient height for sweep-net sampling. A single sample is 10 sweeps of a sweep net. When the average number of adults and nymphs in a sample is equal to or greater than the average height of the alfalfa stand, insecticide treatment is warranted. For example, if the alfalfa is 6 inches tall and the average number of leafhoppers is 6 or higher, insecticide treatment is warranted. If the average is lower, the grower should re-sample in a few days.
In glandular-haired, leafhopper-resistant alfalfa, the economic threshold is 3X the normal threshold, or three leafhoppers per inch of growth (18 leafhoppers for 6 inch tall alfalfa, for example). However, if the resistant alfalfa is a new planting this spring, growers might want to use thresholds meant for regular alfalfa during the very first growth from seeding. After the first cutting, growers can then use 3X times the normal level threshold. More information on potato leafhopper, including how alfalfa growing conditions might affect the threshold, is available at http://ohioline.osu.edu/ent-fact/pdf/0033.pdf .
Ohio Weather Outlook
The overall trend remains in place with above normal temperatures and slightly below normal rainfall. However, it does look like temperatures will relax to only slightly above normal the next 2-3 weeks and rainfall will increase again to be only slightly below normal for a state average as a whole.
After a much above normal start to the last week in May, temperatures will drop to below normal for late this week into this weekend before going back to slightly above normal next week when combining high and low temperatures. Average highs are 75-80 and average lows are in the 50s. When everything settles out, temperatures will average slightly above normal but no intense heat is expected like the Memorial Day weekend saw.
Rainfall was scattered from the early week storm but most places saw less than a half inch. Spotty totals up to an inch fell in small areas with thunderstorms. A more widespread rainfall is expected late in the week, late Thursday into Friday. Most place will get 0.35 to 1.00 inches with isolated higher totals. Another system could bring a few showers during the weekend but they will be light. There will be yet another system early to mid week next week. With normal rainfall for 2 weeks near 2 inches, most places will average near or a little below that the next few weeks. The more constant duration of rainfall of light to moderate events every few days could impact things such as hay, but will also recharge top soils conditions some.
Finally, May is averaging about 7 degrees above normal for temperatures with rainfall averaging about 50-75% of normal. So May will go down as a much warmer and drier than normal month overall in Ohio. The spring of March to May will likely go down as the warmest on record in 117 years! However, data is still preliminary and we won't have final numbers until early June. Needless to say, spring 2012 is quite opposite to 2011 which is what we were saying at the Ohio Seed Growers Conference in January 2012.
You can follow the NOAA/NWS/Climate Prediction Center Climate Forecasting System Model month by month at:
These are not the official outlooks but rather the climate models. The official outlooks can be found at:
Other Insect Concerns on Field Crops
Last week we received reports of other insects in sufficient populations to cause grower concern, including true armyworm on wheat, corn, and other grasses, bean leaf beetle on soybean, cereal leaf beetle on wheat and oats, and slugs on numerous field crops.
As we mentioned in previous articles in this newsletter, the mild winter and warm spring has brought these pests to the forefront much sooner than usually, at a time when most field crops are still small, and in some cases, just now germinating and emerging. Along with other possible pests, these are some of the insects that should be scouted for potential problems that might need management.
See past C.O.R.N. newsletter articles, or the field crop insect web site, http://entomology.osu.edu/ag/, for information on these insects along with a list of insecticides that will offer control.
What to do with Thin Soybean Stands
Many farmers continue to debate about replanting thin soybean stands. Some fields receiving heavy rains were crusted over while other fields have been far short of optimal moisture and soybeans have been slow to emerge.
Purdue University has a fact sheet entitled “Thin Soybean Stands: Should I Replant, Fill In, or Leave Them Alone?” Framers can access this on the web at http://www.extension.purdue.edu/extmedia/SPS/SPS-104-W.pdf
- Debbie Brown (Shelby),
- Bruce Clevenger (Defiance),
- Matt Davis (Northwest ARS Manager),
- Anne Dorrance (Plant Pathologist-Soybeans),
- Nathan Douridas (FSR Farm Manager),
- David Dugan (Adams, Brown, Highland),
- Mike Gastier (Huron),
- Mark Koenig (Sandusky),
- Amanda Douridas (Champaign),
- Suzanne Mills-Wasniak (Montgomery),
- Tony Nye (Clinton),
- Les Ober (Geauga),
- Pierce Paul (Plant Pathology),
- Steve Prochaska (Agronomy Field Specialist),
- Adam Shepard (Fayette),
- Alan Sundermeier (Wood),
- Harold Watters, CPAg/CCA (Agronomy Field Specialist)
- Peter Thomison (Corn Production),
- Ron Hammond (Entomology),
- Andy Michel (Entomology),
- Jim Noel (NOAA/NWS),
- Glen Arnold (Nutrient Management Field Specialist)