C.O.R.N. Newsletter 2009-31

Troubleshooting Incomplete Ear Fill Problems in Corn

Authors:Peter Thomison

During the past week, I have received questions about ears of corn with unfilled tips. In some cases, no kernels are evident on the last two or more inches of the ear tip. Several factors may cause this problem. The ovules at the tip of the ear are the last to be pollinated, and under certain conditions only a limited amount of pollen may be available to germinate late emerging silks. Pollen shed may be complete before the silks associated with the tip ovules emerge. As a result, no kernels form at the ear tip. Severe drought stress may result in slow growth of the silks that prevents them from emerging in time to receive pollen. Uneven plant development within fields may have magnified this problem. Pollen feeding and silk clipping by corn rootworm beetles and Japanese beetles also contribute to pollination problems resulting in poorly filled tips and ears.
Incomplete ear fill may also be related to kernel abortion. If plant nutrients (sugars and proteins) are limited during the early stages of kernel development, then kernels at the tip of the ear may abort. Kernels at the tip of the ear are the last to be pollinated and cannot compete as effectively for nutrients as kernels formed earlier. Stress conditions, such as heat and moisture stress, nitrogen deficiency, hail, and foliar disease damage, may cause a shortage of nutrients that lead to kernel abortion. Periods of cloudy weather following pollination, or the mutual shading from very high plant populations can also contribute to kernel abortion. Some agronomists characterize the kernel abortion that occurs at the end of the ear as “tip dieback”. Kernel abortion may be distinguished from poor pollination of tip kernels by color. Aborted kernels and ovules not fertilized will both appear dried up and shrunken; however aborted kernels often have a slight yellowish color.
Is the presence of barren tips a major cause for concern? Not always. In many cornfields this year, favorable growing conditions may have resulted in a larger number of potential kernels per row than normal. So even if corn ear tips are not filled completely, due to poor pollination or kernel abortion, yield potential may not be affected significantly, if at all, because the numbers of kernels per row may still be above normal. The presence of ears consistently filled to the tip may actually indicate that a higher plant population is needed to optimize yields.
For more incomplete ear fill, including images check the following:
Nielsen, R.L. 2009. Effects of Stress During Grain Filling in Corn
Available at http://www.kingcorn.org/news/timeless/GrainFillStress.html
Thomison, P. and A. Geyer. 2007. Abnormal corn ears. Ohio State University Extension. ACE-1. available at https://agcrops.osu.edu/corn/documents/AbnormalCornEarsPoster_000.pdf

Cooler Temperatures and Crop Maturity - Any Possible Prob

Analysis of this year’s growing season temperatures reveals that we have been a little behind on growing degree day (GDD) accumulation this summer. The extent of GDD deficit does depend upon your geographic region however. Northwest Ohio has not really been behind on GDDs at all this year (from May 1 to the present). Northeast and Western Ohio is a little over 200 GDDs behind this year. The deficit observed is really noticeable from early July to today. Until mid-July, GDD accumulation was tracking right with long-term averages. Since mid-July, GDD accumulation has been behind significantly as a result of cooler than average temperatures.

Couple the cooler summer with late planting dates due to a wet spring and one starts to wonder about corn and soybean harvest this fall. Are we likely to be delayed? Absolutely. There is evidence of this in Northwest Ohio where corn silage harvest has been delayed. So should we be concerned about an early killing frost? In some geographic regions absolutely. Should you be concerned about your corn? (Will your corn achieve physiological maturity (black layer) before the first killing frost?) It likely depends upon when silking occurred.
Dr. Bob Nielsen noted in a recent Purdue Pest and Crop Newsletter that the 2009 growing season bears some strong similarities to 1992 in terms of GDD accumulation. Based on results of a Purdue-Ohio State University study conducted in 1992, for planting dates where silking occurred late July, kernel black layer formation occurred by 21 September. When silking occurred in early August, kernel black layer occurred by 11 October. Where silking occurred about mid-August, kernel black layer formation was complete by 27 October, but occurred 10 to 14 days AFTER a killing freeze event. All of the earlier silking dates (late July and early August) successfully reached kernel black layer prior to a killing freeze.
Data from a study conducted in 2006 and 2007 at the Northwest Research Station revealed that late planted corn (as late as mid-June) could reach full maturity even when GDD accumulation was below average. In both years the first “killing frost” was not experienced until mid to late October. Would our observations have been changed if the killing frost had occurred sooner – maybe? In addition to dealing with high grain moisture at harvest, growers also need to recognize the potential for increased stalk lodging if they plan to rely heavily on field drying. In 2007, stalk lodging in late planted corn averaged over 40%, whereas lodging in early planting lodged less than 8%.

Reference

Nielsen, R.L. 2009. Cool Days, Cold Nights, Slow Corn, What's Next?
URL: http://www.kingcorn.org/news/articles.09/CropProgress-0901.html

Soybean Aphids and Multi-Colored Asian Lady Beetles

Authors: Ron Hammond, Andy Michel, ruce Eisley

As soybeans near maturity with many fields entering the R7 growth stage (beginning yellowing), we are finding larger than expected populations of soybean aphids in many fields. Growers should know that the aphids in yellowing fields are no longer of economic importance. These higher populations are being found throughout the state, and of special interest, we found extremely large populations in southern Ohio last week. High soybean aphid densities were found in Adams, Brown, southern Highland, Pike, and Scioto Counties. This is the first time we are aware of aphids achieving high numbers this far south in the state since their arrival in the early 2000s. We would mention that other states are also seeing large aphid numbers farther south in their states than previously observed. Again, most aphids are no longer of economic concern because the soybeans are beginning to mature. But this increase in aphids in southern Ohio will demand attention in coming years.

We also became aware of another occurrence that might become an issue within the next few weeks to a month. In parts of Ohio where we are seeing the higher aphid densities, we are also observing a significant increase in the presence of multi-colored Asian lady beetles. While of no direct concern in soybeans, these lady beetles might begin going to fruit crops, especially grapes grown for wine. In previous years with high populations of soybean aphids and lady beetles, wine producers had significant problems with the beetles. We then see these lady beetles going to people’s houses and entering homes, becoming a major hassle for homeowners in the fall. If not disposed of carefully, these beetles will give off a foul odor and stain walls when squashed. While perhaps not being a statewide concern, we do expect certain areas of Ohio to be affected, especially parts of northeast and southern Ohio.

Overseeding Cover Crops

Authors:Alan Sundermeier

An option for getting an earlier establishment on fall seeded cover crops is to over-seed. This practice requires using a helicopter, airplane, or ground rig with high clearance to apply seed over the top of soybeans or corn before harvest. By doing so, the cover crop seed has more time to become established versus waiting until after grain harvest. The risk with this method is that seed to soil contact is more difficult and seed may not germinate until after a significant rainfall.

The most adaptable cover crop to use with overseeding is cereal rye. It has a denser seed with more weight: therefore, higher percentage of the seed will fall through crop canopy to make soil contact compared to lighter seed such as annual ryegrass. Spreading patterns with cereal rye when using aerial application will also be more accurate. Overseeding into soybeans or corn should be completed before leaves drop. When leaves yellow and begin to droop down is a good time to overseed. Seed will more easily reach the soil and be covered with the dead leaves which will help retain moisture and aid in germination. Cereal rye will continue to grow throughout the fall even as temperatures drop into the 40’s. This growth will add organic matter to the soil, help correct soil compaction, and could be grazed or harvested for forage in early winter or next spring.

Oats may also be overseeded. It is best suited for southern Ohio after mid-September application to give enough time before killing frost. Overseeding oats into corn will provide an excellent grazing option in late fall corn stalks.
Overseeding Austrian Winter Peas into soybeans is a practice that we continue to research. Since Winter Pea is a larger seed, it needs to be placed into the soil versus a surface seeding. Soil heaving through the winter may also damage a Winter Pea stand that is surface seeded. To improve success, wait until after a significant rainfall and aerial apply Winter Pea. The seed may then penetrate the soil enough to improve germination.

Soybean Rust Find in Kentucky – One pustule in one lesion on one leaf out of 100

Authors: Anne Dorrance

Soybean rust has made it to both Tennessee and Kentucky last week as two additional counties were turned red last week on the national soybean rust map. Both finds are the first for this year in those states and these finds were at the barely detectable stages (one leaf out of 100 leaves with only 1 to few lesions with only 1 pustule, see http://sbr.ipmpipe.org/cgi-bin/sbr/public.cgi. Soybean rust is an invasive species that was first found in the US in 2004 but has not been found on soybeans in Ohio. Soybean rust has overwintered the past few years in Florida, Alabama, and Louisiana on kudzu but has not made it to Ohio in any of the previous years. These low levels found this year in Tennessee and Kentucky are earlier than years previous but still make it questionable whether or not it will make it to Ohio in time to be found. There is no risk to our crop at the current growth stages across all planting dates. In addition, much of the crop is already turning yellow. Scouting activities will continue to monitor for the presence of rust until the crop has lost all of its leaves.

Bt Corn Stover…Does it Persist Longer?

Authors: Greg Roth

During the past week I have had several inquires about the persistence of corn stover and in particular whether Bt hybrids produced stover that breaks down more slowly. It seems we have more problems with stover when planting in high yielding corn on corn fields than before. If Bt corn stover did break down more slowly, it might be a good thing from a carbon sequestration standpoint. Theoretically this could be due to a change in the corn stover composition in Bt lines, increased stalk strength or some impact on the soils microbial community that inhibited the breakdown.
During the past two years several papers have been published addressing the issue. One study, conducted by a team of USDA scientists in South Dakota (Lehman et al., 2008) evaluated the breakdown of Bt and non Bt corn stover from two pairs of hybrids from different companies. They did not detect any differences in the decomposition rates over 384 days due to the Bt genes (both cry1Ab and cry3Bb1 genes) and also did not detect any difference in the stalk strength measurements they conducted. They also did not find any consistent compositional differences that would impact stover decomposition. Also, they compared stover sample decomposition in the root zone of both Bt and conventional hybrids and found they actually decomposed faster in the root zone of the Bt hybrid. Another study (Tarkalson et al. 2008) conducted in Nebraska monitored the decomposition of Bt and non Bt residues from two hybrid pairs for 23 months. They also concluded that there was no difference in decomposition rates due to the Bt genes and they should cause no difference in carbon sequestration in the soil where Bt hybrids are used. A third study (Kravechenko et al., 2009) conducted at Michigan State evaluated whether cropping with Bt corn for seven years led to an increase in soil carbon. They found no evidence that use of Bt corn resulted in higher soil carbon levels.
Although these are not the only studies on this topic, the data indicates that Bt genes are not the reason for the perceived slower breakdown of stover and will not likely lead to higher soil carbon levels compared to conventional hybrids.

Prepare Grain Bins for Fall Harvest

Authors: Curtis Young

Now is time to prepare storage facilities and harvest equipment before things get too busy. No one needs the added stress of equipment breakdowns or messes to clean-up once harvest begins. There are several suggested measures one should take to reduce slow-downs during harvest, protect personal safety, and prepare the storage facility to maintain as high a grain quality as possible. These measures include: facility inspection and repair, sanitation, and empty-bin insecticide treatments.
Storage facilities should be inspected closely for signs of deterioration, especially for leaks and holes through which insects, birds or rodents can gain easy access to the stored grain or rain and snow can drip or blow in onto the grain to produce wet spots that can lead to mold growth. While inspecting for physical problems, one should also test aeration fans and driers for functionality. Check belts, bearings and gear boxes for wear and proper lubrication. Check electrical systems for corroded connections and frayed wiring before harvest. Mice like to nest inside electrical boxes where they are safe from predators. They will strip insulation from wires for nesting material and their urine causes corrosion. While inspecting control boxes, be sure to seal any openings where mice could get in. Be sure that guards and safety shields are in place over belts, chains and intakes. Seal all leaks and make repairs to the equipment before you need them to manage the grain. .
The interiors of the storage bins should be thoroughly cleaned. Walls, ceilings, ledges, rafters, braces, ladder wrongs and handling equipment should be swept, brushed or vacuumed clean of all debris, dust and grain. Fans, aeration ducts, exhausts and when possible, beneath slotted floors should be cleared of debris as well. Dispose of all debris in a lawful manner and away from the storage facility. Once all cleaning has been completed, an empty-bin application of an appropriately labeled insecticide is advisable, especially in bins with difficult to clean areas and/or in bins with a history of insect problems. For empty-bin insecticide treatments that are applied as a liquid, allow a minimum of 24 hours for the sprays to dry before loading grain into the bin. It is preferable to have empty-bin treatments applied at least two weeks prior to harvest.

Registered empty-bin insecticides include: Tempo Ultra SC ™ (cyfluthrin), Storcide II ™ (chlorpyrifos methyl plus deltamethrin), Suspend SC ™, and several pyrethrin products can be used to apply a surface treatment to the inside of the bin and provide a residual. Other products that contain diatomaceous earth and/or silicon dioxide such as Insecto, Protect-It, Perma-Guard and others may be utilized. Refer to the individual product labels for lists of insects controlled and application directions. If a bin is known to be heavily infested with insects, an empty-bin fumigation may be required to knock down insect populations before applying one of the above insecticides. The most readily available product for this purpose is phosphine gas producing materials such as aluminum phosphide and magnesium phosphide sold under a wide variety of trade names. Phosphine is an extremely toxic material and fumigations should be conducted by trained, experienced, licensed applicators.
Another measure one might take to reduce the chance of insect infestation is to apply a perimeter spray around the base and up the outside walls of the bin about 15 feet. This may only be necessary in areas where grain infesting insect movement has been observed on the outsides of the storage bins. There are several synthetic pyrethroids (cyfluthrin, deltamethrin, permethrin, resmethrin, etc.) that can be used for this purpose as long as they do not come in contact with the grain.
Grain storage insecticide labels tend to change frequently. As always, check to make sure you are following the instructions on the product label and using the appropriate product for your situation.
Last but not least, review your safety procedures for working with flowing grain, grain harvesting and handling equipment, and personal protection. Anyone who works around the bins and grain handling equipment should know where to find shut-off switches, fire extinguishers, and emergency phone numbers. Being prepared for harvest will reduce the risk of accidents, and knowing how to react in an emergency can save lives.

Farm Science Review 2009

Authors: Harold Watters

If you didn’t already know, then let me tell you that the Farm Science Review is the largest farm show in Ohio. Typically there are 120,000 and more attendees over the three-day period – this year September 22, 23 & 24 in September – next week. The site for the show is the Molly Caren Agricultural Center located just north of London, Ohio at the intersection of US 40 and SR 38. And also if you didn’t know, the site is owned by The Ohio State University and operated by the College of Food, Agriculture and Environmental Sciences – making it the largest show in the country that provides a site to talk with all of your suppliers but to also access a very large pool of research-based, unbiased university faculty.

At 2100 acres the site is also a working farm, and not only do they provide a place to visit with exhibitors, researchers and others farmers – but they also have on-site demonstrations of the equipment that you can buy this fall or expect to purchase in the near future. And the future is the key, we want to help you make it through another season, profitably, and we want to see that continue into the future. The theme for this years show is about the farmers and citizens of Ohio (and nearby states), “Your 2009 Bale Out” starts with your visit to the site and ends when ALL of your questions are answered.

Highlights of this years show:
• Animal Welfare, ask about Issue 2
• The Gwynne Conservation area, invasive species a problem – ask here, need replacement trees for you ash - again ask here.
• Disabled but still need to farm to provide for your family – we highlight AgrAbility this year in the Ag Engineering area of OSU Central.
• Field demonstrations – corn harvest, soybean harvest, tillage, planting, GPS, manure applications – see the new equipment here.
• Small Farms – have a small enterprise and want ideas on crops, livestock enterprises and marketing ideas (real important), – see it all in the Center for Small Farms.
• Small plot demonstrations – between the parking lot and the main exhibit area, we have set out small plots of weed control, disease management, “antique corn” and maximum yield. And you can ask about all of these in the OSU Central area of the OSU Agronomic Crops Team members – in the Extension Education and Research Tent.
• And a whole lot more.

Buy tickets at any Ohio State University Extension office across Ohio, many of them have also placed tickets with your local retailers offices, prices are $5, or buy tickets at the gate for $8. The OSU Farm Science Review gates are open from 8AM to 5PM, Tuesday and Wednesday September 22 & 23 and from 8AM to 4 PM on Thursday September 24th. See their website: http://fsr.osu.edu if you need more information.