C.O.R.N. Newsletter 2008-24

Western Bean Cutworm Update

Authors: Bruce Eisley, Ron Hammond, Andy Michel

In the last week, we have had some important developments regarding western bean cutworm, which is a pest of corn expanding its range eastward. First, our trap counts continued to increase. From July 22 to July 28, our traps caught an additional 70 moths, which brings the total for this year to 114. Second, we collected our first moth in Wayne Co. on July 24 at OARDC. To our knowledge, this is the farthest east that western bean cutworm has been collected in the US. Third, Dr. Chris DiFonzo at Michigan State University reported a highly infested field in northwest Michigan. She has a well-detailed report with good illustrations that can be found at: http://www.ipm.msu.edu/field-cat.htm . Click on the “Read More” link in the WBC story.

We have collected most of our moths in northwest Ohio. However, the collection in Wooster suggests that this pest has significantly expanded its range. Because of this, we are recommending to scout for eggs and larvae not only in NW Ohio, but the rest of the state. So far scouting by extension educators and entomology specialists has not detected eggs or larvae - but this does not mean they are not there. To scout for western bean cutworm, inspect 20 consecutive plants in 5 different areas or 10 plants in 10 areas. Make sure to inspect corn at different stages, which may be likely considering the amount of replanting this year. Female moths prefer to deposit eggs in late-stage whorl or pre-tassel corn and on the upper surface of the 3-4 topmost leaves. Egg masses contain 5 to 200 eggs, with an average of 50. They are first white in color, then tan, and then to purple within 24 hours of hatch. Larvae have 3 distinctive brown stripes behind the head. In pre-tassel corn, they may be found within the whorl. Once tassel emergence occurs, larvae move down to the silks to feed and later, to enter the ear. Recommended threshold is 5% of plants infested with either egg masses or larvae. Many insecticides are labeled for control of WBC, including most synthetic pyrethroids. Please notify your extension educator or entomology specialists if you suspect the presence of eggs or larvae.

New Insecticides on Corn and Soybean

Authors: Bruce Eisley, Andy Michel, Ron Hammond

There are numerous insects causing injury to field crops in Ohio, including rootworm adults and Japanese beetles on corn silks, potato leafhopper on alfalfa, and various defoliators on soybean (bean leaf beetles and Japanese beetle adults). Bulletin 545, “Control of Insect Pests of Field Crops”( http://ohioline.osu.edu/b545/pdf/b545.pdf ), lists the various foliar insecticides that are labeled for these and other insect pests of field crops. However, over the past year, we have mentioned in this newsletter various new insecticides that have become labeled that are not yet listed in Bulletin 545 (we will be updating that bulletin this winter). The following are the new foliar insecticides that we are aware of that are now available to growers.

Leverage 2.7, a product of Bayer, is a combination of imidacloprid and cyfluthrin (same ingredient in Baythroid) now labeled on soybean. Among the insects listed on the label are soybean aphid, bean leaf beetle, grasshopper, green cloverworm, adult Japanese beetle, and Mexican bean beetle. It is important to note the long preharvest interval (PHI), 45 days. Soybean producers will have to consider potential harvest dates before deciding to use this product in August.

Hero, a product of FMC, is labeled on soybean and corn and contains the combination of bifenthrin and zeta-cypermethrin (same ingredient in Mustang Max). Along with controlling many of the same insects that are on the Leverage label along with the rootworm and Japanese beetle adults on corn, Hero also has two spotted spider mites on the label for both crops, with bifenthrin giving the mite control. Hero has a relatively short PHI of 21 days on soybean.

Cobalt, a product of Dow, is a combination of chlorpyrifos (Lorsban and others) and gamma-cyhalothrin (Proaxis and others). It is labeled on alfalfa, corn, and soybean for the usually mix of insects, including twospotted spider mite (because of the chlorpyrifos). Its PHI on soybean is 30 days.

Respect, a product of BASF, contains zeta-cypermethrin (the same ingredient found in Mustang Max). It is labeled on alfalfa, corn, and soybean.

Kaiso 24 WG, a product of NuFarm Americas, contains lamda-cyhalothrin (the same ingredient found in Warrior and others). It is labeled on alfalfa, corn, and soybean.

Corn Lodging and Corn Rootworm

Authors: Bruce Eisley, Andy Michel, Ron Hammond

Previous articles have discussed larval injury and possible plant lodging. We are getting reports of corn fields throughout the state having significant lodging in corn following corn, first year corn fields, and in refuge areas planted along with transgenic hybrids. However, before assuming that the lodging is because of rootworm root injury, growers should dig roots, wash them, and rate the roots for larval injury. There are many causes for plant lodging, rootworm feeding being only one of them. With the significant rain we received the past few months, many fields experienced conditions leading to poor root development followed by plant lodging. See the CORN newsletter, 2008-22, http://corn.osu.edu/index.php?setissueID=242#H for instructions how to dig and rate rootworm injury. Make sure the root tips show rootworm feeding before calling it rootworm injury; short root tips with rounded ends is not rootworm injury.

Planting Winter Cover Crops to Supply Nitrogen – A Recent Multistate Assessment

Authors: Peter Thomison

With nitrogen (N) fertilizer prices soaring, some Ohio farmers are showing renewed interest in the potential of winter cover crops to supply N in corn production.

At the recent Northeast Branch Meeting of the American Society of Agronomy, Dr. Quirine Ketterings and her colleagues at Cornell and Pennsylvania State Universities presented a paper (“Cover Crops for Nitrogen Conservation in the Northeast”) reviewing past university research on the use of winter cover crops to supply and conserve N in corn cropping systems. The review indicated considerable variability in the findings of past studies concerning the potential of winter cover crops to supply N to a succeeding corn crop. Studies from the early 1980’s to the present were evaluated. Cover crops studied included hairy vetch, bigflower vetch, crimson clover, red clover, arrowleaf clover, and cereal rye. While the paper focused on the northeast, studies in Maryland, Kentucky, Wisconsin, Illinois, Michigan, and Nebraska were also considered. The review’s stated objectives included identifying cover crops most suitable for use as winter cover crops in corn cropping systems in the Northeast and evaluating the N fertilizer replacement value of winter cover crops for a succeeding corn crop and the environmental and management variables that most influence N fertilizer replacement values, N uptake and synchronization of N release with the N needs of the next corn crop.

Some of the review’s conclusions follow:

•The N fertilizer replacement value for vetch was greater than for clover while the N fertilizer replacement value of cereal rye was often zero or negative.

•More than half the studies indicated a N fertilizer replacement value for hairy vetch greater than 70 lbs N/A while 80% of the studies found N replacement value for hairy vetch of 50 lbs N/A.

•The N replacement value of cereal rye was often negative probably due to N immobilization in soils with limited residual N.

•This N immobilization associated with cereal rye or small grain could be overcome by allowing 2 to 3 weeks between cover crop kill and planting, or by the addition of N fertilizer or manure following cover crop kill/turnover.

•The limited research available suggests that chemical kill of cover crops without soil incorporation tends to result in slower decomposition and more gradual N release over time than mechanical kill (soil incorporation). However, the authors note that under drought conditions, moisture conservation due to surface mulching with legume cover crop residues can result in greater corn N uptake in no-till systems.

•When leguminous cover crops are planted following small grains or interseeded into standing corn or soybean in late spring, fall N accumulation can be substantial. If seeded after corn silage or grain harvest, legume N accumulation in the fall is generally considerably lower than for cereal grains and grasses.

•When cover crops are planted to capture residual N from the soil profile, cereal grains or grasses are recommended. According to the authors of this review, this capture does not appear to result in an N credit to the succeeding corn crop but more likely contributes to accumulation or maintenance of soil organic N. For N-deficient situations, cover crop legumes are more appropriate winter cover crops.

Reference
Ketterings, Q.M., S.N. Swink, S.W. Duiker, K.J. Czymmek, D.B. Beegle, and W.J. Cox. 2008. Cover crops for nitrogen conservation in corn systems in the northeast. Program and abstract book. Joint meeting of the Canadian Society of Agronomy, Canadian Society for Horticultural Science, and the Northeastern Branch of the American Society of Agronomy, Crop Science Society of America and Soil Science Society of America. July13-16, 2008. Montreal, Canada ( http://www.montreal08.org/PDF_Document/Plant_Soils_Montreal_08_program_book.pdf )

Pre-Tassel Stalk Breakage in Corn may be "Green Snap"

Authors: Peter Thomison

Last week I received reports from NW Ohio of stalk breakage in several corn fields. Such stalk breakage is often referred to as "green snap" or "brittle snap". The stalk breakage may have occurred during recent thunderstorms that were accompanied by strong winds. Corn plants are more prone to green snap during the rapid elongation stage of growth between V8 and tasseling, especially during the two week period prior to tasseling.

Breaks in the stalk usually occur at nodes (along nodal plates) below the ear. When soil moisture and temperature conditions are favorable for growth during this stage of plant development, plants elongate rapidly but stalks are unusually brittle. Stalk brittleness is greatest in rapidly growing corn under high temperature, high soil moisture conditions. There is speculation that rapidly growing plants are more susceptible to snapping-off for several days during the few weeks before tasseling because there has been little time for plants to develop lignified tissues at the nodes.

Although we've observed green snap periodically in Ohio, it's usually a more serious problem in the western Corn Belt. In Nebraska, where wind storms are more common, green snap has caused major stand losses in the past. Vulnerability to green snap damage does vary among hybrids. However, all hybrids are at risk from such wind injury when they are growing rapidly prior to tasseling. The use of growth regulator herbicides such as 2,4-D or Banvel has also been associated with stalk brittleness, especially if late application or application during hot, humid conditions occur. Once the crop tassels green snap problems generally disappear.

Based on studies in 1993 and 1994, Nebraska researchers observed that it was often the most productive fields with the highest yield potential that experienced the greatest green snap injury. They concluded that factors promoting rapid growth early in the growing season also predisposed corn to greater green snap injury.

August 2008 Weather Outlook

Authors: Jim Noel

It still looks like near normal temperatures and rainfall is the best forecast for August. Even though the trend lately has been drier, the trend will be to see increasing rainfall but it may continue to be drier than normal this week before the more normal regime sets in. Some will see a decent rain but some will continue to see minor rains. I expect temperatures to be close to normal over the next several weeks with some ups and downs.

Summer Field Day to be held in Mercer County

Authors: Todd Mangen

Plan to attend the Summer Field Day in Mercer County on August 7, 2008 at 8398 Celina-Mendon Road, Celina, Ohio. The program begins at 9:00 a.m. (registration starts at 8:30 a.m.). Attend and earn pesticide credits for Core, Category 1 and 10.


SPEAKERS:

Anne Dorrance – Plant Pathology
Anne is a nationally recognized researcher in management of soybean diseases and will be able to give an update on what’s happening with this year’s crop.

Erdal Ozkan - Ag Engineering
Erdal will discuss some new ways to be more efficient and safer in spraying our crops.

Todd Mangen - OSU Extension Mercer County
Todd will talk about grain bin insect control and update us on what products are available for insect control.

Lunch provided by VanTilburg Farms at noon (please RSVP by calling 419-586-3077.)

Water Quality Trading Program on August 19 & 20 in Troy Ohio

The Conservation Technology Information Center (CTIC), in conjunction with the Environmental Trading Network (ETN), the Water Environment Federation (WEF) and Certified Crop Advisers, is hosting a two-day water quality credit trading workshop. This will be a detailed, intensive training program on water quality trading for agricultural operators, ag advisors, potential water quality trading aggregators and municipal wastewater facilities.

Expert speakers will introduce the concepts, benefits and challenges of trading and the steps involved in developing a trading program. The training will include interactive "breakout" sessions to give participants specific skills to develop or participate in a trading program. Case studies will be highlighted so participants can learn from programs that are already in place.

The workshop will take place August 19 and 20, 2008, at the Troy-Hayner Cultural Center in Troy, Ohio. Registration deadline is August 5. For more information or to register for the workshop, please see:
http://www.conservationinformation.org/?action=events_trainingworkshops_wqttroy
or contact CTIC at 765-494-9555 or ctic@conservationinformation.org.