Heat unit models for corn rootworm have projected egg hatch about May 16 for central Indiana. Wet soil conditions throughout the state and short-term weather forecasts indicate that corn planting will not get into full swing until mid to late May at best. Since rootworm egg hatch will likely coincide with the next round of corn planting, consider using reduced rates of some soil insecticides for larval control.
Data from soil insecticide research conducted in producers’ fields in Indiana have shown that little to no loss in root protection occurs where the rate of Counter CR and Lorsban 15G is 3/4 the labeled rate. Data on all other granular soil insecticides suggest that the labeled rates are close to the minimum rates needed to provide adequate protection.
The use of Counter CR and Lorsban at below labeled rates is an option that some producers may choose to try. If using reduced rates it is important that:
Producers who experiment with reduced rates do so with the understanding that they are solely responsible for the performance of the product. The soil insecticide manufacturer is under no legal obligation when their product is applied at less than labeled rates. Other soil insect pests may not be controlled with reduced insecticide rates. Also, Purdue University is not responsible for the performance of insecticides used at reduced rates.
Data for liquid soil insecticides (i.e., Capture, Furadan, and Regent) used at reduced rates are not available. The consistency of performance of these liquid products has been erratic at full rates so lowering the rate on any of these products is not recommended.
The following article was originally written by Marlin Rice, Iowa State Extension Entomologist, for the “Integrated Crop Management” newsletter (May 6, 2002). With his permission, we have modified the information for Indiana’s conditions and situation.
Because of the constant wet conditions this spring, most corn fields yet to be planted have not had tillage or herbicides applied. Winter annual and spring weeds are thick! In addition, black cutworm moths continue to arrive with these many storm fronts. For the majority of fields that have yet to be planted, the question of whether to use a preventive insecticide for black cutworm with the burn-down herbicide is valid. Below are several points to consider before purchasing and applying an insecticide solely for the prevention of black cutworm.
Concern 1: Necessity of preventive insecticide treatments. The basic principles of integrated pest management ask the following questions: Can the insect be scouted for? Can the economic damage be predicted based on field scouting? Can a rescue insecticide be applied, if needed? and Can the rescue insecticide provide equal or better control when compared to the preventive insecticide? The answer to all four questions is “yes.” The use of an insecticide applied as a preventive treatment cannot be economically or environmentally justified when a rescue treatment can provide equal or better control.
Concern 2: Black cutworm migration and egg laying are spotty. Black cutworm adults (moths) are migratory and fly into Indiana from southern regions. Captures of male black cutworm moths in pheromone traps tell us when they arrive, but the trap captures do not tell us in what fields females lay their eggs, how many eggs they laid, what the cutting potential is, or whether the moths stayed within the county where individuals were trapped. In fact, the moths may continue their migration the following night into Ohio, Michigan, or Ontario Canada. For moths that do remain in Indiana, they may not lay eggs in all fields. Previous crop residue (soybean is preferred over corn), tillage, soil moisture, and winter annual weed growth all affect where moths will lay eggs.
Concern 3: Potential for cutworm damage is low. The last significant black cutworm outbreak occurred in Indiana in the year 2000, before that was 1994. Information collected in 1978, considered the “mother” of cutworm years throughout the Midwest, strongly suggests that the threat of black cutworm damage on a large scale is overrated. During that outbreak season, “severely” affected counties in Indiana were surveyed. It was found that 5% of the fields sampled had detectable levels, NOT economic levels! Said another way, 95% of cornfields didn’t have detectable levels.
Concern 4: Insecticide cost is expensive. These insecticides are not cheap. For the low- and high-end label rates, cost could range from $5.00 to $17.00 per acre, depending on the product used and dealer incentives, application costs, etc.
Concern 5: Insecticide performance guarantees. One company may guarantee that its insecticide provides control of cutworms when applied as a preemergence treatment, whereas another company may state that with one preplant application for cutworms, you have one less problem to worry about. Do not be lulled into a false sense of security with insecticide guarantees or claims. Any guarantee or claim is subject to the condition that the field must be scouted for insect damage. Just because an insecticide was applied to the field at planting does not preclude the possibility of crop injury by the insects later in the season.
Alternative to insecticides. There is a better alternative to black cutworm management than buying unnecessary insecticide and increasing on-farm input costs. This alternative is to have the fields scouted when first cutting is expected. Watch for black cutworm cutting projections in this and future issues of the Pest&Crop in the “Weather Update.” Then you should scout the field, look for early signs of injury, and determine whether the economic threshold has been reached. Based on your findings, insecticide can be applied if it is really needed. Remember that black cutworm females may not lay eggs in your field and that it is to your advantage to use insecticides wisely and economically. SCOUT YOUR FIELDS!!
The wet spring of 2002 has delayed corn planting in many corn fields around Kentucky. While growers pray for more favorable planting weather, the clock is ticking. Research has shown that yield potential may begin to drop when corn is planted after May 15. Additionally, there is also an increased risk of insect attack due to southwestern corn borer. Recent research at the UK substation in Princeton has shown that when corn is planted early or on time, the risk of losses due to southwestern corn borer is very low. However, when corn is planted after May 10 in the western half of the state, there is a significant risk of losses due to this pest. The later the planting date, the larger the potential risk.
Corn planted before mid May is still attacked by southwestern corn borer, but will generally escape the worst of the damage. Late planted corn is still in the field when the southwestern corn borer begins to girdle corn plants in September. This is the most serious damage caused by southwestern corn borer. Larvae girdle the stalk by chewing a complete or partial internal groove around the stalk near the base. This leaves only a thin outer layer of the stalk for support. These stalks fall to the ground with only a mild wind.
There is some good news for 2002. As reported in a March issue of the Kentucky Pest News, the southwestern corn borer spring survey indicated that there was low survival of overwintering larvae. This means that the first generation moth populations should be reduced. However, growers planting corn after May 15 should have a plan to manage southwestern corn borer if it appears late in the season in their fields. Early harvest is one option. Early harvest reduces the exposure to stalk girdling in September. Shorter maturing hybrids and grain drying facilitate early harvest. Late planted fields should also be scouted for southwestern corn borer in late July and August. There are several insecticides that are effective against this pest.
Bt corn offers corn producers a practical control for southwestern corn borer with late planted corn. While Bt corn has been developed for European corn borer control, the full-season protection afforded by some Bt corn also provides excellent southwestern corn borer protection. Before using Bt corn, be sure that the market for your grain will readily accept this grain. In some parts of the state, this is not a serious issue but in others it is.
This article reprinted with permission from the “Kentucky Pest News,” Number 950, May 6, 2002. The information is appropriate for Southern Indiana.
When the skies eventually clear and farmers are able to proceed with fieldwork they’ll need to be careful not to fill the air with herbicides that could blow onto a neighbor’s field or yard.
Ill-timed rainfall in April and early May has hindered many Indiana farmers from getting corn and soybeans planted. The pent-up frustration could cause producers to rush herbicide applications when the precipitation ends and fields dry. That could lead to unintended spray drift problems, say two Purdue University Cooperative Extension Service specialists.
“Farmers are under a lot of pressure to get things done, which means that when things break loose everybody’s schedule is going to be the same,” said Fred Whitford, coordinator of the Purdue Pesticide Program. “Every farmer is going to want to have his field sprayed by a commercial business or they’re going to want to spray their property themselves, and they’re going to do it immediately.
“The problem is that they’re going to be making applications in the spring when the winds are going to be high, and there lies the problem — that everybody’s going to be out there doing this, whether the conditions are the best or not the best.”
Weeds already are beginning to appear in fields, and farmers will want to knock them out with herbicides as soon as possible. But the same chemicals considered safe for use on row crops can cause serious damage to vegetable plots, fruit trees, vineyards and home landscapes if the wind carries them to surrounding land, said Bruce Bordelon, Purdue Extension grape and small fruits specialist.
“At this time of the year with sensitive crops like grapes and tomatoes already being leafed out and planted in the ground, they’re at their fastest growth phase and they’re very sensitive to the 2, 4-D and dicamba-type growth regulator herbicides,” Bordelon said. “Exposure at this time of the year through drift or volatility can cause shoot stunting and, in many cases, a dropping of the flower clusters, resulting in an almost complete loss of the crop for the season.”
Damage can extend beyond a single crop year, Bordelon said. “There can be some long-term damage,” he said. “A direct drift application onto tomatoes or grapes might either kill the plants or set them back so that it might — in the case of grapes — take two or three years for those plants to grow normally again.”
Spray drift occurs when herbicide droplets hang in the air and are blown acres, or sometimes miles, away from the application site. The problem is worse on humid, breezy days.
Laws permit farmers to treat their fields with herbicides in a responsible manner. The Office of the Indiana State Chemist regulates herbicide use and can fine farmers for spray drift violations. About 50 spray drift complaints are filed each year with the state chemist, Whitford said.
The applicator is liable in all cases, he said. A commercial applicator hired by a farmer to treat a field cannot pass the responsibility on to his client.
“This is really a private property rights issue,” Whitford said. “In the state of Indiana we have the right to make applications on the property that we own, so a farmer can make those applications or can hire somebody to do it.
“On the other hand, we are responsible to protect somebody else’s property. If you can imagine a fence line, whether it’s a real fence line or imaginary fence line, once that spray crosses over then the commercial applicators are responsible for what they put out. The labels basically say, ‘Don’t drift.’ Even if farmers pressure the commercial guys to make those applications, the commercial person is always responsible for their actions.”
Surveys Whitford conducted with 2,000 farmers in 2001 show producers are aware of spray drift issues. More than one in 10 said they’ve had a property owner complain about spray drift, and a large majority conceded they’d applied herbicides in less-than-ideal conditions.
“About 13 percent of our farmers have experienced a drift complaint where they allegedly damaged somebody’s property,” Whitford said. “We’ve estimated that we’re probably well in excess of a million dollars worth of property damage every year statewide.
“In the surveys farmers understood that their neighbors had private property rights the same as they did. They told us that they would respond to phone calls when somebody alleged that they’d damaged their property, and that they understood that the best application is when the winds are not blowing toward other people’s property. About 70 percent acknowledged that they’d made pesticide applications even when weather conditions were not favorable.”
Farmers can reduce spray drift in many ways, including
Farmers who receive spray drift complaints from neighbors are advised to respond immediately, gather information about and take photos of the alleged affected area and contact their insurance agent as soon as possible.
“Educating the applicators and the farmers around them is the best thing they can do,” Bordelon said. “If everybody understands the potential for damage, I think that everyone will try to avoid having a problem. That’s the main thing, to get out and talk to folks and try to be a good neighbor.”
Bordelon added, “Certainly the number of vineyards and tomato plantings are relatively small compared to the acreage of corn and soybeans in the state, so it’s difficult for a farmer to understand that ‘Just because you wanted to grow grapes next to my field that I have to change my practices.’”
For more information on spray drift, read the Purdue Pesticide Programs Extension Bulletin No. PPP-51, “Stay on Target: Prevent Drift.” The publication is available online at <http://www.btny.purdue.edu/Pubs/PPP/PPP-51.pdf>.
We are at the point of the season that a forage producer has to seriously ask whether the cool-season grass and legume forages intended for a late March or April seeding should be kept in the seed bag until August 2002 or late March/April 2003.
What stresses increase with a late seeding?
If seed is on hand and you do delay seeding, store seed in a good environment. High heat and high humidity are not conducive to good long-term seed quality. You should contact the seed vendor to see if he has good seed storage facilities if you do not. Seed tags should be checked to see if legume seed was preinoculated with rhizhobia and when the expiration date occurs. Preinoculated seed that has expired can be reinoculated at the time of seeding by applying “fresh” inoculant. Individuals seeding “friendly endophyte” tall fescue should also be advised that this endophyte dies with time in storage, as does the unfriendly endophyte responsible for fescue toxicosis.
After a weekend of wonderful drying weather, the rainfall that began again Monday morning threatens to delay corn planting throughout the state even further. One of the obvious decisions that farmers need to be considering as planting is further delayed is whether or when to switch from their normal “full season” hybrid maturities to earlier maturity ones in response to the ever-shortening growing season.
That decision is somewhat murky because the definitions for “full season” maturity vary from one farmer to the next. The definitions that I use are listed in Table 1 on the geographic basis of USDA Crop Reporting Districts. The hybrid maturities are described both in terms of ‘comparative relative maturity’ (CRM) and growing degree days (GDDs). As a reference point, the CRM values and associated GDDs correspond most closely with those used with Pioneer™ brand hybrids.
Some will look at the hybrid maturity values in Table 1 and wonder where on earth I come up with some of the definitions for “full season” maturities for parts of the state. In particular, growers in the northern and east central areas of Indiana often plant hybrids with later maturities than those listed in Table 1 in an attempt to capture higher yields with fuller season hybrids. Such later maturities, though, ‘push the envelope’ in terms of their riskiness for maturing safely before a typically-occurring first fall frost. The values listed in the table more closely address a goal with normal planting dates for grain maturation to occur about two to three weeks prior to the average first fall frost (32°F).
By contrast, some growers in southern Indiana may wonder why the hybrid maturities listed in Table 1 are so ‘early’. Indeed, the available GDDs in southern Indiana would allow the use of hybrid maturities that are five to ten days CRM later than what are listed in the table. Over the years, though, growers have discovered that the earlier maturity hybrids will yield as well as the true ‘full-season’ hybrids, but will dry down earlier in the season.
Given the “full season” maturities listed in Table 1 for normal late April – early May plantings, when should earlier maturities be substituted as planting is delayed? Some years ago, Peter Thomison (Ohio State Univ.) and I collaborated on field research that investigated the effects of delayed planting on the GDD needs of different hybrid maturities.
That research, conducted by former graduate students Greg Brown and Tony Halter, indicated that delayed planting decreases hybrid GDD requirements from planting to maturity. In fact, as planting is delayed beyond about May 1, the number of GDDs from planting to kernel black layer (physiological maturity) decreases by about 6.8 GDDs per day of delayed planting. The consequence of this research is that adapted “full season” maturities can be planted much later than previously thought and still mature safely prior to the average date of a killing freeze in the fall.
Based on our research, we can more accurately determine when to “pull the trigger” for switching from fuller season to earlier season hybrid maturities with delayed plantings. The good news is that hybrid maturities adapted for Indiana (Table 1) will mature safely when planted throughout most of the month of May. Once planting is delayed further, the ever-shortening growing season (measured by estimated available GDD) finally exceeds the fuller-season hybrids’ abilities to adjust their developmental GDD needs.
Table 2 lists the hybrid relative maturity values that should safely mature prior to a fall frost (32°F) when planted from late May through early June in Indiana. These ‘safe’ hybrid maturities were estimated for the various Crop Reporting Districts according to the available length of growing season for each planting period, the average date of the first fall frost (32°F), and adjustments based on the hybrid GDD response to delayed planting.
BEAR IN MIND that these estimates of safe hybrid maturities are aimed at achieving grain maturation no later than the average (50% probability) date of the first light freeze (32°F) in the fall. Such frost events normally injure corn leaves, but do not kill the corn plant. These dates generally range from the first through the third weeks of October from northern to southern Indiana. Also recognize that northern Indiana farmers who already ‘push the envelope’ by planting 113-day CRM maturities or greater should begin switching to more adapted maturities of about 109-day CRM maturities by about May 20.
Hybrid maturity ratings have always been a sort of mystery to farmers and consultants alike. One factor that contributes to the mystery is that your definition of ‘maturity’ may not be the same as my definition.
Agronomists usually refer to ‘maturity’ as that point in time when maximum weight per kernel has occurred. The usual term for this is ‘physiological maturity’ and is often associated with the development of the black layer at the tip of the mature kernel. Grain moisture content at the onset of physiological maturity ranges between 25 and 35 percent.
Another definition of ‘maturity’ is that point in time after physiological maturity when a hybrid can be safely harvested with minimal harvest loss, either by kernel loss or kernel damage. My term for this is ‘harvest maturity’ and is usually associated with a grain moisture content of around 25 percent.
The traditional method for rating hybrid maturities (i.e., ‘days to maturity’) is based on comparisons among hybrids near the time of ‘harvest maturity’, with the assumption that grain moisture loss in the field is about 0.5 percentage point per day. For example, if the grain moisture content of a new hybrid is two percentage points wetter than that of a ‘standard’ hybrid with an assigned relative maturity value of 110, the new hybrid is assigned a relative maturity value of 114.
Historically, folks have added the word ‘days’ to this hybrid maturity rating value (i.e., 114-day hybrid), but it is important to recognize that this value does not refer to actual calendar time between planting and harvest maturity. Consequently, traditional relative maturity ratings of hybrids are of little help in determining whether a hybrid will safely mature before a killing fall frost.
The other common method for assigning relative hybrid maturities is based on the thermal time between planting and physiological maturity. Terms used to describe thermal time include ‘growing degree days’ (GDD), ‘growing degree units’ (GDU) and ‘heat units’ (HU). GDD values represent the amount of heat accumulated over a period of time. Since this method depends on actual measurement of thermal time, there is no need to compare hybrids in order to assign maturity rating values. Common values for such maturity ratings range from about 2500 (earlier maturity hybrids) to 2800 (later maturity) for hybrids commonly grown in Indiana.
The relationship between these two maturity rating methods is close but not always exact because each is based on a different definition of ‘maturity’, the difference being the time period between physiological and harvest maturity. If hybrids vary for rates of grain moisture loss, their comparative maturity values may differ between the two maturity rating methods. Neither method is perfect, either, because of the influences of climatic conditions and plant stress on the grain maturation process.
Another ‘fly in the ointment’ is the fact that there are no agreed upon standards within the seed industry for the application of either method for assigning relative hybrid maturities. Minor differences in methodologies among seed companies often result in the farmer’s frustration in comparing maturity values among different brands of hybrids.
Unfortunately, the lack of industry standardization can make it difficult for growers who need to make a hybrid maturity decision for late planting situations based on remaining GDD availability (see my related article). Fortunately, one of the larger seed corn companies rates their hybrids according to GDD accumulations from planting to kernel black layer. Consequently, we can describe the relationship between their relative hybrid maturity ratings and growing degree days to kernel black layer (Figure 1.)
One can use this relationship to estimate the GDDs from planting to black layer for other companies’ hybrids of similar relative maturities. For example, if the relative maturity of a hybrid is comparable to a 112-day (CRM) Pioneer™ brand hybrid maturity, then Figure 1 suggests that the GDDs from planting to black layer would be approximately 2700. With this estimate in hand, growers can then begin the process of determining safe hybrid maturities for late planting situations.
Don’t forget, this and other timely information about corn can be viewed at the Chat ‘n Chew Café on the World Wide Web at <http://www.kingcorn.org/cafe>. For other information about corn, take a look at the Corn Growers’ Guidebook on the World Wide Web at <http://www.kingcorn.org/>.
As the calendar days in May pass with very little of the corn or soybeans planted in Indiana, the temptation mounts to do tillage or planting operations when soil conditions aren’t fit. The planting that has been completed thus far has been on fields that dried faster earlier, so the waiting now becomes even more challenging. Does the recommendation for acceptable soil moistures for field operations change between late April and mid-May or late May? In short, the answer is “No”. Here are ten guidelines on how to avoid or minimize soil compaction in a wet spring.
The 2002 Forage Day will be held on June 13 at the Milco Dairy Farm near Newcastle, Indiana. The Milco Dairy Farm is operated by Nicco and Millie Niessen. This year’s Forage Day is sponsored by the Purdue Cooperative Extension Service, the Indiana Forage Council, and the Indiana Professional Dairy Producers. Forage Day combines educational workshops with equipment demonstrations. Presentations cover various topics in the production, utilization and marketing of forages. Forage Day is the only annual event in the state where one can see a live demonstration of harvesting equipment. Contact Keith Johnson with questions (765) 494-4800 or e-mail: firstname.lastname@example.org
“Research Update: Aeration’s Effects on Permanent Pasture and Hay Fields” – Brad Shelton, Purdue Agronomy Graduate Student
“Managing Soil Fertility in the Alfalfa Field” – Kess Berg, Purdue Agronomy Graduate Student
“Managing Insects in Your Forage Crops” – Larry Bledsoe, Purdue Entomology Department
“Boots, Buds, and Blooms…What Do they Mean to Your Livestock?” – Dr. Mark Sulc, Ohio State Forage Specialist
Hay Quality Contest