Agronomy Notes

August, 2002

Contents:

SOYBEANS
WEED CONTROL
RICE
CORN
SOIL AND NUTRIENT MANAGEMENT

 

SOYBEANS
Dr. Alan Blaine

The time frame for making late season management decisions is fast approaching, but do not get in too big a hurry. Worm populations normally do not begin building until early to mid August as is the case with most foliar diseases. If you applied a material such as Dimilin, Quadris, or Topsin M in early July, the residual would carry you 20-25 days at best. That would be about August 1. Most foliar problems do not start cropping up until this time or later, so I think you can see how important a role planting dates and the calendar can play in this decision.

Current labels for these materials suggest applications should be made between the R3 and R5 growth stages. The difference between today and when these labels were developed is that 70 percent of the crop is planted 30 to 40 days earlier and we are not planting Group VI and VII varieties. Earlier planting dates help avoid many late season concerns. They also intensify the need to look hard at the calendar in addition to the stage of crop growth and current growing conditions when making these decisions.

We are currently checking SMART program fields from Tunica to Natchez in the Delta and Blue Mountain to West Point in the hills. Although our verification fields do not represent every field in the state, they do represent a fairly good cross section.

Based on what we are observing and the time of year, you are encouraged to check fields at least once a week from this point on.

Problems that will possibly need attention late summer are primarily threefold 1) stinkbugs 2) late season worm populations, and 3) foliar diseases. However, isolated populations of three cornered alfalfa hoppers, potato leaf hoppers, bean leaf beetles, and grasshoppers are present but very erratic at this time.

Every field is not a candidate for some form of late season management. Problems that are normally observed late in the season are often avoided on early planted/early maturing varieties, one of the advantages of early planting.

Syngenta is currently offering an incentive program for the use of Quadris and Karate Z in soybeans. This program is based on a tank mix of the two products, an excellent combination but not all fields will be candidates.

The recommended stage of application is R3 to R5. In our fields we are hoping to let our Group V's get 7-14 days past the R5 stage before making an application. This should be based on what is in the field at the time and the time of year. When you look at the calendar regarding historic late season problems, it is easy to see that you could possibly spray too early.

Talk to your dealer/Syngenta representative regarding this program. You must leave a check area and apply both materials at the recommended rates to participate. If the application does not give you a yield increase above the untreated area, they will refund the cost of the application.

It is almost a given that stinkbugs will need to be hit. Many may not do it, but odds are it will be necessary in most fields. If it stays dry, foliar diseases will be minimal, but keep in mind, most late season problems do not show up until late summer.

Last week (7/18) we started seeing a lot of bollworm moths, so we may see an outbreak of pod feeders soon. They are probably going to be found more in row beans or beans that are just starting to fruit. We have some excellent options, but when you start finding numerous pests in a field, it makes decisions more difficult and costly.

Current plans are to make this application on all SMART program fields, primarily Group V's since the Group IV's are early. Give some serious consideration to applications needed in late season management. Give high priority to irrigated beans, but other acres may qualify if late season weather contributes to above average growing conditions.

WEED CONTROL
Dr. John Byrd

This summer has been a time to evaluate several potential new herbicides for warm season forages. Outrider from Monsanto is a herbicide that has excellent activity on johnsongrass and nutsedge and outstanding tolerance in bermudagrass and bahiagrass. We've got several experiments throughout the state to evaluate rates of Outrider and combinations of Outrider with other products to broaden the weed control spectrum. We included Plateau in for comparison and don't see near as much injury from Outrider on bermuda or bahiagrass as we see with Plateau. However, the weed control spectrum is much narrower than that of Plateau.

We've got Plateau in an experiment in Clarke county to evaluate lower application rates (1, 2 and 4 oz/A) applied before sprigging hybrid bermudagrass. Our first set of treatments were applied last week with the intention of applying those rates every week until 2 weeks after sprigging. This is an extension of some greenhouse work done earlier this year looking at preemergence control of johnsongrass, broadleaf signalgrass, and crabgrass with these rates of Plateau. The overall objective of this work is to see if lower rates of Plateau could be used safely on sprigged bermudagrass and provide acceptable weed control. This site contained heavy pressure of spiny amaranth, smallflower morningglory, broadleaf signalgrass, crabgrass, and nutsedge. First application was applied to these weeds, with following applications applied after producer applied Roundup. We should have some idea of the activity of Plateau on these weeds postemergence.

Dow and UAP products are being evaluated on general pasture broadleaf weeds. Spiny amaranth was the primary weed at one location, while horsenettle was primary weed at another. I can't see much advantage to "improved" formulations or UAP mixtures in these experiments over the standard 1 quart/A of Grazon P+D or Weedmaster.

Cogongrass has gotten much attention lately. This may partly be due to several state legislators attending a meeting called by Dr. Spell early this summer. Several TV and newspaper articles have followed that meeting in which Dr. Spell called for the formation of a cogongrass taskforce. Our research has revealed nothing new for control, yet. We've been looking at seedhead suppression with several herbicides and growth regulators that are currently registered for turf. My graduate student is in the process of evaluating seed germination and seedling vigor to determine if any treatments impacted this reproductive mechanism. No treatments completely eliminated seedhead production, although there were some treatments that delayed seedhead production. Next year we'll look at treatments more closely timed to seedhead emergence. We've also been looking at sequential applications of lower rates of Roundup for control.

Three or four applications (monthly starting in March) at 1 quart per acre seems to provide better control than 5 quarts per acre applied once in March. However, long-term control can not be evaluated until next season. We've also looked at the effect of application volume on control with a variety of herbicides, including Roundup, Asulox, Arsenal, Select, Touchdown, and Hyvar. Increasing application volume to 80 gpa, in both experiments, decreased cogongrass control with most herbicides, compared to control with lower application volumes (20 or 40 gpa).

Lastly, we had another chance to evaluate the Burch Wet Blade for cogongrass control using a 50% Accord solution applied at 1, 2, or 2.5 gpa following mowing to 12 or 24 inch stubble height. Visual control data shows cogongrass control is better in 24 inch tall stubble than 12 inch, and control is best with a 2 or 2.5 gpa application of the 50% solution.

Cogongrass identification may be an issue for many individuals. Perhaps the fluffy seedheads are the easiest method of positive identification, but even this can cause confusion. There are basically two species along Mississippi highway rights of way with fluffy white seedheads: cogongrass and silver beardgrass. Cogongrass blooms in the spring, usually during late April and early May. Silver beardgrass, by comparison blooms during July and August, so don't confuse the plant blooming on roadsides right now with cogongrass. Another feature of cogongrass is the populations develop in circular patches. You rarely see an individual cogongrass plant. It is not a bunch grass, as is silver beardgrass, fescue, or broomsedge.

RICE
Dr. Joe Street

Crop Situation: In general, the rice crop looks good. Some fields have a little more grass coming through the canopy than we would like to see and this seems to be the year for red rice. The high red rice incidence could be attributed to the cool weather early in the season, which did not let the canopy close as early as usual. With an abundance of rice on the market, it will be critical to produce high quality rice for marketing. Although the price is very low, heading time is not the time to cut costs in protecting the crop.

Stinkbug control: As this is written, the big question is what happened to the stinkbug population. The high populations of stinkbugs that we were seeing in rice in mid July disappeared or were drastically reduced. The stinkbugs have at lease moved lower in the canopy and are not on the heads during the hot part of the day. According to Jim Robbins, entomologist at the Delta Research & Extension Center, there was a combination of factors that contributed to the decline in the stinkbug population. Rain in early July, heading grass around the field that is more attractive than rice, a parasitic Tachinid fly, as well as milo and soybeans, which are still attractive to the stinkbug. These factors may have reduced the number of stinkbugs entering the rice fields. As milo is harvested and soybeans mature, expect stinkbugs to move into the rice. As I have said before, those growers who initiated stinkbug control with an insecticide with residual activity (Karate or Fury) have had less peck damage than those who started with a non-residual insecticide. Apply an insecticide when the grains are filling with milk and starting to turn down and the threshold of 3 stinkbugs per 10 sweeps is reached during the first two weeks of heading or 5 per 10 sweeps two weeks after heading. Much of the older rice is already in the milk stage and perhaps will be fairly mature before the stinkbugs return to threshold levels.

Sheath Blight: Most of the early rice is beyond the stage for sheath blight treatment. If the field is fully headed and sheath blight is below the flag leaf, treatment will probably not be of significant benefit. On the later planted rice, treat only after the threshold of greater than 35 percent is reached and the sheath blight is moving up the plant on susceptible varieties such as Cocodrie or Clearfield. With Wells and Priscilla, a fungicide will generally not return the investment. I have seen a lot of sheath blight but in most fields, it is not moving up the plant and thus, treatment has not been needed.

Smut Control: Cocodrie, Priscilla and Clearfield varieties are susceptible to kernel smut and although we have not had significant smut during the past two years, a preventative fungicide treatment should be considered. Weather conditions during flowering that favor kernel smut are high humidity, light showers, and cooler temperatures of 77 to 86 degrees. Kernel smut is more severe under high fertility conditions and rank growth. It is usually more severe on lighter soils but it can be severe on clay soils.

Blast: Leaf blast has been detected on late-planted Wells in western Bolivar county. Careful scouting should continue on Wells and the Clearfield varieties. Cocodrie and Priscilla are both rated susceptible to blast but no problems have been observed in the field with either variety. Weather will play a very important role in the severity of blast. Optimum conditions for blast development are average daily temperatures of 73 to 86 degrees, prolonged leaf wetness and high humidity. Blast fungicides must be applied as a preventative treatment to protect the heads. If blast symptoms occur on the leaves before heading, two applications of Quadris or Gem may be required. Scout carefully for blast and if symptoms occur treat before the heads are fully emerged.

Harvesting: The best milling yield with Priscilla has been obtained when it was harvested at high moisture and dried slowly. If at all possible, harvest Priscilla before it goes below 16 percent grain moisture. Cocodrie has a wider window for harvesting without reducing milling yield.

CORN
Dr. Erick Larson

Borers Necessitate Early Harvest - High populations of southwestern corn borers in the Delta and northeast MS will certainly cause substantial harvest losses this year if the corn crop is not harvested promptly. Third-generation southwestern corn borers literally cut stalks down by girdling the stalk internally a few inches above ground level. This "girdling" action predisposes stalks to nearly certain lodging, particularly when followed by moderate wind. Girdling activity normally commences about 30 days after egg laying. Since the third generation of southwestern corn borers normally occurs in early August, producers should try to finish corn harvest before labor day weekend.

Grain moisture dockage - Corn may be harvested any time after grain reaches physiological maturity, which occurs at around 30% moisture. However, corn may not be safely stored until considerable moisture loss occurs. Thus, grain elevators discount wet corn to account for drying expenses and moisture weight loss during drying. Moisture dockage schedules between elevators may vary significantly, so thoroughly compare rates. Most schedules discount about 2.5% per each percent moisture above the standard, and may increase as moisture content rises. Water evaporated during drying (shrinkage) accounts for 1.18% of the dockage per each percent moisture. The producer loses this weight regardless of whether they sell wet grain to the elevator, dry it mechanically or let the grain field dry. Thus, a producer should subtract this value from the dockage rate to show their realized or "actual" dockage.

Harvest losses - Harvest losses are just as important as moisture dockage rate in evaluating your harvest timing decision. The longer corn stays in the field, the greater the likelihood of substantial field losses. Factors such as stormy weather and southwestern corn borer damage can cause considerable lodging in unharvested fields. Abundant July rainfall has also promoted morningglory growth in some corn fields, which can greatly inhibit harvest efficiency. Each of these factors may cause substantial field loss, which would considerably outweigh moisture savings. Producers should also consider their harvest capability -- the longer it takes to complete harvest, the earlier you should start harvest. Growers should harvest non-Bt hybrids infested with corn borers, early maturing hybrids, and those possessing below average stalk quality promptly and before other hybrids. Producers should closely check for loss while the combine is harvesting and make adjustments accordingly. Two corn kernels per square foot or one dropped ear per 100 feet of row equals about 1 bushel per acre yield loss. Research generally indicates combine efficiency is best (harvest losses are lowest) when corn grain moisture is about 20-22%. Thus, growers seeking maximum profitability should always strive to finish harvest before grain moisture falls below 15%.

Don't Give Away Corn - Producers selling corn at less than 15% moisture are giving away profit. A producer harvesting 150 Bu./A. corn at 14% moisture is losing $3.54 per acre or $7.08 per acre at 13% moisture (at $2.00/Bu.). This loss is solely from reduced grain weight due to lower moisture content. This moisture weight loss closely approximates the "actual" dockage most elevators charge for high moisture corn. Since corn loses approximately 0.6% per day during the harvest season, begin harvest early enough to guarantee all corn is harvested before it reaches 15%.

Aflatoxin tips - Improper grain handling, particularly with high moisture grain, can quickly promote aflatoxin development after harvest. Wet grain should be immediately dried to below 15% moisture or hauled to an elevator (which will dry the grain). Wet grain should not be stored in trucks, combines, bins or any non-aerated site more than 4-6 hours before beginning drying. These conditions are critical to grain quality, because the fungal growth which causes aflatoxin will escalate to excessive levels very quickly in wet, warm grain. Conversely, fungal growth becomes dormant when grain moisture drops below 15%. Producers should also thoroughly sanitize handling and storage facilities before and during harvest.

SOIL AND NUTRIENT MANAGEMENT
Dr. Larry Oldham

It has rained! Things looked good to me on a swing through the center of the state this week. However, it's not too early to think about the next cropping cycle with corn coming out of the field in the next few weeks.As the crops are harvested, look for problem areas in your fields. If you are using yield monitors, combine those maps with the two oldest remote sensing devices known to agriculture -- your eyes.

At a recent conference, we were told an excellent method a researcher found for a consultant to use to define a soil management zone in a field: ask the farmer. I continue to believe that nothing beats experience.If you are not on a regular soil testing program, this fall is the time to begin! If your results call for lime, look at applying this fall for maximum neutralization of soil acidity.Remember to buy good quality lime, and remember that good quality depends on fineness of grind and purity. The finer grind, the better. The higher the CCE, or Calcium Carbonate Equivalent the better.We had a recent report that someone was promoting their material for its' ability to store well in the turnrow until it could be applied. The ability to sit there has absolutely nothing to do with the value of a liming material, and may instead indicate a poor material for liming. The quarry next to where I grew up sold road gravel which stores well, but is useless for liming.Therefore, pay attention to your fields as to where the crop is coming from, check your soil fertility needs, and lime if needed, using only good quality materials.

Department of Plant and Soil Sciences
Box 9555
Mississippi State, MS 39762

Will McCarty, Ph.D.
Extension Leader

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