Missouri Cotton News
JUNE 1999

"Root-knot nematodes, attack nearly all crops," Wrather said. "It is important to note that only the `Southern Root-knot Nematode', damages cotton in Missouri."

Al Wrather of the University of Missouri Delta Center, Portageville, MO, said, "MU scientists recently surveyed for cotton parasitic nematodes in Dunklin, New Madrid and Pemiscot counties." These areas produce 98 percent of Missouri's cotton. Southern root-knot nematodes were present in 20% of the fields sampled in New Madrid County, 27% in Pemiscot County, and 43% in Dunklin County. "Symptoms of root-knot infection are easily seen on cotton roots 6-8 weeks after planting and look like galls, or knots, on roots," Wrather stated. "Swellings of root tissues can be found on the cotton taproot and lateral roots. The galls are easier to detect if the cotton plants are carefully dug, not pulled, from the soil."

Management and control techniques include crop rotation with root-knot resistant varieties of soybean and nematicides. "An integrated approach that uses both methods usually is the most effective and profitable," Wrather said. "Strategies that may be practical for one grower may not be feasible for another."

Details about the procedure for sampling are included in the guide. Attention to detail and speed of diagnosis are critical. "Good soil samples that accurately represent nematode populations are essential for prudent management decisions," Wrather said.

Obtain guide sheet G4259, "Cotton Nematodes in Missouri: Your Hidden Enemies," from your local extension center or view it on the World Wide Web at aes.missouri.edu/delta/muguide/g4259.htm

With Roundup, the rules are straight forward- use it over the top through the 4-leaf stage. Afterwards, you must POST-direct Roundup. As long as you are running a directed sprayer- you might as well use a Bladex-type plus MSMA or DSMA. A week after treatment Roundup and Bladex + MSMA look more or less the same. However, three and four weeks after treatment the Bladex-type programs are still holding while new weeds are germinating in Roundup- only programs.

However, if there isn't a height differential, Roundup (or anything else for that matter) works poorly when sprayed at the base of weeds growing in the drill.

Buctril has more over-the-top flexibility than Roundup. Although there is a 60-day preharvest cutoff, Rhone Poulenc brags that Buctril can be sprayed over top all season long. In our research, the rules have differed slightly from Roundup's. If cotton's a solid 6" tall, you have a height differential and your primary weeds are cocklebur and mornin glory- spray Buctril AGAIN and POST- direct later. With Buctril and Roundup there are still situations for Staple. If you have 6", 6-leaf Roundup cotton and no height differential, Staple is your only overtop option. While we've had some success with reduced Staple rates, we continue to see situations where the label rate is needed for adequate weed control. Staple is good on morningglory and velvetleaf, but for heavy cocklebur, teaweed or velvetleaf, use the labeled rate. Check the height restrictions on the weeds- Staple doesn't kill foot-tall stuff.

Staple is a particular benefit to buctril because of Buctril's weaknesses on pigweeds. However, pigweeds have also began challenging Staple. The current wording on the Staple label says that it only suppresses Palmer amaranth. This further supports the labeled rate. Also, we have observed Staple (or ALS) resistant Palmer amaranth at the Delta Center and have field reports of the same. Palmer amaranth is a major problem.

Finally, Staple is also a perfectly good, stand-alone herbicide for early POST sprays. As with Buctril and Roundup, it works best when followed with traditional directed sprays.

With all of the new technology, we see more escaped nutsedge where we remove Cotoran and MSMA. We also see more escaped grass in Buctril and Staple programs since they aren't grass herbicides.

Bladex-type products continue to be a favorite choice for later directed sprays. Their strong fast burn activity combined with just the right amount of residual activity give them a edge over other directed materials. However, this is likely to be the last year that we will be able to use Bladex and Cypro. In anticipation of this, we have been testing Bladex against all other POST-directed herbicides. Yes, Bladex and Cypro products are probably best over the long haul. But in any given year, it's hard to tell one directed product from another on typical weeds. All directed herbicides require a good height differential and all can fry some cotton leaves when you get spray on them. While we've traditionally considered Cotoran a bit expensive (and reserved it for the early directed spray), it's broadcast price is actually a tad less than Roundup. Of course, the addition of MSMA or DSMA will bump the price slightly higher than Roundup, but for the residual activity, it's worth it.

While all of the new cotton weed control technology has been great, the traditional POST-directed sprays have an important place in a weed control program. Buctril, Staple and Roundup-based programs all benefit from traditional POST-directed sprays.

With the wheat harvest in full swing producers will soon be getting their fields ready to plant soybeans. With this small window of time, many farmers are too rushed to collect soil samples and apply lime and/or fertilizer. This may not be a good strategy. Soybeans are a sensitive crop to soil pH and the proper application of lime can increase yields. Low levels of Potassium (K, potash) also limit soybean yield. Both of these problems are easily diagnosed by soil testing. If you tested your soil last fall and followed the fertilizer recommendations you should be in good shape. If you have not, now would be a good time to soil test. The Delta Regional Soils Testing Lab, located at the Delta Center, Portageville, Missouri, is ready to help any way we can. We offer a quick turn around time; samples received today are analyzed tomorrow. Results and recommendations can be phoned, faxed, or e-mailed to you or your fertilizer dealer. If you are in a hurry, bring your soil samples directly to the Delta Center. Our biggest bottleneck is soil drying time; it takes 16 hours to dry a soil sample. However, if we receive a dry sample by 9:00 a.m. we can have results back to you that afternoon. Care must be taken to properly dry a soil sample. Drying temperatures above 105 degrees F give lower readings for K than properly dried samples.