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Should you use in-furrow fungicides?

Blessed with good planting weather the last three season, cotton farmers might believe that in-furrow fungicides are no longer necessary. Cutting in-furrow fungicides arbitrarily, however, could be a mistake for many cotton producers.

The saying is “People don't plan to fail, they just fail to plan.” Another season is fast approaching and the question of the day is: Where or what can I cut out of my cotton production program without sacrificing yield? The past three seasons have taken their toll and combined with depressed commodity prices, producers are looking to cut costs.

While the overall seasons have not been favorable in the past three years, we were blessed with good planting weather. That, I am sure, has given producers the impression that in-furrow fungicides are no longer necessary. That is not necessarily true.

While in-furrow fungicides are not always needed, producers should not arbitrarily cut in-furrow fungicides without first assessing the situation.

A productive season begins with a good stand — defined as two to three uniformly spaced plants per foot of row. Seedling disease pathogens, namely rhizoctonia, fusarium, and pythium, if not controlled, will compromise a good stand by killing seed and seedlings.

In addition to reductions from seedling disease, producers may jeopardize stands by cutting seeding rates of transgenic cottons in an effort to save on technology fees.

So what can a producer do to get off on the right foot? Getting off to a good start requires that a producer consider several factors before planting. Seed germination and establishment is affected by seed quality, soil temperature, soil moisture, and field history.

First and foremost, producers should use only high-quality treated seed. High-quality seed will have a percent germination of at least 80 percent and a cold germination (cool test) of 60 percent or higher.

In most cases, poor-quality seed is just as expensive as high-quality seed, but the consequences associated with poor-quality seed can be devastating.

Replanting (if you can get back into the field) costs producers time and money. Research has demonstrated that even in the absence of seedling disease, fields planted with poor-quality seed are typically not as high-yielding as fields planted with high-quality seed. If producers have to use poor-quality seed, they should plant it when the threat of seedling disease is low — usually mid-May — and consider using an in-furrow fungicide.

Knowing what conditions favor seedling disease and avoiding those scenarios will reduce the threat of seedling disease without costing the producer a dime. Seedling disease is favored by soil temperatures less than 65 degrees F and high soil moisture.

Producers should not place a seed in the ground until the 4-inch soil temperature has been 65 degrees F (preferably higher) for at least four days and there is no threat of a cold front or excessive moisture. Soil moisture should be adequate to allow planters to place seed at the desired depth and close the furrow around the seed, allowing good soil-to-seed contact.

Producers can monitor temperatures with a soil thermometer. Readings should be taken during the morning (8 to 9 a.m.). Readings taken during mid-day or afternoon are usually higher than the average and will be misleading.

Historically, the best-yielding cotton in Louisiana is planted during the first week of May. In general, the risks associated with seedling diseases are greater for early-planted (before May) cotton than for cotton planted late.

Planting too late may also create other problems. Therefore, select a planting date with the whole picture in mind: adequate moisture, weed management, insect management, disease management, etc.

There are no magical formulas or dates to determine if seedling disease will be a problem. The objective is to minimize the risk associated with seedling disease and other problems. Unfortunately, producers can do everything right and still get burned.

Field history is another consideration. Problematic fields should be avoided. However, if these fields must be planted to cotton, the producer should use an in-furrow fungicide and plant the fields during early to mid-May.

It is important to determine which pathogens are associated with each problem field. Rhizoctonia is the predominant seedling disease pathogen in Louisiana; however, pythium can also be a problem at times.

Knowing which pathogens are associated with their fields will dictate which in-furrow product is needed and might save the producer some money. Products vary in price from around $5 to $20 or more per acre. Some products give protection against both pathogens while other products only provide protection against rhizoctonia or pythium.

Most of the time you will always need a product for rhizoctonia, but the need to manage pythium will vary. If pythium is not a problem, producers can cut in-furrow costs by several dollars per acre. However, determine that pythium is not a problem before arbitrarily eliminating the in-furrow for this pathogen.

Using high-quality, treated seed and planting when conditions are favorable for seed germination and seedling establishment are the best defenses against seedling disease. However, producers are not always able to follow these guidelines. That is when in-furrow fungicides should be considered.

In-furrow fungicides are not bullet proof. Sometimes the best decision is to not plant. In-furrow fungicides will probably not hold up during extreme environmental conditions (excessive cold and/or excessive moisture) or when poor-quality seed is planted during adverse weather or planted in fields with histories of seedling disease.

Under these conditions, in-furrow fungicides will probably make the decision to replant more difficult. In-furrows should be considered when soil temperatures are slightly below 65 degrees F or when there is a threat of a cold front or excessive rain, conditions most likely to occur during April.

Additional information about in-furrow fungicides can be found on the Internet at:

A variety of in-furrow fungicides are available. Rates vary from a few fluid ounces to several quarts and from 5 to 10 pounds per acre. In most situations either granules or liquids will provide satisfactory results. However, liquids offer more options. Tank-mixing liquids (a rhizoctonia product and pythium product) gives the producer more control over the rates for each pathogen. For example, a high rate of a rhizoctonia product and a low rate of a pythium product may be used. This is not an option with a granule formulation; we are limited to a high or low rate for both products.

To summarize:

  1. Purchase high-quality treated seed.
  2. Plant when conditions are favorable for seed germination and stand establishment.
  3. Identify problem fields and avoid them if possible.
  4. If you are forced to plant in problem areas, identify the source of the problem and take appropriate action.

Boyd Padgett is a research/Extension pathologist with the LSU Agricultural Center.

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