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Checklist for Early-Season Disease Control in Peanuts

Checklist for Early-Season Disease Control
Bob Kemerait

Disease and nematode management is a critical component of successful peanut
production; the foundation for achieving success is established even as the seed is closed in
the furrow. Within the next month, the 2018 peanut season will have begun in earnest. In
fact, some peanuts will be planted within the next two weeks.

Management of diseases in our row crops differs significantly from management of insects
and weeds in at least one aspect. When managing insects, we talk about “thresholds”.
When managing weeds, we talk about getting herbicides on them when they are “two inches
or smaller”. When we talk about diseases, we talk about “preventative applications”.
Diseases become increasingly difficult to control once infection has occurred and a disease
is established in a crop. Therefore, “best management practices” often focus on initiating
management programs prior to infection and early in the season. Sometimes referred to as
“The First 40 days,” the time just prior to planting, at the time of, and for the next few weeks
after planting constitute a critical period for the start of disease and nematode management.
Additionally, some “windows of opportunity” for disease and nematode control are only open
early in the season; if missed, the opportunity does not come again.

The degree of urgency for deployment of specific tactics for management of diseases and
nematodes early in the season is largely dependent on three factors. Poor crop rotation
increases populations of pathogens and nematodes in the soil and crop residue. Weather
favorable for disease can make the crop more susceptible to damage and loss. Colder and
wetter soils within the first 40 days slow the germination and development of the peanut
seedlings and increase risk to Rhizoctonia seedling blight and Cylindrocladium black rot.
Hot and dry soils at planting can damage the tender seedling leading to increased severity
of Aspergillus crown rot; warmer soils can also lead to early outbreaks of stem rot (white
mold). Planting more-susceptible, less-resistant varieties increases risk for diseases like
tomato spotted wilt, leaf spot, and root-knot nematodes. Planting varieties with greater
resistance reduces the risk to damage.

Below is a “checklist” of options and opportunities for establishing strong disease and
nematode control for the early part of the season and for laying a foundation that helps to
insure successful control throughout the season. Again the urgency of the deployment of
specific tactics, or combinations of tactics, is based upon the risk to diseases and
nematodes in a field.

Prior to Planting
1. Use Peanut Rx 2018 to assess risk to tomato spotted wilt, white mold and leaf spot in a
field and to develop a plan to reduce the risk, where possible.

2. Carefully consider varieties that are available with increased disease and nematode
resistance and where planting them may be beneficial.

3. Consider what fungicides and nematicides may be needed during the season and insure
the availability of the products. Also, consider what products are likely to provide the
most effective control of diseases and nematodes and if they should be incorporated into
your program.

4. Plan to incorporate debris from a previous crop that could harbor disease-causingpathogens
as early as possible so that it can break down/rot.

5. Where Telone II is to be used, insure that sufficient time is allowed between application
and planting to avoid issues with phytoxicity. Also, insure that soil conditions
(temperature and moisture) are appropriate at time of fumigation.

At Planting
1. Consider conditions at planting (temperature, moisture, weather forecast) to insure that
seeds will germinate rapidly and uniformly and with subsequent vigorous growth to
reduce risk to disease losses.

2. To the best of your ability, insure that seed is of high quality with good germination.

3. Insure that seed has been thoroughly treated with a fungicide seed treatment.

4. Consider the need/potential benefits for use of an in-furrow fungicide to supplement the
seed treatment and to offer further protection for disease like Rhizoctonia seedling blight
and Aspergillus crown rot. In-furrow fungicides are also used as management tools for
Cylindrocladium black rot and early-season white mold.

5. Assess need for use of a nematicide such as Velum Total or AgLogic 15G. If a rootknot-nematode-variety
has not been planted and Telone II not used, then growers may
want to consider these other products. Both Velum Total and AgLogic 15G are effective
in managing nematodes and in controlling thrips. Velum Total also helps to manage
seedling diseases as well.

6. Thimet 20G is not the only product that is effective in the management of early season
thrips on peanut, but it is the only product that reduces risk to tomato spotted wilt. Use
of Thimet 20G is one way growers can reduce their overall risk to this disease.

After Planting

1. Use of irrigation to cool soils may help to reduce threat from Aspergillus crown rot, a
seedling disease, when dry weather and high temperatures affect the early season.

2. Banded applications of Proline over the peanut rows from 3-5 weeks after planting can
help to reduce losses from early season white mold.

3. Growers can also initiate early-season white mold control with broadcast applications of
tebuconazole + chlorothalonil approximately 45 days after planting, or Elatus at
approximately 30 days after planting. Depending on the rate, Priaxor at 40-45 days after
planting may also help in early season white mold control.

4. Growers should begin their leaf spot program within 45 days after planting.
The first part of the season is a critical time for the management of diseases and
nematodes. Growers should take special care to take advantage of the opportunities and
tactics available; successful management early often has impact season long. Failure to
manage diseases and nematodes early in the season certainly will have season-long
implications.