Bob Kemerait
Early-Season Disease and Nematode Threats, You Get One Chance
When asked about their disease management program, growers will likely focus on the fungicides that
they will use over the course of a season to protect their crop from leaf spot, white mold, and possibly a
few other diseases such as Rhizoctonia limb rot. Obviously, these diseases can take tremendous yields
away from a grower. Using the right product at the right time is critical for a successful growing season.
However, essential decisions must be made very early in the season, often at the time of planting, that
have impact on the yield potential for the remainder of the season. The following is a “laundry list” of
actions that a grower MUST consider in order to protect the seeds and seedlings.
- Peanut seeds can be easily damaged by a number of fungal pathogens that can kill germination
and also emerging seedlings. These include Aspergillus niger, Aspergillus flavus, Rhizopus, and
others. Protecting the seeds from seedling diseases is a three-step process. The first step,
where possible, is to plant high-quality seed with a strong, documented, germination rate. It is
difficult, if not impossible to recover when poor-quality seed is planted. The second step is to
plant under conditions that result in rapid, uniform germination and vigorous growth. Cool, and
wet soils, or planting just ahead of a cold rain, can slow germination and plant growth. Such
gives the fungal pathogens, “the bad guys”, the chances to play catch-up with the peanut seeds
and seedlings, infect and then damage them. Planting in hot and dry soils not only delays
germination, but also increases risk to diseases like Aspergillus crown rot and Diplodia collar rot.
The third step is to ensure that the seeds are well-protected with a fungicide seed treatment.
Today, most of the peanut seed is treated with either Rancona from UPI or Dynasty PD from
Syngenta Crop Protection. Though these seed treatments are different, each contains a mixture
of three fungicides. (Note: In 2020, Rancona has been more effective in management of
Aspergillus flavus that has been affecting seed germination.) - Protecting seeds and seedlings from death and loss of vigor is an important task for growers. In
addition to the steps outlined above, growers can use in-furrow applications to compliment the
performance of seed treatments and to further protect against seedling diseases. Where highquality seed that has been treated with a fungicide is planted into warm, moist soils, there may
be no need for use of an in-furrow fungicide. However, where the quality of the seed is in
question, especially if Dynasty PD was used, then a grower should consider use of an in-furrow
product to further compliment the seed treatment. Where Velum Total has been used for
nematode control, no further in-furrow product is needed to control seedling diseases. Where
Dynasty PD was used on the seed, Proline will be a better option than Abound or other
azoxystrobin products. - Reducing risk to tomato spotted wilt disease is extremely important. Once the furrow is closed,
there is nothing else that can be done to protect the crop from this disease that is vectored by
thrips. Growers should consult Peanut Rx 2020 to determine the best ways to manage spotted
wilt. Variety, planting date, seeding rate, selection of thrips control product, especially Thimet,
and other factors can affect a crop’s risk to this disease. - Peanut root-knot nematodes can be devastating to a peanut crop, especially in areas of
southwestern Georgia and where fields are planted too often to peanuts. Peanut root-knot
nematodes are especially problematic in sandier areas of a field. The best way to determine
that root-knot nematodes are a problem in a field is by taking soil samples at harvest, or by
examining roots and pods of affected plants. Areas in a field, especially sandier areas of a field,
where plants remain small and stunted despite adequate moisture and soil fertility, may be
affected by nematodes. (Low soil pH, zinc toxicity, and herbicide injury are other reasons for
poor growth early in the season.) Growers can minimize damage from peanut root-knot
nematodes by a) planting a variety like Tif NV HiOL, by fumigating with Telone II, or by using
Velum Total (18 fl oz/A) or AgLogic 15G (7 lb/A) in-furrow at planting. - Lastly, use of in-furrow products can reduce not only seedling diseases and damage from
nematodes, but also damage from CBR and, to a lesser degree, white mold. For management of
CBR, use of Proline (5.7 fl oz/A, in-furrow) is recommended.
Growers have the opportunity prior to, and at planting time to manage important problems that include
seedling diseases and seed rots, nematodes, Tomato spotted wilt, CBR, and even white mold. Growers
are encouraged to carefully consider their options and to make informed decisions to best protect their
peanut crop at this critical part of the season.