Hockley, Cochran, Lamb Counties
The root-knot nematode
(Meloidogyne incognita) is widely distributed throughout much of the southern
High Plains and is capable of causing significant yield loss. Since 1996 I have
soil sampled IPM Program scouting fields in Hockley and Cochran Counties for
root-knot nematodes. Eighty percent of all samples have contained a damaging
level of root-knot. The remaining 20%
are fields which are routinely rotated with another crop such as peanuts. Symptoms
associated with root-knot damage consist of poor vigor, stunting, yellowing of
leaves and wilting. A characteristic feature of root-knot nematodes is the
formation of galls that occur on the roots.
In addition, infected plants may
exhibit nutrient deficiency-like symptoms, as M. incognita females feed on
cotton roots and disrupt the plant’s ability to acquire water and nutrients.
The amount of damage observed is more severe when nematode populations are
high. Furthermore, this damage may be enhanced by other stresses such as
drought or herbicide injury.
Several cotton varieties with
partial resistance to root-knot nematodes are now available. The varieties
Fibermax 2011GT, Deltapine 174RF, and Phytogen 367WRF have been evaluated and
are known to have partial resistance and/or improved tolerance. Field studies conducted in 2013
indicate that other varieties such as Deltapine 1454RN B2RF and Stoneville
4946GLB2 also possess root-knot resistance and yield similar to the
aforementioned varieties. Furthermore, Phytogen 417WRF greatly reduces nematode
reproduction and may be an option for fields that are severely infested.
Second stage juveniles of the southern root-knot
nematode.
Crop
rotation with a non-host is a good way to reduce nematode densities, but M.
incognita populations can build up quickly the next year cotton is planted.
With the loss of Temik 15G, chemical management options for nematodes are
limited. Performance of the seed treatment nematicides, such as Acceleron-N,
the Aeris Seed Applied System and Avicta Complete Cotton are somewhat
inconsistent and should not be used as stand-alone in high-risk fields. A new
product called Velum Total from Bayer has been tested as an in-furrow applied
liquid. This product will be available for demonstration purposes in 2015. Foliar
applications of Vydate® are labeled for use in cotton; however, research is
currently being conducted evaluating usage rates and application timings in
order to maximize efficacy and increase profitability. Research I have
conducted here in Hockley and Cochran Counties has shown that Vydate is most
effective when applied soon after emergence when 2-3 true leaves are present at
a 17 ounce broadcast rate per acre. This would be followed by another 17 ounce
application 7 days later. A band application can be made in order to save on
chemical cost as long as a uniform application can be made. The soil fumigant
Telone II has been used to successfully manage nematodes in the High Plains;
however, usage is limited. This is due to availability and cost of the product,
as well as constraints that affect application (i.e. specialized equipment and
adequate soil moisture at the time of application). Other new and even some
older products are being tested for efficacy against cotton nematodes, but data
is limited at this time. Information from these and other studies will be made
available as they become available.
Root-knot nematode damage on cotton roots.
