What to do now to reduce nematode and disease problems this spring

In Southeast Farm Press

By Bob Kemerait, University of Georgia plant pathologist

Winter months are for many farmers the “off season” for row crop disease management.  This occurs not only because cotton, corn, soybeans, peanuts and most other agronomic crops are out of the field, but also because cold weather and soil temperatures affect the pathogens or disease-causing agents.

Perhaps of greatest interest to growers is the survival of plant-parasitic nematodes, such as the southern root-knot nematodes affecting cotton, corn and soybeans, the renifom nematodes affecting soybeans and cotton and the peanut root-knot nematode.  These nematodes cause significant damage to southern row crops; all feed exclusively on living hosts. 

Until the crop is destroyed at harvest, or killed by freezing temperatures, nematodes will continue to feed.  Cotton producers should take careful note of such.  Even if cotton stalks are “mowed” following harvest, the roots will remain alive and thus a food source until killed by freezing temperatures.

Although the nematodes do no more damage to the cotton crop once it is harvested, continued feeding following harvest may allow for increase of the population for the next season.  Under optimum conditions, root-knot nematodes may complete a life cycle, from egg to an adult female that can produce eggs, in 20 days.  Hence, if cotton is harvested in early October, but not killed by cold weather until mid-December, the possibility exists that two more complete generations of nematodes will be present in the field.  If stalks are destroyed earlier, then the increase in nematode population will be reduced.

The growth and development of the plan-parasitic nematodes is affected by soil temperature.  Once soil temperatures drop below 65°F, the nematodes will become inactive and likely stop feeding.  Once soil temperatures drop below 50°F, growth and development of the nematodes will stop.  Root-knot nematodes will survive during the winter as egg; others, such as reniform nematodes, survive as eggs, juveniles and pre-adults.  Populations of plant-parasitic nematodes can be reduced by planting non-host crops (crop rotation), planting nematode-resistant varieties, and by managing weeds that are also hosts to the nematodes.  As soils warm in the spring, nematodes will become active once again.

Read the rest of the story in Southeast Farm Press.

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