Crop Protection and Management Research Unit How to Identify Nematode Problems and Why It Is Important Richard F. Davis USDA-ARS Crop Protection and Management Research Unit Tifton, GA

What is a Nematode? An Animal Biologically similar to insects Damage is similar to soil-borne diseases Damage plants by physically damaging roots and affecting plant physiology

Annual Losses in Cotton to Nematodes in the U.S. Losses to all nematodes were estimated to be 4.7% in 2005 Typical losses are 10 to 30% Losses can be greater than 50% Losses of 10 to 15 % can easily be overlooked Nematode parasitism often increases losses to fungal diseases (Fusarium wilt and Thielaviopsis black root rot)

The Most Important Nematodes of Cotton in the U.S. Southern root-knot (Meloidogyne incognita) Reniform (Rotylenchulus reniformis) Columbia Lance (Hoplolaimus columbus)

Damaging nematode species are NOT present in all fields

The Damage that Nematodes Cause Physical damage to roots that impairs the plant’s ability to move water and nutrients Root-knot nematodes cause physiological changes in the plant that direct some of the plant’s energy into feeding the nematode rather than making cotton fibers

Symptoms of Nematode Damage Most aboveground symptoms are generic expressions of damage to the roots Stunting Premature wilting Yellowing Apparent nutrient deficiencies Root-knot nematodes cause distinctive galls on the roots

Although damaging nematode species are widespread… Damaging species are not present in all fields Damaging species may be present at levels too low to cause measurable yield loss (below threshold levels) So, the first steps in minimizing losses to nematodes are to identify which nematodes are present identify how many of each damaging species are present To accomplish that, you need to submit a soil sample to a qualified lab

Soil sample must be representative

To get accurate results 1) Soil samples must be protected from drying out 2) Soil samples must be protected from getting too hot Seal samples inside a plastic bag Keep plastic bags out of direct sunlight or high heat Fill out submission forms as completely as possible (include cropping history if asked)

Lab results should tell you which nematodes need to be managed, but… Labs differ in the amount of soil they analyze (100 cm3, 500cm3, pint, etc.) Labs may base conclusions on different action threshold levels, which can vary because of Different extraction methods Geographic location Soil types Other factors Therefore, it is usually best to use a lab familiar with your area, and use the threshold levels provided by the lab that performed the analysis

Don’t be hesitant to.. Ask for more information Ask for more explanation Factor in your own knowledge of specific fields