Early Detection and Treatment Critical in Reniform Nematode Control, Expert Says

	Auburn, Sept. 10, 2002 --- More than a decade ago, a low-yielding cotton field prompted 
one baffled west Alabama cotton producer to ask a question.
 	“My family has been growing cotton in this field for more than 100 years, so why am I 
picking almost 400 pounds less cotton?” he asked, pointing out that he had done as much as, if 
not more than, earlier generations to maintain the field’s fertility.
	The question was directed to Dr. Bill Gazaway, an Alabama Extension plant pathologist, 
who offered a simple, straightforward answer: reniform nematodes, a problem earlier generations 
likely had never encountered in all the years they farmed the field.
	First detected in Alabama more than four decades ago, reniform nematodes have spread 
to all of the major cotton-producing areas in the state and are now considered the state’s most 
destructive nematode.  While most of the problems associated with nematodes were originally 
confined to south and central Alabama, serious outbreaks have occurred in the Tennessee Valley 
of North Alabama since 1994.
“Their spread throughout the state shouldn’t surprise anyone,” Gazaway says, 
“considering their ability to thrive in the soil, survive under adverse conditions, and reproduce on 
a wide variety of crop and weed hosts.”
Nematodes can be spread by flooding, contaminated cotton seeds and even animals, 
though contamination most often occurs when farm equipment is carried from infested fields into 
uncontaminated ones. That is why Gazaway and other experts recommend washing or steaming 
equipment before it is used in “clean” fields.  
Gazaway retired from the Alabama Extension System in 1999, but his retirement has 
provided no harbor for the nematodes.  He continues to conduct research on the pest and to 
advise farmers on what they can do to contain their damage.
Based on 20 years of close observation of reniform nematodes, Gazaway stresses that 
early detection and treatment are critical factors in controlling the pest. 
	The first rule of thumb, he says, is to never underestimate the nematode’s adaptability.	
	“The reason they spread so easily is because of their unique ability to survive in dry soils 
and dry weather conditions,” Gazaway says.  “They can survive in a clod of completely dried dirt 
for six months.  All it takes is a little moisture for them to become active again.” 
	“Very few other types of nematodes survive under these conditions.”
	Second, but perhaps most important of all, is getting a handle on the nematodes before 
they damage cotton seedlings. 
	“Reniform nematodes begin feeding on the roots of young cotton seedlings soon after the 
seed germinates,” Gazaway says.  “It’s very important to protect cotton seedlings from 
nematodes at the point of emergence, say from six to eight weeks.”
	“That’s the critical time.  Control measures used later in the crop seasons to combat 
heavy infestations are also important, but you really want to suppress populations long enough 
get the plants with established root systems off and growing.”
	Gazaway often describes reniform nematodes as a stress pathogen – and for good 
reason.
	 “Reniform nematodes devitalize the root system’s ability to take up water and nutrients,” 
he says.  “Cotton plants can do pretty well so long as moisture and other growing conditions are 
adequate.  But as soon as adverse weather conditions set in, that’s when these nematodes really 
add the kick.”
	This, Gazaway says, is another reason why it is vital for producers to sample their fields 
for signs of the nematodes and, if the sample turns up positive, to treat for nematodes early in the 
season to reduce pests’ changes of getting a sufficient toehold on the plants’ root systems.