"Having the soil checked for the presence of nematodes still remains the best method to find out if plant nematodes were a problem for crops, gardens or flowers this past year," Overstreet says, adding, "Nematode levels are still high this time of year, so they are easy to identify in the soil."
Because of that, Overstreet says November should be a good month to have fields, gardens or flower beds checked for plant nematode problems.
"Since heavy rainfall across the state has soils fairly wet, samples should be collected as soon as you can get back into the fields or gardens," the LSU AgCenter specialist advises. "Often it is so dry in September and October that it is extremely difficult to collect good nematode samples, but that shouldn't be the case now."
Overstreet says many fields have a previous history of some type of nematode problem. But he also says nematode populations can change rapidly throughout the year.
"Cropping patterns greatly affect nematode levels - especially depending on whether susceptible, resistant or immune crops are used," he explains.
There also can be changes in the types of nematodes found within a field, according to Overstreet.
"Two types of nematodes, the reniform and soybean cyst nematode, have been introduced into the state within the past 75 years and continue to spread from field to field," he says, adding, "Root-knot nematodes can be spread easily in gardens and flower beds by either contaminated equipment or transplants."
The expert says nematode samples should be collected by a method similar to those used for general soil testing, and he offers these tips:
-Break fields down into areas with similar soils and cropping patterns.
-Collect one sample from your garden or flower beds unless you have several different locations.
-The smaller the area represented, the more accurate the sample will be.
-Break large fields down into 15- to 20-acre blocks and collect a sample from each block.
-Soil should be collected using a soil probe, shovel or trowel down to a depth of 6-8 inches.
-Try to collect from 10-20 spots in the field or garden, so that the field is well represented by the combined sample.
-About a pint of soil should then be placed in a plastic bag (quart freezer bags work best) for mailing.
-A nematode assay sheet should be filled out for the samples to provide specific information about the sample, its history and future plans. The sheets can be obtained from your parish LSU AgCenter Extension Service office.
The local LSU AgCenter county agent can then mail the sample to the Nematode Advisory Service - where the sample will be processed and the nematodes extracted and counted. A result form will be mailed back to the individual who sent the samples with nematode types, numbers and any necessary management recommendations.