Economics of Root-Knot Nematode Control on Cotton by DBCP Fumigant on the Texas High Plains.

21 -+ 1 C with a 16-hr photoperiod for 9-14 days. Duration of a test was from start of seed preparation to termination. Seedling growth was determined by fresh weight of roots (blotted to remove moisture), length of tap root, length of longest lateral root, and total number of lateral roots. An estimate of nematode penetration was made by determining the number of specimens which emerged f r o m roo t s y s t e m s incubated ind iv idua l ly for 1 week in 100 ml of continuously aerated deionized water. In eight tests, an average of 7% of the inoculum was recovered. Growth reduction of the inoculated root system (when compared to the uninoculated system) was taken as the criterion for a successful test system. Consistent responses to l e s i o n n e m a t o d e s for all four roo t measurements could be obtained using a total of 8000 or 10,000 nematodes/seedling applied over 5 days in five inoculations. Since significant reductions in growth were apparent using all four parameters (Table 1), sacrifice of the plant to obtain root weight data is not necessary. Research Notes 69