ECONOMIC IMPORTANCE OF 1,3-DICHLOROPROPENE OR FENAMIPHOS TO MANAGE MELOIDOGYNE-JAVANICA IN FLORIDA TOBACCO

Twelve tobacco (Nicotiana tabacum L.) nematicide field trials were con ducted over ten years in north-central Florida, U.S.A., on sites conta ining fine sandy soil. In each of these trials, 1,3-dichloropropene (1 ,3-D), fenamiphos 3 SC and a control were utilized. The 1,3-D treatmen ts were applied with a single chisel in the row at rates between 68 an d 102 kg a.i./ha. Fenamiphos was applied broadcast at 6.7 kg a.i. in 1 85 L water/ha and double disc-incorporated. Plots were two rows wide ( 1.12 m wide/row) and 6.1 m long. Tests were arranged in a randomized c omplete block design with six replicates. Tobacco leaves were harveste d 34 times upon maturity and cured weights recorded. Root-gall index r atings were made at or near final harvest from four plants in each plo t and rated on a 0-4 scale where 0 = 0 and 4 > 76% of the root system galled. Compared to untreated controls, 1,3-D treatments increased yie ld of cured tobacco by 943 kg/ha providing added gross average value o f $3134 (U.S.)/ha at average prices paid to Florida growers in 1995. A verage cured yield increase of tobacco in the fenamiphos treatments wa s 646 kg/ha, providing an enhanced value of $1983/ha. Root-gall index ratings averaged 3.2 for the control and 1.0 and 1.1 for the 1,3-D and fenamiphos treatments, respectively. Fenamiphos and 1,3-D have perfor med consistently over the years in the deep sands where tobacco is gro wn in Florida, with 1,3-D providing greater Yield and economic benefit s.