Telone II® and Temik® Efficacy on Root-knot Nematodes in Cotton

Field studies were conducted at four western Maricopa County commercial sites in 1994 to determine whether Temik 15G® would suppress rootknot nematode at low to moderate populations. Three of the experiments were on Upland D +PL 5415 with the fourth on Pima S-6. Sites were chosen based on preseason sampling with individual field populations ranging from 0.005 (low) 3.6 (high) rootknot nematode juveniles per cubic centimeter (cc) of soil volume. Each study consisted of four treatments with six replications. The following treatments were used at all test sites: (1) Untreated check, (2) 5 lbs. Temik 15G at planting, (3) 5 lbs. Temik 15G at planting, 15 lbs. Temik 15G sidedressed at pinhead square, (4) 5 gal. Telone 11® pre plant. Sampling for thrips and lygus was conducted at all test sites to provide insight regarding yield effects resulting from control of insect versus those due to suppression of nematode. There were no significant yield differences between the untreated check and either Temik treatment. However, significant yield increases were measured with Telone versus all treatments at all locations. Insect pressures were minimal in all cases. Temik 15G did not suppress nematode damage at any population level. Introduction A statewide cotton nematode survey was conducted by Dr. M. McClure (U of A Nematologist) in 1992. The survey results indicated that over 50% of the land utilized for cotton production in Maricopa County had detectable populations of rootknot nematodes. However, rootknot nematode populations and field distributions are highly variable with a variable yield effect due to population density . It is well recognized by cotton producers that nematodes can have a significant yield loss effect if sufficient populations are present and are widely distributed within a field. Telone II® is the only soil fumigant widely used for controlling nematodes on cotton. However, Telone II is expensive (approximately $60 /acre at the recommended 5gal. /acre rate) and requires specialized application equipment. In addition, there are no existing Telone treatment thresholds which could provide the producer information relevant to expected yield loss and/or economic return expectation with the use of Telone. Several field studies conducted across the United States cotton belt have shown Temik® to have a nematode suppression effect at low to moderate populations. A field study conducted on a farm in western Maricopa County in 1993 utilizing the same treatments described above yielded some extremely interesting results (Table 3). 5 lbs. /acre of Temik at planting resulted in approximately a 200 lbs. /acre lint yield increase, roughly matching the yield increase effect of the 5 gal./ acre Telone treatment ( known nematicide). When Temik was applied at 5 lbs. /acre (at planting) and again at 15 lbs. /acre (at pinhead square), yields were increased approximately 450 lbs. lint/acre over the untreated check and approximately 250 lbs. /acre over the Telone treatment. These results were exciting because they suggested nematicidal effects as well as systemic insecticidal activity of Temik. However, insect counts and damage evaluation was not included in the 1993 experiment. Therefore, it was difficult to attribute the resulting yield increases to insect or nematode control separately. The results of the 1993