On-farm cotton nematode control studies were established to evaluate several nematicides, rates, and application methods for control of Meloidogyne incognita in one location and Hoplolaimus columbus in another. Generally, treatments containing Telone II soil fumigant (1,3 dichorapropene) at 3 to 5 gal/A gave a better control/yield response than non-fumigants. However, non-fumigants such as Temik 15G (aldicarb), Nemacur 15G (phenamiphos), Furadan 15G (carbofuran) and uc 70667 IOG yielded significantly higher than controls- Highest yield in both locations occurred with the combination treatment (Telone 11 (3 gal/A row basis, injected at planting) plus Temik 15G 13.5 lbs/A row basis, in-furrow). This treatment shows promise for replacement of ethylene dibromide (EDB).

Very little or no phytotoxicity was observed where Telone II was injected 12 inches under row at planting at 3 and 5 gal/A. No differences were noted between application methods for non fumigants.

A study of different levels of chemical control in various combinations with different levels of variety tolerance or resistance to the root-knot-Fusarium wilt disease complex was conducted in an irrigated field with low to moderate root-knot and low incidence of F. oxysporium f. sp. vasinfectum. Growth and yield increased with level of treatment, but did not correlate with accepted tolerance grouping of varieties. Maximum treatment (Telone 11 - 5 gal/A) gave highest yields for all varieties, including the variety considered most "resistant" (McNair 235). Highest yield at each treatment level was recorded with the "least tolerant" variety (Stoneville 825). Further study is needed where root-knot and wilt incidence is greater.