Field experiments were conducted in 1999, 2000, and 2001 to investigate PRE and POST applications of halosulfuron-methyl in combination with clomazone plus ethalfluralin for control of several broadleaf weeds in cucumber and pumpkin. Halosulfuron was applied PRE or POST to cucumber and pumpkin at 9, 18, and 27 g ai/ha in combination with a PRE application of clomazone at 175 g ai/ha plus ethalfluralin at 630 g ai/ha. Halosulfuron applied POST at 27 g/ha in combination with clomazone plus ethalfluralin controlled weed species greater than 62%. Smooth pigweed control by addition of halosulfuron at 27 g/ha PRE or POST was greater than 88%, and common ragweed control was greater than 78% PRE and 88% POST, but control of ivyleaf morningglory and tall morningglory was 43 to 67% PRE and 62 to 76% POST. Cucumber injury with addition of halosulfuron did not exceed 13% PRE or POST, but pumpkin was injured as much as 43% with addition of halosulfuron PRE and 27% by POST applications. In a separate study without clomazone plus ethalfluralin PRE, smooth pigweed up to 13 cm tall was controlled 83% by halosulfuron at 27 g/ha in 2000, but rapidly growing smooth pigweed 15 to 40 cm tall was controlled only 58% in 2001. Cucumber and pumpkin yields were not affected by halosulfuron rate but were higher than yields produced by cucumber and pumpkin treated with only the mixture of clomazone plus ethalfluralin. In these studies, cucumber and pumpkin were tolerant to halosulfuron at 9 to 27 g/ha PRE or POST, making this herbicide acceptable for use in combination with clomazone and ethalfluralin for controlling several common weed species.
Nomenclature: Clomazone; ethalfluralin; halosulfuron; common ragweed, Ambrosia artemisiifolia (L.); ivyleaf morningglory, Ipomoea hederacea (L.) Jacq; smooth pigweed, Amaranthus hybridus L; tall morningglory, Ipomoea purpurea (L.) Roth; cucumber, Cucumis sativus (L.) ‘Dasher II’; pumpkin, Cucurbita maxima (Duch.) ‘Appalachian’.