Abstract: Field trials were conducted in 1997 and 1998 at two locations in Israel to evaluate the efficacy of imazapic applied postemergence (POST) to sunflower for broomrape control under irrigated and nonirrigated conditions. Two sequential treatments of imazapic at 1.5 followed by (FB) 3.0, 3.0 FB 4.5, or 4.5 FB 6.0 g ai/ha on sunflower plants 12 ± 3 and 55 ± 5 cm tall, respectively, reduced sunflower broomrape throughout the growing season under irrigated and nonirrigated conditions. Sunflower growth was not affected by imazapic treatments. It was confirmed, in accordance with an earlier report, that when sequential treatments of imazapic included an application at the sunflower inflorescence developmental stage, the herbicide decreased seed yield in proportion to the applied rate.

Nomenclature: Imazapic; broomrape, Orobanche cumana Waller; sunflower, Helianthus annuus L.

Additional index words: Parasitic weed, herbicide.

Abbreviations: fb, followed by; POST, postemergence; PRE, preemergence.