Cotton was planted to approximately 919,000 acres in 2000. “Approved” San Joaquin Valley Acalas accounted for 59 percent, non San Joaquin Valley Board approved “Uplands” was planted to 25 percent and Pima 16 percent of California acreage. Defoliation decisions have to be made on a field by field bases due to the wide range of varieties and maturities. Most fields this season experienced good cutout and had a good uniform boll load, while some of the late-planted fields were more vegetative with a smaller boll load. Fields that evenly cutout and had a good boll load were much easier to defoliate. Because of the different types of cottons, numerous varieties, planting dates, and soil types there is not an easy formula when making a defoliation decision.

The California cotton season conditions for 2000 had a warm spring, cool summer, and a warm open fall. The conditions during defoliation had high temperatures with 90-95 F. during September and October. The first rain occurred on October 10 with approximately .30 inches and again on October 29 with .54 inches. After the last rain cool temperatures followed with daytime temperatures below 60 F.

Because of the optimum conditions for upland varieties and a strong boll load with a defined cutout most treatments worked for the upland types. The defoliation treatment applications were as follows for most growers during September through October: Ginstar 6-7 oz. with or without Prep or Finish, Def/Folex with Prep or Finish, Chorate plus paraquat or Ginstar combinations on uplands, Chlorate plus 21 oz. Starfire after October rains. On Pima-high rates of Ginstar, Def/Folex, and combinations with Chlorate, Cotton Quick, Harvade, and Cotton Aid were mostly used.

Some of the advantages and disadvantages of a few of the major harvest aids in California are as follows. Sodium Chlorate is cheap, can still be somewhat effect under cooler conditions, but should generally used only once because of a salt buildup. Def/Folex are very effective however there are concerns with odor and spray restrictions. Ginstar is very effective and is excellent for regrowth control but has plantback restrictions.