Defoliation is never an exact science, but a systematic approach may help growers and PCAs take some of the guesswork out of the art. Bayer's Ginstar two-shot system was designed to simplify harvest aid decisions, assist in leaf drop and prevent re-growth. After initial trial work, the concept was refined last season by Bayer technical reps.
The first shot is a combination of 10 to 16 ounces of Finish 6 Pro and 3 to 6 ounces of Ginstar applied when a grower would normally begin defoliation, according to Steve Gamble, Bayer CropScience sales representative. Temperature and nodes above cracked boll (NACB) are important factors in timing the first application. For best results, the first shot should be applied when daytime highs are in the 80s and are forecast to remain there for the next 7 to 10 days. Then the second shot is applied 7 to 10 days later with a full defoliation rate of Ginstar (6-12 fluid ounces and ethephon.
“We've seen about a 5 percent better defoliation with the two-shot system as compared to the grower's standard,” Gamble says. “The first shot works best when timed at 4-6 nodes above cracked boll. Our research has seems to indicate it works better if you push the timing to 6 NACB.”
The goal is to knock off the top leaves with the first application and open up the canopy for more thorough coverage on the second shot. The approach usually eliminates the need to come back with a third application of sodium chlorate or paraquat typically used as a final burn down in a sequential defoliation program.
The two-shot system is a softer approach well suited for sprinkler irrigated fields as well as fields in sensitive areas where the use of Gramoxone could be an issue. It also reduces dependence on sodium chlorate, which has the disadvantage of adding unwanted salts to the soil. It's a system designed for warm temperatures. While higher rates and harsher materials may end up frying leaves under warm temperatures, the two-shot system minimizes that problem and results in a better defoliation job.
“Stay away from adding a dessicant to Ginstar on the first shot,” Gamble cautions. “And stay away from Ginstar and Accelerate. They're not compatible.”