Harvest Aids for Cotton Owen Gwathmey University of Tennessee, Jackson Tom Barber University of Arkansas, Little Rock
Harvest Aids: What are they? • Harvest aids are chemicals that prepare the crop for mechanical harvest by: • Removing leaves • Opening mature bolls • Suppressing regrowth • Selected and applied correctly, harvest aids can improve harvesting efficiency and preserve lint quality. Image courtesy Bayer Crop Science
Herbicidal (contact) defoliants • Herbicidal defoliants injure the plant, causing it to produce ethylene, which promotes defoliation. • Examples: Folex®, Def®, Aim®, ET® • At rates too high for the temperature, these defoliants can kill the leaf. • Desiccation or “stuck leaves”. • More leaf trash in harvested lint. • These defoliants do not promote boll opening or suppress regrowth.
Hormonal defoliants • Hormonal types increase ethyleneproduction, promoting defoliation. • Some also inhibit auxinproduction. • Examples: • Dropp® SC, FreeFallTM, others (thidiazuron) • Harvade®, Lint Plus® (dimethipin) • Leafless® (dimethipin + thidiazuron) • Ginstar® (thidiazuron + diuron) • These products do not open bolls. • Thidiazuron products inhibit regrowth.
Boll Openers • Ethephon products generate ethylenein the plant. • Examples: • Ethephon 6, PrepTM, Super Boll®, others. • Mainly used as a boll opener in cotton. • Need temps >60°F to work well. • Examples of ethephon pre-mixtures: • Finish® 6 Pro (ethephon + cyclanilide) • CottonQuik®; FirstPickTM (ethephon + urea sulfate)
Regrowth Suppression • Regrowth is suppressed by auxininhibition • Products containing thidiazuron or cyclanilide. • Examples: • Dropp® SC, FreeFallTM SC (thidiazuron) • Finish® 6 Pro (ethephon + cyclanilide) • Useful when: • Harvest is delayed • A late flush of soil N occurs • Late rains occur after drought
Role of Desiccants • Desiccation is rapid drying of plant tissue due to cell membrane disruption. • Typically, desiccated leaves do not shed. • Examples: • Gramoxone® (paraquat) • Defol® (sodium chlorate) • Used in stripper cotton to reduce moisture. • Poor boll opening and regrowth control. • Possible tank-mix problems.
Problem Scenario # 1Early, drought stressed cotton • Problem: • Tough leaf cuticle ® uptake problems • Low boll load ® low yield potential • Hot weather ® potential to stick leaves • Example tank mixture: • Thidiazuron SC ~1.6 to 2.4 oz/A • Ethephon 6 ~16 to 24 oz/ac • Nonionic surfactant ~0.25% v/v (avoid herbicidal-type materials)
Problem Scenario # 2Late cotton with rank growth • Problem: • Thick canopy ® coverage problems • High boll load ® high yield potential • Late maturity ® unfavorable weather • Example 1st Application: Ethephon+cyclanilide (Finish 6), 6 oz/A + Thidiazuron (Dropp), 2 oz/A • Example follow-by: Carfentrazone (Aim), 0.5 to 1.0 oz/A + COC + Ethephon, 32 oz/A (limit 42.6 oz total/year)
Problem Scenario # 3After early freeze or frost • Problem: • Light frost (brief 30 – 32°F) ® turns leaves. • Hard Freeze (sustained <30°F) ® locked bolls. • Cold weather ® harvest aids don’t work. • Important! Wait until day temps > 55-60°F. • Example after light frost: Carfentrazone (Aim), 0.75 to 1.0 oz/A + COC + Ethephon, 36 to 42 oz/A • Example after hard freeze: Perhaps Carfentrazone, 1 oz/A + COC (or maybe none?)
Example Budgets Product prices from 2009 Tennessee Farmers Coop list prices, not including application costs.
Take Home • Harvest-aid prepare the crop for harvest. • Realistically budget for harvest aids. ~ $15 to $35 /ac • Match the crop with harvest-aid chemicals. • Early and short?Late and rank? • Consider the weather during and after app: • Hot?Warm?Cool?Frosty?Freezing? • Use multiple, complementary modes of action. • Read and follow label directions. • Be patient! Have realistic expectations.