Why early season square retention rarely matters for high yielding Bollgard 3 In Australia

Abstract

Industry data indicates cotton crops are commonly sprayed twice during squaring to regulate retention. For operational convenience insecticides are usually applied simultaneously with glyphosate for weed management. However, not only is the economic benefit of this practice unverified, additional insecticide both disrupts integrated pest management and contributes to the industry's environmental footprint. The impact of square loss in commercially grown high yielding Bollgard 3 fields was assessed from Emerald to Griffith over three consecu ve seasons. In each field three square removal treatments (from frui ng branches 1-5, 6-10 and 1-10) were replicated with an undamaged control, and growth and yield component responses were measured. For 33 out of 34 sites, total square removal from the first 5 fruiting branches prior to flowering had no impact on crop maturity, lint yield or quality. Compensation was rapid, occurring via additional bolls retained on sympodia immediately above or on distal fruiting positions adjacent to lost positions. Compensation was not reliant on additional mainstem node production, explaining the negligible impact on crop maturity. The data has been used to revise industry recommendations for early season fruit retention on that aim to balance the need to spray with the capacity of cotton to compensate square losses.