AVG combined with NAA control pre-harvest drop of 'Mcintosh' apples better than either chemical alone
2010
Robinson, T. | Hoying, S. | Iungerman, K. | Kviklys, D.
In 2008, we evaluated whether the combination of aminoethoxyvinylglycine (AVG, trade name = Retain) and napthaleneacetic acid (NAA) would give better pre-harvest drop control of ‘McIntosh’ apple than AVG or NAA alone. AVG (832 g Retain/ha or 416 g Retain/ha) was applied 3, 2 or 1 week before normal harvest. At either the 2 or 1 week before normal harvest, a combination of AVG and 20 mg•L-1 (ppm) NAA was also applied. Pre-harvest fruit drop from untreated control trees exceeded 20% by September 21 and by the end of September had reached 60% drop. The traditional drop control treatment of 20 mg•L-1 NAA applied alone on September 7 did not reduce drop at any date. AVG applied alone reduced fruit drop if applied 3 or 2 weeks before normal harvest but not when applied 1 week before harvest. The addition of 20 mg•L-1 NAA to the AVG sprays, either 2 or 1 week before harvest, improved pre-harvest drop control compared to AVG alone. The combination spray applied 2 weeks before harvest resulted in the lowest pre-harvest drop of any treatment. However, if AVG + NAA was applied 1 week before harvest then its efficacy was reduced but was still similar to AVG alone applied 3 or 2 weeks before harvest. When a reduced rate of AVG (416 g/ha) was combined with NAA, the efficacy in preventing drop was very similar to the full rate of AVG. The best AVG + NAA treatment gave similar drop control to treatment with sprayable 1-methycyclopropene (Harvista).
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