AVG COMBINED WITH NAA CONTROL PRE-HARVEST DROP OF ‘MCINTOSH’ APPLES BETTER THAN EITHER CHEMICAL ALONE

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).

XI International Symposium on Plant Bioregulators in Fruit Production

T. Robinson, S. Hoying, K. Iungerman, D. Kviklys

Malus × domestica, retain, naphtaleneacetic acid, mechanism of action

https://doi.org/10.17660/ActaHortic.2010.884.40