Professor offers fruit growers suggestions to return bloom

AFP Correspondent

SMITHSBURG, Md. (June 27, 2017) — At the early June twilight meeting of fruit growers at Barr Orchards, Penn State tree fruit professor Robert Crassweller offered numerous tips for enhancing return bloom of apple trees.
He explained that flower initiation is inhibited by gibberellins produced in the seeds and shoots, and transported down both the fruit stem and the shoot stem.
Moreover, the total number of seeds per tree relates to return bloom.
More seeds mean less return bloom.
Applying the hormonal-type chemical thinners NAA and ethephon in the summer counteracts the effects of seed produced and shoot produced gibberellic acid and stimulates more flower bud initiation.
It is thought that this occurrence is due to a temporary reduction in shoot growth rate.
Products include Ethephon 2, Motivate, Ethephon 2SL, Fruitone L and Refine, he said.
The application should be four weekly sprays of a low dose of NAA 5 to 7 ppm or two to three ounces per acre.
If using ethephon, the application should be four weekly sprays of a low dose at 25 ppm or 8 ounces per acre.
The lower rates should reduce unwanted side effects such as premature ripening.
Also, the application should begin after June drop and with fruit at least 30 mm in diameter.
Crassweller cautioned orchardists to not apply sprays past mid-July to cultivars that ripen before MacIntosh, for example, and Ginger Gold especially when using ethephon sprays.
The sprays can be used with normal cover sprays.
But growers may want to avoid strong surfactants in the mix, especially when using ethephon.
Do not apply when daytime temperatures exceed 85 degrees Fahrenheit, Crassweller warned the growers.
Penn State recommendations note that chemical thinning is important to obtain adequate return bloom for the subsequent season.
Further, enhancing return bloom on cultivars that have a biennial bearing tendency is especially desirable if they have a full crop load.
Consequently, the supplemental application in summer of NAA, ethephon, and the others mentioned are suggested at low rates.
Crassweller also advised growers to be prepared for the label changes of paraquat to occur in 2020.
The label statement will highlight human toxicity.
In addition, application then can only be by certified applicators.
He suggested becoming familiar with how other products perform in their particular orchards before the paraquat label change.