NEWA Carbohydrate Model Run for May 28, 2021

You will notice that some sites do not have a thinner recommendation. The reason is that the model is only calculated out to 35 days following the full bloom date you entered. As mentioned in previous alerts we chose green tip and full bloom for Gala. If you have later blooming cultivar(s) you need to enter the date(s) in the Bloom Date box at the top of the table. I have listed the dates I used for the various locations we reported on this spring in the table below.

All sites with recommendations for today indicate a need to use higher thinner rates. This is due to a combination of cooler temperatures and large fruit size. The efficacy of the thinner application through May 30 is listed as mild.

At Rock Spring we have quite a range of apple cultivars. Our latest full bloom date was recorded on May 3 for Topaz, Crimson Crisp, Nittany, and York Imperial. Therefore, we have added an additional table from our orchard representing those cultivars in today’s alert. The later bloom date had increased the days that the GDD was favorable being between 200 and 250 hours. The ideal window with the earlier bloom occurred May 22–24, as indicated by the green shading in the Accumulated GDD column. The later bloom resulted in favorable GDD accumulation occurring May 24–27. You can also note that there were more days that recommended decreasing the chemical thinner rate for the April 29 full bloom scenario. The table with the May 3 full bloom showed four dates when the recommendation was for a standard thinner rate.

What does all that mean? Well, the orchards at Rock Spring are not uniform by any means. We have different tree ages, cultivars, rootstocks, and planting densities. At best we have to tweak some areas by adding additional thinning chemicals. We will evaluate our thinning program later in the season and hope we do not have too much hand thinning.

2021 Green Tip and Full Bloom Dates by Location

*note full bloom date for Piney Mtn is for the lower farm with 4/28 date for the upper farm.