Mike Hutchinson of crop protection specialist Hutchinsons said the emergency approval, which started on 12 April, will help top fruit growers to thin their crops and create the right balance of crop load and fruit size. He added that growers have been looking forward to getting a reliable chemical thinner ever since carbaryl was withdrawn in 2001.
"Maxcel won't negate the need for hand thinning altogether, but it will make it quicker, more cost-effective and easier to manage in terms of staffing numbers," said Hutchinson.
"All apple varieties can suffer from irregularity of cropping to some degree. Quite a few of the newer varieties, such as Gala, Jazz, Braeburn and Kanzi, have a tendency to be precocious and over-crop and will benefit from the application of Maxcel.
"If a tree is left to over-crop, it not only affects this year's fruit size and quality but also next year's because the tree tends to under-crop the following year. This biennial cropping pattern helps no-one."
Maxcel selectively thins by using inter-fruitlet competition. Because it is used earlier than hand thinning, when the fruitlet is 8-12mm in size, it optimises the fruit size and picking quality. "Hand thinning for misshapen or damaged fruits tends to be done later, after natural fruit drop has occurred," Hutchinson explained.
He advised growers to apply the regulator at the correct growth stage of the crop and when the weather was suitable. "In a perfect world the fruitlet would be 10 mm and the weather warm and sunny. You have a good range of fruitlet sizes to go for, but make sure it is warm enough. I would advise that Maxcel is applied as a special treatment on its own."
Maxcel should be applied when the king fruitlet has a diameter of 10-12mm. Maxcel supplier Interfarm UK will be providing suitable measuring tools to help growers with this assessment.
Applications should be made at the start of the warming trend when maximum daily temperatures for the two to three days after application are expected to be at least 18 degsC. It should not be applied when they fall below 15 degsC. One application can be made per year.
Maxcel is based on the active 6-benzyladenine, which is a naturally occurring compound. It is recommended at dose rates of 350-750ml/per 100 litres of water. It is important to ensure adequate coverage of fruit and foliage without excessive run-off, with water volumes being adjusted according to tree size and spacing.
It is also important to use a water volume that allows for a sufficient amount of Maxcel to be applied, depending on the variety and its ease of thinning.