Insecticide trial shows timing is key factor

Crops grown under protection can be particularly vulnerable to scorch following insecticide applications, but one strawberry grower has undertaken a trial that has shown the importance of application timing in delivering crop safety.

Bisley Nursery, near Deal in Kent, produces 1.5 million to two million protected strawberry plants a year under contract with Kent-based Berry Plants. With 1ha of modern glass and 1ha of polytunnels, it also produces lettuce plants and pea shoots on benches.

The nursery undertook a trial in May to test the crop safety credentials of insecticide Spruzit (a registered trademark of Neudorff KG) on its strawberry crops. Nursery representative Norman Sole said: "We were specifically interested in testing younger plants, which are more susceptible to damage."

He added that they tested a variety of mother strawberry plants - including Red Glory, Albion, Everest and Promise everbearers and new numbered developments EM 1315 and EM 1276 as June bearers.

Derived from a natural pyrethrum, Spruzit - unlike many alternative products - contains low levels of pyrethrin (0.5 per cent). It also contains rape seed oil, which provides a built-in anti-resistance strategy and contributes towards a residue reduction strategy.

In addition, it is also approved for organic use, under specific derogation from Organic Farmers & Growers (OFG) and the Soil Association, for control of a range of pests.

Sole said that timing according to weather conditions on the day of application was an important consideration, particularly because the nursery grows under protection.

"If we are spraying plants, we always seek to avoid hot, sunny conditions," he said. "Applications made on an overcast day or in the evening are best."

He noted that because the trial plots of strawberries would not be harvested, a double rate of Spruzit was applied to really put crop safety to the test.

Although there were no pests present at the time of the trial to test insect control, Bisley Nursery was very pleased with the crop safety results. Sole said there were no phytotoxic effects, and that the appearance of the leaves was in fact enhanced.

"The leaves had a glossy, shiny appearance for over four weeks. Not only do the plants look bright and healthy, but the leaves are stronger," he said.

Since the trial application there have been no problems with the treated plants. "We always make sure we are careful with our spray applications to avoid scorch and other issues, and this is the advice I would give to other growers," Sole said. He recommended testing products on a single plant to establish crop safety before treating a whole crop.

- For information, call the Certis technical helpline on 01980 676501.

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