Root-vegetable growers can use Fazor (maleic hydrazide) to suppress re-growth and help maintain quality in carrots and parsnips until 2007, without fear of exceeding the MRL, Dow AgroSciences has advised.

The time for applying Fazor is approaching and according to Dow AgroSciences, best results are achieved using a conventional sprayer when crop foliage is mature, but not actively growing.

It is typically applied from mid-October at five- 25 per cent leaf yellowing, and when the crop begins to lean. It is sometimes applied to carrots in November following a dry summer and wet autumn, which encourages a late growth flush.

Application timing should be judged on a crop-by-crop basis but must be before the first frost, the company has advised, and on balance it is better that applications are made slightly later than too early as this can cause yield reduction if the canopy is not mature.. In addition, the company said it should not be applied less than three weeks before harvest. If the crop is to be over-wintered, growers need to allow at least four days after application before topping or covering the crop for frost protection.

Fazor inhibits respiration and suppresses cell division in crops and stops development of whole-top growth and of external lateral root hairs in the following spring. It stops plants from metabolising sugars as root hairs grow, and this process helps to maintain the taste, tenderness and processing quality of the over-wintered root crop. In parsnips, Fazor can also prevent woody core and glazing in late-lifted crops.

“Prolonging the time that carrots and parsnips can be left in the ground, and so extending the lifting period, means that loading into pack houses is spread and the season is extended for locally-supplied produce. It means that the supermarkets can more easily source supplies of home grown UK root vegetables,” the company said.