TOO DRY FOR TELONE?

Posted 1 October 2003

POTATO GROWERS SHOULD CAREFULLY consider the effects of the weather before applying nematicide, according to researchers at Harper Adams University College, Shropshire.

Nematologists Dr Pat Haydock and Dr Ivan Grove, of the Crop and Environment Research Centre at Harper Adams believe soil may be too dry for certain nematicides.

“With the continued period of dry weather growers who are considering getting in a contractor, to apply Telone for the control of Potato Cyst Nematodes, should think whether their soil is too dry for the fumigant to be really effective,” said Dr Haydock.

“Good soil conditions are the key to an effective application with soil temperature from seven to 15 degrees C at 20cm depth and soil moisture content at 40 to 60 per cent of field capacity being ideal.”

“Soils in the West Midlands may contain sufficient moisture following irrigated potatoes but following cereals the soil moisture deficit is in the order of 85 to 100mm, which is much too dry for Telone application,” added Dr Grove. “The situation in the East of England will be even worse.”

“We advise growers in these situations to delay application of Telone until after there has been sufficient rain or to consider irrigating land prior to application.”

“For a sandy loam soil (17 per cent AWC) with a 100mm SMD, the grower needs to apply 25mm of irrigation at least 48 hours before fumigation. This would bring the soil back within the 40 to 60 per cent of field capacity required for Telone application. “Most specialist potato growers have the irrigation equipment available and unused during the late summer and autumn. Provided sufficient unused abstraction licence or lagoon water is available, this is a practical possibility.

“The total cost for the application of 25mm of water is in the region of £60 to £120 per hectare but it can be argued that the fixed costs of irrigation should have already been covered by the potato enterprise and so the application should be costed on a marginal basis.

“Even costed at £60 per hectare, the use of irrigation to achieve optimal soil conditions for Telone application adds only 11 per cent to the cost of Telone at £570 per hectare and it could make the difference between achieving 20 or 80 per cent reduction in nematode viability!”

Dr Haydock and Dr Grove advise growers to always remember these key points for the successful use of Telone:

1) Take soil samples and have PCN population densities estimated in the spring after potato crops are harvested so that the need for Telone can be predicted and planned into the rotation.

2) Telone is effective at any stage of the rotation.

3) Before considering Telone II application, always seek the advice of your local Telone II specialist.

4) Good soil conditions at application are the key to efficacy.

5) Soil temperature at 20cm depth should be seven to 15 degrees C.

6) Soil moisture content should be at 40 to 60 per cent of field capacity.

7) Consider irrigating soils to achieve 50 per cent field capacity after harvesting cereals whilst soils are still warm.

8) Soil should be prepared before Telone application to give a light well aerated structure, which is free from cultivation pans.

9) A good surface seal following application is essential.

(Ends)

Notes to Editors:

§ The authors do not accept liability for any error or omission in the content, or for any loss, damage or other accident arising from the use of products mentioned in this article.

§ Dr Pat Haydock (Photograph available in electronic format, please contact the press officer on nbarnes@harper-adams.ac.uk to obtain a copy) is Reader in Plant Nematology at Harper Adams University College and Dr Ivan Grove is Senior Lecturer in Crop Production at Harper Adams.

§ Further information is available from Dr Pat Haydock on phaydock@harper-adams.ac.uk