29 November 1996

Concern over fungicide boost to toxins in grain

New ways with fungicides and insecticides gave delegates plenty to think about at last weeks Brighton Crop Protection Conference. Charles Abel, Andrew Blake, Robert Harris and Brian Lovelidge report

POISONS in grain which could hit animal and human health may be boosted by some fungicides, according to a Scottish researcher.

In a session highlighting the complexity of controlling the wide range of fusarium diseases, notably ear blight in wheat, Felix DMello said laboratory tests showed mixed effects on single species.

In some cases, mycotoxins produced by the fungi and implicated in a range of human disorders, were apparently increased by spraying.

Field trials have given conflicting results. But one in particular worried Dr DMello. It showed a combination of tebuconazole and triadimenol reduced ear blight, but gave a 16-fold rise in the amount of nivalenol toxin in the grain.

"It is a little disturbing. It suggests, perhaps, that we should look at the problem in another way."

Dr DMellos main concern is the apparent lack of knowledge of the mycotoxin status of UK grain. One fusarium-produced toxin in particular – zearalenone – which has been linked to infertility in cows, has received little attention. But with the current debate over falling sperm counts in men it ought to be considered, he claims.

"We must bring it into the picture when considering all the other factors, such as pesticides and oestrogens, that are being talked about."

lTebuconazole (as in Folicur) has given up to 75% control of fusarium ear blight in German trials. But timing and application technique is critical, according to Bayers Anne Suty. Best effect came from a split treatment at GS55 (ear half emerged) and GS65/69 (mid-end flowering).

Ensuring the ears are coated both sides is important, she says. Double fan nozzles, one set pointing forwards, the other backwards, have given much better results than a single set alone. &#42

Fine tweaking with spray additives to make insecticides more selective was one of a range of crop protection possibilities discussed at the Brighton conference.