7 June 1996

Novel weapon in aphid fight

SUGAR beet growers limited aphicide arsenal should be enlarged next season provided a novel compound goes through its final approval stage with no problems.

The new chemical, triazamate, has good activity against both susceptible and resistant strains of virus yellows-transmitting peach-potato aphids.

It also has other properties essential to the success of a modern insecticide: Complete systemicity, good persistence within plants to minimise the number of treatments needed for effective control, and it breaks down rapidly in the soil. It is also said to be safer than most other aphicides to beneficial species including aphid predators, bees and game bird prey.

Last year, one of the worst ever for aphids, triazamate performed well in large plots tests, according to IACR-Brooms Barn entomologist, Alan Dewar. In one demonstration site on a farm at Little Wilbraham, near Cambridge, where an untreated plot had the highest aphid numbers ever recorded on the crop, it gave a very high level of control.

It was compared with the standard foliar-applied aphicide, pirimicarb, and imidacloprid seed treatment. Sprays of triazamate and pirimicarb were applied when the peach-potato aphid reached a threshold of one aphid/four plants on May 22, June 5 and June 28.

The results can be seen in the table. The reduction in aphid numbers on July 11, particularly in the untreated plot, was largely down to the activity of predators such as ladybirds and lacewings. "We found that triazamate was still controlling aphids 10 days after its application," claims Rob King, Cyanamids insecticide product manager.

"Over the past five years growers have applied an average of 1-1.5 aphicide sprays a season in addition to seed or seed-bed treatments. We expect a control programme with triazamate will be at least as economic as one with other foliar sprays and in line with the cost of imidacloprid seed dressing."

Mr King says all the indications are that aphids will pose a much smaller threat this season. This is confirmed by Dr Dewar, who says populations of species like Myzus persicae (peach-potato aphid), which overwinter as adults, were considerably depleted by severe frosts.

He is continuing a trial with triazamate this season and believes it will have a useful role thanks to its good persistence, efficacy against resistant aphid strains and specific pest activity. "It is one of the best aphicide sprays that we have ever tested," he says. &#42


Performance of aphicide active ingredients in Cyanamid Cambs demonstration site 1995

June 27July 11July 19

Aphids/plantAphids/plant% plants with

virus yellows

Untreated492988

Pirimicarb243.127

Triazamate3.50.86

Imidacloprid1.72.86

Alan Dewar sees triazamate as an extra weapon against virus yellows.