Crop spraying a complex business

Waimarino Bulletin, Volume 3, Issue 36, 18 February 1986, Page 10

Crop spraying a complex business

Merv Anderson, resident expert on market gardening chemical sprays, is one of those self-taught kind of experts — no qualifications but a head full of practical useful information. Merv came into the district 30 years ago and, with a background in the timber industry, worked at Bennett and Punch timber mill. When the mill closed he had to get another job or leave the area, so went to work for F.C.D.C., later Dalgety Crown, as a storeman, while at the same time worked part-time for Radleys, an Auckland produce auctioneer. He was already "mucking around with gardening" and was interested in chemical weed control. "In those days gardeners weeded carrots by hand until Shell-W appeared, which was basically a

refined form of kerosene, and they carted it round in brass knapsack sprays which took more skin off the back than weeds out of the ground!" he said. Aerial spraying had started in a limited way by 1968 and Peter Taylor, manager of F.C.D.C., could see there was great potential. "In those days we used to mix the chemicals in 40 gallon drums and bucket them into the plane which was parked just beyond where' the Turoa Alpine Village is now," said Merv. The primitive nature of the spraying technique led to some disasters such as the destruction of a cauliflower crop, probably through aircraft not being properly decontaminated and the wrong spray creeping in. After that accident a method of recording was developed, which with refinement is still used today, where a representative of Dalgety Crown is present to record the sequence of chemicals going into the machine, to allow for correct decontamination. "The sequence of chemicals and sequence of spray-1 ing locations has to be organised the night before — the pilots have enough to do flying without organising that as well," he said. Technology New spray technology, such as D.C.A.s, or droplet control spray applications, uses 150-300 micron sprays and less water per hectare, to spread the same amount of spray further, and to keep prices down. . The new system allows a Fletcher aircraft to spray 28 hectares in one trip against 10 hectares the old way, and gives a far more even spray distribution than with conventional sprays. As a result of good planning and the new technology, the cost of spraying is down approximately $10 a hectare this year, surely the only agricultural input to drop in price in recent years. Merv says that this wet summer means that fungal disease is a major problem, and for some reason there is not as good control as usual of chewing insects such as caterpillars. There is also an increase all round in fungus and bacterial rot-, partly due, Merv believes, to the increased acreage in brussel sprouts, which are so big and stay in the ground so long that they create their own microclimate, as well as the usual

problem of disease-prone monoculture. Organophosphate insecticides, which break down after three days in the soil, are highly toxic and fatal in minute doses, and as growers don't like using them aerial spraying is preferred. Merv says the greatest of care has to be taken with these chemicals and spraying is not permitted near houses. The organophosphates are largely superceded now by synthetic pyrethroids which have no residual

effect and are less toxic than common salt. When market gardeners have problems with their crop they come to Dalgety Crown and ask Merv's advice. He can usually help them, but if he is not sure he posts samples off to the Levin Agricultural Research Station where tests can be made. Merv worked his way through correspondence courses on sprays and found it fascinating, but when summer came on he was too busy with his own garden and couldn't be bothered learning Latin names "at my age." Merv Anderson is a practical man with practical knowledge.