Alternative Chemicals

Press, Volume CIX, Issue 32221, 13 February 1970, Page 8

Alternative Chemicals

Alternative pesticides to control insects now controlled by D.D.T. were now at hand. Mr G. A. H. Kelson, chief advisory officer (entomology) of the Department of Agriculture, said last week after the announcement had been made about the ban on the use of D.D.T. from the end of June this year.

“The main use of D D T on farm land in New Zealand today is for the control of grass grubs.” Mr Helson says. “We have had. for some time. non-residue-producing chemicals for the control of other major insect pests.

“The two prime alternatives to D DT. are fensulfothion and diazinon. These belong to the group of chemicals known as organophosphates. We have been particularly interested in using these as alternatives to D.D.T. “These insecticides break down rapidly after application and. generally, have disappeared several weeks after application,” says Mr Helson. “This prevents them from producing unacceptable residues in our primary produce as D.D.T. has done.

“Trials over several years have shown that fensulfothion applied at the rate of 21b of active ingredient per acre, from now to May, in pelleted form, gives good control of grass grub. Its limitation is its cost and toxicity.

“Diazinon, applied the same way, is also an alternative chemical. However it

must either be applied during rain, or followed by sufficient rain or irrigation within a week to wash it into the soil,” he said. “This illustrates the dependence of some of these chemicals on the weather. "The alternatives to D.D.T. are more expensive. The cost to the farmer, for materials only, of enough chemical to treat an acre qf land is about $8.50 for fensulfothion and about $4.90 for diazinon.

"We must face the fact, however, that D.D.T. has fallen from grace,” Mr Helson says, "and we do have alternatives. We have no option but to adapt to them.

“Farmers will need to acquire a greater knowledge of these new pesticides and more preci ion in their use to obtain the maximum benefit from them. A prime project of the department's farm advisory officers throughout the country at the moment is to help them acquire this,” he said.