Chemical Control Studies

Press, Volume CIV, Issue 30739, 1 May 1965, Page 10

Chemical Control Studies

TN the field of chemical conA trol of insect pests, Mr W. Kain has just completed an investigation of the action of two systemic insecticides — an organophosphate and a carbamate—against the cereal aphid. In the glasshouse and laboratory he has been looking particularly at the toxicity of the granulated forms of these insecticides, their effectiveness, and how they compare for efficiency with spray applications, and how they can best be applied.

Dr. Harrison said that the results indicated that they would give efficient and effective control if they were applied in the furrow with the seed, but if they were applied away from the seed, either on top of the soil or at the side of the furrow, their effectiveness then depended on whether or not the material was water soluble and whether the insecticide was quickly released from the granule or not In the artificial conditions in the glasshouse Mr Kain has detected some side effects from the use of granules resulting in delayed germination of plants and subsequent stunted growth and the marginal burning of leaves. Dr. Harrison said that certainly more work was needed to see whether this sort of damage occurred under field conditions.

A Malayan student, Yoong, who hopes to join the Department of Agriculture or some similar organisation as an entomologist when he returns home, has been looking into the chemical control of leaf miners, a problem that may be of some significance in his home country for rice and perhaps some other crops. He is using a New Zealand leaf miner in the laboratory to investigate the toxicity of various chemicals when the miners are in the adult stage and when they are maggots. Dr. Harrison says that leaf miner control is not a very well documented aspect of entomology and Yoong hopes to be able to indicate what the best materials are for this purpose.

Mr R. Buchanan is beginning work aimed at finding the best insecticide to use for control of Argentine stem weevil. This follows on work done by Dr. R. P. Pottlnger in sorting out the biology of the weevil and will involve

the screening of various groups of insecticides for their toxicity to the adult of the species. The work will be carried on in the knowledge that the uncertain migratory habits of the adult may mean that normal spraying of pastures or application of insecticides may not be the answer with the weevil. Two other masterate students are studying aspects of the resistance of certain insects to insecticides. Mr G. Ballantyne is looking at the resistance of the red spider mite, which is resistant to the organophosphates in many areas. There was no real understanding of this resistance or of its mechanism, said Dr. Harrison, and by laboratory tests in which the insects were treated individually with insecticides and by a programme of breeding Mr Ballantyne hoped to determine the inheritance of resistance.

Mr G. Thiele is at the same time studying cross resistance to Insecticides in the red spider mite. He wants to find out whether a mite that is resistant to an organophosphate is also at the same time resistant to a cholorinated hydrocarbon or a sulphur based insecticide or any other group of insecticide.