MINERAL OILS.

New Zealand Herald, Volume LXVII, Issue 20721, 14 November 1930, Page 4

MINERAL OILS.

USE AS SPRAYS. In 11 rccorit report to (ho American Chemical Society, Dr. K R. do One, of San Francisco, said that Iho uso in orchards of highly-refined petroleum oils as insecticides has become a common practice over the entire Pacific coast. The work first, became established in Iho citrus groves of southern California and then extended info the deciduous orchards of central California. The movement has been recommended by the entomologists of tho Pacific North-West as a supplement to the lend arsenate spray programme in I lie apple orchards. Organic forms of sulphur, combined with petroleum oils in cyclic series, have been found very effective as insocticides and also as fungicides. Experiments (luring the last two years have shown that such preparations can bo used roadilv on trees in foliago as well as those in the dormant stage. Tho ralo of volatilisation of the oil has a direct bearing both on the insecticidal value arid plant tolerance. Lubricating oils aro superior to kerosenes, principally because they aro less volatile and sufficiently viscous to resist being readily displaced. In tho control of red spider, ' kerosene has been found to kill a low ' percentage of eggs and to disappear from ; tho foliago so quickly that satisfactory f contiol is not attained. Similar results have been noted with tho more resistant 1 .v'ale insects. In the same circumstances, lubricating oils of viscosities from 70 to ] 100 and rather high volatility have given • goori control. As toxicity <o the insect £ increases with a high volatility, however, c the danger to the plant also increases. t