Since 1946, a major project at the Vineland Station laboratory has been one on the indirect effects of pesticides on populations of injurious arthropods in peach orchards of the Niagara Peninsula. Plant-feeding mites have been the most readily affected. This paper describes the gross changes in mite populations produced by the pesticides and considers their economic importance and the possibility of reducing their injurious effects. The controversial problem of the means whereby some pesticides, particularly DDT, promote mite increase is still under study and will be treated in later papers.

A simulation model is described for the population dynamics of the European red mite, Panonychus ulmi (Koch). The model incorporates the following features: (a) development rate is dependent on effective daily temperature; (b) division of each population component into distinct daily age classes; (c) emergence of individuals from each population component is dependent on a log-normal probability distribution, and a temperature related development vector to accumulate a measure of the temperature effect on development. Validation runs on a mini-computer in 1976 and 1977 adequately described actual population curves determined from daily orchard sampling. A model of this type which can be used with small computers should prove useful in investigating the main factors affecting the population dynamics, and control strategies for this and other pests.

Numbers of the European red mite (Panonychus ulmi Koch) increased but those of the brown mite (Bryobia arborea Morgan & Anderson) and the peach silver mite (Vasates cornutus Banks) decreased after sprays of Sevin (N-methyl-1-naphthyl carbamate) were applied to peach trees. Sevin practically eliminated the predacious mite Typhlodromus rhenanus Oudms., and larvae and pupae of Stethorus punctillum Weise, and greatly reduced the numbers of adults of S. punctillum, chrysopid larvae, and spiders.

Evaluation of three types of vineyard sprayers by measurement of carbaryl deposit, dye distribution, :rnd control of powdely milderv ancl two-spotted mite. Can. J. Plant Sci. 53: 189-197. One high-volume hydlaulic sprayel with hoocled-booms, and two low volumc air-carrier sprayers were used to appiy folpet (fungicide), carbaryl (

The relative toxicity of Kelthane (1,1-bis (p-chlorophenyl) -2,2,2-trichloroethanol), and parathion to Phytoseiulus persimilis Athias-Henriot and its prey, Tetranychus urticae K. (= telarius (L.)), was determined using a Potter Spray Tower. Parathion was found to be far more toxic to P. persimilis than was Kelthane. The LD50 values for Kelthane were 0.051% and 0.29% for T. urticae and P. persimilis respectively, and for parathion were 0.050% and 0.0044% respectively. The LD95 values bore a similar relationship to each other. The two materials were equally toxic to T. urticae. Therefore, use of Kelthane rather than parathion in an environment where P. persimilis and T. urticae were interacting would favour the beneficial species. The statistical aspects of the test method are discussed.