The Effect of Soil Soluble Salts and Cultural Practices on Mite Populations on Hothouse Tomatoes

Abstract

More than 10 times as many mites, Tetranychus bimaculatus, were found in greenhouses where 2 tomato crops were grown annually than in greenhouses when the annual tomato crop was alternated with radishes, cress, or lettuce. A significant positive correlation was found in 1946 between the soluble salt content of greenhouse soils and the mite population. Although this relationship was not evident in 1947 and 1948, both the soluble salt content and the mite population showed a marked decrease. This was apparently due to a decrease in the use of fertilizer (36% decrease over a 5-yr. period) by the greenhouse operators. Straw, the most widely used mulch type, did not discourage mite introductions and there is no apparent relationship of clover to mite introductions.