The Effect of Glasshouse Red Spider Mite (<i>Tetranychus Urticae</i>Koch) on the Yield of Cucumbers

Abstract

The effect on yield of cucumbers of different degrees of damage caused by different levels of mite populations was determined. Yield was unaffected until the foliar damage rose above a level which corresponds to about 30% of the total leaf area. It is shown that when a spraying programme reduced the leaf injury below this level the crop would be unaffected, and that between four and eight sprays per season would be adequate to do this instead of the present average of twelve. Decrease in the frequency of chemical applications should slow down the development of populations resistant to specific materials.