A procedure for determining relative densities of brown almond mite populations on almond trees

Brown almond mites reside on woody portions of their fruit tree hosts, from which they make excursions to feed on leaves only during favorable periods of the day. Changes in temperature and possibly in sunlight greatly affect their migrations back and forth on almond trees. Their excursions for food introduce serious errors in sampling whenever attempts are made to compare different populations on a basis of mites counted in samples of plucked leaves.

The method described here avoids this difficulty since the mites are counted in samples of leaves and wood. Mites present on a clump of almond foliage are shaken onto a sheet of paper and permanently fixed in position by crushing. Derivation of numerical data from the patterns of crushed mites and appropriate statistical analyses are included in the discussion. The design indicated as being adequate for testing relative efficiency of treatments requires plots of four or five similar trees. Thirty individual twigs from each plot are usually sufficient.