WIREWORM POPULATIONS IN RELATION TO CROP PRODUCTION: IV. POPULATION CHANGES DURING A BARE FALLOW

Changes in wireworm populations during a bare fallow were studied on twenty-three fields in 1943 and 1944. In every case populations were much reduced, sometimes to less than 10% of the original level. Wireworms of all sizes were affected, but the larvae less than 5 mm. in length were practically eliminated from the populations.
Evidence is presented that the reduction achieved is greater in fields ploughed in February and March than in fields ploughed in May.
As the populations in the grass 'controls' decline during the same period the entire reduction cannot be attributed to the fallow. The reduction in the bare fallow, however, differs from that in the controls in that it is permanent and continues through the autumn when the counts on the 'controls' are rising.
The practical implications of the results are discussed.