THE EFFECTS OF DEFOLIATION AND LOSS OF STAND UPON YIELD OF SUGAR BEET

Seedling pests of sugar beet cause defoliation and loss of stand. Attempts were made to assess the effects of these types of injury by means of field trials in which the defoliation and loss of stand were produced artificially shortly after singling. The main effects of these treatments were to modify the size of the plants without greatly influencing their percentage sugar content. Little loss of crop resulted until 50% of the leaf area or 50% of the plant population had been destroyed. The yield from re-sowing after removal of all the plants was inferior to that from stands depleted of half or two-thirds of their initial plant population. The relation between the results of artificial injury and the injury produced by seedling pests is briefly discussed.