Mechanical damage to annual weeds and carrots by in‐row brush weeding

Abstract

Field experiments were carried out in order to assess the selectivity of in‐row brush weeding in carrots with a natural flora of annual weeds, represented by Urtica urens L., Stellaria media (L.) Vill., Chenopodium album L., Senecio vulgaris L., Capsella bursa‐pastoris (L.) Med., Chamomilla suaveolens (L.) Pursh Buch. and Matricaria inodora L. The mechanisms by which the weeds and carrots were controlled (uprooting vs. soil covering) were studied using a portable vacuum‐cleaner. Weeds at the two‐ to four‐true‐leaf stage proved to be more sensitive to brushing than carrots with two to four true leaves but, for later development stages of the weeds, there were no differences. Weeds at the six‐ to eight‐leaf stage were only killed to an extent of 20–50%. Uprooting generally accounted for 45–90% of the weed mortality at the two‐ to four‐leaf stage, whereas most of the mortality in carrots was the result of soil covering. The vacuum‐cleaning method proved to be a simple and rapid way of determining whether plants had been killed by uprooting or soil covering. It was concluded that the major mechanism of weed control obtained by brush weeding is uprooting.