Cheeseweed (Malva Parviflora L.) Competition with Cabbage and Lettuce on Maui. Hawaii

Abstract

In four field experiments transplanted cabbage was grown with cheeseweed sown at transplanting at densities from 0 to 70 weeds per 0.1 m2. Cheeseweed emerged in 3 to 7 days and overgrew the cabbage in 42 to 49 days. At harvest cabbages were trimmed to two wrapper leaves and weighed. Final weed densities and weed fresh weights were recorded. Curvilinear and linear relationships between trimmed cabbage fresh weight and weed density were defined by regression equations. Regression equations were also calculated to define the relationship between cabbage fresh weights and weed fresh weight. In two additional plantings, subplots with cabbage only, cabbage and cheeseweed, and cheeseweed only were harvested weekly. Reductions in cabbage plant fresh weights occurred when cheeseweed attained and surpassed the height of the cabbage. One experiment was conducted with transplanted lettuce and cheeseweed sown to densities from 1 to 15 weeds per 0.1 m2. The relationship between trimmed lettuce head fresh weights in grams (y) and the number of weeds per 0.1 m2 (x) was best expressed by the linear equation y = 842 - 49.4x. When y was regressed on weed fresh weight in grams per 0.1 m2 (x), the equation was y = 929 - 2.3x. In addition to reduced head weights, losses due to rot Increased with increasing weed densities, with a stand reduction as high as 80 percent at 5 weeds per 0.1 m2.