Urochloa plantaginea (marmeladegrass)

Integrated Management in Soyabean

A good crop canopy inhibits the germination and/or establishment of B. plantaginea seedlings. Once established, however, the weed may outgrow the soyabean canopy (Kissmann, 1991).

Turnip, lupin and rape residues prevented germination of B. plantaginea seed.; winter barley, rye and turnip provided greatest weed control. Crop mulches showed allelopathic effects which modified the weed flora (Almeida, 1985).

Crop residues combined with glyphosate treatment gave the best control of B. plantaginea (Val, 1988).

On loamy podzolic soils in Brazil, yields of upland rice were not significantly affected by weed competition during the first 45 days of the crop. However, weeds that developed between 45 and 60 days after sowing had depressed yields (Oliveira and Almeida, 1982). The critical period for competition from weeds such as B. plantaginea in upland rice cv. IAC164 grown on a red, yellow podzolic soil was 30-60 days after crop emergence. Plant height, number of panicles/m² and grain weight were adversely affected by competition but 100 seed weight was not (Azevedo et al., 1989).In Santa Barbara, Sao Paulo, Brazil, uncontrolled weed infestation decreased cotton yields by 94%. If weeds were controlled for 3 weeks after sowing the yield was decreased by 41%. Control for 5 weeks or more after sowing did not reduce yields significantly when compared to plots in which weeds were controlled throughout the growing season (Blanco and Oliveira, 1976).In carrots grown on a clay soil, where B. plantaginea was the major weed, weed competition 15-50 days after sowing caused significant yield reductions. Top quality carrot roots were most affected, except where competition was allowed for only 15-20 days after sowing (Deuber et al., 1976). The combined effect of B. plantaginea and B. pilosa was studied in beans (Phaseolus vulgaris). Final bean stand and pods per plant were influenced by weed density. Yields were reduced by 37%, mainly due to light competition, with B. plantaginea noted as less competitive than B. pilosa (Carvalho, 1983). In field experiments in Vicosa and Coimbra, Brazil, eight bean cultivars were evaluated for competition to B. plantaginea. A 30-day weed-free period was enough to avoid crop yield reductions under a weed density of 400 plants/m². Crop height was not affected by the weed (Kramm et al., 1990). B. plantaginea at 16-52 plants/m² and B. pilosa at 183-222 plants/m² reduced the growth of beans. Shading caused by the weeds was the factor which most affected the dry weight of the above-ground parts of the bean plants; neither weed affected the mineral status of the beans (Carvalho, 1980). The development, plant height, pod number per plant, seed number per pod, seed production and the harvest index were reduced by weed competition. Critical periods in plant/weed competition were initial crop development and flower pod formation (Kranz et al., 1982).In a weed community of Galinsoga parviflora, G. ciliata, Cyperus rotundus, B. plantaginea and Digitaria sanguinalis, a lettuce crop was either kept weed-free for 14-42 days after transplanting before allowing weeds to grow freely until harvest, or not weeded for 14-42 days and then weeded until harvest. The unweeded control gave the lowest yield of 1.67 kg/15 plants and although all weeded treatments gave higher yields, 3.05 kg was achieved by weeding for 21 days after transplanting (Appezzato et al., 1983).Weed competition was studied in a sugarcane crop where B. plantaginea and D. sanguinalis were the dominant weeds. The critical period was found to be between the 30th and 90th day after planting cane (Rolim and Cristoffoleti, unda).Weed control in the second to fourth week after crop emergence avoided yield reduction in soyabean. Broad-leaved weeds were severely restricted under high densities of B. plantaginea (Cunha et al., 1997). Weed densities from 70 to 780 plants/m² caused yield losses of 18-82%. Regression studies indicated that yield loss increased by 4.8% for every 100 weed plants (Fleck, 1996).B. plantaginea is a highly competitive weed, with losses due to competition, harvest losses (low efficiency of thrash/cleaning combine systems) and increased humidity in soyabean grain.