Weed seed predation in vegetable production systems: Most significant seed predator is the invasive fire ant.
Marino, Paul 1, Pullaro, Thomas2, Jackson, Michael3, Harrison, Howard3, Keinath, Anthony4, 1 College of Charleston, Charleston, South Carolina2 NOS/CCEHBR, Charleston, South Carolina3 U. S. Vegetable Laboratory - ARS, Charleston, South Carolina4 Clemson University - Coastal Research and Educational Center, Charleston, South Carolina
ABSTRACT- The feasibility of killed cover crop mulches as an alternative to methyl bromide fumigation was investigated in spring bell pepper (Capsicum annuumL.) and fall collard (Brassica oleracea L., acephala Group) production. Experiments were conducted at the U. S. Vegetable Laboratory in Charleston, SC during summer and fall 2000 and summer 2001. Post-dispersal predation on weed seed, percent weed cover, invertebrate activity, activity of red imported fire ant (Solenopsis invicta Buren), and crop yield were compared among plots having killed cover crop mulches versus conventional production. Vertebrate exclusion cages of 1.3 cm2 wire mesh (which allowed both fire ants and larger invertebrates to enter) and 0.32 cm2 wire mesh (which allowed only fire ants to enter) were used to quantify predation of weed seeds by invertebrates. In three experiments, 5047 weed seeds were removed from cover crop mulch plots compared to 1860 seeds from standard production plots, within treatments, predation increased significantly with decreasing seed size. S. invicta was the main predator of weed seed. In the two bell pepper experiments, weed cover per m2 was 31.8% less in standard production than in cover crop mulch plots. The mean number of invertebrates (other than fire ants) captured in pitfall traps was 5.8 ±0.1 plot-1 versus 3.8 ± 0.8 plot -1 for cover crop and conventional treatments, respectively. There were 5734 fire ants captured in mulched cover crop plots compared to 1278 in conventional production plots. There was no significant difference in crop yield among treatments. The results suggest fire ants were more abundant where there was mulched cover and were important predators of weed seed in killed cover crop plots.–
Key words: Capsicum annuum, killed cover crop mulch, Solenopsis invicta, weed control
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