A study was conducted to gauge the relative efficacy of mowing twice, discing, and solarization in controlling invasive weeds. The two specific objectives were to test whether solarization could be used effectively for weed control in a cool, coastal region, and to compare this approach with other methods of weed control in terms of effectiveness, cost, and time required for implementation. The study was conducted in an area within a 1-ha fallow field in California, USA that had not been cultivated for ten years. Non-native annual grasses dominated the vegetation, primarily ryegrass ( Lolium perenne subsp. multiflorum), but also soft brome ( Bromus hordeaceus), oats ( Avena spp.), and foxtail barley ( Hordeum murinum). Mustard ( Brassica rapa) and radish ( Raphanus sativus) were also common non-native weeds. The site is about 7 km from the ocean, so it experiences a strong maritime influence. The solarization treatment was the most effective method for controlling weed cover at Triple M. All treatment areas had similar weed cover beforehand, and treatments differed in their effectiveness. Although all treatments were equally effective in reducing non-native annual grass cover, both the disking and mowing treatment areas were invaded by the annual/biennial bristly oxtongue ( Picris echioides) during the study. This species comprised 85% of the posttreatment weedy forb cover in the disked area and 98% in the mowed area, but was not found in the solar-treated area. This is the first study to demonstrate effective weed control using solarization in a cool coastal region.
