Most weed control decisions are made with the benefit of some information about weather conditions and actual weed densities. This study is an investigation of the value of adjusting weed control decisions in response to these types of information. For a specific example, it is found that the expected value of information can reach 15% of expected gross margin. The value of information about yield prospects is higher than that for weed density. The value of information is markedly affected by the degree of risk aversion and the type of decision rule adopted. Use of information reduces the expected level of herbicide usage.