How Long Should it Take Before the Weevils Control the Giant Salvinia?
This is difficult to predict because of many factors, and often the factors themselves are unknown or poorly understood. The bottom line is that although you can predict the safety of a biological control organism, you cannot predict its effectiveness. However, a major point in the weevils favor is its success in other parts of the world where, in tropical areas, it controlled over 90% of the giant salvinia within 2 years. Control in temperate areas took longer but was still considered successful. Generally, a biological control agent that has worked in other places is usually successful when deployed in new areas with a similar climate. It should be noted that the majority of biological control agents do not successfully control the target weed. However, when an agent is successful, the benefits usually overwhelm the costs of previous failures.
