D3059: Managing agricultural drainage ditches to improve conservation biological control

Ditch habitats may provide valuable ecosystem services to producers by enhancing natural enemies of pests and increasing their biological control. Conservation biological control provides an alternative for a sustainable approach to managing pests by enhancing natural enemies through providing their ecological needs. To date, little research has been conducted on the natural enemies found in agricultural drainage ditches in farm fields. Here, we attempt to demonstrate the value of ditch management to improve conservation biological control for farmers. Two studies were conducted. The first one, using a sticky trap, natural enemies were sampled weekly from cleared and uncleared ditches with potted Chinese cabbage Brassica Rapa plants. The second trial was conducted in two different locations. To evaluate the activities of the natural enemies in cleared and uncleared ditches, ten third instar diamondback larvae were placed on the upper leaves of four randomly selected Chinese cabbage plants on each side of the ditches. To evaluate the impact of environmental factors on larvae survival, plants infested with larvae were placed inside the cages. After 24 h of exposure in the field, the remaining larvae were counted to determine the number of larvae consumed by predators or missed. The preliminary result indicated high abundances of the natural enemy population in the uncleared ditches compared with the cleared ones, and on average, six larvae/pot missed in the uncleared ditch in location 2. However, there were a high number of missing larvae in a cleared ditch in location 1. Further research is underway.