Publication Date

Spring 2015

Degree Type


Degree Name

Master of Science (MS)


Environmental Studies


Rachel O’Malley

Subject Areas

Environmental studies


Eighty three percent of the strawberries consumed in North America are grown in California, where the widespread use of insecticides has become hazardous to public health. The intensive use of pesticides for growing strawberries causes serious health risks to farm workers, in addition to contaminating the soil and groundwater. The cost to the environment and public health in the United States is estimated at $12 billion annually. Finding effective nontoxic management strategies for insect pests has become essential for long term sustainability. One strategy strawberry producers can use to promote sustainability is to increase the effectiveness of biological control techniques. Field experiments in other crops suggest that arachnid diversity and abundance may provide such a role in controlling insect pests and that agroecosystem diversification can enhance arachnid populations. This study therefore evaluated the composition, abundance, and pest control potential of arachnid communities in an organic strawberry field in California. The study found that by integrating alfalfa trap crops into organic strawberries, arachnid populations were substantially increased. Results reflected substantial increases in both male and female arachnid populations in and near alfalfa strip crops, with spider and harvestman arachnid families increasing most dramatically. Preliminary data suggest that an increase in alfalfa trap crops may lead to a reduction of the primary strawberry insect pest, Lygus hesperus, which is consumed by arachnids. These results provide useful new information for California farmers.