Agriculture is a critical component of the national and global economies as well as food security. Agricultural crops exist as part of an ecosystem, in which they interact not only with pest species but also with a wide range of "mutualists," including pollinators, beneficial soil fungi, and natural enemies of pests. In spite of the great diversity of interactions in agroecosystems and the financial value of mutualisms, the vast majority of research and effort in agriculture is focused on reducing pest impacts, without consideration of the broader context of both antagonisms and mutualisms that combine to affect crop yield. This project takes a broad approach to addressing how interactions amongst both damaging and beneficial species affect crops and pollinators by examining three different economically important systems in Massachusetts.
The first of these is interactions between beneficial fungi and herbivores in cucumber. Nearly one million tons of cucumbers were harvested in 2006 for a value of $400 million nationally. Over 1,336 acres of cucumbers were grown in Massachusetts alone. Despite their ubiquity and importance in nutrient transfer, we are only beginning to understand how soil fungi influence interactions between cucumber plants and other organisms. Because soil management practices in agricultural systems can have profound effects on soil fungal communities, it is important that we understand how mycorrhizae (fungi that grow in association with the roots of a plant in a symbiotic or mildly pathogenic relationship) affect interactions between crops and insect herbivore pests that limit plant growth and yield.
The second of these systems encompasses interactions between a parasitic plant and herbivores in cranberry. In 2008, the total value of U. S. cranberry production was $444 million, with more thatn 80% of that production coming from Massachusetts and Wisconsin. The parasitic plant dodder is a serious pest in cranberry in both these states and one that can profoundly affect yield. Knowing whether certain cranberry varieties are more prone to parasitism could inform decisions about when and how to manage dodder. Furthermore, understanding cranberry varietal response to dodder infection and resistance mechanisms could lead to the development of resistant varieties, reducing herbicide inputs for this crop.
The third examines how pesticides and naturally-occurring plant defenses against herbivores affect performance of managed bumble bee pollinators. The value of pollination services in agriculture and rangelands has been estimated at $117 billion per year in the United States. Recent declines in managed and native bees due to pesticide use, disease and parasites indicate that management of pollination may be essential to maintain crop yield. Pollinators are exposed to a wide range of naturally-occurring plant compounds in both nectar and pollen. Such compounds have the potential to affect pollinator preference and performance, both of which could have significant agricultural impacts. However, recent work suggests that nectar defense compounds could confer resistance against pathogens in bumble bees. Bee preference for nectar with secondary compounds may differ depending on disease status. Pesticide residues will be addressed in future work.