Spider Mite Management
Spider mite (Tetranychus urticae) outbreaks are being reported by South Carolina extension agents with increasing frequency and earlier in the season than is typical. There are also cases of miticide failure. Spider mites can cause serious yield losses. Outbreaks are attributed to applications of broad-spectrum insecticides, which have non-target effects on the natural enemies that otherwise control spider mite populations. Little is known about the abundance or diversity of naturally occurring (non-released) spider mite predators in vegetables. Additionally, monitoring spider mite populations for miticide resistance development will allow extension personnel to provide growers with advance warning of products that are losing efficacy. Tetranychus urticae is known as the most resistant pest species, with resistance to 95 active ingredients documented. If spider mite outbreaks can be reduced through conserving natural enemies, miticide resistance development could be slowed or halted.
Many management practices implemented by growers have the potential to impact biological control of pest arthropods by natural enemies. In conventional agriculture, broad-spectrum pesticides can cause direct harm to natural enemies through non-target effects. Landscape simplification reduces the diversity of resources available to natural enemies and regular cultivation practices, like tillage and weed control, reduce the amount of available non-crop habitat. Biological control can play a critical role in organic systems, especially because chemical options for pest management are limited. Implementation of conservation biological control can have positive outcomes, resulting in lower pest pressure and reduced pesticide applications. However, striking a balance between conserving natural enemies and using agricultural inputs to maximize returns on high value crops, like vegetables, is challenging. Identification of natural enemies is crucial because not all natural enemy groups are conserved through the same practices. Additionally, knowledge of which natural enemies are important in particular systems allows for the creation of targeted extension material regarding the identification and biology of particular species. Therefore, we seek to provide regional- and crop-specific information regarding best practices for natural enemy conservation.
Soil Health Impacts on Insects
There is an increased emphasis on examining the farm as an entire agroecosystem, including impacts of soil management on later, seemingly unrelated, aspects of management. One critical component is arthropod pest management. Evidence is mounting that below-ground effects move upward and have the potential to alter how pest insects respond to a host plant. Soil management practices alter macro- and micronutrient soil composition, physical characteristics of the soil (e.g. aggregate stability), and the microbial community. All of these effects have the potential to alter crop plant defensive compounds, tissue nutrients, and volatile production. In turn, these traits can change the response of arthropod pests in the environment to the host plant. A better understanding of when these interactions occur and what causes them will have substantial benefits. First, we may be able to recommend specific soil management practices to growers not just for soil health benefits, but also for their ability to help with specific arthropod pest problems. Additionally, examining the mechanism behind these interactions will enhance our understanding of basic ecology, providing a valuable addition to the expanding field of below and above-ground interactions.