- Vegetables: cucurbits
- Crop Production: cover crops, intercropping
- Natural Resources/Environment: biodiversity
- Pest Management: biological control, botanical pesticides, disease vectors, integrated pest management
- Production Systems: agroecosystems, organic agriculture
Squash bugs can be a serious insect pest for organic summer squash growers. The purpose of this research was to evaluate two methods to control squash bug populations. The first experiment involved planting cover crops adjacent to summer squash. Diversifed plantings have been shown to attract natural enemies, which sometimes help to keep insect populations low, or break up the farm landscape and make it more difficult for insect pests to find their way to the crop. Natural enemies were attracted to the plots, but did not significantly reduce squash bug populations. This may have been due to other food sources in the plots, such as pollen, nectar, and aphids. Also, summer squash yields were negatively affected by the cover crop treatments. The second experiment evaluated the efficacy of organic insecticides on squash bug adults and nymphs. Results of this study showed pyrethrin-based sprays are best for controlling squash bugs.
Squash bugs are the most notorious of the summer squash insect pests, inflicting serious damage. They cause feeding damage and transmit Serratia marcescens, which causes cucurbit yellow vine disease (CYVD). This disease has varying effects on yield, with crop losses from 5-100% (Bruton et al., 2003). CYVD has been identified in several states, including Georgia (Besler, 2014; Bruton et al., 1995). Plants infected with CYVD turn yellow, wilt and eventually die. Squash bugs adults and nymphs obtain the bacterium when probing the plant for feeding. The bugs harbor the bacterium while overwintering and transmit it to cucurbits when they begin feeding the next year (Pair et al., 2004).
Organic farmers utilize several methods to manage this insect pest including row covers, crop rotation, and organic insecticides, but substantial yield loss due to squash bugs is common. One method that may help reduce squash bugs involves conservation biological control. This method focuses on enhancing natural enemy populations to decrease natural pest populations. Squash bug adults secrete a foul odor when handled, so predation of adults is rare, however, nymphs and eggs have several natural enemies. Lady beetles, big eyed bugs, damsel bugs, web building and hunting spiders have been shown to be top squash bug predators (Schmidt et al., 2014). There are several other squash bug predators including: ground beetles, rove beetles, green lacewings, and spined-soldier bugs (Beard, 1940; Decker et al., 2008; Snyder, 2014; Snyder et al., 1999).
One way to increase natural enemy populations is to diversify the farm landscape by planting floral resources or cover crops near cash crops. There has been a great deal of research investigating how diversified plantings affect insects; clear benefits are debatable. In a survey of 219 peer-reviewed studies, 51% of the studies found lower insect pest populations in polyculture plantings compared to monoculture, while 49% of the studies found higher insect pest populations, no change in insect pests, or mixed results (Andow, 1991).
Non-organic growers do not have similar problems with squash bugs because there are several conventional insecticides available for squash bug control, but are not permitted for organic production. Studies using insecticides on squash bugs have focused primarily on conventional insecticides, however, there are several insecticides approved by the Organic Materials Review Institute (OMRI) that are labeled for use on squash. Some of these may provide adequate control of squash bug adults and nymphs. OMRI-approved insecticides include Monterey neem oil, Monterey horticultural oil, Monterey garden insect spray, PyGanic, Azera, and Safer Soap. There has been little research done involving squash bug and most OMRI approved insecticides, but pyrethrin has been shown to be effective at killing squash bug nymphs (Watkins, 1946).
The goal of this project was to evaluate practices to reduce squash bug populations in organic summer squash plantings. Project objectives were to:
- Evaluate cover crops as a strategy to decrease squash bug populations in summer squash
- Evaluate cover crops as method of attracting natural enemies
- Evaluate cover crops as method to discourage squash bug populations
- Evaluate the effect of cover crops on summer squash yield
- Evaluate OMRI-approved insecticides for squash bug adult and nymph control