- Vegetables: cucurbits, tomatoes
- Crop Production: catch crops
- Pest Management: trap crops
A comparison of the effects of different organic and sustainable non-crop vegetation and soil management techniques such as trap crops on striped cucumber beetle population dynamics. A Blue Hubbard trap crop provided some early season protection, but the trap crop effect broke down late in the season, and was not as effective a control method as floating row covers. Including a tomato intercrop or adding a cucurbitacin spray or a pyganic spray to the trap crop failed to improve the trap crop’s effectiveness. Data were gathered on MSU campus at the Student Organic and Horticulture farms.
In recent years there has been an increasing interest in, and demand for, organic produce (Tavernier 2003). Organic production faces many of the same pest challenges as conventional production, but often cannot incorporate conventional pest management solutions, which commonly focus on spraying crops with pesticides. Organic growers need to satisfy organic labeling restrictions which limit the types and amounts of chemical inputs (Phelan et al. 1995, Caldwell et al. 2005), often requiring them to employ different pest management techniques than conventional growers. In addition, some growers have a desire to grow fresh produce free of pesticide inputs, whether organic-compliant or not.
Cucumbers, Cucumis sativus L., are a major vegetable crop in the United States (Swiader and Ware 2002). The striped cucumber beetle, Acalymma vittatum Fabricius (Coleoptera: Chrysomelidae), is a major pest of cucumber. This pest is of great concern to vegetable growers in both organic and conventional production due to the feeding damage that adult beetles cause to the plant’s seeds, foliage, flowers, and fruit; the adults’ ability to vector bacterial wilt; and the larvae feeding on plant roots (Chittenden 1923, Foster et al 2005). Striped cucumber beetles overwinter as adults and emerge to feed early in the growing season, badly damaging or killing young cucurbit seedlings or new transplants. After emergence the adults feed and lay eggs in the soil around the base of their host plant. Striped cucumber beetles are univoltine in the north central United States, and can be bivoltine in the warmer southern gulf states (Chittenden 1923, Davidson & Lyon 1979, Capinera 2001). The larvae feed on roots, but they are less of a threat to cucumber production since they do not begin feeding until the plants are large and they do not transmit bacterial wilt (Chittenden 1923, Foster et al. 2005). The larva does not cause fruit scarring as long as the fruits are not in direct contact with moist soil (Chittenden 1923). The striped cucumber beetle host range covers most cultivated Cucurbitaceae, including squash, melons, and cucumbers.
While there are several insecticides available for striped cucumber beetle control (Bird et al. 2008), few are certified for use in organic production systems and, like other insecticides, they can harm beneficial organisms such as natural enemies and pollinators (Johansen 1977). In areas where bacterial wilt is infrequent, such as in many parts of the north central United States (Hayward 1991), cucumber plants can withstand up to 25% defoliation without exhibiting significant yield loss (Burkness and Hutchison 1998). In these conditions, organic-compliant techniques to manage cucumber beetle are possible and some, such as trap cropping, are employed with varying degrees of success.
Trap cropping is used in commercial settings for striped cucumber beetle management, but the technique commonly relies on the application of an insecticide to the trap crop once beetles are detected, which is not desirable for some organic producers (Hokkanen 1991, Javaid and Joshi 1995, Shelton and Badenes-Perez 2006). On muskmelons, C. melo L., 82% of northern corn rootworm, Diabrotica howardi Barber (Coleoptera: Chrysomelidae), and striped cucumber beetles were found on the trap crop rather than on the muskmelon crop (Metcalf 1985). In another study, striped cucumber beetle densities were 42% to 81% higher in an NK530 squash perimeter trap crop, Cucurbita maxima Duchesne, than in the main melon crop, C. melo L. (Caldwell and Stockton 1998, Caldwell et al. 1998). In an extension program, all participating growers stated that their pest control using a perimeter trap crop of Blue Hubbard squash, C. maxima Duchesne, around their green and yellow summer squash, C. pepo L., was “much better” than in previous years without a trap crop (Boucher and Durgy 2004). Radin and Drummond (1994) recorded that at least 70% of striped cucumber beetles were in a squash trap crop, C. maxima cv. ‘Sweet Mama’, compared to 30% in a cucumber crop. Squash trap crops also protect watermelon, Citrullus sp., and muskmelon, C. melo, from striped cucumber beetle (Cline 2004, Hoffman 1999). Blue Hubbard squash is a particularly promising candidate for a trap crop because striped cucumber beetles prefer it over most other cucurbit species (Reed et al. 1984, Pair 1997, Boucher and Durgy 2004, Shelton and Badenes-Perez 2006).
Increasing plant diversity in the field through intercropping and polyculture is an organic-compliant approach which can cause a 10 to 30 fold reduction in striped cucumber beetle populations compared to a monoculture (Bach 1980). The addition of a non-host tomato crop, Solanum lycopersicum L., to a field of cucurbits in some cases reduces the number of striped cucumber beetles present (Lawrence and Bach 1989). In comparison, trap cropping tends to be more effective at reducing phytophagous insect pest populations than intercropping (Banks and Ekbom 2004), but it is not clear whether in combination the effects are additive.
A trap crop’s attractiveness to an insect pest can sometimes be enhanced with biological attractants such as kairomones (Hokkanen 1991, Javaid and Joshi 1995, Shelton and Badenes-Perez 2006). The addition of biological attractants can significantly enhance trap crops in the control of the Colorado potato beetle, Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae) (Martel 2005). Kairomones that attract striped cucumber beetle and which may be useful in trap crop enhancement have been identified and are commercially available (Lewis et al. 1990, Fleischer and Kirk 1994, Brust and Foster 1995, Jackson et al. 2005). Attractive kairomones were used to enhance the attractiveness of sticky traps to reduce cucumber beetle populations by 50% by placing 40 kairomone enhanced sticky traps per acre around field edges (Hoffmann 1996). Such kairomones were also used in several different striped cucumber beetle baits (Fleischer and Kirk 1994, Burst and Foster 1995, Schroder et al. 2001, Martin et al. 2002, Jackson et al. 2005).
This study focuses on investigating organic-compliant non-insecticidal methods for managing striped cucumber beetles in cucumber production by increasing the level of plant diversity using a trap crop and an intercrop. Specifically, a comparison was made between the effectiveness of a squash trap crop, a cucumber and tomato polyculture added to the trap crop, and a squash trap crop with added biological attractants in reducing striped cucumber beetle densities on cucumbers. Floating row covers placed over the cucumbers and use of an organically approved insecticide were also included in the comparison of organic-compliant techniques.
Intermediate-term: Catalyzing co-learning, knowledge and innovation among organic and transitioning farmers, and improving the sustainability and profitability of cucumber production in the Midwest.
Short-term: A sustainable pest management plan for cucumber beetle using improved trap crop effects, adding to scientific and outreach literature, and generating informed discussion about sustainable approaches to agriculture among growers.