Bitter melon (Momordica charantia), also known as bitter gourd, karela, or balsam pear (Palada and Chang, 2003), is a popular vegetable for many culture groups in Canadian urban centers, such as the Greater Toronto Area. Consumption of bitter melon has also been shown to be beneficial for the management of some symptoms of type II diabetes (Abascal and Yarnell, 2005). It is estimated that there is a CAD$12.4 million/year market for bitter melons in just a few of the largest Canadian metropolitan centers, and a potential countrywide market of CAD$37–66 million/year (Zheng, 2010).
Currently, the majority of bitter melons sold in Canada are imported from other countries such as Honduras (Zheng, 2010). However, for the imported bitter melons, the lost freshness due to a short postharvest life of the fruits (Palada and Chang, 2003) negatively affects their price, and Canadian consumers also worry about food safety of imported bitter melons. Moreover, there is hardly any organic bitter melon in Canadian market. Although there is a demand for local, organically produced bitter melon, the supply of such products is currently limited by Canada’s cold climate (Zheng, 2010). Bitter melons, which are native to southern China and eastern India, grow well in tropical and subtropical climates (Behera et al., 2010). In Canada, OF production of warm-season crops such as bitter melons is difficult unless some means are employed to improve the growing environment (Waterer, 2003).
HTs, as low-cost protective structures, can create a warmer microclimate for plants and have been used worldwide to promote earlier crop production, higher yields per unit area, and better-quality products compared with OF production (Lamont, 2009; Ogden and Van Iersel, 2009). However, since HTs are unheated and passively ventilated structures, the actual benefits of HT production for different crop species are determined by local environmental conditions (Carey et al., 2009). There is limited information on HT production under Canadian climatic conditions, especially in Ontario. In Saskatchewan, it has been reported that crops of muskmelon, pepper, and tomato in HTs matured 1 to 2 weeks earlier and produced substantially greater fruit yields before frost than those in low tunnels (Waterer, 2003). However, no information is available on whether HTs can be used for bitter melon production in regions with similarly short growing seasons, such as Ontario.
For organic production, the use of anti-insect netting on the vents and doors of HTs is often recommended, since it can provide a nonchemical way to effectively exclude many insect pests (Teitel, 2001). For bitter melon production in tropical and subtropical regions, the most common insect pests are fruit flies, beetles, thrips, aphids, and mites (Palada and Chang, 2003). These pests have been found in other cucurbit crops in southern Ontario. To exclude these pests, the maximum mesh size of anti-insect netting needs to be small; up to around 200 μm (Bethke and Paine, 1991). However, fine mesh size also impedes air flow through the netting and may thus increase temperature inside HTs (Fatnassi et al., 2006). During summer in southern Ontario, solar radiation intensity often exceeds most crops’ requirements (Llewellyn et al., 2013). Excessive solar radiation can increase air temperatures beyond the optimum for growing crops in protected agricultural structures that use passive ventilation, including HTs (Zhang, 2001). It is therefore important to test the impact anti-insect netting has on HT temperature and organic bitter melon production, including growth and harvest metrics as well as incidence of insects and diseases.
The objectives of this study were to explore the feasibility of organic production of bitter melons in HTs in southern Ontario, and to determine the effects of anti-insect netting on HT production of organic bitter melon.
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