The carrot weevil, Listronotus oregonensis (Le conte), is the most significant pest of carrot (Daucus carota L.) crops in Quebec, where more than 40% of the crop may be damaged if the weevil is left uncontrolled (Zhao et al., 1991). Carrots become attractive to the weevil at approximately the four-true-leaf stage. The female lay eggs in slits on the petioles of the leaves. Newly hatched larvae fall to the ground and begin feeding externally on the root. Damage is usually limited to the crown and top one-third of the root, causing the carrot to lose its fresh market value. In Quebec, the maximum damage tolerated by growers is ≈2% (Boivin, 1999).
Management of this pest is done mostly through chemical insecticides; however, concern over pesticide use has increased considerably among growers and the general public. The potential adverse effects of pesticides on the environment coupled with the development of insect resistance suggest that there is a great need to evaluate alternative control strategies to replace or reduce pesticide use.
Agrotextile floating rowcovers are already being used successfully to manage insect pests and the viruses they transmit to vegetable crops such as radish (Rekika et al., 2008; Wells and Loy, 1985), cauliflower (Millar and Isman, 1988), muskmelon (Perring et al., 1989), zucchini (Costa et al., 1994), melon (Farias-Larios et al., 1999; Orozco et al., 1994), and winter squash (El-Zammar et al., 2001). In carrot, rowcovers have prevented carrot fly attack in a strategy to reduce pesticide use (Davies and Collier, 2000) or for organic production (Peacock, 1991).
In addition to pest control, floating rowcovers modify the microclimate surrounding the plants and potentially provide a less stressful growing environment (Lamont, 2005). However, under some conditions, they can create supraoptimal temperatures deleterious to the crop and must be removed (Benoit and Ceustermans, 1990). To reduce this problem, lighter agrotextile materials were developed to alleviate heat stress allowing them to remain on the crop for longer periods for insect protection. Floating rowcovers readily allow percolation of water and spread the impact of the water droplets over a larger surface area, reducing soil compaction (Lamont, 1996; Wells and Loy, 1993). This feature is particularly important for seeded crops such as carrot in which soil crusting caused by rainfall or irrigation and occurring shortly after sowing is a major cause of poor emergence (Finch-Savage, 1986; Hartz, 1994).
The objectives of this study were to evaluate the influence of an agrotextile floating rowcover on germination and growth of carrot and to determine its effectiveness in preventing carrot weevil damage in relation to varying covering periods.
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