Individual study: Volatile allelochemicals in the Ageratum conyzoides intercropped citrus orchard and their effects on mites Amblyseius newsami and Panonychus citri
Kong C.H., Hu F., Xu X.H., Zhang M.X. & Liang W.J. (2005) Volatile allelochemicals in the Ageratum conyzoides intercropped citrus orchard and their effects on mites Amblyseius newsami and Panonychus citri. Journal of Chemical Ecology, 31, 2193-2203
This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.
Grow non-crop plants that produce chemicals that attract natural enemies
A controlled study in 2001-2003 in Guangzhou, China (Kong et al. 2005) found that more predatory mites Amblyseius newsami occurred in orange Citrus sinensis orchards with a tropical whiteweed Ageratum conyzoides ground cover (0.3 mites/orange tree leaf) than in control orchards (0.09 mites). The pest citrus red mite Panonychus citri was also less numerous in orchards containing tropical whiteweed (0.03 mites/leaf) than control orchards (0.18 mites). Odour choice tests in the laboratory found that Amblyseius newsami was strongly attracted to volatiles from fresh leaves (61% of choices versus a control) or essential oils (95% of choices) from tropical whiteweed. The study compared an orchard with a tropical whiteweed understorey grown for two years, and a control orchard with a groundcover of naturally growing weed species (but with tropical whiteweed removed). Mite counts took place in June 2003 using 15 randomly selected orange trees.
Use chemicals to attract natural enemies
A controlled study in 2003 in Guangzhou, China (Kong et al. 2005) found that more predatory mites Amblyseius newsami occurred in orange Citrus sinensis trees treated with essential oils of tropical whiteweed Ageratum conyzoides (0.41 mites/leaf) than on control trees (0.09 mites) after 24 hours. However, 48 hours after treatment, numbers of predatory mites had dropped to 0.13 mites/leaf. Fewer pest citrus red mites Panonychus citri were found on treated (0.05 mites/leaf) than control (0.18 mites) trees after 24 hours, but numbers increased to 0.19 mites/leaf on treated trees after 48 hours. A 5% emulsion of tropical whiteweed essential oil and a water control were applied to 18 and nine orange trees, respectively. All trees were more than 15 m apart. The authors found that a tropical whiteweed ground cover increased predatory mite numbers (see 'Grow non-crop plants that produce chemicals that attract natural enemies') and they suggest this may attract the predator for longer than using essential oils.