Sustainable control of powdery mildew (Pseudoidium nephelii) of rambutan (Nephelium lappaceum Linn.) using medicinal plant crude extracts
Thailand produces a range of tropical fruit including mangosteen (Garcinia mangostana Linn), durian (Durio zibethinus Linn.) and rambutan (Nephelium lappaceum Linn). Rambutan produce is severely affected by powdery mildew (Pseudoidium nephelii). Affected fruit are rendered unacceptable to the market. To avoid the problems of chemical residues a number of medicinal plant extracts were screened for their ability to control powdery mildew. Crude extracts from eight medicinal plants, wood vinegar, calcium bicarbonate, and the fungicides carbendazim, tridemorph, copper oxychloride and sulphur were tested in vitro. Extracts of Curcuma longa, Streblus asper, Allium sativum, Zingiber cassumunar, Polygonum tomentosum and Antigonon leptopus at a concentration of 0.5 g mL-1, wood vinegar (0.5 µL mL-1), carbendazim (0.2 mg mL-1), tridemorph (0.25 mg mL-1), copper oxychoride (1.25 mg mL-1) and sulphur (1.25 mg mL-1) all gave 100% inhibition of oidial germination. Extracts from Alpinia galanga and Zingiber officinale at concentration of 1.0 and 0.5 g mL-1 and calcium bicarbonate (1.0 mg mL) were ineffective. In a field trial, carbendazim (6.92% infection severity) and wood vinegar (9.29% infection severity) were the most effective, being significantly different (p=0.05) from the next group which comprised of Curcuma longa extract (13.78% infection severity), copper oxychoride (12.82% infection) and the farmer's conventional application of tridemorph and wood vinegar (13.20% infection severity). Other treatments had greater efficiency than the control treatment (61.06% infection severity). Curcuma longa reduced disease severity and enhanced marketable yield, resulting in a 70.60% increase in good quality marketable fruit. Therefore, Curcuma longa extract and wood vinegar can be considered as alternatives to chemical control of powdery mildew on rambutan.
Preecha, C., Visuthipath, V. and Sripiak, P. (2017). Sustainable control of powdery mildew (Pseudoidium nephelii) of rambutan (Nephelium lappaceum Linn.) using medicinal plant crude extracts. Acta Hortic. 1178, 179-184
medicinal plant, crude extracts, sustainable control, powdery mildew, Pseudoidium nephelii, rambutan, Nephelium lappaceum