Effective Plant Extracts as Repellents for Sugarcane White Leaf Disease Vector Deltocephalus menoni (Hemiptera: Cicadalidae)

Sugarcane White Leaf Disease (WLD) is one of the major threats to the sugarcane industry in Sri Lanka, and it is transmitted by a vector, Deltocephalus menoni (Hemiptera: Cicadellidae). An experiment was conducted in the Sugarcane Research Institute (SRI), Uda Walawe, with the objective of determining potential repellents for D. menoni. A preliminary choice test was conducted using six plant extracts, i.e., Neem, Marigold, Mustard, Garlic, Lemongrass, and Citronella, with repellent effects for hemipterance. The most effective plant extracts were selected to develop gel vaporizers. The effectiveness of each vaporizer to repel vectors and effective distance was studied in the field. Also, phytotoxic effect, retention of odor, keeping quality, and yeast and mold count of each were studied in the laboratory. Among selected plant extracts, four, i.e., Marigold, Mustard Leaves, Lemongrass, and Citronella, were effective as repellents and toxic for WLD vector. All four effective treatments showed significant repellence to the vector, i.e., mustard (p > 0.0007), lemon grass (p > 0.0007), citronella (p > 0.0008), and marigold (p > 0.0003) at 3 m distance. The highest effective distance was recorded for Citronella and marigold. It was 9 m from the gel vaporizer. Effective distance for mustard was 6 m, and it was 3 m for lemongrass. Accordingly, citronella and marigold showed the highest repellence to the WLD vector in the menace of repellent character and effective distance. Odor retention of the all four selected gel vaporizers was in good quality for a 2-week period, and after 2 weeks it was in a diminishing trend in an open environment. Under both cold and dry conditions, keeping quality was observed to be in a good state. For all the prepared gel vaporizers, the yeast and mold count was zero initially. According to the results, lemon grass, marigold, mustard, and citronella gel vaporizers were effective in repelling D. menoni in different extents and had good potential in repelling vectors from the plants.