In recent years, cicadas have spread rapidly and caused serious damage in many coffee-growing areas of Vietnam’s Central Highlands and beyond, significantly reducing both yield and production.
Traditionally, coffee farmers relied on chemical insecticides to fight cicadas, but this approach was costly and delivered limited results. Recent research by the Plant Protection Institute has identified two far more effective control measures: using plastic mulch (nylon sheeting) and applying lime powder, both of which outperform insecticides.
Scientists have identified six cicada species that attack coffee in the Central Highlands, with Dundubia nagarasingna being the most common. Despite species differences, they share key biological traits: nymphs (juveniles) emerge from the soil at night to climb onto coffee branches and leaves for their final molt into adults. Adult cicadas live only 2–4 weeks. They suck sap from branches and stems, weakening the plants, and lay eggs in small twigs, which can kill or damage those twigs. Underground, the nymphs feed on roots, slowing growth and causing yellowing leaves, fruit drop, and—in severe infestations—even plant death.
Plastic Mulch (Nylon Covering)
This manual method involves covering the soil around the base of each coffee tree with nylon sheeting during the period when nymphs emerge to molt. When the nymphs try to surface, they are trapped and die. The plastic also prevents newly hatched nymphs, which drop from tree branches, from burrowing back into the soil.
Lime Powder Treatment
A 2% lime-water solution (lime powder mixed with clean water) is applied at a rate of about 5 liters per coffee tree during July–August. Within 5–10 minutes of application, roughly 16–40% of cicada nymphs will crawl up out of the soil. Farmers can then collect the nymphs by hand or release chickens or ducks to eat them.
Important note: After 5–10 minutes, any remaining nymphs that are not collected will re-enter the soil. Farmers should then lightly cover the holes with soil. The lime solution does not kill the nymphs; it merely forces them to the surface temporarily.
Comparison with Pesticides
Chemical insecticides show relatively low effectiveness against cicada nymphs. The best result recorded was Bitox 40EC at about 60% effectiveness 21 days after application; Motox 5EC achieved 56–57% after 14–21 days; most other chemicals stayed below 30% even after 21 days. The biological preparation Metarhizium (250–500 g per tree) required 45 days to show results and achieved only 17–33%. Mineral oils had no effect at all.
These findings show that plastic mulching and lime-water treatment are currently the most practical and cost-effective strategies for controlling cicadas in coffee plantations.