It has only taken two years after its arrival in Vietnam for a new species of larva to wreak havoc on thousands of hectares of grapefruit and orange crops in the Mekong Delta.

The larvae, locally called ‘sau hong’ (reddish larva) and scientifically known as citripestis sagittiferella, have consumed hundreds of billions of dong worth of investments from local farmers, while what most concerns the latter is the insecticide capable of killing these creatures is yet to be found.

While traders are paying high prices for grapefruits, local farmers in Ben Tre and Tien Giang say they have no fruit to sell due to the “reddish larva epidemic.”

The pests have destroyed the grapefruits from inside, causing the fruit to drop, and leaving farmers upset with their destroyed crops.

Phan Thi Thuong, a farmer in Mo Cay Bac District, said the larvae has eaten away 80 percent of her 150-tree grapefruit plantation.

“I have tried every possible preventive solution but still cannot get rid of the larvae,” she lamented.

Citripestis sagittiferella is a species of snout moth in the genus Citripestis. It has long been found in Indonesia, Malaysia, Singapore and Thailand, but only emerged in Vietnam in the last two years, according to recent research by Can Tho University.

The larvae penetrate the fruit of their host plant, thus avoiding death by pesticide. The pests cause rotting and premature dropping of the infested fruit.

According to the Southern Plant Protection Department, reddish larvae also attack other citrus fruits such as oranges and lemons.

Oranges are most likely the next victim as there is little grapefruit supply left for the larvae, the department warned.

Preventive methods

The reddish larvae epidemic has spread through all of the localities in the Mekong Delta, infecting some 8,000 hectares, or 10 percent, of citrus tree crops. The figure still continues to gradually rise, the department said.

The plant protection department has worked with Can Tho University to figure out the best possible preventive solutions for the issue.

“Out of the suggested solutions, wrapping the fruit seems the most effective,” said department director Ho Van Chien.

Specifically, farmers are advised to wrap the grapefruits with plastic bags when they are one month old.

“The success rate for this method is more than 80 percent,” Chien said.

“The cost is some VND2,000 per fruit, but as each fruit yields nearly VND100,000 after harvest, this method is not so costly,” he added.