Cassava plantation near Bogor (Photo: Simon Roughneen)

the-edge-review-logo – app/digital magazine available here (subscription required)

Wasps touted as antidote to mealybug infestation

BOJONG KEMANG – Saiful Santoso, 47, has been growing cassava for 17 years on his half-hectare farm a half hour drive from Bogor in west Java.

But for the past 4 years Saiful’s crop has been eaten into by phenacoccus manihoti – the cassava pink mealybug – costing him between 20 to 40 per cent of his cassava each year since then.

2014 might not be as bad as other years, Saiful told The Edge Review. “It’s been raining, and the mealybug likes dry weather.”

But the weather won’t be a permanent defence against the insatiable white bugs – and is no help three hundreds miles away in eastern Java, dryer than on the western stretches of the island.

“In places where there is low soil fertility and where the climate is dry, which the bugs like, then the damage can be up to 84 per cent of the crop,” says Dr Kris Wyckhuys, an entomologist with the International Center for Tropical Agriculture (CIAT).

Here in west Java – as in Cambodia, Laos, Thailand, and Vietnam – cassava is a cash crop, sold to the starch industry or for biofuels. Cassava is the third most important carb source in the tropics, after rice and maize, and is grown by around 500 million farmers worldwide, according to the United Nations’ Food and Agriculture Organisation.

Four years since the mealybug was first detected in Indonesia, where one million hectares of land is covered in the 2-4 meter tall cassava plants, the spread has prompted concerns over what wonks call “food security.” In east Java, cassava is food – boiled, fried, made into snacks. “58 per cent of Indonesian cassava is for food,” Wyckhaus told The Edge Review.

Mealybugs are vegetarian vampires – sucking the life out of plants. But in a horror movie insect judo, the two-millimeter A. Lopezi wasps lay eggs in the bugs, before larvae eat the host from the inside out – leaving nothing but the shell.

Scientists pitch the wasps as a no-spray cassava saviour to the Indonesian government. The idea, if the government allows, would be to release hundreds of thousands of wasps into the cassava plantations, and hope for a mealybug genocide.

A trial release of 2,000 wasps last week could be the first phase of a wider assault on the mealybugs.

Naturally-occuring predators – such as the lacewing – do not just target mealybugs, unlike the wasp, which hunts nothing else but the bugs. “We have the local natural enemies, but they often don’t work until the infesting population is high. That is already too late,” says Aunu Rauf of Bogor Agricultural University.

“You dont have to worry it will attack any other animal or plant,” Aunu tells The Edge Review.

Wyckhuys says that the wasp proved effective in Africa during the 1980’s, and more recently in Thailand – where the cassava crop was similarly-menaced by mealybugs that likely stole across the Indian Ocean from Africa, in ships carrying cassava plant cuttings.

“The success rate was high to very high, giving a yield loss reduction of 90 per cent,” Wyckhuys says.

Follow us on Twitter