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Insects to munch invasive species

Posted by: Saving Water SA (Cape Town, South Africa) – partnered with Water Rhapsody conservation systems – 12 January 2011

A team of Rhodes University scientists has been awarded a R9-million contract by Working for Water to research biological ways to control invasive aquatic weeds.

Water hyacinth can double the area it occupies in 7 days

The team from the university’s zoology and entomology department has enlisted pupils, disabled people and even a former prisoner to breed and release millions of insects that munch the alien pests hogging water resources, clogging waterways and destroying indigenous plant life.

South Africa loses 9% of its invaluable water runoff to alien invasive species such as the water hyacinth, parrot’s feather, salvinia, water lettuce and red water fern, according to Rhodes entomology professor Martin Hill, who heads the project.

The plants, especially the water hyacinth, thrive in often polluted waterways that provide them with high levels of phosphorous and other plant nutrients.

Water hyacinth is originally from South America but has spread throughout the world. It can take over huge expanses of water quickly, doubling the area it occupies in seven days.

“So if it occupies a hectare of water today, in a week’s time it would have taken over 2ha,” said Hill.

Herbicides had a limited effect, often affecting indigenous insects, fish and other plant life. The answer was to use the plant’s natural insect enemies from their region of origin, he said.

Hill has spent many years doing this. He introduced insects with such success in waterways around a Ugandan village that the local chief wanted to reward him with a house and wife.

He said weevils, moths and bugs were quarantined and studied for at least five years before release. It had to be ascertained they fed only on targeted weeds.

“These insects are totally safe and pose no threat to indigenous or economic plant species.”

Alicedale’s New Year’s Dam was almost completely cleared of water hyacinth.

Hill said the insects would not eliminate the weed altogether but reduce it to an acceptable level.

By: Adrienne Carlisle
Source: Times Live

1 comment to Insects to munch invasive species

  • Stephen Klaber

    Watch out for biological controls – evolution happens! The insect that cannot survive in your environment except on the Water Hyacinth will soon find ways to digest a new food – perhaps your rice crop. To make mechanical control work, you must make a profit on the harvest. WH can be compressed into biomass briquettes and used as fuel in low pollution stoves that produce charcoal as a byproduct. It can be digested into methane along with sewage. It can be used to feed livestock. New ways to use its fiber appear on the internet everyday.

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