All pig tracks lead to pond apple

More than 22,000 pond apple trees have been hand treated along creeks in the Upper Murray region this year in an effort to blitz the invasive species that is being spread by flood. Following the treatment of 115 hectares last year, ground teams have expanded their search to take in Corduroy and Boar Creeks in the Murray catchment.

A weed of national significance, pond apple was introduced to Australia in 1912 as grafting stock for commercial custard apple crops and is now a major environmental weed in the Wet Tropics. Removal work is part of Terrain NRM’s “Fish Homes and Highways” project and is funded by the Australian Government’s Reef Trust.

Terrain’s Deb Bass says the spread of pond apple is especially worrying for its potential to impact mangroves.

“Pond apple forms dense stands in swampy areas and is capable of replacing mangrove or freshwater wetland ecosystems if left unchecked. We’ve treated approximately 150 hectares this year.”

Seeds are usually spread in big quantities in flood waters so the ground team is working from the upstream reaches out toward the coast. Feral pigs are also proving to be prolific seed spreaders.

“Whilst pond apple is not considered good to eat by humans, feral pigs think the fruit is pretty tasty.  The weed team are guaranteed to find big clumps of pond apple when they follow the pig tracks into the forests,” said Ms Bass.

The silver lining is that the seed bank is only viable for two years. Some weeds have seeds that will germinate many years later, but pond apple can be effectively controlled by treating the same area two years in a row.

Ms Bass said it is critical that weed management programs are properly funded and managed.