Residents along the shoreline of Hartbeespoort Dam in Broederstroom are suffering from swarms of midges.
“We cannot go out of our homes, spend time outside or do anything in the area. There are trillions of them swarming in the air,” a resident at Estate D’Afrique said. “It is so bad that potential buyers in the estates immediately leave when they see the plague.”
Some residents are under the impression that the bugs are biological control bugs that eat the hyacinth. It is not. The swarming insects are midges, the Centre for Biological Control at Rhodes University said.
“These swarms are definitely not Megamelus scutellaris, the water hyacinth biocontrol agent. Their numbers are still growing on the dam and no winged adults have been observed on the dam. When we start to suspect that they might start flying (around January), we will alert residents. They are harmless though and will just be looking for more water hyacinth to eat,” said Dr. Kelby English.
“Regarding the midge plague, weather and breeding conditions have been optimal over the last month, increasing the breeding swarms which residents have witnessed. The water level has also dropped quite a bit when the sluice gates were opened for agricultural irrigation. If this is a species of midge that develops in stagnant water or mud, the water level dropping would have caused puddles to form and exposed mud which helped them increase their numbers. These insects are harmless, they don’t bite us or our animals,” said Dr. Kelby English.
These insects explode in the warmer months and in response to poor water quality.
According to water scientist Dr. Bill Harding, midges are very common in shallow enriched vleis and the maturation ponds of wastewater treatment works. “Rate of water movement is not a factor but large numbers and extended nuisance periods are a clear indicator of (often worsening) water quality issues. They are always present in small numbers but assume pest proportions in polluted waters,” he said.