HARRISBURG, Pa. (ErieNewsNow) - Many people are looking forward to warmer weather, but as temperatures increase, so do pesty insects, like gnats. 

Gnats, also known as black flies, can lay multiple generations of eggs in rivers and streams throughout the summer months. 

The Pennsylvania Department of Environmental Protection (DEP) Black Fly Program controls black fly populations throughout 1,700 stream miles and 36 counties around the commonwealth. Thanks to adequate funding and resources in recent years, DEP Secretary Patrick McDonnell says the program has been successful. 

“Two years ago, we had over 7,000 complaints about black flies within the program. Last year, that was less than 300 complaints. So, it just shows, when we have the resources, we're able to deliver a good quality program that allows people to enjoy the outdoors, recreate, and farm,” said McDonnell. 

The program sends biologists to sample and research areas where the flies are located. Once an area is determined to have a high population, helicopters are then used to drop an organic material known as Bti. 

“It's based on a soil bacterium, it's photodegradable, it doesn't build up in the environment, it's not a chemical. It's organic, it's used in organic farming and other things. So, it's very safe,” said McDonnell. “We've been using it for over 30 years.” 

Doug Orr, the Environmental Group Manager for the DEP Vector Management Program, says if you’re out on the water and hear a helicopter, don’t be startled and do your best to make your presence known. 

“If you're on a river stream and you hear a helicopter coming, please make yourself noticeable to the pilot,” said Orr. “Because sometimes with glare or trees, it is hard sometimes to pick out a fisherman or a boater. The pilots do reconnaissance and look for people in the rivers. We do not want to target people or spray them. The pilots are instructed to move up or downstream if they see people in the spray site,” said Orr. 

Bti can also be sprayed by officials on the ground using what's called a "backpack sprayer."

Officials say black flies do not carry diseases in Pennsylvania, but they do bite and are certainly a nuisance when the weather gets warmer. 

Officials say they’ve made great progress with water quality by cleaning up rivers and streams in recent years, but that means a better environment for black flies, which thrive in clean, flowing water. 

“We’ve obviously made great strides across the commonwealth in terms of water quality, and one of the things that black flies need is clean water,” said McDonnell.