Hi Vonnie –
There are definitely ways to fix your problems without adversely affecting your lake. In order to improve the conditions with your lawn, I would suggest the Ringer Lawn Restore to give it a pep in it’s step. There are directions on the packaging as to how much you should add and when. If you end up getting close to the water line of your lake, it may simply raise the nitrogen levels, but not to the point where it would harm any aquatic life. The fertilizer contains 0% phosphate so it will NOT contribute to algae blooms.
If you are wondering about getting rid of weeds in your lawn as well, the only other option besides adding Concern Weed Prevention Plus to your lawn (in early spring) would be to use a product called AllDown Organic Herbicide. This product is made from acetic acid and citric acid so there is no worry of nasty chemicals leeching into the lake. The only downside is that it is non-selective and will kill the surrounding grass in which case you would need to wait for it to grow back on it’s own.
Regarding your mosquito problem, I would suggest the use of Mosquito Dunks in order to prevent mosquito larvae from hatching and causing a fuss around the house. Each dunk covers 100 square feet of water, so apply as many as needed near the water line around your house. These will last up to 30 days, but may need 48 hours to begin working at full speed. These are also harmless to aquatic life as well as pets, children, and wildlife.
Now, onto the fungus gnats. These annoying little critters LOVE moist, wet environments. If there is a way to reel in the watering for a little, this may helps to discourage them from breeding around the lawn. Applying beneficial nematodes will help immensely and they are also safe to be around your lake. Each box is packed with 10 million active units that will cover between 285 to 550 square feet. They will also kill off any other unwanted pests that may be lurking in your soil.