I MUST HAVE ABOUT 100 HOUSE PLANTS WHICH I HAVE BEEN GROWING FOR MANY YEARS. MY PROBLEM IS THAT THERE ARE THESE BLACK TINY KNAT TYPE PESTS WHICH ARE ALWAYS SWARMING AROUND THE PLANTS AND THROUGHOUT MY HOUSE. 2 TEARS AGO, THERE WERE SO MANY KNATS AROUND MY HOUSE , I TRIED MANY PLANT PESTICIDES, BUT THIS ONLY SEEMS TO KEEP IT UNDER CONTROL TO A POINT, BUT DOES NOT TOTALLY GET RID OF THEM. MY HUSBAND WANTS TO THROW OUT EVERY PLANT IN THE HOUSE, I HAVE HAD SOME OF THESE PLANTS FOR 30 YEARS. PLEASE TELL ME WHAT I CAN DO TO GET RID OF THE KNATS FOR GOOD. THX FOR YOUR HELP.
Gnats are a sign of keeping the soil too wet. They breed (fly maggots) in wet soils. Let your plants dry out sufficiently between waterings.
Water by weight. put a saucer under the pot. Water and let the plant sit in the excess water for 5-10 minutes. after that time pour off any excess water in the saucer. Pick up the pot. It should feel heavy. Don't water again until it feels considerably lighter in weight. The soil will be light in color/not dark and wet. You can always poke your finger into the soil to see how far down it is wet. Indoors check your plants every 3-10 days. Watering frequency depends on many factors (sun exposure, wind, day temps, etc.). Not all your plants will need watering at the same time.
To help get rid of the gnats after you start watering correctly here are few ideas.
You could buy a safer soap pesticide (professionally formulated) and apply it as a soil trench. Read the directions for use as a soil drench. It will kill the worms in the soil. You may need to follow up with another treatment 14 days later. You can also spray the foliage with the safer soap pesticide.
They make yellow sticky plastic cards to put near the plants to attract the adults and kill them.
You could also sprinkle a teaspoon of turf lime over the soil to sweeten (raise the soil pH - make less acidic) the soil. Acidic soils attract gnats.
Get to a local garden center/nursery and quiz them on a solution to your problem. You may have to go to more than 1 garden center to find someoene knowledgeable. Take a sample (dead or alive)of the gnats in a sealed plastic bag for someone there to ID the insect..Buy your products from them and they should be more than happy to help you.
Rick in southern NJ