Tips - Yellowing Leaves

When detecting yellowing leaves, it’s time to get in action. If it’s in the last weeks of flower, there’s less concern, but it’s still a problem. Here are a few reasons why it is happening, and how to fix it. Use this information as a check list; hopefully this will solve your problem. Prevention is the key to growing. Fixing the problem before it happens.

Red Spider Mite

They are there, even if you think there not. They are blood suckers! Buy a good pesticide from your local shop. Most pesticides only kill the mites, and not the eggs. If you find a pesticide that kills them both, buy it. When mixing the pesticide with water in your spray bottle, add four to five drops of dishwashing detergent, per litre of mixture. This will help the pesticide to stick to the leaves, and suffocate the mites also. Using 10ml per litre of GreenIt in the mix, will help the plant with stress, and repair cell structure. If you have mite infestation, give the plants a good spray, and repeat after a few days. As prevention, spray once every 7 to 14 days, even if you think they're not there. Always spray with the lights off, and have air circulation.


They are little black flies (fungus gnats) that are found around the top of the pot in the soil. They lay hundreds of eggs in the soil, and when they hatch, the larvae eats the roots, which cause root rot, which causes the leaves to go yellow and the plant to die. Sciarid flies love damp soils, so if there is infestation, dry out the soil, buy a sciarid fly drench, and follow the instructions. Prevention is the key. When it comes to sciarid fly, you don’t want infestation. Here are a few biological and safe ways to fix it. A little work at the beginning will save you a lot of pain and stress. There is a product you can buy at your local store, which is crushed glass. Lay 10-20mm of the product on top of the soil, so when the flies try to go in or out of the soil they shred themselves. River sand or propagation sand can also be used. Lay 20-30mm of sand on top of the soil. The flies can’t get in the soil or out the soil and die. There are two biological ways to control sciarid fly. The first way is using Predatory Mites (Hypoaspis miles) which are beneficial mites that eat the larvae and eggs. The second way is using Beneficial Nematodes, which attack sciarid fly larvae. The cheapest and easiest way is using propagation sand. All these methods must be implicated at the beginning of plantation.


Sometimes it could be the nutrient, lacking a element in the nutrient solution, which causes leaves to go yellow. Then you have to go to your local store, and buy additives to fix the problem. Nowadays you can look up pictures on the internet, to see what deficiency you have. This is why E&G has specially designed a nutrient, with all the elements a plant needs, eliminating one major problem. Use a good nutrient and follow the feed schedule. Small plants, small amount of nutrient, bigger plants, bigger amounts of nutrients. Also buy a TDS/PPM meter, which will tell you how much nutrient you have in your reservoir. Ask your local store owner about them, and how they are used.

Over Feeding

Over feeding can cause root rot. If using coco, let the medium dry, and use a fungicide, following the instructions. If your using other methods of growing, eg. DWC and so on, check if the root system is nice and white. If they are a brownish colour, and have a strange smell, you might have root rot, use a fungicide. If using coco, buy a moist meter from your local hardware. This will tell you if your over feeding or under feeding your plants.

Under Feeding

Under feeding also causes the leaves to go yellow. Make sure the timer and water pump are working. Check the feed line for kinks, and feeders are not blocked. Make sure that all the plants are getting the same amount of water. Use a moist meter if you’re not sure.

These are just a few reasons why the leaves are going yellow. So the check list and action plan is;
  • Don’t be lazy
  • Check the feeding
  • Spray for mites
  • Kill the Sciarid fly and larvae
  • Fungicide the plants
  • Check the nutrients and pH
We at E&G Fertilizers are trying to make life Easier and the plants Greener, for you to succeed.

Yellowing leaves on outdoor tomato plants

Tell tale signs off spider mite infestation

Close up of a sciaridfly