A 2 lamp T5 fixture is great to supplement light coming in from a window. If it is the only source of light, it would be considered medium to deep shade, when compared to outdoors. If you run the light about 18 hours a day, it will help, but at best 2 lamps is still considered fairly low light. I use 4 lamps of T5 for my shade loving orchids. I use 6 lamps or 8 lamp 48 inch T5 fixtures for my tropical trees that want half a day of sun if they were outdoors. I use 18 hour day length.
When is it time to spray with a chemical? When you get tired of repeatedly spraying with water, or with home remedies and still find you have aphids. While the home remedies can work, one needs more persistence than I have, and to be really effective you must spray daily with the home remedy. I resort to chemical warfare early in the game for insects. I have too many plants, and not enough time to fool around with sprays that are only marginally effective.
So go to a local big box nursery, and start reading labels. READ, READ, The label has a bunch of parts, as required by law, and it is ''technically'' against the law to use any pesticide in a manner different than the label direction. As a home owner or hobby grower, you won't be held to this requirement, but anyone professional, like a farmer, or nursery, one can get in big trouble not following the letter of the directions on the label. Manufacturers put a lot of work into making sure the labels are correct. (I'm a part owner, very small part, of a farm, so I must tell you to read labels) Regardless, it is really important you take the time to read and understand labels BEFORE you buy a pesticide. Make sure it is safe for where you want to use it. Big box stores and most full service nurseries will only sell products that are approved for home owners and hobby growers to use. Some are meant for indoors, some for outdoors. Read.
If you can take the plants outside on a mild day (best if a shady work area) and spray outdoors, allow the spray to dry, no drips, then bring inside - this is a way to use sprays that are labeled for lawn and garden use, but not labelled for indoor use.
Neem oil sprays - can work well, Neem is an antifeedant, causes insects to quit feeding. It also has other effects, including mild fungicidal effects. Not a bad product, available as an organic approved pesticide. Available in sprays for indoor use. Neem has a several day residual activity. Read the label to find out how often you need to re-apply.
Pyrethrin based insecticides - used to be excellent, the pure Pyrethrin is available as an approved for organic product. Bonide and other companies make versions that are sold at big box stores, approved for use in a residential home. Unfortunately, depending on where your aphids come from, there are populations of aphids that have developed some resistance to pyrethrins that have not been chemically altered. Piperonyl butoxide is commonly included in Pyrethrin formulations, the piperonyl in its various forms tends to amplify or potentiate the effectiveness of pyrethrins, helping to overcome any acquired pest resistance. One benefit of pyrethrin is that it has a very short life once diluted and sprayed. In the presence of sunlight it can break down in hours. It is a contact spray, you must cover every surface of the leaf & stems and branches to physically wet the aphids. It will not kill eggs, you must spray a second time in less than the number of days it take an aphid egg to hatch and the new young aphid to grow up enough to start laying eggs again. At 69 to 70 F (around 18 C) it take an aphid 7 days to go from egg to adult. At 80 F degrees (26 C) it only takes an aphid egg 4 days to a new adult ready to lay eggs. So in summer you need to spray every 3 to 4 days, in winter every 5 to 7 days. Key is you must spray at least twice. I spray as frequently as needed, and I keep repeating until I have sprayed an additional time after seeing no pests. For me, using the mix I use, this is usually 3 times if I start with a heavy infestation, Once cleaned up, you should be able to go months without reinfection. Every summer pests get into our trees while outdoors, or come into the house and recolonize our houseplants.
Ortho and many other chemical companies put out synthetic pyrethrin sprays which are chlorinated, you will recognize pyrethrin as part of the name of the active ingredient. These are more effective, my ''go to'' pyrethrin spray is one of these types.
Malathion - this is not intended to be used indoors - very potent noxious odor. It is an organophosphate, different mode of action than pyrethrin. Definitely not approved for organic use. But it is an ''old school'' broad spectrum pesticide. If you take your plants outside to spray them, this one is effective against aphids. Spray while outside, let the plants dry, return to the house. It does break down, its residue is active for ??? I think I remember 3 to 5 days, I have forgotten. Read the label before you buy.
There are several different pesticide formulations that use imidacloprid, which is a systemic. Definitely not for organic use. Imidacloprid is absorbed by the plant, moves through the plant's tissue, and renders the plant poisonous to any insect that bites the plant. It has an effective residual time that is several weeks, even months. Read the labels. Bonide has various versions, as does Bayer and Ortho. Some versions are granular, where you shake a measured amount on the surface of the potting media. Other formulations are liquid and can be sprayed on. Spend time reading labels at the store, choose the one that works well your your set up. I believe Bonide has a granular version for use indoors on house plants. But I am not certain the name. Bayer trade marked Merit as the active ingredient Imidacloprid. NOT FOR USE ON ANY PLANT USED FOR FOOD. This includes fruits or nuts. At least one year must pass before fruit or nuts are considered safe from a tree treated with imidacloprid.
Imidacloprid is popular because often one application per growing season is sufficient. It is the ''lazy gardener's'' pesticide. Unfortunately some insects have developed resistant populations. So there are situations where it won't work.
There are others, but this is a good start.
