Answer: From your description, it is difficult to identify the insect pests. I would strongly recommend you stop spraying Windex on your plants, though. While you may find soap in the product, you'll also find alcohol and other chemicals which can harm your gardenia. Your plant will be better off if you spray it with plain water or purchase an Insecticidal Soap that is manufactured for use on plants.
Various scale insects and spider mites feed on gardenias, though the most commonly reported insects are whiteflies, Japanese wax scales, and aphids. Here are the descriptions to help you identify the pests:
Citrus whitefly -The leaves are coated with honeydew and sooty mold. Flat, pale-green scales (about 1.5 mm long) and occasionally whiteflies are found on the leaf bottoms.
Japanese wax scale -White, waxy blobs (up to 6 mm in diameter), often accompanied by sooty mold, appear on limbs and twigs.
Melon aphid -New growth is curled and stunted by small, green or brown aphids feeding on leaves and new shoots.
Twospotted spider mite- Tiny chlorotic dots or stipples appear on the upper leaf surface; tiny mites or eggs appear on the lower surface.
Once you've identified the pest, you can use a control measure that's safe for your gardenia.
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