Neudorff Indoor Plant Spray for House Plants and Greenhouse, Kills Spider Mites and Scale, 32 oz Review (2026)

What it treats and how it works

This spray is a contact insecticide and ovicide, meaning it kills pests it directly touches at every life stage, including eggs, larvae and adults, rather than working systemically through the plant. According to the manufacturer, it targets a broad range of pests including fruit flies, fungus gnats, stink bugs, thrips, mites, aphids, beetles and scale, which covers most of the common problems that show up on indoor bonsai, particularly spider mites and scale, two pests that are notoriously persistent on trees kept indoors during winter when humidity is low and air circulation is limited. Being labeled for edible crops up to the day of harvest also signals a relatively mild toxicity profile compared to harsher synthetic pesticides.

Active ingredients

The formula is built around pyrethrins at a low concentration alongside canola oil, a combination the manufacturer classifies as suitable for organic gardening. Pyrethrins are a botanical insecticide derived from chrysanthemum flowers, acting quickly on contact against a wide range of soft-bodied insects, while the canola oil component contributes to smothering effects on eggs and scale insects, which are notoriously hard to kill with contact sprays alone because of their waxy protective coating. Together this positions the product as a broad-spectrum but relatively gentle option compared to synthetic pesticides, which matters for anyone spraying trees kept indoors near living spaces.

Application for bonsai specifically

The manufacturer's instructions call for thoroughly wetting all parts of the plant without causing runoff or dripping, and repeating the treatment after one to two weeks if pests persist, which is a realistic expectation for scale in particular since a single spray rarely eliminates an established infestation in one pass. For bonsai, this means covering the undersides of leaves and any bark crevices where scale insects like to cluster, not just the top surfaces that are easiest to reach. The label caps application at 20 fluid ounces per 100 square feet, which for most home bonsai collections translates to plenty of coverage per bottle even accounting for repeat treatments.

Size and storage

The bottle holds 32 ounces and weighs about 2 pounds, sized at roughly 9.25 by 4.94 by 2.20 inches, a size that fits easily on a shelf near a bonsai bench for regular use. The manufacturer specifies keeping it in its original tightly closed container when not in use, stored in a cool, dry area away from children and animals, and notes the container is not meant to be refilled or reused once empty. These storage notes are standard for a ready-to-use pesticide spray and worth following closely given the product will likely sit on a shelf between the recommended follow-up applications.

Where it fits in a bonsai pest routine

This product works well as a go-to spray for common indoor bonsai pests, especially since it is labeled specifically for house plants and greenhouse use rather than only outdoor garden application. Growers dealing with an active scale infestation should plan on the recommended one to two week follow-up treatment rather than expecting a single spray to finish the job, since scale's protective coating makes it one of the more stubborn pests to eliminate. For general prevention or catching an early infestation of spider mites, aphids or fungus gnats, a single thorough application is often enough to bring the problem under control quickly.

Frequently asked questions