6 Best Insecticide For Petunias | Target These 3 Bugs

Check Price on Amazon

Mix once, pour at the base, and let the roots do the hard work for six weeks.

This is the easiest option for whole-season petunia protection because you never have to spray a leaf. You mix the concentrated 32 oz bottle with water and pour it directly around the base — plants absorb the treatment through their roots, making every petal and stem toxic to insects. It covers Japanese beetles, aphids, borers, and common rose diseases like black spot and powdery mildew in one go, which is a huge time saver if you have multiple flower beds.

Buyers report it reduced sawfly damage on 20 rose bushes when used every six weeks (4 times per season), and they combined it with fungicide and fertilizer for best results. Unlike the granular Sevin below, there is no waiting for rain to activate it — you control the timing. The main catch: do not apply while bees are foraging, since the systemic action can kill pollinators that visit the flowers.

At 32 oz of concentrate, one bottle makes enough drench to last many applications across a typical garden, and it goes much further than a ready-to-use spray like the Ortho (24 oz). For pure ease-of-use, this is the pick.

Check Price on Amazon

A single gallon jug that kills aphids, powdery mildew, and spider mites without harsh synthetic chemicals.

This is the most versatile bottle on the list — it acts as a fungicide, insecticide, and miticide (a product that kills mites) all in one. The active ingredient is neem oil extract, which smothers soft-bodied insects and fungal spores on contact. At 128 fluid ounces, it holds 128 fl oz, compared to the Bonide spray oil at 32 fl oz below, making it the best value if you have lots of plants to treat. It won’t harm your petunias when used as directed, and it is labeled for organic gardening.

Owners mention it stops mildew on hibiscus, roses, tomatoes, and blueberries — using it weekly prevents mildew from coming back and keeps leaves and harvests healthier. One catch: the built-in sprayer on the gallon jug is clumsy — customers note it has only about 4 inches of coiled tubing to reach plants, so you may want to transfer the liquid to a better pump sprayer for ease of use.

Compared to the Bonide Rose Rx systemic above, this is a contact-only treatment — you must hit every surface of the leaf, and it does not travel through the plant’s system. But for the price of a single jug, you cover three problems at once.

Check Price on Amazon

A ready-to-use spray that kills over 100 insects on contact and then keeps working systemically for weeks.

This is what you grab when you walk outside and see Japanese beetles or aphids actively chewing your petunias. It works by both contacting the bugs directly and then absorbing into the plant so future pests that bite the foliage get killed too. Ortho says it protects for up to 4 weeks, which is stronger than a pure contact spray like the Garden Safe neem oil that relies on direct coverage. It won’t harm blooms or the plant itself when used correctly.

Reviewers point out mixed results on the systemic side — one reviewer noted it is weak against larger infestations like mealybugs, while another bought it for Japanese Beetles on roses and confirmed it did the trick with bi-weekly spraying. At 1.5 lbs per bottle, it is lighter than the Sevin granules (3 lbs) and easier to handle for spot treatments. The downside is the 24 oz size runs out fast if you have many flower beds — consider the larger 1-gallon Garden Safe if your garden is big.

This sits between the heavy-duty systemic of the Bonide Rose Rx and the gentle organic of the Monterey B.t. It is a solid middle-ground option for the typical petunia owner who wants a single spray that works now and keeps working later.

Check Price on Amazon

A mineral oil spray that smothers overwintering pests and disease spores without toxic residue.

If you want to start the season clean, this is the product to apply in late winter or early spring while your petunias are still dormant. It coats the bark and stems with a thin layer of mineral oil that suffocate insect eggs, scale, mites, and fungal spores like powdery mildew and rust before they ever get a chance to feed. Because it is an oil-based smothering agent rather than a chemical poison, it leaves no toxic residue and is approved for organic gardening.

Shoppers say it effectively treated a 25-foot Spanish Broom without chemical odors, though they noted it required soaking the plant and keeping it hydrated for maximum absorption. One reviewer warned that the included hose-end sprayer is poorly calibrated and wasteful — they recommended using a pump sprayer instead for cost-effective and even coverage. At 32 fluid ounces, it is the same size as the Monterey B.t. but one-quarter the volume of the Garden Safe neem oil jug.

This is not your everyday grow-season spray. For active summer bugs on petunias, the Ortho or Bonide Rose Rx will give faster results. But as a preventative winter treatment, nothing else on this list does what the All Seasons Spray Oil does.

Check Price on Amazon

Spread it on the soil around petunias and let rain activate a barrier that lasts up to three months.

This is not a spray — it is a 3-pound bag of granules you shake around the base of your plants and then water in. Once wet, the insecticide moves into the soil and kills both above-ground and below-ground insects, including ants, grubs, and fleas that can stress your petunias from the roots up. It works on lawns, fruit and vegetable gardens, and ornamentals, so a single bag handles the whole yard if you need it.

Buyers report it works well for ant problems in wooded areas, with one reviewer saying it solves their yearly pest issue and protects their cherry trees from ants. The granules are heavier than any spray — at 3 pounds, they weigh 3 lbs, while the Ortho spray bottle weighs 1.5 lbs — but that weight translates to significant coverage. Just note that unlike the Rose Rx systemic drench, this is not absorbed by the plant itself; it stays in the soil and kills insects that walk through or live in the ground.

For petunias specifically, this is best used as a perimeter treatment around the flower bed to stop ants and soil-dwelling pests from reaching your plants. For budworms or aphids already on the leaves, you still need a foliar spray like the Garden Safe or Ortho.

Check Price on Amazon

A caterpillar-specific biological spray that kills budworms without harming bees, earthworms, or your petunias.

Petunia budworms are the most common caterpillar pest for these flowers — they chew buds from the inside, causing blooms to fall off before opening. Monterey B.t. (Bacillus thuringiensis, a soil bacterium that produces proteins toxic to certain insects) is a biological larvicide that caterpillars ingest and die from within days, but it has zero effect on birds, earthworms, honeybees, or beneficial insects. It is OMRI-listed for organic gardening, meaning it meets USDA organic standards.

Owners mention it worked well on Texas Laurel and on cabbage loopers that destroyed flower seedlings the previous year, with one reviewer saying they cannot garden without it now. The ready-to-use 32 oz spray bottle comes with a measuring spoon for precise mixing if you buy the concentrate version later. One key difference from the other sprays here: it kills only caterpillars and worm-type insects (cabbage loopers, gypsy moth, bagworms, etc.) — it will not touch aphids, spider mites, or beetles. That makes it the most targeted tool on this list.

If you have confirmed budworm damage on your petunias and want to protect pollinators at the same time, this is your only choice. For everything else, pair it with the Garden Safe neem oil or the Bonide Rose Rx.