Early spring is a welcome change. Gardens burst into life. Hardy hibiscus comes out of dormancy, puts on new growth, and gardeners get excited for the season ahead.
Spring is also the season that aphids catch onto all those nutrient-rich plants. Some can see some overwintered eggs hatch from the soil, get their nasty antennae into a leaf, then start producing offspring.
Hibiscus are heavy drinkers. The leaves are rich sources of sugary sap for aphids and similar sharp-mouthed bugs to get stuck into.
The worst part – these are asexual so it only takes one to settle for a colony to take over.
Detailed below are the steps to take to get rid of aphids naturally with minimal damage done to the plant.
Hold back on feeding to slow growth down. That decreases the population size. Provided aphids are regularly knocked to the soil. Most are wingless and cannot climb back. Beneficial insects eat them, and neem oil prevents sooty mold from developing on the excrements they leave on leaves.
Hold back on watering
One aphid is the start of the colony. When you have any, you get many. The newer growth on the plant is the tastiest for aphids. New growth has the richest nutrients.
The instant aphids are identified, cut back on watering and fertilizer. The more you feed the plant, the more growth there is for aphids. The population will soar.
The very start of the process to knock back the size of the colony is to make the plant less appetizing.
When the size of an aphid colony grows too big, it loses its vigor and is a common cause of hibiscus wilting.
Overwatering and underwatering cause plants to wilt, however, an overwatered hibiscus will be a breeding ground for aphids.
As much as hibiscus are water-loving plants, aphids have a bigger appetite and will drain it dry.
As odd as it seems, start your plant on the road to recovery by stressing it a little more.
As with above for holding back water, do the same with fertilizing.
The best fertilizers for hibiscus are slow-release. Bloom busters are not the way to go because the faster the plant grows, the faster the aphid population grows too.
Besides, plant food described as “super bloom” contains an extremely high amount of phosphorous. That binds up other minerals leading to an iron deficiency.
Then iron chelates need to be added, then to correct the yellowing, a little nitrogen cannot hurt, right?
Yes, it can!
Nitrogen promotes green growth; the greenery feeds the photosynthesis process and the potassium in the fertilizer promotes blooming.
Feed them all in high doses in quick succession and your plant will grow like crazy. Aphids will have a field day devouring all those sweet juices.
These pests breed fast enough without making their habitat more inviting for breeding.
Help the plant breathe by pruning
Hibiscus benefit from frequent pruning, which is much more than pinching spent flowers. There are a few different pruning techniques to use. Corrective, selective, hard pruning, and a full prune.
Corrective pruning is how to prune hibiscus to remove damaged parts of the plant. Selective pruning is how to control the direction of growth.
Pruning opens the plant up and that increases air circulation. When the foliage is crowded, rather than promoting plant growth, the plant becomes a breeding ground for aphids.
Once they make a start, if the plant is not cut back to increase air circulation, it will require more hosing down to knock the aphids from the leaves, stems, and branches.
Knock them off with water
Given how big a hibiscus gets, a regular garden hose may not be the right tool for the job.
Aphids hang around on the underside of leaves. In any bush, you need to get the hose into the bush and under the leaves to knock aphids off.
On a hibiscus plant that is still small, placing your thumb over the end of the hose can be sufficient at creating the pressure needed to get the aphids off the leaves and onto the soil. Most are wingless and will not climb back onto the plant.
On larger plants, a longer hose is needed, preferably with a 90-degree angle and with broad coverage.
When using a hose to blast aphids off a hibiscus, be careful which way the hose is pointing. It is possible to blast these with a high-pressure jet spray of water forceful enough to carry them to another plant.
The aim of blasting them with water is to get them onto the soil. The vast majority of aphids are wingless so once on the ground, they cannot get back onto the plant so starve.
If they land on another plant, the problem just gets moved.
When water is not enough to make a dent in an aphid infestation, certain insects will.
A few beneficial bugs that are effective at reducing aphid populations are ladybugs, lacewings, hoverflies.
You can buy these in batches of thousands of bugs to release in the garden. Or you can plant the plants that attract them.
The main difference between good bugs and garden pests is their mouthparts.
Bad bugs, which include aphids, mealybugs, thrips, whiteflies, and scale insects have sharp antennae that puncture plants to suck the sap. The sugars that are in the plants’ sap are a source of carbohydrates.
Good bugs do not have sharp antennae, but they still need nectar for carbs. They get that from shallow flowers.
Companion plants to attract the beneficial bugs are any that produce a lot of nectar that is easy to access, so plants with shallow flowerheads.
Think sunflower, dill, zinnia plants, and the ever-popular sacrificial marigold that gets used as a trap plant because numerous insects eat marigolds.
Treating damaged foliage with an insecticide
For leaves that are damaged either by yellow spots on the leaves or developing sooty mold caused by the honeydew aphids secrete, wash it off with neem oil, which is a contact insecticide, miticide, and fungicide in one.
You can buy a ready-mixed neem oil foliar spray or the concentrate to make a diluted solution by following the instructions. Each concentrate is different strengths. Most are diluted to 8 ml neem to 1 gallon of water.
When treating hibiscus with neem oil, do it early morning or in the evening to avoid leaf burn. Leave it to work for about 30-minutes, then rinse the plant thoroughly to wash away the oil residue.
Frequently Asked Questions about getting rid of aphids on hibiscus
Is Diatomaceous earth effective at killing aphids?
Diatomaceous earth will dehydrate all soft-bodied insects that cross it. It can be sprinkled onto the soil. It is only effective when dry though. As most of the aphids tend to cluster on the underside of leaves, it is difficult to coat the leaves with this. A foliar spray is more effective.
Is vinegar safe to use on hibiscus plants?
Vinegar does work as a contact insecticide. It is also an effective weed killer. Spraying vinegar directly on aphids on the leaves will kill the aphids and the plant along with them. For hibiscus plants, diluted vinegar alters the soil pH. The roots can cope, the leaves and flowers cannot.
Marcel runs the place around here. He has a deep passion for houseplants & gardening and is constantly on the lookout for yet another special plant to add to his arsenal of houseplants, succulents & cacti.
Marcel is also the founder of Iseli International Commerce, a sole proprietorship company that publishes a variety of websites and online magazines.