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Aphids and ants on hibiscus killing off flower buds

Aphids on a hibiscus flower

All the species and varieties of Hibiscus are vulnerable to aphids. Here are the symptoms of such an invasion, and how to treat it.

A flower shrub that tries to bloom but can’t because of little black insects on the flower buds deserves a little help, doesn’t it?

Aphids on Hibiscus key facts:

NameAphis sp., Calaphis sp. & others
Lifespan – 1 month on average (unless hibernating)
Size – 1/16th to 1/8th inch (1 to 3 mm)

Symptoms – flowers fail to open, weak growth, sticky substance
Danger to plant – not fatal on hibiscus
Side effects – often associated with ants. Rarely transmits viral diseases
Beneficial – not a beneficial species

Appears in – spring & fall (year-round indoors)
Contagious – very (winged and carried by wind)
Treatment – hosing down & biocontrol

Symptoms of aphids on a hibiscus plant

Hibiscus plants both grown outdoors and indoors are vulnerable to aphids.

Symptoms of the presence of aphids

Aphids tend to concentrate on portions of the shrub that have tender tissues. For Hibiscus, colonies typically appear on:

  • flower buds
  • underside of leaves
  • young shoots and new growth only a few days old at most.

The tiny insects cluster around the most favorable spots. They secrete a sweet substance called honeydew.

Honeydew is essentially what’s left of the hibiscus plant’s sap once the insects are finished feeding from it. Many other insects take advantage of this honeydew themselves, since it still contains many nutrients. Ants often appear near aphids, and even bees are known to collect honeydew to feed on.

Symptoms on the hibiscus itself

Hibiscus Althea buds stunted due to aphidsA severe invasion will take such a toll on the hibiscus that it has trouble growing properly.

  • The shrub will lose its vigor and grow less branches and flowers, and these will tend to be smaller.
  • Flowers might not even be able to open up and unfurl.
  • Leaves and shoots are deformed and stunted, and don’t reach their normal size.
  • In some cases, a fungus develops on all the honeydew residues. This fungus is called sooty mold.

Flower buds are the most appealing part of the plant for aphids. The insects will tend to congregate there. In case of heavy rain, they might take refuge on the underside of leaves, which they can also feed from.

The buds tend to be covered in insects at all stages of maturity: small, light-colored younglings, large, brownish or blackish mother aphids, and even dry hulls of dead aphids that still cling to the plant. Usually these are all wingless, but some might have a pair of wings when colonies get larger.

In extreme cases, the bud will seem to be nibbled on and petals are twisted and clumped together in a roundish shape that doesn’t resemble the typical lance-shaped hibiscus flower bud at all.

Treating against aphids on hibiscus flowers

Treating against the aphids

Natural treatments against aphids on hibiscusThree types of fermented weed tea are particularly effective against aphids. The compounds in the tea interfere with the aphid’s normal feeding and reproduction process. These are weed teas prepared from stinging nettle, ferns, and rhubarb leaves. Of course, you can ferment these together if you’ve got them all on hand.

Hosing the shrub down works well, too, but has to be repeated daily for about a week. Indeed, aphids hidden in buds aren’t washed away; repeating the task lowers their numbers to a manageable count.

Treating against ants which protect and spread aphids

Several plants developed biochemical weapons that repel ants: tansy, French lavender… Plant these nearby. There also lots of tips to get rid of ants or redirect them elsewhere here: dealing with ants in the garden naturally.

Bring on the beneficial helpers

Bird eating aphids off an hibiscusLadybug, lacewing, hoverfly, the list of beneficial insects that will devour your aphids is endless, and all you have to do is make your garden appealing for them to move in!

Even certain species of birds will help out! For instance, goldfinch will pick aphids off hibiscus with great gusto!

How to prevent aphids from appearing on your hibiscus

There are ways to hinder aphids from even appearing on your hibiscus. These methods will also slow the growth of aphid colonies.

Decoy plants

You should know that Hibiscus isn’t the favorite host of aphids. Only small portions of the plant are appealing to aphids. This means that if provided with another more “tasty” plant, aphids will tend to migrate to that more appealing plant instead.

Typically, a plant like nasturtium is like a magnet for aphids. If you grow a couple nasturtium vines near your hibiscus plants, you won’t see many aphids on the shrubs anymore.

Moreover, the aphids on the nasturtiums will attract ladybugs, green lacewing and other beneficial insects that will of course cleanse your hibiscus from stray aphids on their way to the feast down below!

Aphid-repelling plants

Some plants such as French marigold and lavender repel aphids naturally. Planting them immediately under and around your Hibiscus will also protect them, too.

Don’t use chemicals

It’s tempting to spray insecticides to get rid of the aphids. Spraying pesticides is very effective, but it has severe drawbacks for your garden in the long run.

Natural pesticides such as those based on pyrethrum (a Chrysanthemum extract) is much better than chemical and petroleum-based products.

However, such sprays kill blindly, wiping everything out and wrecking havoc in the plant’s own defense system. Indeed, it destroys the microscopic beneficial bacteria and fungus that live on leaves, leaving the plant completely bare. Other more aggressive fungus and bacteria can then easily infect your plant or its neighbors. And, of course, any beneficial insects will be wiped out as well.

Image credits (edits Gaspard Lorthiois):
Public Domain: Scot Nelson
Nature & Garden contributor: Dwayne Cutshall
CC BY-SA 2.0: Sandy Poore, Tracie Hall
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