Common Garden Pests of Hawaii


A well cared for garden will provide you with a wealth of tasty and nutritious produce throughout the year. 

Your garden is a little ecosystem in itself, with a wealth of creatures living and thriving from large animals to insects, to microscopic bacteria. A lot of these organisms are wee garden superheroes and are beneficial to the growth of your garden. But some are unwanted!

Gardens can attract a range of undesirable pests that can affect the quantity and quality of your harvest.  As unwanted as these pests may be, they are part of the ecosystem and necessary for there to be a balance.  But because we live in Hawai’i, there may not be a natural predator to keep their numbers in check.

We’ve put together a list of some of the most common invertebrate pests you may find in your Hawaiian garden, how to identify them and what to do about them.


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Whitefly

Whiteflies are tiny, white and resemble flies.  The first sign of these pests will be yellowing leaves. You will normally find them on the underside of leaves where they will be sucking sap from the plant, causing leaves to lose their green and die.

Whiteflies can transmit disease from plant to plant and will also attract more pests who come to consume the honeydew they produce.

These insects reproduce quickly and will evolve resistance to pesticides. Continual spraying may help control them but manually removing them will be more effective. Typically I take each leaf and spray them off, but it can be an everyday chore so I tend to stay away from plants that whiteflies love, especially bell peppers.

Whiteflies are repelled by reflective surfaces, using aluminium foil will help deter them from feeding on your plants.

On the flip side, they tend to flock towards yellow pigment so if you use sticky traps to remove them, make them yellow to increase your catch!

Fire Ants

If you’ve ever been unfortunate enough to have found a fire ant nest with your hand or foot you will know these little guys are incredibly unpleasant. Some say that lemon will help ease the painful bites, but normally only time will heal.

They won’t do any damage to your plants but can pose a risk to you and your animals as you work in your garden by getting agitated and stinging you.  Animals can lose vision when bitten too much around the eyes.

The ants can get into your clothing and throughout pots, soil and wood and once they have settled in they can be particularly hard to get rid of.

You’ll want to start putting out baits such as Tango, Amdro or poisons such as Bifen to control them.  They are recently introduced into Hawai’i and have no natural predator.  Unfortunately the only effective methods of control have been poison and poisonous baits.

Slugs

Slugs love to munch on your lovely leafy greens, leaving large holes and sticky residue all over them.

Slugs are prone to drying out if they do not have any cover. They will find shelter under piles of wood, boards, logs, leaves and many other manners of organic material we all have around in our gardens.

Cleaning up these areas around your plants will deter the slugs from hanging about as they will have no nearby shelter to get away from the sun.

You can also use other natural home remedies such as salt, beer and eggshells to keep slugs at bay.

I have found the most effective method is to have a jar of saltwater, some tongs and a flashlight and go out on a moist evening and pick away.  They love my water tank.

It is especially important to remove slugs from your property in Hawai’i because of a disease known as Rat Lungworm.  It is spread by slugs when eating raw produce that slugs have visited.  And trust me when I say this, it is a disease you do not want to get.

Related: Growing Cucumbers In HawaiiOpens in a new tab.

Cabbage Moth

The cabbage moth is a large white butterfly. They are distinct by the black spots on the wings and their love for brassicas.

Apart from seeing them fluttering about your cabbages, a sure sign of their presence is the blue/green dropping they leave on the leaves as they eat through the plants.

My favorite way to keep the cabbage moth in check is just to pick them off by hand and feed them to my chickens. If your kids are looking for jobs, send them out to the garden and give them a quarter for every cabbage moth they return to you!

Aphids

Aphids are a small but mighty insect. So small that when you first see them on your plants, they look like some sort of mold, but on closer inspection, you will see rows of these little insects.

Another sign of an aphid infestation is the new leaves of a plant coming out small and curled. Aphids use a gnarly needle-like mouth to inject hormones into leaves to cause deformities and feed on vital nutrients.

Aphids will respond to pest sprays or horticultural soap or oil sprays.

Rhinocerous Bettle

The rhinoceros beetle’s favourite snacks tend to be some of the best tropical trees including coconut, banana and pineapple. 

The beetles can cause serious damage to these trees and can even kill the plants. Either by demolishing them or damaging them enough to expose them to other pests or pathogens.

These insects are best removed manually and the leaves burnt to stop any reinfection from hatchlings residing in the leaves.

They are a new pest in Hawai’i and are closely being monitored.  If you find one, kill it right away.

Banana Skipper

Named after the plant they live on, banana skippers are a non-native butterfly whose larvae feed exclusively on the banana leaf.

Signs you have a problem with banana skippers include rolled-up banana leaves with larvae tucked inside. They are deposit a large amount of frass (caterpillar poop) which will be falling out from these rolled leaves.

Parasites that prey on the egg, larvae and pupae stage of this species has been introduced to Hawaii specifically to control the impact of these.

Thanks to these helpful parasites you do not usually need to spray any chemicals on your banana plants to protect them. Remove any caterpillars when you see them to help control the banana skippers.

If things do end up out of control and you need to spray, opt for natural sprays so you do not harm the helpful parasites.

Related: Growing Carrots In HawaiiOpens in a new tab.

Rose Beetle

Now, these tricky insects are harder to see to identify as they are nocturnal. They tuck themselves away during the day and come out at dusk to chomp away on your garden undisturbed.

Signs you may have rose beetles include a “lace-like” pattern on the leaves of your plants. This pattern is due to the way the beetle feeds.

Rose beetles do most of their feeding in the first few hours after the sun goes down. To deter them from feeding you can light up your garden beds with spotlights at this prime feeding time. Put the lights on a timer so they are only on for a few hours when the beetles are most active. 

Scale

These small white insects attach themselves to the underside of leaves, feeding on sap the plant produces. They will suck all the nutrients away from the plant and leaves will yellow, then turn brown and die completely.

Spray pesticides are useless for these insects as they possess a hard and waxy exoskeleton that protects them from the effects of chemical sprays.

If you have an infestation of scale, it is best to prune the plant right back and take away the scale insects food source so that they move on elsewhere.

Biological control is also possible. A small black ladybug is on the Island of Hawaii and love to eat scale. If you can find these insects on a plant nearby, introduce them to the affected area and they will quickly reduce the effects of scale.

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Sean Jennings

Sean has been living simply Off-Grid in Hawai'i for over 18 years. He lives debt free on Hawai'i Island with his family and over 40 chickens. When he's not tinkering around the homestead, he's off exploring the shorelines for fish & surf.

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