13 Common Watermelon Pests: How to Identify, Prevent, and Treat Them

Adult thrips are tiny, winged insects that can be yellow, brown, black, or white. They are about the shape of a grain of rice but are considerably smaller. Identify them by shaking the foliage over a sheet of white paper and then looking with a magnifying glass.

Thrips can be difficult to prevent, as they are common and difficult to spot. By the time you know they are there, likely, some damage will already exist, and the population will be significant. Attracting predatory insects can help control pest populations. Plant nectar-rich plants to draw lacewings and wasps. Keep your plants well watered and fertilized so they are strong and resilient.

Thrips typically won’t do enough damage to necessitate chemical control. Most of their damage is cosmetic. It’s difficult to wipe them out with insecticides because of their varying life stages and feeding behaviors. Pruning and keeping your area clean is most helpful. Neem oil can be effective in knocking down populations.

These South American weevils are about 1/2 inch long and grey to brown with white stripes along their bodies. They have wings but are flightless. They use their pointed snout to feed on the edges of leaves, leaving a notched or chewed-on appearance. Their larvae are small, white, and C-shaped with a distinct head. They grow up to 1/2 inch long and live in the soil.

Check for grubs before planting your crops. Crop rotation is very helpful, as these pests dislike small grains and legumes. Rotating these around your beds every three to four years will help to prevent whitefringed beetles.

Proper cultural hygiene is the best way to remove habitat for these beetles. Diatomaceous earth is safer and non-toxic and will kill the grubs that make it to the soil level. Clove essential oil solution may deter them.

Whiteflies are easy to identify. Shake the vine, and you’ll see these tiny flying pests launch into the air and flutter around before settling back down. They are very small, about two millimeters long, so they are hard to see when they are crawling on the underside of leaves. But, when they are all fluttering around, they are unmistakable.

Seaweed spray is an effective deterrent for this insect. They won’t lay their eggs on it. Keep your plants healthy and attract natural predators to your garden.

Repeated application of neem oil is effective in eliminating whiteflies. An insecticidal soap sprayed on the plant is another safe and non-chemical way to eradicate them.

Click beetles are small, reddish-brown insects with a hard shell. If you flip them over they will make a clicking sound as they pop up and right themselves. The larvae, which are the main problem, vary in size and appearance over time. Initially, they are very small, and white, at this stage, they are not usually an issue. However, as they grow, they form hard bodies and are rust-colored, growing up to 3/4 of an inch long. They have pincers on their heads.

Control weeds in your garden, and maintain good drainage to deter wireworms. Avoid rotating grasslike crops in your garden, and instead, rotate crops they find unappealing, like brassicas and onions. They aren’t typically drawn to melons, but are opportunistic and will feed on them if they are available.

You can trap wireworms using a potato trap. Bury raw potato pieces on a stick in infested areas, they will be attracted to the potato. Remove daily and kill any insects in your traps. Crop rotation is effective for eradicating them over time, and parasitic nematodes are a good non-chemical control.

Spider mites are very tiny, so you won’t see them, but you probably will see their webs. If you start to notice stippling on leaves, check underneath for fine webbing. This is a telltale sign of spider mite infesatation.

Spider mites have natural predators like lacewings, predatory mites, and minute pirate bugs. Keep these beneficial insects around by avoiding the use of insecticides, and planting plenty of nectar sources. Keep your plants well watered and fertilized, as this will help them stand up to mite damage.

An insecticidal soap sprayed on your watermelon vines and leaves will help get rid of them. Garlic extract is an effective miticide and will help deter them if you plant it nearby. Rinse off as many mites as you can with a stream of water, and treat with horticultural oils if needed.

Beet armyworms are moth larvae. They are small, just over an inch long, and bright green. They have a telltale black spot on either side of the segment directly behind their heads.

Beet armyworms have many natural predators, and attracting these to the garden will help prevent them from causing problems. Birds, rodents, and skunks all feed on these, and while rodents and skunks aren’t what you want to attract, birds are great to have around.

If you catch these insects on your plants, there are a few ways to get rid of them. Applying Bacillus thuringiensis acts as a poison to these pests, but won’t harm beneficial insects. You can apply a 5% cottonseed foliar spray to control the larvae and eggs but use caution as it can harm the plant.

Neem oil disrupts the lifecycle, leaving this insect unable to reproduce and also repels other pests. If you find a small infestation, you can also handpick these from the plant and drop them in a bowl of soapy water. Or put them directly in your bird feeder.

Adults and nymphs are both an issue for your plants. The eggs are small, shiny, and brown, and you’ll find them on the leaves of your cucurbits. Nymphs are pale gray with black legs and antennae and tend to congregate in groups. Adults are larger and darker and tend to be more solitary.

Trap crops are a good way to prevent these insects from going after your melons. They also have natural predators that you can lure to the garden with nectar-rich plants. They don’t like nasturtiums, and planting these nearby will help to repel squash bugs.

Sprinkle diatomaceous earth around the soil to dehydrate squash bugs. You can handpick them from your vines if you have the time and the infestation isn’t too extreme. Spraying them with neem oil disrupts damaged nymphs and young squash bugs. Insecticidal soaps are another good treatment for squash bugs.

You’ll see these guys if you’re looking. Small green to brown bugs congregate on stems, sucking the life out of your plants. Flip over a leaf in the area, and you’re likely to see hundreds more. They will cause leaves to distort and become chlorotic.

Unless you want to use insecticides it’s difficult to keep them away. They tend to be resistant to most aside from neonicotinoids anyway. The best defense against aphids is predatory insects. If you attract these guys, like lacewings and ladybugs, to the garden, you stand a chance. Both of their larvae can take down a colony of aphids pretty efficiently.

Melon aphids, as I mentioned are resistant to many insecticides. They are more vulnerable to horticultural oils and insecticidal soaps. Neem oil suffocates them, and you can knock them out with soapy water. A strong stream of water will knock them to the ground, and remove their mouthparts. Plant marigolds or garlic around your patch to repel them, and never underestimate the power of drawing predators.

Mature larvae are the easiest to identify. They are roughly two centimeters long and mottled in brown and gray. They typically live in the soil and curl up into a C shape when disturbed. They come out at night to feed.

Diatomaceous earth worked into the soil will help to control these insects. Tilling your soil in the spring can help to kill overwintering larvae. These larvae like to live in areas with weeds and other plant debris, so keeping your beds clear of these things will help keep them at bay. Overall the best defense is a cloche or critter cover to keep the moths from laying eggs on your melon vines.

You can use diatomaceous earth to help eradicate cutworms, as well as in prevention. Beneficial nematodes carry a bacterium that will kill these insects. Cornmeal in the soil is another way to get rid of them. They like to eat it, but can’t digest it, and it will prove fatal.

Leafminers leave a pattern on leaves that is difficult to miss. It looks like something has tunneled throughout the leaf leaving little squiggly lines all over. Which is exactly what they do! Leaves may also curl and are likely to distort as the miners consume interior tissue.

Leafminers overwinter in the soil, so crop rotation is an effective means of control. They can also take shelter and feed on weeds, so keeping these to a minimum is a preventive measure. Natural predators are the best defense, so make your garden friendly for these beneficial insects.

Hand picking is your best removal method for leaf miners. Simply snap off damaged leaves as you notice them and throw them in the trash. While insecticides can work, they are often not effective enough to rely on.

The adults are about a half-inch long and shiny with black and yellow stripes that go lengthwise down their bodies. They can also have spots rather than stripes depending on the species. They have long, black antennae. The larvae are slender and whitish, with short legs and darker areas at each end.

Predatory insects are the best prevention, so keep doing what you can to keep them around. Mulching around your plants will discourage egg-laying, especially if you use reflective plastic. Plants like nasturtium, marigold corn, and radishes are repellant to cucumber beetles. They don’t like clove oil, and baited traps are effective for these as well. Use a protective cloth over your melon vines to keep them from accessing them.

Again, traps are effective in getting rid of cucumber beetles. However, traps attract beneficial insects that could be controlling these pests. If you see only a small number, hand removal is effective. You may need to treat with insecticidal oil or neem oil to get rid of newly hatched larvae in the coming weeks.

Keep your garden clear of weeds and debris, as this will discourage them from overwintering. Pyrethrin is the most effective insecticide for getting rid of these insects, but it should be a last resort.

These guys are difficult to identify, as they are small and live in the soil. You will know they are there when your seedlings wilt and die off in a matter of days after sprouting.

Fortunately, there is a small window where these maggots are an issue for melons. You can avoid them by waiting to start your seeds until the soil warms to 80°F (27°C), or by starting your seeds indoors. Late-season planting is best, as the seedlings develop faster and there is less opportunity for the maggots to feed on their preferred food.

Insecticidal soil drenches and treatments are effective at eradicating these. However, they will also kill off beneficial insects and affect your soil, so we don’t recommend this. It’s better to adjust your planting methods to avoid them altogether.

Grubs are larvae of beetles, and the most common are June beetles and Japanese beetles. They are small and mostly white with reddish heads and three sets of legs toward the front of their bodies. They have a habit of curling into a C shape when disturbed.

If you have a history with these pests, beneficial nematodes are the most effective control. Apply two treatments in spring two weeks apart. Use fertilizer, and when you water, do so deeply and infrequently. Soil that is consistently moist encourages females to lay eggs.

Milky spore is an effective treatment. You can treat them in the fall when newly hatched grubs are present. This will help to keep numbers down next season.