Garden Blog

The Ultimate Pest Watch Guide

The Ultimate Pest Watch Guide


Aphids are probably one of the most common pests you’ll come across in your garden. And they can be incredibly sneaky. You think you plants look great one day and then the next they’re covered in aphids in huge numbers! Plants that have too much nitrogen or are over fertilized will be ripe targets for aphids. Plants need to be healthy but not with overly succulent foliage. 

A heavy stream of water from a hose sprayer can help to dislodge the aphids from the plant. Typically they cannot just climb back up so easily. Regular applications of neem oil or insecticidal soap can help at least keep large numbers at bay if you begin applications early enough. Ladybug larvae feast heavily on aphids and can help keep populations in check. Of course, introducing ladybugs  works really well in greenhouses and other enclosed places but if you have a naturally large population of them and see their larvae eating, let them be. 

Aphids can come in different colors including green, white, or black

Colorado Potato Beetles

Our most common and irritating potato pest. Meet the Colorado potato beetle. They can also be found on other Solanaceae plants such as eggplants, tomatoes, or peppers but are primarily found on potatoes. While it’s native to the Rocky Mountains, it’s spread rapidly all over the country and even into Europe. These highly recognizable beetles and their larvae can defoliate entire crops. Further, many pesticides are ineffective due to the insects’ natural resistance, though a combination of tactics can help to reduce their numbers in your garden. Handpicking is number one, especially starting early as your potato plants are coming out of the ground. You can try working with a trap crop of potatoes, starting one crop in late February and another one in late March. The beetles will come after the first crop to come up and, as they do, you can remove the crop and burn it, saving you a lot of trouble on your true crop. 

Adult Beetles

Flea Beetles

Flea beetles are tiny black beetles that are mainly recognizable because of the way they jump away when disturbed, very much like a flea. They are often found on Brassicaceae and Solanaceae plants and will leave small, round holes in the leaves that they occupy. A large infestation will leave many holes creating a lacy appearance to the leaf and minimal ability to photosynthesize. They are mainly a risk to seedlings, as established plants can withstand some damage.  

Some people recommend row cover but this would only really be necessary when just putting out seedlings. Once your seedlings are established, you may have skipped the worst of it. Regular applications of diatomaceous earth can help lower populations. And if you’re having trouble getting anything established and need a last resort, we’d recommend using neem oil. Long term control of the flea beetles could involve the use of beneficial nematodes which eat the larval stage of the flea beetle that lives in the soil. 
Flea beetles and damage / Photo Credit

Mexican Bean Beetles

Speaking of pests that leave your leaves looking lacy let us introduce you to the Mexican Bean Beetle. These guys can be found, yes of course, on beans, but also on corn, squash, and okra. In their adult stage they look a lot like ladybugs except for their distinctive orange color. But in their larval stage they appear fluffy, yellow, and definitely squashable. 

Early in the infestation, handpicking is a pretty reliable way to tackle them as seeing them is so easy, but an early and intense infestation can take out whole plants, while if the infestation is later in the season, you’ll still probably get some production from your crop. It’s important to note that if you’ve had one severe infestation, the next year will often bring the same. Get into the habit of installing a floating row cover over your beans for the first several weeks of growth or until flowering to help give them a chance to establish. 

From top clockwise: Adult, Eggs, Larvae / Photo Credit


There are many different types of mites but typically they look like tiny black or red specks. Spider mites are a type of mite that’s pretty common and leaves a kind of web from stem to stem of your crops. They tend to thrive in hot, dry weather, so keep a close eye on your crops during a drought. You may see the signs of them before you notice the actual mites. They can cause yellow leaves, sickly plants, and all around reduced vigor. They work similarly to aphids in that they’re a sucking pest - they make tiny holes in plants to eat sap. They can also be treated similarly to aphids in that knocking them off with water may help as will regular neem oil applications! 

Note: if you’re seeing relatively large, red, sort of velvety-looking mites, those are actually a predatory species that eats spider mites - don’t kill them! Spider mites are so small they’re barely visible, and leave distinctive webbing on plants.

Spider mites are not always red but they do leave this distinctive web / Photo Credit


Do you often find oddly shaped holes in your plants that don’t seem to have any pattern? These are likely from slugs, which love to come out at night and feast. Every gardener has their own tip or trick to manage a slug infestation from putting beer in a shallow pan (to disorient and drown the slugs) to lining copper wire around the bottoms of their plants which is said to repel them. Mulching heavily can welcome slugs to your garden, but there are so many perks to mulching that we certainly don’t recommend not doing it! Some other folk tips are creating wide barriers of wood ash or diatomaceous earth around your seedlings. Handpicking slugs works great as well. Iron phosphate (an organically certified slug repellent) is useful as well but there is controversy surrounding its use in organic gardening.

Squash Bugs

These bugs can have explosive population growth and prey upon plants in the Cucurbit family, like squash, cucumbers, and melons. Their damage causes local necrosis of the foliage and eventual death of the plant. Their eggs are golden/yellow to reddish and can be found in clusters along the stems and leaf spines. They look very different during each developmental stage. They start out as small black and green bugs, maturing to gray, and then brown adults. 

Early control of the eggs is critical. Lift up the leaves to look underneath for egg clusters. Using duct tape to remove the eggs is effective though they can also be squished. Daily strolls to search for them can help to control the population. 

Adult Squash Bug / Photo Credit
Nymphs / Photo Credit
Squash Bug Eggs / Photo Credit

Tomato Hornworm

These caterpillars wreak havoc on your tomato plants but they are pretty amazing to come across. They are the larval stage of the hummingbird moth! Though, we can all agree, these larvae have no place in your garden. 

The tomato hornworm will voraciously eat the leaves and the fruit of tomato plants and can become a major problem if they’re left unchecked. There are a few ways to manage these little guys though. As always, you should keep a close eye on your tomatoes. If you find one of these guys, remove it! Feed them to your chickens or squish them. However, if you see a tomato hornworm with little rice-like grains coming off of its back, leave them be! These hornworms have become a host to the parasitic Braconid wasp. If you let them live, you’ll likely find their mummified corpse in a few days. The wasp lays its eggs on the worm to provide food for its offspring. Having these wasps in your garden is an amazing sign! 

If all else fails, a serious infestation can be treated with Bt, a naturally-occurring bacteria that targets soft-bodied insects. 
Tomato Hornworm
Tomato Hornworm that's become a host to family of parasitic wasps!


There are beneficial nematodes and there are parasitic nematodes. The main difference is that the beneficial nematodes actually attack soil-borne pests and can be an effective part of pest management. The parasitic nematodes attach to the roots of your plants and suck nutrients out. They can cause major problems if they are present in large numbers. The problems they cause on the aerial parts of your plants are fairly typical to a lot of different kinds of issues but their calling card is what’s called root galls. Once you find these you can be sure you have a parasitic nematode problem. If it’s severe you may consider resting your growing area under a tarp for a season with a process called solarization. This can kill large populations of nematodes. Nematicidal marigolds are also said to kill populations of nematodes in the location they are grown, so growing marigolds in a whole bed for a season may be beneficial to the cause. 

Damage of the Parasitic Nematode / Photo Credit

Japanese Beetles

This invasive species feeds on most everything, but they may be most noticed as they chew up the delicate petals on your rose bushes. They tend to skeletonize leaves on the plants. Ornamental plants can often survive this but vegetables tolerate less. These beetles damage actually emit airborne chemicals that attract even more beetles to the delicious feeding spot! So if you see these pests, you’ll definitely want to handle it. They are very easy to see, so handpicking can be a good solution. Their larvae often nest in the soil underneath their feeding spots so using beneficial nematodes that attack these larvae can help. If you’re able to till in the early spring also, you’ll bring up the grubs from underground, making them a ripe and juicy snack for the surrounding birds. 

Adult Japanese Beetles

Carrot Fly

While named “the fly,” it’s actually the larvae that hurt your crops. They’re born on the surface of the soil and they burrow down and feed on the roots of carrot family plants such as carrots, parsnips, and parsley. While their feeding can affect the foliage, often you won’t realize the damage until you pull up the carrots. Lightly damaged carrots, while not marketable for a market farmer, are still fine to eat. Severe damage may leave them inedible. 

Using floating row cover for the duration of growing your carrot crop can prevent the eggs from being laid by the flies at all, ultimately protecting your crops. Because the flies are attracted by scent you can try to interplant with garlic or chives or other highly aromatic plants to cover the scent. If it’s a continued and unmanageable problem you can also utilize beneficial nematodes applied to the soil to help mitigate the population and damage. 

Carrot Fly Damage / Photo Credit

Cabbage Loopers

Cabbage loopers are the larvae of the cabbage moth which is a white or brown moth that is often seen dancing around cruciferous vegetables. The eggs of the moth are laid on the undersides of the leaves of your cabbages, kales, broccolis, and other Brassicaceae relatives. Their eggs are small, yellow, and round and can be often found in clumps together. When found, crush them! Once hatched, they’ll become small, green caterpillars that camouflage impressively for an insect. The damage they leave behind and their dark green droppings, often toward the crown of the plant, will give them away. 

Prevention of an infestation is often the best technique. Cabbage moths tend to start laying eggs from May to June. Before they come out in hoards, cover your cruciferous crops with bug netting or row cover! Make sure the fabric is well-pinned to the ground so no moths could squeeze through to lay their eggs. If you already start to see some damage take a close look at your crops. Find and squish the eggs as well as the larval loopers. Keep a watchful eye on them to make sure you didn’t miss any. If the infestation is past handpicking severity, Bt will kill the pests in their larval stages, though it won’t stop the moths from laying more eggs on your plants. 
Cabbage Looper on Cauliflower
Cabbage Looper Damage / Photo Credit
Cabbage Moth / Photo Credit 
Cabbage Looper Droppings / Photo Credit

Cucumber Beetles 

There are two main types of cucumber beetles you may come across - the striped cucumber beetle and the spotted cucumber beetle. While they do cause foliage and fruit damage, they also carry bacterial wilt and the cucumber mosaic virus, which could mean big problems in your garden. They can cause damage to all members of the cucurbit family including melons, cucumbers, and squash. Their eggs are pale orange to yellow and are laid in groups, often on the undersides of leaves. 

Using a cucurbit trap crop and keeping your true crop covered in row cover until flowering can be effective. Once your trap crop is infested, be sure to pull and burn the plants to avoid movement from one crop to the next. Regular applications of neem oil once an infestation starts can help reduce population growth. 

Spotted Cucumber Beetle and Striped Cucumber Beetle / Photo Credit
Striped Cucumber Beetle Damage / Photo Credit

Vine Borers

Vine Borers most often attack zucchinis, winter squash, and pumpkins but they can sometimes be found going after other cucurbits. Though, notably, it’s said they don’t love butternut squash. As we’re learning is a pattern, vine borers are in fact the larvae of a moth. Adults will lay eggs at the base of plants and the white grubs hatch and bore into the stem to feed. This boring blocks the flow of water and nutrients to the rest of the plant which eventually causes death. Your plants will start to wilt and you can check for holes at the base of the stem. In there you’ll see orangey goo which is the excrement of the borers. 

Because squash vine borers overwinter in the soil, it is recommended to rotate the planting of your squash so they don’t wake up next spring with their food right on top of them! Covering the stems and bases of the plants with aluminum foil can prevent egg laying as well as boring. If caught very early, you can even slice into the stem to find the borer. One plant can house several grubs so make sure you remove all of them. Once removed, the stem can then be covered with moist, rich soil to promote secondary root growth and healing. 

Squash Vine Borer / Photo Credit

Article Written by: Hannah Gibbons

About the Author: Hannah Gibbons, an employee at Sow True Seed since 2020, has nearly a decade of experience in the agricultural industry. Their passion for environmental education and regenerative agriculture has been the cornerstone of their work, aimed at making gardening accessible to all.