How To Manage, Treat, and Mitigate Garden Pests and Diseases
Nothing’s worse than taking a leisurely stroll through your garden to admire your flourishing plants and all your hard work only to realize that you’ve got a problem: A pest, a disease, or something that’s otherwise wreaking havoc in your garden beds. Probably the worst part about this is when the problem can’t be easily identified. After all, how are you supposed to address garden pests or diseases if you don’t know what it is?
We’ve compiled this list to help you on your quest to rid your garden of any pesky problems. Here’s an in-depth look at eight of the most common garden pests and diseases, plus tips to help you ID and mitigate the problem before it’s too late.
Common Garden Pests
Garden pests can range in size from the very small (and barely detectable) to larger, more obvious critters like deer and rabbits. Here are five of the most common ones, plus details on how to be rid of them once and for all.
As one of the smallest pests on this list, aphids can also be some of the hardest to identify correctly. This is partially because there are so many different kinds of aphids and also because they may be targeting other plants at different times of year. For example, a group of aphids raiding your veggie beds in the summer may move on to a nearby perennial shrub in the winter months.
One thing nearly all varieties of aphids have in common is that they feed off plants by sucking out the sap, which often translates into curling or yellowing leaves that feel sticky to the touch (this is the sap). Although many aphids are nearly invisible to the naked eye (often under ¼ inch in size), you may be able to see them on the underside of the leaves of the infected plant. They often have pear-shaped bodies with long antennae.
The solution: If you suspect you have aphids running rampant in your garden, try mixing up a soapy neem oil solution at a ratio of two tablespoons of soap and two tablespoons of neem oil for one gallon of water. Then cover the perimeter of your plant with the mixture (usually a few cups’ worth). This mixture will act as a systemic pesticide to kill any aphids that try to feed on the plant.
Much like aphids, spider mites are so tiny they can be challenging to detect. That being said, there are a few key signs that your garden is suffering from an infestation. The most common indicator of a spider mite problem is that you’ll find tiny white or yellow spots and silky webs on or around leaves. If you have a more severe infestation, entire plants or trees will give off a bizarrely yellow or bronze appearance.
To determine if spider mites are the issue, grab a white piece of paper and shake the affected leaves over the paper. If you do have mites, they’ll fall off and look like black specks on your paper.
The solution: Fortunately, treating spider mites is reasonably straightforward. You can use a high-power hose to spray the bottom leaves of the infected plant and blast away these nasty pests. Just be sure to find a healthy balance of water pressure so as not to cause unnecessary harm to your plants.
Moving up the food chain, cutworms are another nasty pest that’s slightly easier to identify. Roughly the size of a fat caterpillar, cutworms have a special affinity for munching on young plants very early in the season, particularly common garden veggies like asparagus, beans, corn, lettuce, and peppers.
If you find a plant that’s been “cut” very close to the ground, run your fingers through the soil looking for worms. They’ll appear curled in a letter “c” if you find one. Another way to search for cutworms is when they’re actively feeding on plants—which tends to be in the evening or nighttime hours.
The solution: Bring a flashlight into your garden for a nighttime raid and search for cutworms. If you find any, remove and kill them. If you’re concerned you may have more cutworms than can be manually removed, consider introducing some beneficial nematodes into your garden. These natural pest control experts can be purchased at your local gardening center and are a great way to kill soil-borne pests (like cutworms) without using pesticides.
Another slimy pest to be aware of in your garden is slugs. Since they tend to gravitate towards shady parts of the garden, you’ll rarely have to worry about them in a well-weeded sunny garden. But if your vegetable patch has a significant ground cover (where slugs can seek respite) or when it comes to low-lying fruit like strawberries, you’re much more likely to find suspiciously slug-like bites being taken from your favorite ornamentals and edibles.
The solution: If you suspect you have slugs nibbling away at your garden, spend some time lifting up leaves and ground cover to look for them. These garden pests typically aren’t that hard to spot, and you’ll want to remove and kill any that you find. Barring that method, you might also consider setting up “slug traps” such as shingles or damp newspaper. Slugs are active in the evening, so be sure to check under these shade-bearing objects in the morning to see if you’ve attracted any slugs. Several natural predators like birds and some species of beetles can also be effective at killing slugs. Since successful slug mitigation will depend a lot on the conditions where you live, it’s best to speak to your local garden care center about the best way to address a slug problem in your garden.
Deer & Rabbits
As the largest pests on this list, these can also be the most destructive. All it takes is a few minutes for your veggie patch to become the best snack in the neighborhood. Fortunately, these critters aren’t very difficult to spot, and there are several effective ways to keep them out of your garden. If you suspect you have one of these pests, the main thing to keep in mind is that deer are not delicate eaters. While rabbits tend to nibble low-lying plants that are close to the ground, deer will munch and tear plants—leaving them looking torn and jagged, with very little plant matter left.
The solution: If you suspect you have unwelcome rabbit visitors, try installing fake predator deterrents like rubber snakes or plastic owls around your garden. You might also use chili flakes or oil on their favorite plants (this also works for deer). Last but not least, consider investing in some Liquid Fence. This smelly non-toxic liquid formula is safe for plants and animals, but it’s also one of the best products for keeping deer and rabbits out of your garden. Word to wise: Apply downwind, as this repellent smells equally abhorrent to humans as it does to pests, and you definitely won’t want to get splashed.
Common Plant Diseases
Besides garden pests, common plant diseases that may be running rampant in your garden are equally important to understand and address. Here are three of the most common plant and tree diseases, plus our best tips for getting them under control.
Although it can be devastating to your garden, rust is also very easy to identify—and if you can catch it earlier rather than later, a whole lot easier to treat. As the name would suggest, rust appears in wet, humid gardens on leaves as small rust-colored spots. These spots can burst and carry infected spores onto neighboring plants as a fungus.
The best treatment for rust is prevention. Avoid spraying water over the leaves of your plants as this can spread rust spores, and instead water at the base of the plants. You’ll also want to clear debris between plants to keep any fungus that’s growing on one from spreading to its neighbors. Good spacing and air circulation between plants can go a long way in preventing a devastating rust outbreak.
The solution: If you find rust on your plants, you’ll need to remove and destroy the infected leaves immediately. If your garden is exceptionally wet or humid and prone to rust, consider dusting the leaves of your plants in sulfur at the beginning of the season. For intense outbreaks, consult your local nursery for recommendations on rust fungicide.
Another troublesome fungus found in gardens, powdery mildew can be a hard one to get under control once it’s spread. The good news is that many infections really start to become problematic later in the season, just before leaves fall to the ground. The bad news is that this fungus can actually overwinter and affect the early growth of your plants the following spring.
Powdery mildew first appears on leaves as yellow spots or powdery white ones, anytime between early spring or mid-summer, depending on where you live. Larger blotches may eventually cover entire leaves, with more prolific infections appearing as weakened or wilted leaves or even prematurely ripening fruit.
It’s also worth noting that this fungus is more likely to affect certain plants over others depending on where you live. In the Midwest, powdery mildew is often found on the leaves of members of the gourd family, like watermelon, squash, and pumpkins. In the West, you’re more likely to find it on species of lilac bushes or birch trees. Overall, powdery mildew favors dry leaves in areas of high humidity and low light.
The solution: Much like plant rust, powdery mildew is best treated with prevention. Ensure proper spacing between plants for better circulation and remove and destroy any affected leaves you find. You’ll also want to disinfect any garden gloves or tools you used on the infected plant before using them in other areas of your garden. For more rampant forms of the disease, consider treating the infected plants with neem oil or with a homemade mixture of baking soda and horticultural oil. For this blend, combine one tablespoon of baking soda and 2.5 tablespoons of horticultural oil in a gallon of water and apply liberally to infected plants.
This fungal disease is common enough on vulnerable species of trees (often ash, elm, maple, and fruit trees). However, it can be hard to identify correctly— especially since most trees and shrubs suffering from verticillium wilt will simply appear as underwatered. Most trees and shrubs suffering from wilt will have yellowing, curling, or wilting leaves. They may also have branch dieback or even result in the total death of the tree.
One way to verify whether your plant is suffering from water stress or wilt is to look closely at the branches. Wilt is a vascular disease that’s caused by a soil-inhabiting fungus. Once this fungus invades the plant, it spreads into water-conducting tissues. Wood under the bark of your tree may exhibit discolored streaks or bands. You can look for this by using a paring knife to peel back a portion of the bark from an infected branch. Be sure to do this only on a smaller branch you can then remove from the tree to avoid further damaging it.
The solution: There’s no easy solution or chemical cure for treating verticillium wilt, but sometimes the affected tree or shrub can overcome it simply by improving its growth conditions. Trees under environmental stressors are more likely to become infected, so they may improve by offering more water (or even moving small enough trees to a different location).
Start by pruning back infected branches and offering more water. You might provide a balanced fertilizer (like 10-10-10) to help the tree in its recovery. Avoid high nitrogen fertilizers as these can worsen the wilt.
The Final Word
Garden pests and diseases can vary from slightly menacing to downright devastating. If you suspect your plants or trees are suffering from an unknown pest or disease, the best thing to do is consult an expert. Call up a local gardening pro or visit your local nursery to get help diagnosing the problem. Be sure to bring photos of the affected plants, sealed bagged samples of pests, and any other information that may help troubleshoot the problem.