Fall Gardening: How to Identify and Control Common Fall Garden Pests

As summer winds down and the cooler weather sets in, many gardeners turn their attention to preparing their gardens for fall planting. There are many benefits to fall gardening, such as cooler temperatures, fewer weeds, and ideal growing conditions for many plants. Many assume that cooler temperatures mean the end of pest problems. Unfortunately, this isn't always the case. While some common pests may become less active as the weather cools, others emerge or linger, causing potential harm to your fall crops and flowers. If you're not careful, these pests can damage your garden and impact your late-season harvest.

In this blog, we'll explore common fall garden pests, how to identify them, and effective strategies for managing them, so your garden can thrive well into the colder months.

Why Pests Persist in the Fall

Pests don't necessarily vanish just because summer is over. In fact, many pests are still active in fall and are often searching for food as their natural sources become scarce. Additionally, pests that might have gone unnoticed in the lush greenery of summer gardens can become more visible as plants die back or lose their leaves. Some pests even lay eggs in the fall that will overwinter in your garden, leading to bigger problems come spring.

Common Fall Garden Pests and How to Manage Them

Here's a detailed look at the most common pests you're likely to encounter in your fall garden, along with identification tips and effective management strategies.

1. Aphids

Aphids are small, soft-bodied insects that come in a variety of colors, including green, yellow, black, and brown. They feed on plant sap by piercing plant tissue and sucking out the juices, which weakens the plant and can lead to stunted growth or wilting. Aphids are particularly problematic in the fall because they cluster on tender new growth and can transmit viruses between plants.

• Identification: Look for clusters of tiny insects on the undersides of leaves, along stems, or near the growing tips of plants. You may also notice sticky honeydew (a sugary substance aphids excrete) on leaves, which can attract ants or lead to sooty mold.
• Management:
• Natural predators: Ladybugs, lacewings, and parasitic wasps feed on aphids. Encourage these beneficial insects by planting nectar-rich flowers like dill, fennel, and yarrow.
• Neem oil or insecticidal soap: Apply these organic treatments to plants to reduce aphid populations. Spray thoroughly, targeting the undersides of leaves.
• Water spray: A strong jet of water can dislodge aphids from your plants, although this is a short-term solution.

2. Cabbage Worms

Cabbage worms, the larvae of small white moths known as cabbage butterflies, are notorious for attacking fall crops like cabbage, kale, broccoli, and cauliflower. These green caterpillars chew through leaves, leaving large holes and ragged edges on your plants.

• Identification: Look for small, white butterflies fluttering around your brassica crops. The worms themselves are green and can blend in with the foliage, making them harder to spot. Damaged leaves with large, irregular holes are a telltale sign of an infestation.
• Management:
• Handpicking: Regularly inspect plants and handpick the caterpillars, dropping them into a bucket of soapy water.
• Floating row covers: Prevent the adult butterflies from laying eggs by covering your plants with lightweight row covers. Ensure the edges are securely buried in the soil to block access.
• Bacillus thuringiensis (Bt): Bt is an organic microbial insecticide that specifically targets caterpillars while being safe for beneficial insects. Apply it to infested plants as soon as you notice damage.

3. Slugs and Snails

Slugs and snails thrive in the cool, damp conditions of fall, making them one of the most persistent pests at this time of year. They feed on a wide variety of plants, including leafy greens, tender young seedlings, and even ripening fruits, leaving behind slimy trails and large, ragged holes in leaves.

• Identification: Slugs and snails are most active during the night or in damp conditions, so check your garden early in the morning or after a rainy day. They leave behind silvery slime trails that are easily visible on plants, soil, or pots.
• Management:
• Handpicking: Go out in the early morning or evening with a flashlight and pick slugs and snails off your plants. Dispose of them in soapy water or relocate them far from your garden.
• Beer traps: Bury shallow containers filled with beer at ground level. The scent attracts slugs and snails, which drown in the liquid.
• Copper barriers: Slugs and snails dislike crossing copper surfaces, so placing copper tape around garden beds or pots can deter them.
• Diatomaceous earth: Sprinkle diatomaceous earth around your plants to create a barrier. The sharp edges of the microscopic particles deter soft-bodied pests like slugs.

4. Cutworms

Cutworms are the larvae of certain moth species that typically feed at night, cutting down young seedlings at soil level, which can cause significant damage to a fall garden as plants are trying to establish themselves. These pests are especially harmful to crops like lettuce, spinach, and other leafy greens.

• Identification: Cutworms are fat, smooth, and usually gray or brown. They tend to curl up into a C-shape when disturbed. If you notice seedlings suddenly falling over or being severed near the soil line, you likely have a cutworm problem.
• Management:
• Collar barriers: Place cardboard or plastic collars around the base of seedlings to prevent cutworms from reaching the stems.
• Handpicking: Dig around affected plants in the evening and remove any cutworms you find hiding in the soil.
• Beneficial nematodes: These microscopic organisms can be introduced into the soil to target cutworm larvae. Nematodes are harmless to plants and humans but will parasitize and kill many soil-dwelling pests.

5. Spider Mites

Spider mites are tiny pests that thrive in dry, warm environments but can continue to cause problems in the early fall. They are sap-sucking insects, and their feeding weakens plants, leading to discolored leaves and even plant death if left unchecked.

• Identification: Spider mites are tiny, often red or greenish-yellow, and can be difficult to see without a magnifying glass. You may notice fine webbing between leaves and stems, as well as yellow or speckled leaves, which can eventually turn brown and drop off.
• Management:
• Water spray: Mites dislike moisture, so spraying the leaves with water can help reduce their populations.
• Insecticidal soap or neem oil: These organic treatments are effective against spider mites. Apply regularly and thoroughly coat the undersides of leaves where the mites congregate.
• Encourage predators: Predatory mites and ladybugs can help control spider mite populations. Avoid broad-spectrum pesticides that might kill these helpful insects.

6. Flea Beetles

Flea beetles are small, dark-colored beetles that jump like fleas when disturbed. They are common pests in the fall, especially in gardens where brassicas like kale, arugula, and cabbage are grown. Flea beetles are a serious threat to fall crops like radishes, arugula, and other leafy greens, chewing tiny holes in leaves, creating a characteristic "shotgun" pattern. This damage can stunt plant growth and reduce yields.

• Identification: Look for small, black or brown beetles that jump when disturbed. The damage they cause appears as small, round holes scattered across leaves.
• Management:
• Floating row covers: These can protect young plants from flea beetles, especially during the critical early stages of growth.
• Diatomaceous earth: Sprinkle diatomaceous earth around your plants to deter flea beetles.
• Neem oil: Apply neem oil to deter feeding and reduce beetle populations.

General Fall Garden Pest Management Tips

While knowing how to identify and manage specific pests is crucial, there are also some general practices you can adopt to make your fall garden less hospitable to unwanted visitors.

1. Clean Up Debris

Pests often overwinter in plant debris, so make sure to clean up dead plants, leaves, and other garden debris at the end of the growing season. Composting healthy plant material is fine, but diseased or pest-infested plants should be discarded to prevent problems in the spring.

2. Use Floating Row Covers

Floating row covers are lightweight fabrics that can be placed over your crops to keep pests out. They're especially useful for preventing caterpillars and flying insects like cabbage moths from laying eggs on your plants. Be sure to anchor the covers securely and allow enough space for the plants to grow.

3. Rotate Crops

Planting the same crops in the same place year after year can attract pests that target specific plants. Practice crop rotation by moving crops to different areas of your garden each season to reduce the buildup of pests and soil-borne diseases.

4. Use Companion Planting

Certain plants repel pests or attract beneficial insects that help control pest populations. For example, planting marigolds can deter aphids and nematodes, while dill and fennel attract predators like ladybugs and lacewings.

5. Encourage Beneficial Insects

Introducing or encouraging beneficial insects, such as ladybugs, lacewings, and parasitic wasps, can help control pest populations naturally. Planting a variety of nectar-rich flowers and herbs can attract these helpful insects to your garden.

Stay Vigilant and Enjoy Your Fall Garden

Fall gardening is incredibly rewarding, offering the chance to grow cool-season crops and extend the harvest well into winter. But like any season, it comes with its own set of challenges—pests included. By staying vigilant, learning to identify the most common fall garden pests, and applying targeted management strategies, you can keep your garden healthy and productive. Take the time to prepare and protect your fall crops, and you’ll be rewarded with a bountiful harvest as the year winds down.