July Vegetable Gardening

Now is the time to Attract Beneficial Insects while Deterring Harmful Insects and Diseases

*Hippodamia convergens* (native convergent lady beetle) sucking on an aphid, on Common Milkweed. Photo by Katja Schulz

By now you’ve realized that you’re sharing your garden with insects. The good news is that many of these insects are beneficial to your garden. Healthy gardens need and welcome pollinators, parasites (they lay eggs in harmful insects), and predators (they eat harmful bugs). Insects to welcome include bees, butterflies, native lady beetles, spiders, flies, parasitic wasps, lacewings, native praying mantis, and ground beetles. To attract more of these helpful insects, vegetable gardeners often plant nectar-rich flowering plants, such as dill, mustard, sunflowers, Black-eyed Susans, parsley, and goldenrod among their vegetables or nearby.

Consider incorporating certain aromatic flowering plants and herbs to deter and repel garden pests like rodents and mosquitoes, including marigolds, lavender, lemongrass, garlic, garlic chives, rosemary, basil, catnip, bee balm, petunias, and a variety of mints. Consider making plant extracts such as pepper or garlic sprays to spray on melons to help deter these pests. Adding soil amendments, such as blood meal, poultry grit, and eggshells, might also deter slugs and squirrels. Try using rough or sharp materials as deterrents, such as diatomaceous earth, pine needles, or wood chips.

Most gardeners are hesitant to use a pesticide when they’ve spotted insect damage, especially on edible plants. Some broad-spectrum insecticides kill not only unwanted pests, but also pollinators and other beneficial predator insects. Instead of applying pesticides, inspect your garden daily for pests and identify insects to determine whether they are beneficial insects or pests. Check out these resources to help you identify your insect visitor and use cultural controls to minimize pests and disease. Strategies may include picking the offenders off your plants by hand, using a strong blast of water from a hose on the infected area/plant, or pruning away the damaged plant part. Try shaking plants above a bowl of soapy water or spray with a soapy water solution. Be also sure to remove any eggs or larvae left behind. If the problem persists, try some insecticidal sprays that are available at most stores with garden departments.

*Photo: Powdery Mildew on crucifer by Scot Nelson*

Be vigilant for any early signs of common vegetable garden diseases. If you discover, for example, mildew on your basil, cucumber, and squash plants, act quickly: Prune away the diseased bits (throw away, do not compost!); thin out the plant to allow for more air circulation; or remove the plant entirely to avoid spreading to other plants. Consider using disease-resistant varieties of seeds and transplants for your garden or growing alternate varieties (e.g., Thai or lemon basil) that may be less susceptible to disease. Learn more about identifying and managing mildew on basil and cucurbit plants.

Remember, your Extension Office is ready to help you with your insect and plant disease problems!

In general, reasons why your plants don’t thrive may be attributed to not enough sun, crowded conditions, too much or not enough nutrients, poor genetics or maturation, root stress or buds hit by late frost. If your garden doesn’t have enough beneficial insects, some fruiting plants might also require help becoming pollinated either with hand pollination or by lightly shaking the plant.

If your garden is struggling because it is not getting enough sun, consider steps to grow plants and cultivate practices geared toward shadier gardens. Some steps you can take include optimizing growing conditions (such as soil preparation, selective pruning, adequate spacing and targeted watering), choosing varieties that yield smaller fruit, growing in movable containers or vertically, using reflective mulch or surfaces or growing in the winter when trees are bare and cast less shade. Check out this list of plants and tips.

Before adding fertilizer to your plants, familiarize yourself with the signs and symptoms of nutrient deficiency and the so-called N-P-K ratio in plant fertilizers: nitrogen (N), phosphorus (P) and potassium (K). For example, a commonly used fish fertilizer for vegetable plants is labeled as 2-4-1 and, therefore, has 2% nitrogen, 4% phosphorous, and 1% potassium. A general rule of thumb for home gardeners is the expression “Up, Down, All Around” meaning nitrogen for green growth (up), phosphorus for root development (down), and potassium for all over health and vigor (all around). Make sure not to over apply these nutrients, especially nitrogen, which can burn roots and kill your plant.

These recorded VCE/MGNV classes will be of special interest: