Cucumber beetles Symptoms: Chewed leaves, irregular, jagged holes.
Yellow sticky traps work well, or you can buy traps specifically designed to catch cucumber beetles. Spray an insecticide, such as Ortho® Insect, Mite & Disease 3-in-1, following label instructions carefully.
Chewing insect control: An effective broad-spectrum insecticide stops a wide range of chewing insects, no matter who's guilty. Sevin Insect Killer Concentrate kills Japanese beetles, earwigs, flea beetles and other listed chewing insects. Then it keeps protecting your plant's leaves for up to three months.
The culprit munching on the leaves of your young plants may likely be the cucumber beetle. Small with black heads and greenish-yellow wings, they can be either spotted or striped. They not only chew on young seedlings, but also spread disease. When found, handpick beetles and destroy.
Pickleworms Can I just pause to say yuck? Pickleworms tunnel into cucumbers. You may need to look no further to find your culprit. And they're pretty icky as they go about creating these holes. The havoc-wreakers are the larvae of a moth, Diaphania nitidalis.
Overwatered cucumber plants are vulnerable to root rot. A primary symptom of that is top leaves wilting, turning yellow, and dropping off. The symptoms move down the vines, the plant loses all its leaves and eventually dies.
Spider mites, caterpillars, and fungal diseases are often the main culprits behind holes in indoor plant foliage.
While true that holes in leaves can be indicative of a nutrient deficiency such as potassium, more often than not this leaf damage is actually caused by hungry herbivores.
Often, damage first appears as a stippling of light dots on the leaves; sometimes leaves turn a bronze color. Heavily infested leaves can turn yellow and drop off. Damage is usually most severe in hot, dusty conditions and on water-stressed plants.
High concentrations of soap can burn plant foliage, especially when plants are stressed, temperatures are over 90°F and humidity is high.
Cucumbers are exceptionally susceptible to a range of formidable pests, including aphids, leafminers, mealybugs, moths & caterpillars, plant bugs, spider mites and other pest mites, thrips, and whiteflies, which can swiftly devastate entire fields if left unchecked.
Cucumber beetles
Symptoms: Chewed leaves, irregular, jagged holes.
If you decide to use insecticides, Bacillus thuringiensis (Bt), neem oil (azadarachtin) or spinosad, which are derived from natural ingredients, can be effective against beetles or caterpillars. For soft-bodied insects such as aphids or whiteflies, try insecticidal soap, Neem oil, or other horticultural oils.
Use repellents. Non-toxic repellents are available in garden centers that naturally repel bugs with such ingredients as garlic or hot-pepper oil. Some are spray-on liquids, others are granular that can be scattered around the base of plants.
Not all cucumber beetles automatically have bacterial wilt, rather they need to feed on a plant that is already infected, then move to an uninfected plant to spread it. A combination of pyrethrin insecticides and neem can effectively manage cucumber beetle, though you will likely need to apply more than once.
Generally, reapplying the spray every few days is effective for ongoing pest control. In areas with heavy pest activity, daily application might be necessary until you notice a significant reduction in pest numbers.
Keep cucumber beetles under control (see above), and plant resistant varieties if possible. mildew in your garden in the past, plant resistant varieties and try spraying preemptively once a week with a baking soda solution: 1 tbsp. baking soda to one gallon of water.
Left: use a cotton bud to get these worms near the stem out. Middle: these caterpillars are easy to get to – flip the leaves over and remove them! Right: Immature cucumber and zucchini worms. The first is manual control – squishing or removing the worms as soon as they are spotted.
The pickleworm adult is a flashy moth with wide triangular wings and a wingspan of about one inch. The wings are mostly iridescent brown with a central band of yellow and thin white borders. The legs are white. The abdomen is mostly brown except for the tail segment, which is white and has a large fluffy tuft.
Slugs. In my neck of the woods, the Pacific Northwest, the most likely culprit for cucumber holes may be slugs. These guys will eat almost anything and will drill holes through both green and ripe fruit. Sprinkling some slug bait around the plants, however, will likely keep them away from your cucumber plants.