Don’t let insects invade your crops and cause significant damage. Be proactive. Learn more about your crop enemies. Along those lines, following is information about two common insects that can invade cucumber fields and destroy plants and fruits. Keep reading to also learn some important management practices to follow to reduce insect and disease problems. As you know, insect damage may lead to disease concerns.
Insect invader #1: Cucumber beetle
Cucumber growers are wise to control cucumber beetles. If they don’t, these pests can do great harm. Cucumber beetles can kill or slow the growth of cucurbits, according to Joey Williamson, a horticultural Extension agent at Clemson University in a report originally prepared by Entomologist Randall Griffin.
Through cracks in the soil, these beetles can burrow down to the seedlings and start feeding, according to Williamson and Griffin. Beetle activity doesn’t stop there. As soon as the plants start to emerge out of the ground, they go to work, feeding immediately on various parts of the plant such as its flowers and fruit. As the season progresses, they continue feeding on the cucumber plants. Constant feeding by cucumber beetles leaves bacterial wilt disease in their intestines. As they feed, they spread bacterial wilt from one plant to another. This feeding on the plant causes it to wilt and die if infected. Williamson and Griffin suggest the larvae of the cucumber beetle can feed on the roots, and they can bore into the roots and stems.
S.E. Webb at the University of Florida warns that adult cucumber beetles can grow rapidly in numbers within a short period of time. They enter a field just as plants emerge.
For identification purposes, adult cucumber spotted beetles are a yellowish-green color. They sport 11 black spots, a black head and a black antenna, according to Williamson and Griffin. Larvae are a yellowish-white color with brown heads. When they reach adulthood, they stretch to about 3/4 inch in length.
Also for identification purposes, the yellow, adult striped cucumber beetle carries three longitudinal black stripes on its top wings, Williamson and Griffin noted. These adult beetles are 1/5 inch long, and its larvae are about 1/3 inch.
They indicate that the adult banded cucumber beetle sports a yellowish-green color and has three bright green stripes flashed on its wings.
Growers can control cucumber beetles with fabric row covers that offer a barrier between the beetle and cucumber plant, according to Williamson and Griffin. To encourage pollination, they advise growers to remove the covers during the flowering stage. The adventurous grower can pull beetles off the plant with his hands, rely on beneficial predators and parasites or simply apply insecticides. Less toxic pesticides might include a pyrethrin and a neem oil extract. Contact pesticides include carbaryl, bifenthrin, cyhalothrin and cyfluthrin.
Read more: Control Cucumber Beetles Early
Insect invader #2: Pickleworms
As growers may know, pickleworms are tunnelers. These caterpillars tunnel their way onto the plant’s flowers, buds, stems and fruits. They just don’t care what they feed on, but they like the fruits more, leaving sawdust-type waste that growers can see coming out of the holes of the targeted fruit, Williamson and Griffin noted. Consumers usually cannot eat this damaged fruit. In severe cases, damage can lead to death of the plant and its flowers and buds.
Larvae work their way to the buds, then blossoms, next the terminals and finally the fruit, Williamson and Griffin noted. In South Carolina, the real feeding damage can occur in summer, and possibly plant death comes during late crops of cucumbers.
Pickleworms sport a brown head and a yellowish-white body, which soon turns to reddish-brown spots on their back after the first molt of four total molt stages. Once the last molt occurs, these caterpillars lose their spots and end up a solid green or copper color, according to Williamson and Griffin. When they stop their feeding process, pickleworms turn a pink to pale-green color and spin a silk cocoon all around itself. This is when it eventually pupates and ends up a pupa, which is a light to dark-brown color. Growers can spot these pupae rolled up on the leaf.
Within seven to 10 days, adults emerge, and these moths become very active at night. Adults, which appear as brownish-yellow moths, sport a brush of hairs on their rear body. Their wings, a brownish-yellow color, appear to have a purplish sheen. In addition, the wings have translucent yellow-white centers.
Webb indicates that in just a few days after moths emerge, the females start to lay eggs in small clusters and can lay about 300 or more eggs total.
Controlling pickleworms is important during the growing season. Williams and Griffin noted that less toxic pesticides that growers can use include a Bacillus thuringiensis, a pyrethrin, a neem oil extract and a spinosad. Contact pesticides include carbaryl, bifenthrin, cyhalothrin and cyfluthrin.
The Integrated Pest Management Center at North Carolina State University reported that growers can establish some important and necessary management practices to avoid cucumber insect and disease problems. Those practices include:
- Keeping good records to see what insects and diseases were present from one year to the next.
- Select adapted cultivars with resistance to downy mildew, powdery mildew, anthracnose, scab, angular leafspot and cucumber mosaic.
- Practice a 12-month, noncucurcurbit crop rotation.
- Select fertile, well-drained fields.
- Sample fields annually for pH, nutrients, nematodes, soil insects and weeds.
- Use certified seed treated with fungicides and insecticides.
- Seed 0.5 to 1 inch deep on raised beds after soils warm to 60 degrees Fahrenheit.
- Place one strong colony of bees per acre after blooms are present.
- Apply a general purpose fungicide shortly after emergence and include an insecticide as needed.
- Diagnose all leafspots and plant abnormalities promptly.
- Use a high-pressure sprayer for fungicide and insecticide applications.
- Irrigate fields to ensure 1 inch of water each week.
- Monitor migration of the pickleworm and spray as needed.
- Reapply nitrogen and potassium after leaching rains.
- Pick three times a week.
- Avoid injuries during harvesting and handling.
- Use chlorine in all dump, wash and handling water.
If growers follow these IPM management practices, they may increase yields, improve quality and reduce insect and disease pressures during the growing season. Learning more about cucumber beetles and pickleworms can help growers earn more profits from their cucumber crop.