University of Maryland Extension

May Vegetable Tips

staked green beans

(More tips from HGIC)

For more vegetable gardening tips, watch our Vegetable Gardening Videos.

Pinch the blooms off flower and vegetable transplants before you set them out. This will help direct the plants’ energies to root development and will result in more productive plants. Gently break up the roots of root-bound transplants.
Begin setting out transplants of warm season crops like squash, peppers, eggplant, and tomato. Be prepared to cover plants with a tarp or light blanket if frost is expected. Mix in a handful of either gypsum or finely ground limestone with the planting soil of each pepper and tomato transplant to prevent blossom-end rot. Set up your tomato support system after transplanting. Very tall tomato transplants can be laid horizontally in a shallow trench with the growing tip gently bent into vertical position. Roots will grow all along the buried stem. Corn, beans and other tender crops can also be planted. Hold off on planting pumpkins until mid- June so that harvest occurs closer to Halloween. Be sure not to plant tender annual plants like basil and eggplant until after the last frost date. Parsley is slow to germinate and basil should not be directly sown in the garden until the soil has thoroughly warmed.
• For an extra boost, apply a soluble liquid fertilizer to the foliage or root zone of newly set plants to get them quickly established.
• Did your garden get overtaken by weeds last year? Take action now, before weeds become unmanageable. Consider the following options around plants and between rows: dried grass clippings, sections of newspaper covered with straw, black landscape fabric or black plastic mulch. The latter two will also warm the soil and hasten the harvesting of warm-season vegetables like melons, eggplant, tomatoes, and peppers.
• Now that it is warming up, you’ll begin to see slugs feeding on all types of vegetable plants. They feed at night and chew holes in leaves and can also shred leaf tissue with their rasping mouthparts. Slime trails are a definitive sign of slug activity. They breed in protected, damp areas under boards, in ground covers and under thick mulches. They can be trapped with shallow pans of water with bread yeast or beer. You can also lay out boards to attract them to be collected and destroyed. Diatomaceous earth, sharp sand or ground crab, and oyster shell can be applied around plants as physical barriers. A product containing iron phosphate is available that slowly poisons slugs upon ingestion. This product is safe to use around food crops.
Salad greens should be grown in rich soil and regularly watered and fertilized for optimum succulence and eating quality.

Insect Pests and Plant Problems

Cucumber beetles- spotted cucumber beetles are yellow with 11 black dots and striped cucumber beetles are yellow with 3 black stripes. They have a wide host range and begin to feed on all plant parts of all members of the cucumber family as soon as they begin to grow in the garden. These pests spread several diseases. The striped cucumber beetle vectors bacterial wilt disease, primarily to cucumber and muskmelon, which causes plants to wilt and die in a short time. The beetles can be controlled with insecticides or excluded with floating row covers. “County Fair” is a hybrid cucumber cultivar that is resistant to bacterial wilt disease. 
Cutworms are nocturnal caterpillars that feed on leaves and stems and can cut large plants off at ground level. They can be excluded with cardboard, plastic, or aluminum collars inserted into the soil around individual plants or apply a rough or gritty material, like ground up oyster shell or sharp sand, around vulnerable plants.
Aphid numbers are high now on a wide variety of landscape and garden plants. It is usually not necessary to spray insecticides or release beneficials to control aphids. Populations of ladybird beetle, green lacewings. and wasp parasites build up quickly to keep aphids in check. You'll see these predators and parasites at work if you observe the aphid colonies closely. Planting a wide variety of flowering plants that bloom throughout spring and summer will help attract and keep beneficial insects in your landscape. If necessary, an application of insecticidal soap or ultra-fine horticultural oil will kill these soft-bodied pests. Avoid pesticides if beneficial insects are present. 
Squash vine borer adult females are large, clearwing moths with orange/black bodies. They begin flying mid-late May in Central Maryland and lay eggs on squash stems, especially zucchini. Use floating row covers to exclude the adult females.
Seed corn maggot feeds on corn and bean seed and young vegetable plants. To avoid seed corn maggot and bird damage, try pre-sprouting bean and corn seed.
• Protect broccoli, cauliflower and cabbage plants from the imported cabbageworm with floating row covers. The adult is a small white butterfly with brown spots on the wings. The small velvety larvae that emerge from eggs laid on your plants can be controlled with a spray of Bacillus thuringiensis, also known as Bt, or Spinosad. This organic, microbial insecticide acts as a stomach poison on young larvae. Floating row covers are made from a spun-bonded polypropylene material and are available from mail-order seed and garden supply companies. They are effective at excluding insect pests and promoting strong early growth.
• Weeds in asparagus and rhubarb beds can be very difficult to control. It is always best to hand pull weeds or cut them off cleanly at the soil line with a small, sharp hoe. Be careful not to cut into crowns or emerging spears. Asparagus beds that are 3-4 years old should not be harvested for more than 2 weeks. In some established beds, spears may come up weak and thin. This could be due to many factors including over-crowding, insufficient fertility, weed competition, fusarium crown rot, cutting for too long a period the previous spring or cutting ferns down in summer rather than allowing them to grow through the first frost in fall. Asparagus beetle adults feed on spears causing scaring and the females lay small black eggs resembling specks of soil. 
Four-lined plant bugs are now feeding on a wide range of woody and herbaceous plants, especially mint. The adults are yellowish-green with 4 black stripes. The nymphs are bright red. The bugs leave rows of small, round dark spots on leaves. Unless severely injured early in the season, plants will outgrow moderate feeding damage.

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