University of Maryland Extension

June Vegetable Tips

root vegetables

(More tips from HGIC)

Check out (PDF) GE 003 - Monthly Tips for Food Gardeners

Large amounts of various herbicides are applied to land in Maryland in spring. Unfortunately, every year we receive reports and samples of tomato plants damaged by herbicides, especially 2,4-D, that have drifted into gardens. Tomatoes are very susceptible to herbicide injury. New leaves will become strappy, twisted and distorted. Injured plants occassionally grow out of the damage and produce a crop. Usually the damage is so severe that replanting is necessary.

The suckers or succulent shoots that develop from tomato plants at the soil line should be removed throughout the season. You can plant these suckers for a late crop. (Watch our YouTube video!)

Now is a good time to (PDF) plant a second crop of radishes, beets, and beans to make full use of available garden space.

Perpetual spinach, Malabar spinach, amaranth, sweet potato leaves, and Swiss chard are good heat tolerant salad greens for Maryland. ‘Grand Rapids’, ‘Red Sails’, ‘Deer Tongue’ and oak-leaf type lettuces are some of the more heat tolerant looseleaf lettuce varieties that can be sown now. ‘Jericho’ is a heat-tolerant romaine cultivar. Keep them fertilized and watered and covered with a shade cloth or floating row cover if possible.

Control weeds by laying down sections of newspaper covered with straw or last fall’s mulched leaves. Be sure to get stakes for tomatoes, cucumbers and pole beans in the ground right after transplanting or emergence. Doing this later in the season when they have grown large is difficult to do and may lead to some root and plant damage.

Pest problems

Many species of insects become troublesome to vegetables this month. Aphids continue to feed on a wide variety of vegetable plants. It is not necessary to spray chemical insecticides. If necessary, an application of insecticidal soap or ultra fine horticultural oil will kill aphids, spider mites, whitefly and thrips. A number of native beneficial insects will attack the aphids and keep their numbers in check.

Handpick Colorado potato beetles and their orange egg masses on eggplant and potato plants. A floating row cover also works well to exclude Colorado potato beetles and straw mulch can also help control this pest.

Cucumber beetles can be either yellow with 11 black dots or 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 plants emerge. These pests transmit bacterial wilt disease, which causes mature cucumber, muskmelon, and squash plants to wilt and die. Controlling this pest early in the season is very important.(PDF) Row covers can be used to cover plants to deter cucumber beetles or you can apply a labeled insecticide. Remove row covers when plants begin to bloom to permit pollinating insects to enter and pollinate the flowers.

Cutworms, 1-inch long caterpillars, cut down seedlings and transplants at ground level and drag the plants into underground burrows. They can also strip foliage leaving bare stems. Try placing a cardboard collar around vulnerable plants that extends 2 inches down into the soil. The collar works very well to prevent the cutworms from getting to the stems.

Flea beetles are a serious pest of eggplant and also affect potato, tomato and members of the cabbage family. The small black insects jump (like a flea) when disturbed and produce small shot holes in leaves. If uncontrolled they can greatly limit production. Floating row covers are also effective but should be removed when plants flower to allow for cross-pollination by bumblebees (see our YouTube video). Spraying plants with “Surround” (kaolin clay) creates a white particle film that can minimize flea beetle feeding. You can also control flea beetles with “Neem”, a botanical insecticide.

Imported cabbageworm is appearing on broccoli and cabbage. They are small, cream colored caterpillars that become velvety green when fully grown. They chew large irregular holes in leaves and leave black droppings. Handpick them or spray with a B.t. (Bacillus thuringensis) product when larvae are small.

Harlequin bugs are very colorful black and orange insects that feed on plants in the cabbage family. The adult females lay barrel-shape white eggs with black rings. Also, look for and destroy the copper colored eggs of squash bugs on the undersides of squash and pumpkin leaves.

 The adults, larvae and eggs of Mexican bean beetle can be handpicked. The adults are coppery with 16 black dots and resemble ladybird beetles. Carefully inspect the upper and lower leaves of your plants for these pests and their egg masses.

Slugs may cause round holes in the leaves of many different plants. Slugs reproduce around garden structures, like rock wall and railroad ties and in shaded, moist areas covered with thick groundcovers. You can control them with shallow containers of beer or a molasses, water and yeast mixture. The slugs crawl into the containers and drown. You can also set out boards and grapefruit rinds which will attract the slugs. Turn the boards and rinds over in the morning and destroy the slugs. Diatomaceous earth, sharp sand or ground crab and oyster shell can be applied around plants as physical barriers. There is a product containing iron phosphate that slowly poisons slugs upon ingestion. Be sure to carefully read the label and follow instructions.

Squash vine borer adults are laying eggs on squash and pumpkin stems. Monitor plants for signs of wilting and entrance holes on lower stems. You may see sawdust-like frass around the hole. Stems may contain more than one larva. They can feed inside the stems for up to 2 weeks. Here’s the easiest and surest method of control: cut a slit above the hole with a razor, remove the 1 inch long white larva with a brown head, and mound up soil around the wound.

Four-lined plant bugs are finishing up now. They feed on a wide range of herbs, especially those in the mint family. 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.


Young tomato plants may be exhibiting symptoms of various leaf spot diseases such as gray leaf spot, septoria and early blight. Remove badly infected lower leaves, keep a thick organic mulch around plants and avoid overhead watering. Applications of tri-basic copper will slow down severe infections. Be sure to offer proper support to growing tomato plants. Learn more about specific vegetable prblems, including diseases.

early blight lesions
Early blight symptoms on tomato leaves

Choanephora wet rot infects squash bloom and young fruits. The fruits shrivel and may develop a fuzzy gray growth. Prevent the problem by removing blooms attached to enlarging fruits. No sprays are recommended.

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