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Wisconsin Yard and Garden Tips

July, 2017

Plant Hardiness Zones Map | Last Spring Frost Map | First Fall Frost Map
UW Extension County Offices
By Sharon Morrisey, Consumer Horticulture Agent, Milwaukee County University of Wisconsin Extension
Wisconsin Yard and Garden Tips is updated monthly by Milwaukee County UW-Extension. Applicability in northern Wisconsin counties may be delayed one to two weeks in spring, and advanced a like period in fall.

Sharon Morrisey, Milwaukee County UW-Extension Although it’s gone from lovely to lousey and back again, plants have loved this weather. Hope you’ve enjoyed the beautiful days, too. The summer seems to be flying by – July 7th already?
Here’s the July 2017 calendar of gardening tasks for you to use as you see fit.

This has been an unusual but favorable growing season so far. Although there have been more than the usual number of lovely days of moderate temperatures and low humidity, there have also been some other unusual ups and downs. Officially, this is already the 2nd wettest season statewide in the past 100 years. There have not been too many 90 degree or higher days but there were some very cold ones in April and May.

Specialists tell us this is a bad year for ticks, mosquitos and aphids. Typically, plant pest problems become numerous in July and August. Discovering pest problems early and treating them is better than waiting until the problem is evere. So, check your plants carefully and often. Your county UW-Extension office is a non-biased and knowledgeable source of information for positive identification and management recommendations.

Make your internet searches more reliable by using only university research-based information. Add “UWEX” before the topic you are searching for. If you add the phrase “” after a topic, you will only get results from educational websites which will be more accurate and science based than searches of the entire internet.

First Week

Watch the leaves of your tomato plants for signs of leaf spot diseases. The most common ones, septoria and early blight, appear on lower leaves first and can sometimes be effectively controlled if leaves are removed as soon as leaf spots are seen. If it has gotten away from you, chemical control is also possible with a fungicide containing chlorothalonil. Organic gardeners can use products containing copper.

To prevent bacterial wilt of squashes, melons, cucumbers, and gourds, control the striped and spotted cucumber beetles. Use carbaryl either as a dust or spray late in the day after flowers have closed and bees are no longer active. Organic gardeners can use products containing spinosad. Plants already infected with the wilt should be removed and destroyed immediately.

Squash vine borer is a difficult to control pest of vine crops, particularly summer and winter squashes. Adults lay eggs on the lowest sections of the stems for a three week period starting in late June. Cover lower section of stems with floating row cover or even aluminum foil to prevent egg laying. Look for and remove by hand any brown egg masses seen on the lower stems. Spraying carbaryl (Sevin) just to the base of the stems is more effective than using the dust formulation. If entrance holes and "sawdust" are seen, slit stems lengthwise to find and destroy the caterpillars. Then bury slit stem section under some soil to prevent drying out.

Garden flowers, whether annuals or perennials, benefit from "deadheading" after flowering. By removing the spent flower heads, energy is used to produce more flowers or foliage and roots. Some will produce another flush of blooms.

In general, flowering requires lots of energy so it can be quite helpful to fertilize flowering annual plants once flowering begins. Fertilize one more time before the end of the season.

Trees and shrubs should not be fertilized until leaves begin to color and drop this fall. Fertilizing is only recommended if trees are stressed by insects or diseases, damage, or environmental conditions such as drought. Symptoms are small, pales leaves or a thin canopy. Fertilizing, like pruning, stimulates new growth.

Fertilize your lawn for the second time of the season. This is optional if your lawn is over 15 years old and has been regularly fertilized for that long. Do not use a weed ‘n feed at this time.

Second Week

Watch for cabbage worms, corn borers, cutworms, potato leafhoppers, potato beetles, aphids, tarnished plantbugs, and thrips on many vegetable crops. Obtain a copy of UW-Extension publication A2088 to help you manage insects in the home vegetable garden. Go to

Keep cole crops and potatoes covered with floating row cover to exclude cabbage worm and leafhoppers. Cole crops such as cauliflower, broccoli, and cabbage can be sprayed or dusted with Dipel (Bacillus thuringiensis), a biological control product. M-trak is a similar biological control for potato beetles.

Seeds can continue to be sown throughout July for late crops of beets, bush beans, carrots, chard, Chinese cabbage, cucumbers, kohlrabi, and corn. For summer planting, moisten the furrows before sowing seeds. Cover with pre-moistened potting soil mix which will not be so likely to crust and crack. To hold in the moisture, cover the rows with a very thin layer of mulch or floating row cover fabric.

Transplants of broccoli, cabbage, cauliflower, Chinese cabbage, collards, kale, kohlrabi, onion sets, and onion plants can be planted for fall crops. “Harden-off” plants before planting, plant early in the day, and shade with floating row cover fabric to prevent sunburn of tender young plants.

Keep tomato plants well mulched and evenly moist to reduce the incidence of blossom end rot and cracking.

Oak, elm, ash, and maples infected with one of the wilt diseases will begin to show typical symptoms as the summer heats up. Bring samples of branches that have recently wilted to your county UW-Extension office.

Begin looking for webs of fall webworm on woody plants. Control by cutting out branches wrapped in webbing where possible. Spraying with the biological insecticide B.t. (Dipel, Thuricide, and others) is very effective while larvae are young.

Third Week

Fertilize asparagus plantings with 10-10-10 fertilizer now.

Summer raspberries should be coming in well now. Watch plantings closely for the many possible insect and disease problems. Harvest fruit often and thoroughly to reduce the number of picnic bugs, yellow jackets and multi-colored Asian ladybeetles competing with you for fruit. Viruses cause plants to be stunted and discolored, and fruits to crumble easily. See UW-Extension publication A1610 for pest descriptions and controls.

Also watch for a new raspberry pest, spotted winged drosophila. It is a tiny fruit fly that lays eggs on ripe fruit including grapes and blueberries, too. The larvae are very small and may not appear until after harvest. Report infestations to your County UW-Extension office.

Ornamental kale, grown for its colorful foliage should be transplanted in mid-July. When planted earlier, this cole family member tends to bolt causing misshapen, cone-shaped plants.

Watch for yellowing and wilted leaves on cole crops such as broccoli, cauliflower, and cabbage. This may indicate black rot or club root, two serious diseases of these crops.

Divide iris plantings every 3 - 5 years to renovate plantings, remove and dispose of borer infested rhizomes and replant the healthy ones.

Fourth Week

Alpine currant shrubs infected with the anthracnose fungus will lose leaves and sometimes completely defoliate by mid-summer. Fallen leaves will be spotted with the fungus and should be diligently removed and destroyed to reduce the infection next year.

Honeysuckles susceptible to the common leaffolding aphid should be sprayed every 10 - 14 days with insecticidal soap. Pruning out infected stems every fall will reduce the population considerably but the prevalence of the insect means that others will probably fly in again. Since many species of honeysuckle are invasive especially in our natural areas, it might be best to consider replacing them with something else.

For more information, contact Home Horticulture Agent Sharon Morrisey.

Plant Hardiness Zones Map | Last Spring Frost Map | First Fall Frost Map | UW Extension County Offices

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