Green Industry Resources
Hort Update- Seasonal Information for the Green Industry
June Garden Activities
Protect honeybees. Use caution when applying insecticides to flowering plants.
During the growing season, cut down suspected pine wilt trees within one month of the tree losing it's green color.
- Pinch chrysanthemums and other late flowering perennials to induce branching- stop by mid-July.
- Botrytis blight is a wide-spread fungal disease affecting many ornamental plants. Occurring in wet or humid weather, a tan to gray fuzzy mold develops on affected plant parts. Blight of coneflowers and peonies is common. Sections of the affected flowers become brown or black and fail to develop. Avoid overhead irrigation and provide maximum air circulation around plants to minimize the problem.
- First fungicide spray on roses for black spot and powdery mildew. Continue rose fungicide spray program throughout the summer as directed on the fungicide label.
- Inspect vegetable garden plants for disease problems and begin foliar fungicide applications if necessary. Reapply fungicide as recommended on the product label. Covering the soil beneath plants with mulch will prevent rain-splash of fungal spores on the plant leaves and slow down infection.
- Plant sweet potato slips after all danger of a frost has passed.
- Inspect squash plants for the presence of egg-laying black and red squash vine borer moths. Stems may be protected from egg-laying by wrapping them in foil or old nylon stockings, or by placing a cardboard collar close around the base of plants. Row covers can also provide protection until plants start blooming. Otherwise, dust or spray the bases of plants with insecticide to kill hatched larvae before they tunnel into the stems.
- Yellowing of lawn grasses could be due to root issues due to excess rain or overwatering. If soils are consistently wet, roots do not function as well and absorption of nutrients, like iron, is affected. Denitrification, resulting in loss of nitrogen, can also occur on wet soils. When watering lawns, moisten the top 4-6 inches of soil, then wait until the lawn shows signs of needing water, such as a darker blue-green color or foot prints remaining after walking across the grass, before watering again.
- Continue mowing throughout the summer at 2.5-3.5 inch height for Kentucky bluegrass and 3-3.5 inch height for tall fescue.
- Watch for the emergence of yellow nutsedge in areas with a history of infestation. Begin control as soon as the weeds emerge, either through continous pulling or chemical applications. Herbicide treatment is most effective if applied before June 21.
- In late June, apply second pre-emergence herbicide for crabgrass and spurge control.
- In early May, watch for the first generation of pine needle scale on affected trees. Tiny, red crawlers are present for a couple weeks after hatching and are susceptible to insecticide control. Make one insecticide application, and repeat once or twice at 7-10 day intervals.
- Second application on spruce control Rhizosphaera needlecast and Siroccocus shoot blight with the application of a fungicide (chlorothalonil). If frequent rains occur, spray trees every 10-14 days through early July for additional control of Rhizosphaera needlecast.
- From April through September, control two-spotted spider mites on juniper, pine, spruce and deciduous shrubs when damage is detected with two insecticide applications 7-10 days apart. Insecticidal soap and horticultural oil work well, although oil will remove the blue needle color on blue spruce. A hard spray of water will also help reduce mite populations.
- In mid June make the first application on cedar/junipers for cercospora blight with copper fungicide, Bordeaux mixture or mancozeb. Second application late July. Additional applications may be necessary at monthly intervals if frequent rains occur in August and September. Use of a spreader-sticker may increase effectiveness.
- In late June, make a second application of copper fungicide to pines for Dothistroma needle blight and spruce for needle cast.
- Watch for the first generation of mimosa webworm in honeylocust trees. Their webs may be broken up with a rake or broom, or with a strong jet of water. Although the webs are ugly, the insects cause little serious damage to plants. Chemical control is seldom required. The second generation appears in August.
- In late June, make the second application to birch trunk and branches with permethrin to control bronze birch borer. Alternative- make a soil drench application of imidaclopirid.
- Narrow strawberry rows to 6-8 inches and thin plants to 6-8 inches apart immediately after completing the harvest.
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