Weeds are making a fast and bold appearance in lawns and gardens this week. I am seeing strong growth of ground ivy, (Glechoma hederacea). Ground Ivy is a perennial weed commonly found in turf. It  spreads by creeping rhizomes, rooting at  the nodes to produce new plants. The purple flowers produce seeds, another way for the plant to spread. Hand pulling is one way to eradicate this creeping vine, but not very effective as the vines break where the nodes are rooting in new spots. It tends to creep through the grass lower than the blades of the lawn mower, thereby not controlled by regular mowings. I find it mostly on the fringes of the lawn, reaching into the flower and vegetable gardens. The best way to kill it is to use a broad leaf weed killer containing 2,4-D or triclopyr. This plant will need more than one application to completely rid the lawn of plants present. New plants will be created from germinating seeds throughout the season. Watch for new invasions and treat accordingly. A pre-emergent herbicide can be used to stop the germination of seeds.

Figure 1: Juniper branch with a mature Cedar-Apple Rust gall displaying gelatinous tendrils. (provided by Dr. George Hudler, Cornell University)C

Figure 4: Juniper with Cedar-Apple Rust displaying a developing gall---the winter survival structure. (provided by Dr. George Hudler, Cornell University)

Cedar Apple Rust fruiting structures are appearing on the branches of cedar and juniper trees this week. They look like an orange sticky sea creature shocking people not familiar with this fungal disease. Cedar-apple rust is caused by the fungus Gymnosporangium juniperi-virginianae. The orange horned structure grows out of the overwintering hard brown gall after a few days of rain and cool weather. Spores are produced from the structure beginning and mid-summer, becoming air-borne and dispersed by the wind. These spores will land on the alternate host in the Malus or apple family to continue its life cycle. Once an apple or crabapple is infected with the new spores, the fungus develops on the leaves, creating spots and eventually turn the leaves yellow. Early defoliation of the malus tree usually follows.The cedar tree retains the deformed tissue some find unsightly.

Control measures used are planting resistant cultivars of trees, sanitation and fungicide sprays.

Resistant cultivars of apple include Delicious, Empire, Jonamac, McIntosh, and Paulared. Resistant crapapples are Ellwangerina, Henry Kohankie, Ormiston Roy, and Red Baron. Resistant junipers are Juniperus chinensis var. sargentii, J. communis cv. Aureospica, and J. virginiana cv. Tripartita.

Sanitation measures reduce the incidence of infection. Cut off all orange and brown growths on the cedar trees. Do not put these in the compost or them might continue to release spores even after being cut.  Bag them for disposal in the the trash. This one action will reduce the amount of spores released in the air. Remove either host trees for up to one mile, although this usually not possible! Fungicide options are available for the apple and crabapple trees, used as a preventative measure before the spores land on the leaves. Fungicide used on the cedar and juniper are not very effective. Rake and remove to the trash any fallen leaves of the apple species. The fungus can overwinter on the leaves to keep the disease cycle going into the next spring.

Fungicide labeled for use on apple and crabapple in Connecticut are chlorothalonil, mancozeb, triadimefon, propiconazole, and myclobutanil. Sulfur can be used as an organic fungicide option. Thorough coverage of all leaves are needed for protection. Follow all label directions, more than one application may be necessary for season long control.

cedar-apple rust on apple leaf

-Carol

Crabgrass is overtaking some lawns by this time of late summer. It is an annual grass weed with wider blades and lighter yellowish green color than the preferred lawn grasses. Crabgrass seeds that germinated last spring are large spreading plants by September. The cooler soil temperatures at the end of summer trigger new plants to sprout, adding to the crabgrass population. All crabgrass plants will die with first the hard frost. As stated above, they are annual plants meaning they grow from a seed to plant, produce seed and die all in one year. Each year, new plants grow from seed make up the entire crabgrass population. Knowledge of the plant’s growth cycle is useful for using the correct control measure.

The first line of defense against crabgrass is healthy soil and a dense stand of turf. Soil pH for turf should be 6.5. Connecticut soils usually are in the below 6 range. A soil test will determine your particular yard’s pH level as well as reveal the nutrients available. Soil testing how to’s can be found at www.soiltest.uconn.edu. After receiving results by mail, make recommended additions to bring your soil into optimum grass growing condition. Turf needs oxygen and water also to support a healthy lawn. If soil is hard to dig and compacted, now is the time to core aerate. Aeration machines remove a small plug of turf and soil, depositing it on the lawn surface. Leave these plugs on top, do not rake them up. Rain or watering and wind will breakup the plugs, redistributing the soil microbes into the top layers. If you want to add more organic matter to the soil, spread a thin, (1/4 inch), of compost over the entire lawn. Compost will add rejuvenating microbial life to the root zone of the grass.

Mid September is the ideal time to overseed bare and thin turf areas. Choose a grass seed mixture that contains a high percentage of fescue grass. Some bluegrass and perennial rye grass is usually included in the mix. Do not chose one with annual ryes as these will die with the cold weather.  Rake the bare spots to break up any crust to give the seed good contact with the soil. Tamp down after spreading seed. Keep seed moist during germination occurs and new seedlings are two inches tall. Next spring, this new grass should fill in nicely.

To keep the crabgrass seed from germinating in the spring, use a pre-emergent herbicide. Crabgrass begins to germinate when the soil temperatures reach 38 to 40 degrees F. Forsythia blooms at the same soil temperatures making it a good plant indicator to help with remembering the timing of herbicide application. Pre-emergent herbicide does not kill the non-germinating seed, only the new little pip emerging from the seed. This new tissue, the pip, is very tender and susceptible to the chemicals in the pre-emergent herbicide. Not all the crabgrass seeds will germinate every year. Some will stay dormant for many years, creating a seed bank. Each year crabgrass is allowed to grow and produce seed, it adds more seeds to the seed bank. Read the label of the pre-emergent to see how long it will last. Some formulations will last two months, some last six months. These anti-germinating chemicals halt the germination of all seeds, broadleafed and grasses. Only one, Tupersan allows desirable grasses seed to germinate. Tupersan only works on the crabgrass seed, but it doesn’t last long, two months most labels advise. An organic option of pre-emergent herbicide is corn gluten meal. Timing is the same as with a synthetic pre-emergent.

Fertilize with the amounts indicated on the soil test report. Starter fertilizer may be used at the seeding stage.

So to recap the step needed to thicken the turf and reduce crabgrass:

1. Soil Test – apply lime as recommended

2. Core Aerate

3. Top dress with compost.

4. Seed with high fescue seed mix.

5. Keep moist.

6. Next spring when forsythia blooms, apply a pre-emergent herbicide.

Result is a lush healthy lawn.

-Carol