| Powdery mildew | Fall webworm |
| Mimosa webworm | Spider mites |
| Euonymus scale crawlers | Bagworms |
| Japanese Beetles | Potato Leafhopper |
| Red headed pine sawfly | Azalea lacebug |
| Japanese beetles were caught in monitoring traps on 6/20 | Leaf & flower gall-azalea |
| Bacterial blight-Lilac | Succulent oak gall |
| Septoria leaf spot-River birch | Apple scab-crabapple |
| Rose sawfly larvae | Azalea caterpillars |
| Oak leaf blister | Birch sawfly larvae |
| Pine spittlebug | Fireblight-Bradford pear |
| Aphids-various plant spp. | Powdery mildew-dogwoods |
| Hawthorn & quince rust | Fall webworm |
Damage is caused by the sucking of the lacebugs. Greatest buildup occurs during late summer. On the deciduous azaleas, it appears to be stippled grayish; but on certain types of evergreen azaleas, it may appear to be coffee colored or bronze.
Repeated treatments may be needed for effective control. Insecticides such as Insecticidal Soap, Summer Horticultural Oils, Dursban, Malathion, Orthene, Sevin may be used depending on the species or cultivar. Always read product labels carefully before purchase. Look for information on phytotoxicity that can occur on sensitive plants or under some environmental conditions.
Regularly check for infestations so that a treatment can be applied before the plants are disfigured by lacebugs. Thorough treatment of the undersides of the leaves is needed for best results.
Mealybugs on Azalea-(also called Azalea Bark Scale) Mealybugs are relatives of the scale insects. They have rather soft scales and soft bodies covered with a white powdery wax. Mealybugs damage plants by sucking sap and producing honeydew, which attracts ants and supports the growth of sooty mold fungi.
Mealybugs occur on outdoor azaleas, blueberries, and other close relatives. Affected azaleas may appear unthrifty and yellow.
Leaf and Flower Gall of Azalea Also known as “pinkster” gall, this disease can be conspicuous and unsightly on landscape and greenhouse plants under very humid conditions. Symptoms appear as succulent thickenings of leaves, flower buds, and shoots that are green or pink in color. Affected tissue eventually turns brown, shrinks, and hardens.
To manage leaf and flower gall, reduce humidity, avoid excessive leaf moisture, improve aeration through increased spacing, and pick off newly formed galls before they turn white. Fungicide applications are not effective.
Rose aphids Rose aphids are only one of the several hundred aphids or plant lice that appear on various plants throughout Kentucky. Aphids are sucking insects and are capable of transmitting diseases to certain plants.
Aphids have a rather complicated life history. At certain times, they lay eggs and other times they give birth to living young. They may also reproduce without mating, and under certain conditions are able to produce either males or females. Aphids will frequently alternate from one host to another.
Since aphid numbers can build up rapidly, frequent monitoring is needed, especially when plants have succulent growth. Some products registered for aphid control include: insecticidal soap, horticultural oil, Dursban, Mavrik, Orthene, Talstar and several others.
Rose Black Spot Black spot is one of the most common diseases of roses. It is apparent as yellowed-ringed black blotches on the leaves. This disease will cause the leaves to fall prematurely and may also affect the blooms and canes.
Heavily pruned hybrid teas and yellow hybrid teas are considered more susceptible than other roses, but all roses can be affected. Wet conditions increase the occurrence of this disease.
For control, clean up fallen leaves and prunings. Prune plants to improve air circulation and avoid overhead watering. Plant resistant varieties whenever possible.
Fungicides labeled for black spot include Daconil, Mancozeb, Thalonil and several others. Black spot sprays are not to used as a cure but rather as a preventative spray.
Ash Plant Bug This common sap feeder on ash tree foliage causes discrete white speckles on the upper surface of the leaves. The leaf undersurface is marked with shiny black specks of excrement called varnish spots.
The feeding stipples are often clustered and in some severe cases, enough speckles accumulate to cause shriveling or browning of the leaves. Premature leaf drop is possible later in the season when the second generation has further stippled the same leaves. Control is seldom warranted except on stressed or newly transplanted trees.
Shade Tree Galls Many galls are now apparent on tree leaves across Kentucky; however, they do not significantly affect the vigor of healthy, established trees. Galls easily noticed now include spindle gall and bladder gall on several varieties of trees, and succulent oak gall on pin oak leaves. Once a gall has formed on a tree leaf, there is no way to control the gall.
Honeylocust plant bugs Honeylocust plant bugs, are 3/16" long light green insects that cause honeylocust and black locust foliage to become discolored, stunted, or deformed. These insects do their damage early in the spring but the symptoms persist through the season. Severe infestation can even cause twig dieback. Adults occur from late May to early July. There is one generation per year. The eggs are laid in the woody tissue where they overwinter. On problem trees, watch carefully for signs of activity in the spring. Examine terminal foliage for presence of the insects. Treat when leaves first open with Insecticidal Soap, Dursban, Malathion, Sevin, or Tempo.
Euonymus Scale Euonymus scale females are dark brown or gray, about 1/16" long, and resemble oystershell scales, but are more pear shaped. They more commonly occur on the stems of host plants. Male shells are smaller, narrow, white, more abundant than the females. They are easy to see on stems and leaves. Euonymus, pachysandra and bittersweet are hosts. Eggs hatch in early May in central Kentucky. First brood crawlers are active in late May; and the overlapping second and third broods are active from late July to early September.
Treatment of scales may be achieved with either horticultural oil sprays, which kill primarily by smothering, insecticidal soap or by conventional insecticides. Oil sprays kill all stages of the scale but caution should be used as some plants are sensitive to the oil. Refer to the product label for guidelines on plant sensitivity and any temperature restrictions.
Contact insecticides should be applied during the growing season when the crawler stages of the scales are present. The presence of crawlers can sometimes be determined by tapping an infested twig or branch over a white paper. Crawlers are often orange, brown or purple and appear as moving specks of dust. Because of their waxy protective covering, other stages of scales are not readily controlled by contact insecticides. Contact insecticide sprays will not reach crawlers that have settled under old scales.
Insecticides registered for scale crawler control on outdoor plants include: Cygon (dimethoate), Dursban (chlorpyrifos), Diazinon, Malathion, Orthene (acephate) and Sevin (carbaryl). Although resistance to insecticides may occur in some cases, failure of contact sprays is more often the result of not timing the applications to coincide with crawler activity. Even when sprays are timed for optimum effect, complete control may not be achieved by single applications if crawler activity is spread over an extended period of time, or if populations are heavy and crawlers are under old scale shells. Thorough spray coverage is essential for good control.
Fireblight The leaves of plants affected by fireblight appear to have been scorched black. Flowering shoots die, and cankers, cracks and dry spots may appear on the base of twigs. Stems affected with fireblight take on a shepherd’s crook appearance.
Fireblight targets members of the Rosaceae family, and plants are most susceptible during flowering. Warm, wet conditions also contribute to the spread of the disease.
For now, all that can be done for control is to prune back infected branches and twigs at least six inches below the damaged area. Pruning tools should be disinfected between cuts. In future years, trees should be sprayed with fixed copper when trees are just breaking dormancy. This will help to reduce overwintering bacterial inoculum. Avoid spraying copper after 1/2 inch green tip so that fruits do no become russetted. Thoroughly wash spray tank following use since this chemical is highly corrosive.
For growers who can only guess whether fire blight is likely to be a problem in a given year, their only choice is to spray with the antibiotic streptomycin at 4-5 day intervals during bloom.
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Unlike adult Japanese beetles, masked chafer adults do not feed on trees, shrubs or other landscape plantings. Damage is caused solely by the larvae which feed on grass roots from July-October. Infested turf develops irregular dead patches, which can be rolled back like a carpet to expose the white, C-shaped grubs. Most damage occurs during late August or September, especially in years when the turf has been drought stress.
The best time to control white grubs is in August, after the eggs have hatched and the larvae are still small. Although it is still too early for treatment, homeowners and turf managers should watch for the adult beetles swarming over the ground at dusk, or around porch lights at night. Large numbers of beetles observed in July could indicate grub infested turf worthy of treatment in August.
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Leaf Spot/Melting Out. The leaf spot phase of this disease appears as dark, elliptical spots on leaf blades and sheaths. They initially are dark brown or purple. As they expand, the center often becomes tan. Affected leaves and tillers turn yellow if the disease progresses slowly. If the variety is susceptible to the melting out phase, the lawn may quickly turn bluish green and then tan, as though suffering from a drought. Cool, wet weather this spring has have favored disease development.
Stripe Smut. Affected leaves turn yellow or sometimes directly become a dried, tan color. Close inspection of leaves will reveal black "sori", very thin stripes of black, sooty spore masses erupting from within the leaf blade. Affected leaves become shredded along these smut sori. The mild weather during much of last fall and early winter coupled with a cool spring have favored disease development.
MANAGEMENT
1. Variety and Species Selection. Varietal susceptibility is by far the major factor determining the severity of either disease. The number one control measure for both diseases is to renovate lawns to a resistant variety or species, if practical. Renovating to tall fescue eliminates both potential disease problems, as well as a host of other problems. Alternatively, if one wishes to stay with Kentucky bluegrass, use a variety that has performed well in UK variety trials, such as Midnight, Eclipse, Glade, Aspen, Indigo, and others.
2. Fertility. High fertility favors infection by the fungi that cause leaf spot, so heavy fertilization during the spring may enhance the disease. However, in late spring, light fertility (no more than .5 lb nitrogen per thousand square feet) can sometimes help the turf outgrow the damage from either disease.
3. Irrigation. To irrigate or not to irrigate? That is the question. If these diseases have been active, the turf will likely exhibit thinning over the summer. Regular irrigation when needed can help slow this process down, but will not prevent it. In fact, without irrigation, stripe smutted plants will often die during the heat of summer. This can obviously be a cause for concern for the homeowner or landscape manager, but at least those tillers won't produce a new crop of stripe smut spores to infect other tillers. Either way, if the variety is susceptible to either disease, than that disease will develop again when conditions favor it. So it is a judgement call whether the homeowner wants to irrigate and favor regrowth during the summer; or let it go dormant, allowing the infected tillers to die out, and start fresh with uninfected tillers when the first autumn fertilizer application is made.
4. Fungicides. By the time symptoms are obvious, curative fungicide applications will be completely ineffective--yes, completely ineffective--at preventing the damage that is there, as well as preventing future damage this spring! The infections have already occurred. We are simply seeing the consequences of that, and this will continue through mid-summer. If fungicides are to be used at all, they must be applied preventatively--before symptoms show up. See the UK Extension publication, "Chemical Control of Turfgrass Diseases, PPA-1", for information on fungicidal control of these diseases.
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