Inspector Findings in Kentucky

Pests to watch for in August

Pest Activity Seen in July

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From the Disease Diagnostic Lab:

Needle Cast Diseases of Conifers

by John Hartman & Deborah Hill

Scots Pine Needle Casts

Lophodermium Needle Cast

In late autumn, but more conspicuously in early spring, small brown sports with yellow halos appear on the current year’s needles. Needles turn yellow, then brown, and are shed throughout the summer. By late summer, only tufts of green current-season’s needles may be left. Spores of the causal fungus are produced in tiny, black football-shaped structures in infected needles, are spread by wind and infect current needles during moist periods from August to October. Infected needle symptoms are seen the following late fall or early spring. Where the fungus is active, a period of cool moist weather in the late summer and early fall can lead to a destructive outbreak.

Needle cast disease reduces photosynthetic capability and reduces growth in small trees. Twigs that bear only diseased needles may wither in early spring, and buds that survive produce abnormally small shoots and needles. Thus the Christmas trees may be stunted and disfigured.

Brown Spot Needle Blight

In late summer, small, dark spots becoming brown with yellow halos appear on current-season’s needles. By fall, needles may be resin soaked, turn brown and begin to drop from the tree, with most needle shedding occurring the following spring. Dark, oval fruiting bodies are found on the needles, and during late spring and early summer, spores of the causal fungus initiate new infections. Infections occur readily and the disease is spread most rapidly during periods of warm, wet weather.

On pines with dense foliage, infection is most common on low branches, leaving bare branches through the winter if infections have been severe. If these branches live, they produce new foliage in spring which may become infected the next season. Light infections may only accelerate the loss of second and third-year needles. Infected trees are not valued as Christmas trees. Naemacyclus Needle Cast. Scots pines grown for Christmas trees are very susceptible to this needle cast; Austrian, mugo, Virginia and eastern white pine are also hosts. The causal fungus is Cyclaneusma minus, formerly referred to as Naemacyclus.

Needle cast disease symptoms begin to appear the year following infection. In late summer and fall, light green spots may be found on second and third year needles. Needles soon turn yellow, having dark brown horizontal bands, then turn brown and drop from the tree throughout the fall, winter, and spring. The causal fungus produces tiny, elongate, protruding, tan colored fruiting bodies in the dead needles. These structures yield spores that initiate infections primarily from April to June but also at low levels throughout the summer and fall. This disease is favored by mild, rainy weather during spring and summer.

Premature yellow and casting of second and third year needles reduces the value of infected trees as Christmas trees. Severely diseased trees appear yellow before needles fall. Current season’s needles show no symptoms and are retained, even though infected; in severe cases the first year needles may be all that are left. Such trees are of little value as Christmas trees.

Control

Apply fungicides, if needed. Fungicide use may be warranted on some highly susceptible, short needled Scots pine types growing in moist locations. Often, only pockets of trees in shaded or north slope sites need preventative fungicides. During disease susceptible periods, apply sprays at 2-3 week intervals. See below for fungicides and application timing: Lophodermium needle cast: Bordeaux mixture, chlorothalonil, maneb. Mid-July through October. Brown spot needle blight: Bordeaux mixture, chlorothalonil. Mid-April through June. Naemacyclus needle cast: Benomyl, chlorothalonil, maneb. Mid April through June and possibly through October during rainy seasons.

Douglas-fir Needle Casts

This disease is often adequately controlled by improving ventilation and air movement around the base of the tree. Weed removal, improved spacing and removing diseased lower branches and trees will help. Fungicide sprays containing maneb or chlorothalonil can be applied in spring when buds first begin to swell. Continue applications every 7-10 days for about a month. Swiss Needle Cast Disease, caused by the fungus Phaeocryptopus gaeumanii, begins from infections that occur during rainy periods in spring and early summer. The infected needles may remain green for one or several years, producing spores from inconspicuous black fruiting bodies on the needle undersides. The diseased needles eventually turn yellow, then brown, and the oldest needles begin falling. Begin fungicide applications for disease control in late spring when the new shoots are 1/2 to 2 inches long, and continue them into early summer if the weather is rainy. Sprays containing chlorothalonil or maneb should be effective.

Needle Cast of Spruce

Infections occur during wet weather throughout the spring and early summer. Thus the fungicide chlorothalonil, applied for disease control, is used during this time. Colorado spruces are very susceptible to Rhizosphaera needle cast. Most other spruces are also susceptible, and even Douglas-fir, and Austrian, mugo and white pines may become infected.

Pine needle Rust

Controlling White Grubs

by R.A. Scheibner, D.A. Potter and L.H. Townsend

All of these grubs have stout, grayish to white bodies with brown heads. When mature, they are 1/2 inch to 2 inches long. Most species are curled into a C-shape when at rest, but green June beetle grubs are more straight-bodied and have the curious habit of crawling along on their backs.

Signs of white grub problems

Japanese beetles are green June beetles are day-time fliers that feed on leaves, flowers and fruit of various plants. May beetles and masked chafers are active at night and are attracted to lights. Masked chafers do not feed, but may beetles sometimes defoliate pin oaks and other plants at night. During July, masked chafers may swarm a foot or so over the turf at dusk.

To determine the degree of white grub infestation, sample the turf in several spots. In each area, cut out a square-foot piece of sod, and inspect the roots closely for grubs. If sampling is done during the early stages of infestation, the grubs will be small and not as easily found as when the grubs have noticeably damaged the sod. An average of seven grubs per sample may indicate a need for an insecticide treatment. In some situations much higher grub populations can be tolerated.

Management and Control Practices

Adequate rainfall during the time when grubs are actively feeding can help hide root injury. Irrigated turf may be able to tolerate 15-20 grubs per square foot before showing damage. Studies suggest that at least 9 or 10 grubs per square foot are required to cause noticeable injury. Chemical Control Chemical control may be necessary if natural and cultural control practices are insufficient at stopping turf damage. Certain insecticides that protected against white grubs for longer than one season have been banned because of their hazard to the environment. Turcam, Dursban, Merit, Mach II, Oftanol, and Sevin are chemicals that are labeled for control of white grubs.

The best time to apply an insecticide to control white grubs is early- to mid-August when grubs are still small and their feeding damage is relatively light. Although a spring treatment will kill grubs that are present, the practice is rarely justified. White grubs seldom cause much damage in the spring unless the turf is particularly droughty or was seeded the previous fall. Killing grubs in the spring affords no protection from reinfestation by beetles flying in from other areas later in the season.

For best results with insecticides, immediately water the turf to wash the insecticide down into the soil where the grubs are feeding. This is especially important for spray applications; if these dry on the foliage, they cannot be washed in by later drenchings. For this reason, granular insecticides may be easier to use since timing of irrigation is not so critical.

Irrigation also brings the grubs up to the surface where they are easier to kill. If possible, apply the insecticides just before a good rain.

Why Treatments Sometimes Fail

More often, poor control results from not completely soaking the insecticide into the soil immediately after application. If spray treatments are allowed to dry on grass foliage before being watered, a thorough soaking later will not wash enough insecticide into the soil to do the job.
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Controls for Greenhouse Ornamental Insect Pests

by Ric Bessin, Extension Entomologist

Cultural Controls

Proper cultural practices which will help prevent pest infestations include: maintain a clean, closely mowed area around the greenhouse to reduce pests that develop in rank growth. Remove all plants and any plant debris, clean the greenhouse thoroughly after each production cycle. Keep doors, screens and ventilators in good repair. Use clean or sterile soils or ground media, tools, flats and other equipment. At the conclusion of the season remove all plants and any plant debris, clean greenhouse thoroughly and fumigate.

Inspect new plants thoroughly to prevent introduction insect or disease infested material into the greenhouse. Watch for leaks or pooled water that can lead to fungus gnat infestations. If possible allow the greenhouse to freeze in winter to eliminate tender insects like whiteflies. Avoid wearing yellow clothing which is attractive to many insect pests which can be carried into the greenhouse from outside. Eliminate infestations by discarding or removing heavily infested material.

Pest Monitoring

Insect monitoring devices are also available. Yellow sticky cards (PT Insect Monitoring & Trapping System, Whitmire) are highly attractive to winged aphids, leafminer adults, whiteflies, leafhoppers, thrips (blue cards can also be used with thrips), various flies and other insects. These can be used to alert you to the presence of a pest and identify hot spots in the greenhouse. One to three cards per 1000 sq. ft. in the greenhouse is recommended and should be changed weekly. If you cannot identify a trapped insect, contact your county extension agent for assistance. Mass trapping products such as sticky tapes are also available for thrips, whitefly, leafminer and fungus gnat detection and management.

Insecticide Resistance Management

As a greenhouse manager, there are several tactics to prevent, delay or reduce insecticide resistance. Countermeasures include reducing the frequency or extent of insecticide treatments, reducing the use of insecticides with long residual action, avoiding treatments which act upon both larva and adults, and including nonchemical methods of biological and cultural control into an integrated pest management program.
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Gypsy moth update

In most of the counties, only a few moths have been caught. This probably is the result of moths being accidentally transported into those areas from infested states. However, in Greenup county, 22 moths have been caught. What this possibly means is small infestations of gypsy moth may have become established in the area. This has also happened in Madison county where eight moths have been caught. In the coming years, these areas will be mass trapped in an effort to get rid of the moths. This is a practice that has worked well in other parts of the state when low-level infestations have been detected.
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Crabapple Disease Resistance Ratings