DISEASE UPDATE
By Kenny Seebold

Hot and dry weather prevailed during the week of August 8th, keeping blue mold in check. According to my sources at the North American Plant Disease Forecasting center, the risk of infection and spread of blue mold to tobacco in the Commonwealth from sources in KY will be low for the next week. However, a moderate risk is posed to crops in eastern KY from known sources of blue mold in NC and VA. These forecasts could change if weather in our region turns rainy or cooler. Please keep an eye on crops in your area and report blue mold to us if it is found. Encourage your growers to scout regularly and apply fungicides if needed. Please check the KY Blue Mold Warning System page for regular updates. We are still seeing a greater-than-normal amount of target spot and frog eye in eastern and western KY. For tobacco nearing harvest, there is probably little that needs to be done in terms of disease control, but late-planted crops may face some risks of disease development. If necessary, Quadris can be applied at 8 oz/A to provide protection against target spot and frogeye. I think we've all been surprised at the severity of black shank this season. Rains early in the season followed by drought have made the black shank epidemic one of the worst we've ever had. It's pretty clear that the disease is more widespread in KY than we realized and that our growers need some help with this problem. By the time many growers noticed the black shank in their fields it was too late to do anything to control the disease. What we can learn from this year's epidemic is that the time to act against black shank is early, before the first plant goes in the ground. Crop rotation is our first and most important control tactic. Next in line is the use of resistant varieties. It's important to emphasize that "resistant" varieties are not "immune" to black shank, and we need to educate our growers on this point. Many have been disappointed with the performance of 'KT204' this year because they've seen losses of 30% or greater; however, this is more or less in line with what we expect from 'KT204' under severe disease pressure. More than one disease control tactic should be employed if we want to have a decent shot at keeping black shank in check. Growers should consider combining black shank-resistant varieties with crop rotation, or with a pre-plant application of mefenoxam to maximize disease control in their fields. Sanitation should also be a consideration. Infected plants from this year's outbreak should be burned or deep-turned, and those fields should be planted to another crop in the coming year if land is available. Every effort should be made to slow the spread of black shank around KY. This year, the widespread use of ponds, creeks, and rivers to irrigate tobacco could result in even more land having the black shank pathogen in the future, although many growers were left with no other alternative to get water on their crops. The 2005 tobacco season has definitely been a tough one - let's all hope that next year brings us more rain and less disease!

For the latest blue mold status and other tobacco disease information, check the KY Blue Mold Warning System online.
http://www.uky.edu/Agriculture/kpn/kyblue/kyblue.htm

For more information about tobacco pests, visit "Insect Management Recommendations".

CHARCOAL ROT ON THE RISE
By Don Hershman

Charcoal rot, caused by the root and lower stem-infecting fungus, Macrophomina phaseolina, is becoming increasingly more common and severe in west Kentucky. Macrophomina phaseolina is worldwide in distribution, and populations of the fungus are quite high in Kentucky fields since both corn and soybean are hosts of the fungus.

The way this disease normally plays out in Kentucky is as follows: Plants become infected in the seedling stage, two to three weeks after planting. These infections then remain dormant until significant moisture stress and high ambient temperatures coincide with plants in the reproductive stages. The levels of colonization in root and lower stem tissues then increase as the plants mature. Plants typically die prematurely and seed yield is often seriously impacted. Field yields can be drastically reduced when enough plants die prematurely. Often, however, premature death is exhibited in individual plants, in patches, or in streaks which coincide with areas in fields subject to the greatest moisture stress. Many times, it is impossible to distinguish the effects of drought from the effects of charcoal rot.

Initially, infected plants look healthy and normal. As the season progresses, plants begin to look unthrifty and wilt during the heat of the day. Leaves of infected plants eventually turn yellow and then die, but remain attached to the petioles. Occasionally, superficial stem lesions will be seen extending upward from the soil line. Roots of diseased plants will be severely rotted and, in advanced stages, the epidermis of infected root and lower stem tissue can be easily scraped off to reveal a charcoal-gray discoloration and a multitude of very small black specks. These specks, which can be seen with the naked eye, have the appearance of very small pepper particles and are called microsclerotia. Microsclerotia are the survival structure of the fungus and they also constitute the primary source of inoculum for plant infection. Macrophomina phaseolina causes disease by mechanical plugging of water conducting tissues (due to the presence of microscleriotia), production of a destructive plant exotoxin, and a rot of water-conducting tissues (roots and lower stem). In severe instances, seed can become severely infected and result in a condition know as "black seed". Infected seed are shriveled, cracked, and elongated. Seed can also be infected without any symptoms being visible.

It is my experience that charcoal rot is only important in Kentucky where serious drought conditions exist. Thus, most instances of charcoal rot cannot be avoided, since few Kentucky soybean producers have the means to irrigate drought-stressed crops. However, producers with the capacity to irrigate crops can avoid charcoal rot by timely applications of water during the later reproductive crop stages. Other cultural controls include, reducing seeding rates, no-tillage systems which help to retain soil moisture, and planting longer season cultivars and/or deploying later planting dates so that later crop reproductive stages are less likely to coincide with drought stress and high temperatures. Planting high quality seed with a high germination and vigor is also important.

TIME TO WATCH FOR THE QUICK CHANGE ARTIST -THE CORN EARWORM!
By Doug Johnson

The corn earworm is most familiar as a pest of sweet and field corn ears. However, this insect has a very wide host range and goes by many names, depending upon the crop and the area of the country that is feeding it. In Kentucky, the corn earworm is also known as the soybean podworm and as a "head worm" of grain sorghum. It's the same insect, just different names for different crops.

I have noticed an increased number of soybean podworm (corn earworm) moths in soybean fields. They probably are there because more and more corn acreage is too mature to attract them. This is a normal occurrence late in every season. However, this year the process is likely to occur earlier due to drought stress on the corn. Regardless of the reason, as corn becomes less attractive to the moths, they will move to other hosts to lay their eggs. Usually, we are most interested in soybean. However, they can and will also infest filling heads of grain sorghum

The adults are buff to light green colored moths with a wingspan at rest of about ½" in. Eggs are white to pink about 1/30" wide and are laid singly. The young corn earworm (or podworm or head worm) larvae are very small but grow to 1-1/2 inches in length when full grown. They are usually tan to pale green in color with several dark stripes down the back. Color may vary greatly with some appearing almost black. o Soybean

The soybean podworm feeds mainly on pods but may also feed on leaves, stems, and flowers. Larvae will eat the pod wall and consume the seed. Full season and / or narrow row spacing soybeans fields form a complete canopy sooner, so they are less likely to have a problem. Delayed maturity may also increase the risks of late-season damage. More severe damage tends to be present when large larvae are present on plants with fairly mature pods. This is because the larvae will now feed on the beans inside the pods rather than foliage.

Sampling for the soybean podworm in wide rows should be made using shake cloth. At each sample site, using a two foot cloth, bend the plants over the cloth and shake them vigorously. Note the number of larvae in a four foot sample area at each site. The number of sites you need to examine in a field is based on the size of the field. The economic threshold for soybean podworm is two worms (caterpillars) per row foot.

In narrow rows the process is more difficult. Because the canopy is so tight, it is almost impossible to get into the field to sample. One must make the best educated guess possible based on pod damage and the presence of worms in areas which can be sampled. Remember you have far more plants per acre in narrow row beans. o Grain Sorghum

In grain sorghum the corn earworm is easer to see and easer to treat, because the heads are exposed. The corn earworm may occur in mixed populations with other "head" feeding worms such as the sorghum webworm (later in September) and the fall armyworm. Regardless of which of these worms are present, control should be considered if the population reaches an average of two small worms per head.

For more information about soybean pests, visit "Insect Management Recommendations".

DRY WEATHER CAN BRING UNWANTED SWIMMING POOL GUESTS
By Lee Townsend

Dry weather has eliminated many temporary pools and intermittent streams over much of the state, prompting many animals to search for alternative water sources. Honey bees needs lots of water to maintain hive temperature and can turn to swimming pools for their water needs, causing alarm to pool owners and users.

Searching worker bees are looking hard now for water. After finding a source, they go back to the hive to recruit others to join them in gathering this precious commodity. Recruiters will use a bee dance to give very specific directions to their hive mates. Over time, hundreds of bees may be coming to a pool. Many will fall into the water and drown but others will keep coming.

Dealing with bee visits to small kiddy pools can be as simple as moving the pool to a different spot in the yard every few days. Bees follow directions very strictly and if the pool is not where it should be, they will not find it easily. You can stay ahead of them with the moves.

Obviously, this strategy is not practical for large above or in-ground pools. About the only available alternative is to cover the pool so the bees cannot get to the water. If the source is not available, then recruiting efforts will decrease and bees will look for different sources. Unfortunately, bees have memories and can continue to return to the site for several days after it is "removed". The pool can still be uncovered and used in the evening when bees are not as active.

DOWNY MILDEW OF PUMPKIN REPORTED IN SOUTH-CENTRAL INDIANA
By Kenny Seebold

A colleague in southern IN reported finding downy mildew on pumpkin recently in south-central IN. Given the proximity of the source, it's possible that the disease is active somewhere in KY on a cucurbit crop. Downy mildew on cucurbits can be an aggressive, fast-moving disease and can be really hard to stop when it gets started. Under the right conditions, infection levels can go from 10% of leaf area infected to 90-100% in less than a week!

Identifying downy mildew on cucurbits can be a little tricky, because symptoms on each species vary to some degree. What's more, downy mildew can be confused with powdery mildew. Both of these diseases are similar in that they are caused by obligate pathogens, meaning that the pathogen must be associated with a host plant to survive. The downy mildew pathogen, Pseudoperonospora cubensis, is not a true fungus. It belongs to the Oomycetes and is related to the pathogen that causes blue mold of tobacco; however, powdery mildew is caused by Podosphaera xanthii and belongs to the Ascomycete group of "true" fungi. Although downy mildew is more common in wet weather, fogs and heavy dews can contribute enough moisture to allow infection during "dry" weather. Powdery mildew is more likely to be a problem when conditions are hot and dry, and it tends to develop gradually over the course of several weeks. In terms of symptoms, the two diseases can be confused. Early on, both can cause yellow spots on the upper surface of a leaf. In the case of downy mildew, leaf spots tend to be small, blocky, and are limited by leaf veins, while spots associated with powdery mildew are round and somewhat diffuse. On the underside of a leaf with downy mildew, lesions will initially appear sunken and slightly water-soaked. As downy mildew progresses, infected leaves will take on a scorched appearance. Leaf yellowing (chlorosis) is more common with powdery mildew, and infected leaves will be covered with a white, talc-like, superficial growth (from which powdery mildew takes its name) that tends to favor the upper leaf surface; however, it is not uncommon to find colonies of the powdery mildew fungus on lower leaf surfaces, stems, or vines if disease is severe. The powdery growth consists of mycelium and conidia (spores) of P. xanthii. One of the key features of downy mildew is the pattern of sporulation, which occurs only on the underside of an infected leaf and has a faint, fuzzy or "downy" appearance. It is generally easier to observe sporulation with downy mildew in the morning when there's plenty of leaf wetness. It's very easy to distinguish the downy and powdery mildew pathogens at the microscopic level; sporangia of downy mildew are formed on sporangiophores that have a distinctive branching pattern that gives them the appearance of "deer antlers". Conidia of powdery mildew are formed in chains on relatively simple structures. If downy mildew is suspected, send a sample in to the Plant Disease Diagnostic Lab in Lexington or Princeton for examination. We need to keep an eye on all late-season cucurbit crops and act as quickly as possible if downy mildew is found. The good news is that downy mildew can be controlled with preventive applications of several fungicides, many of which may already be in use as part of a regular disease management program:

• Chlorothalonil (Bravo, Equus, etc.) 720SC: 1.5-2 pt/A; DRY FLOWABLE FORMULATIONS ARE AVAILABLE - SEE LABEL FOR RATES.
• Mancozeb (Dithane, Manzate, Penncozeb, etc): 2-3 lb/A [cannot be used on pumpkins].
• Maneb 75: 1.5-2 lb/A, 7-10 day spray interval [pumpkins, cucumbers, winter squash, summer squash].
• Maneb 80: 1.5-2 lb/A, 7-10 day spray interval [pumpkins, cucumbers, winter squash, summer squash].
• Manex: 1.2-1.6 qt/A, 7-10 day spray interal [pumpkins, cucumbers, winter squash, summer squash].
• Quadris: 11-15.4 fl oz/A, 5-7 day spray interval.
• Cabrio: 8-12 oz/A, 7-14 day spray interval.
• Flint: 4 oz/A, 7-14 day spray interval.
• Pristine: 12.5-18.5 oz/A, 7-day spray interval.
• Acrobat: 6.4 oz/A, 5-10 day spray interval.
• Reason: 5.5 fl oz/A, 5-10 day spray interval.
• Previcur Flex: 1.2 pt/A, 7-14 day spray interval.
• Ridomil Gold Copper: 2 lb/A, 14-day spray interval.
• Ridomil Gold Bravo: 2 lb/A, 14-day spray interval.
• Fixed copper (Kocide, Cuprofix, etc.) - see label for rates.

In general, excellent protection against downy mildew can be achieved with EBDC's (mancozeb and maneb) or chorothalonil. These products should be applied before disease is observed for maximum effectiveness. If downy mildew is found before fungicides have been applied, use a product such as Quadris, Cabrio, Gavel, Ridomil Gold Bravo, or Reason.

If your growers are not using fungicides at the moment, encourage them to put out an application soon to prevent problems with disease and urge them to stay on a regular schedule. Given the hot and dry weather, a longer spray interval can be used to save on fungicide costs and still provide good protection against downy mildew and other diseases.

LANDSCAPE PINES WITH PROBLEMS
By John Hartman

Many pines in Kentucky landscapes are turning brown or are otherwise appearing unhealthy. Telephone inquiries and observations of diseased pines in the Plant Disease Diagnostic Laboratory reflect a concern for pine tree health. It is likely that County Extension Agents are also getting calls relating to unhealthy pine trees in the landscape. For these pine maladies, the temptation is to blame them on the current severe drought conditions being experienced in many parts of the state. However, many of the problems are related to infectious diseases that may or may not have been affected by dry weather.

There are several common problems that cause browning of pine needles. Some of the problems of pine require laboratory analysis for accurate diagnosis, however agents can make preliminary diagnoses by making good observations and getting accurate information. The following guidelines might help agents deal with the most common of these sometimes difficult problems.

Before trying to diagnose pine diseases and disorders, determine which kind of pine is having the problem. The majority of landscape pines will be white pine (needles soft, flexible, 2"-4" long with 5 needles/cluster), Scots pine (needles stiff, 1"-3" long and twisted with 2 needles/cluster), or Austrian pine (stiff, 3"-5" long with 2 needles/cluster). It is important to know what kind fo pine has the problem because the common diseases of one pine may be quite different from the diseases of the others.

If the tree is a white pine, look for the following:

1. White pine decline causes browning of needle tips, wrinkling of the bark of twigs and small branches, reduced growth, thin and off-color foliage, and whole tree browning. Trees are usually healthy-appearing when young and these symptoms often begin to occur only after the pines are 10 - 15 years old. White pine decline is associated with high soil clay content, neutral to high soil pH, root injury, and soil compaction. These conditions exist in many Kentucky landscapes.
2. Air pollutants such as ozone can cause browning of individual needle tips, similar to needle symptoms of white pine decline.
3. Normal needle drop causes yellowing and shedding of last year's needles.
4. None of the above problems is contagious.
5. White pine root decline causes reduced vigor, yellowing, and then browning of the whole tree, a noticeable patch of resin on the trunk base, and dark staining of the vascular tissues of the trunk flare and root collar area. White pine root decline is caused by the fungus Verticicladiella procera.
6. Phytophthora root rot causes tree decline and death associated with decayed bark of the trunk flare, root collar, and roots. Root rot caused with Phytophthora species is associated with wet, poorly drained soils.

If the tree is a Scots pine, look for the following:

1. Pine wood nematode causes pine wilt disease which results in a gradual fading out and browning of needles over the entire tree or large parts of the tree. Cut into affected branches, and notice that there is no sap or resin flow. For positive diagnosis, laboratory analysis to find the causal nematode, Bursaphalenchus xylophilus is needed. Collect sections of affected lower branches, submitting a foot or so of the part of the branch closest to the trunk. This disease is vectored by long-horned beetles, and tree removal is recommended to prevent spread. Pine wilt nematode also attacks Austrian pine, and occasionally white pine.

If the tree is an Austrian pine, look for the following:

1. Sphaeropsis (Diplodia) tip blight causes browning of needles at the ends of individual branches or browning of entire branches, usually in the lower part of the tree. The fungus causing tip blight, Sphaeropsis sapinea, attacks newly developing shoots of mostly mature, cone-bearing trees. Excess pitch or resin is produced and can be seen on affected branches as white patches of dried pitch. Infected cones and the bases of individual needles may show fungal pycnidia. Tip blight cannot be prevented or cured, but disease progress can be slowed with a lot of effort including diligent pruning and spraying. In addition to Austrian pine, tip blight is common on Scots pines, especially in Christmas tree plantations, and it is found occasionally on white pine.

Drought can affect the speed of development and severity of many pine diseases.

1. Drought could increase the effects of white pine decline and would speed up the death of infected pines with white pine root decline or Phytophthora root rot.
2. Drought could increase the severity and speed of decline of Scots pines with pine wilt disease caused by the pine wood nematode.
3. Drought stress increases susceptibility of pines to tip blight disease.

There are many causes for pine trees turning brown in the landscape and drought can have an effect on some of them. This is by no means a complete list of the problems facing landscape pines, however, a majority of cases of needle, branch, or tree browning fall into one of these categories.

DIAGNOSTIC LAB - HIGHLIGHTS
By Julie Beale and Paul Bachi

Recent samples in the Diagnostic Laboratory have included Stewart's wilt and maize dwarf mosaic virus on corn; brown spot (Septoria), charcoal rot, sudden death syndrome and soybean cyst nematode on soybean; black shank, blue mold, target spot, soreshin, and frenching on tobacco.

On fruit and vegetable samples, we have diagnosed downy mildew on grape; bitter rot on apple; blossom end rot on pepper; Cercospora leaf spot on pumpkin; and early blight on tomato.

On ornamentals and turf, we have seen Pythium and Rhizoctonia root rots and nutritional problems on chrysanthemum; Rhizoctonia root rot on salvia; Alternaria leaf spot on impatiens; Pestalotia leaf spot on azalea; jumping oak gall and Actinopelte leaf spot on oak; cedar-quince rust on hawthorn; bacterial canker on cherrylaurel; summer patch and Curvularia blight on bluegrass; gray leaf spot on perennial ryegrass; and anthracnose, Pythium blight and Curvularia blight on bentgrass.

By Patty Lucas, University of Kentucky Research Center

View Princeton trap counts for the entire 2005 season at - http://www.uky.edu/Ag/IPMPrinceton/Counts/2005trapsfp.htm

Fulton County trap counts are available at -http://ces.ca.uky.edu/fulton/anr/Insect%20Counts.htm

For information on trap counts in southern Illinois visit the Hines Report at - http://www.ipm.uiuc.edu/pubs/hines_report/comments.html The Hines Report is posted weekly by Ron Hines, Senior Research Specialist, at the University of Illinois Dixon Springs Agricultural Center.

NOTE: Trade names are used to simplify the information presented in this newsletter. No endorsement by the Cooperative Extension Service is intended, nor is criticism implied of similar products that are not named.

Lee Townsend
Extension Entomologist

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