Blue mold watch is in effect for all tobacco production areas of Kentucky, except Todd and Christian counties where the advisory was upgraded to BLUE MOLD WARNING on June 13, following confirmation of strong active blue mold in CHRISTIAN COUNTY. A few scattered lesions of blue mold have been found in the central Bluegrass Region, but none were found sporulating in the field, only after careful manipulation in the laboratory.
Weather conditions statewide have been very conducive for blue mold development for several weeks and several strong sources of blue mold are now present nearby in western Virginia and east Tennessee plus that in western Kentucky and western middle Tennessee.
Movement of tobacco transplants from any area where blue mold spores are present remains the most dangerous source of blue mold for Kentucky. It is particularly important now to use only local transplant sources or get them from areas not being threatened by blue mold.
Control programs should be in place statewide.
Several have asked what is the difference between a watch and warning? The Kentucky Blue Mold Warning System is operated by the Plant Pathology Department, University of Kentucky and cooperates closely with the North American Blue Mold Warning and Forecast System. Since 1980 the following guidelines have been used in issuing blue mold status reports as a way of keeping growers informed of the status of blue mold at all times. Three levels of status reports are issued by the Kentucky Blue Mold Warning System as a way of ranking the risk: 'advisory', 'watch' and 'warning'
ADVISORY - carries the lowest level of urgency, as they are used to maintain grower awareness about the disease, in general, and its progress outside the state.
WATCH - is issued before the disease becomes active in an area, but when spores of the fungus are believed to be arriving in an area while the crop and weather conditions favor disease development in the watch area. Growers should remain alert for the disease, reporting active disease to the local county extension office. Controls applied early have the greatest impact on overall blue mold development. Watches can be upgraded or cancelled as the situation warrants.
WARNING - is issued once blue mold activity has been
confirmed in an area, and it remains in effect as long as
conditions remain favorable for continued spread and
development of the disease. Growers should not wait until
warnings are issued to begin controls, steps should be
taken to improve control programs. County extension offices
should be advised of the level of disease in the community
and success or failure of recommended controls. Warnings
are canceled or down-graded when conditions no longer
support blue mold development.
Black shank is now active in many traditional plant beds
and fields of tobacco. However, the typical symptoms of
bright yellow plants with sudden wilting are not present,
because heat and drought stress have been absent. Instead,
infected plants just stop growing and gradually decline,
not typical of the very strong symptoms normally observed
with black shank. But, careful examination and incubation
will reveal the root and stem rots and signs of the
pathogen.
The less obvious symptoms are best observed in test plots
where black shank resistant and susceptible varieties are
set together, with and without Ridomil. Expect typical
symptoms to develop, once sunny and dry weather returns,
and they could be sudden and very widespread.
Even in more typical seasons, black shank development early
in the season is easily confused with many other diseases
and disorders, but this year the events are drawn-out over
a much longer period. Under the weather conditions of the
past month, the aboveground symptoms can be very similar
for black shank, Rhizoctonia root rot and soreshin, Pythium
root and stem rot, black root rot, bacterial blackleg, and
wet-feet syndrome. Since there is not adequate plants, nor
time to keep replanting poorly growing crops, correct
diagnosis of the problem is even more important this year.
So use the diagnostic labs to help sort out what is going
on and to obtain guidelines for helping to reduce the
impact of the problem. We place a very high priority on
these samples, because the results can directly impact the
decision-making steps for the current crop, unlike in most
disease situations when our counsel relates to steps needed
for future crops.
If black shank is involved, it is important to determine
the source of the disease, because if it came with the
transplants, serious losses can be expected by resetting
with this same source of transplants. I expect this year,
more than most, that farmers have set clean transplants of
black shank susceptible varieties into land contaminated
with black shank spores during the floods. In such cases,
it important to either find clean sites or replant with a
resistant variety plus Ridomil. Trying to resolve the
problem in such cases with just Ridomil will be very risky.
Ridomil 2E or Ridomil Gold are very valuable tools in
helping to manage yield on black shank problems. The series
of three treatments, preplant plus cultivation and layby
treatments usually provide the best approach in wet
seasons. Much of the preplant Ridomil applications have
been leached out with all the wet weather we have
experienced.
The same cool temperatures that have kept the 1997 cropping
season behind have kept some pests in season that are
usually out of the picture by now. Tobacco flea beetles
that emerged from their overwintering sites several weeks
ago are still feeding and laying eggs. The black cutworm,
which caused problems in May, has completed its development
and moths are flying now. Fields that have been waiting for
the 1997 tobacco crop have had time to develop a covering
of weed growth that can be very attractive to these moths.
Small variegated cutworms were found on tobacco in Fayette
County research plots last week along with some small
hornworms. Take some time to check fields that have been
set to make sure that there are no potential surprises
lurking in the rows.
BLACK SHANK VERY ACTIVE, SYMPTOMS NOT TYPICAL
by William NesmithTOBACCO INSECT ACTIVITY
by Lee Townsend
The continued pattern of warm, wet weather is not helping to reduce slug problems across the state. Injury has been reported from, or can be expected in, corn, soybeans, or tobacco. Greatest infestation potential follows a heavy corn surface residue or from plowed sod. Much of the following information comes from research articles by Dr. R. A. Byers (PA) and Dr. R. B. Hammond (OH).
The following points come from controlled infestations-
Management and Control Options
The primary means of slug management is tillage, an option
that is not suitable in many situations. The use of row
cleaners to remove soil residue from the seed zone may
impact slug damage by producing slightly warmer, drier
soil. This promotes quicker germination and more vigorous
growth which in turn allow plants to outgrow slug injury.
Current chemical control is based upon metaldehyde, a molluscicide. While the active ingredient is very effective, consider bait formulation, particle size and application method. Small particle size results in more pieces per square foot and, consequently, better kill. Inconsistent formulations (too moist) make applications difficult, too.
Since small amounts (5 to 15 lbs per acre) may be applied, application equipment becomes a potential problem. Most fertilizer spreaders are designed to put out much more material than this.
Alfalfa fields seeded in April commonly suffered from one of two problems, described below. Many fields have outgrown the damage and are now vigorous stands; others have been much less fortunate.
"STEM PINCHING"
Seedlings in alfalfa fields seeded in early to mid-April
commonly exhibited a distinctive superficial girdling
injury to the stem just below the soil line (specifically,
to the cortex of the hypocotyl). This symptoms was not
described in any literature I examined, and for some time
we were uncertain as to the cause. We followed up on a
suggestion of Dr. Bill Fountain, UK Extension
Horticulturist, and actually reproduced the damage in the
growth chamber. We concluded that the damage was
apparently caused by pinching of the seedlings from a
frozen soil crust.
Those seedlings were exposed to subfreezing--but not necessarily lethal--temperatures on the mornings of 9-10 Apr and on 18 Apr. Below-normal soil temperatures kept the soil cool enough that subfreezing temperatures may have allowed a thin soil crust to form (indeed, some farmers reported that this happened). In fields where the alfalfa seedlings were not frozen outright, the uppermost 1/4"-3/8" of the soil may have formed ice, which expanded and pinched the stem at that point. Injury was often just to the outer tissues, and often did not kill plants. However, the injury did stunt the plants severely, with symptoms that were somewhat similar to an outbreak of Aphanomyces root rot. However, in these cases the injury to the stem was clearly apparent with a hand lens; no root rot was obvious; and plants exhibited no yellowing whatsoever.
Many of these fields have completely outgrown the injury, but some fields or portions of fields have been set back enough that weed pressure could be a problem. Producers will need to evaluate those circumstances and refer to UK Agronomy recommendations for weed control.
APHANOMYCES ROOT ROT
This disease has been less common this year than in the
past three years, because of generally below-normal
temperatures in April and May. However, a few cases have
apparently developed in western Kentucky (I say
"apparently", because only one case has been definitively
diagnosed, although others have been reported).
Symptoms at this time will range from extreme stunting, where plants are only a couple inches tall, to stands that may be 8"-10" tall, somewhat yellow, not at all vigorous, with a lot of the soil still showing when one walks through the field. Carefully dig those plants and wash the roots to examine for a light brown root decay. Laboratory confirmation is suggested if there is any uncertainty as to the problem.
Check the level of Aphanomyces susceptibility of the variety sown. That information is available from the seed dealer or information available to county Extension Agents. Severe symptoms of the disease can develop in any variety with a rating of S, LR, or MR (susceptible, low resistance, and moderate resistance, respectively). Moderate symptoms can even develop in varieties with a higher levels of resistance, but in those cases, the plants usually outgrow the disease quickly.
Another note: when this disease develops, it usually affects most or all of the field. This is a bit surprising to anyone who understands how this fungus spreads through swimming zoospores, like the black shank fungus. But indeed, damage across the field is typical of Aphanomyces root rot of alfalfa.
Use only alfalfa varieties with a R (resistant) or HR (highly resistant) rating to this disease when spring- seeding, based on availability, of course.
Midges and gnats are common names for a large number of small, non-biting flies. Many species look like mosquitoes and may form annoying swarms or clouds in the air but they do not bite. The immature stages develop in water in pools, containers, ponds, clogged rain gutters, or in some cases, wet soil or seepage areas. Most feed on living or decaying plant matter and are an important part of aquatic food chains. Many species can survive in very stagnant or polluted water.
Large mating swarms of adults often appear about dusk and may occur for several days, especially after a prolonged wet period. Many gnats are attracted to light and may be a nuisance, landing on people or entering homes or businesses. These tiny flies do not feed. They only live long enough to mate, lay eggs, and die. Eggs are laid in masses in the water or on aquatic vegetation. The life cycle usually takes about 4 to 5 weeks. There may be several generations during the summer but these insects usually disappear with the onset of dry weather. Fortunately, problems are usually temporary and intermittent.
There are no good alternatives for control of the adults, other than some pressurized aerosol sprays containing pyrethrins. These are impractical for treating anything other than small areas. These products only kill insects that are directly hit by spray particles, there is no lasting or residual effect. More gnats will quickly enter the area after the spray has settled. The gnats rest on vegetation and in the grass during the day, so an application of a Cythion (malathion) or Sevin (carbaryl) spray may reduce numbers somewhat.
Long term control requires trying to eliminate breeding sites, wet areas or standing water. Often, however, this is not practical. Water should not be treated with any insecticide in an attempt to control gnats. The potential harm to the environment and wildlife is too great to justify an application for a temporary nuisance.
Abundant moisture and warm temperatures have afforded ideal conditions for mosquito development throughout the Bluegrass. When encountered in the home, around the yard, or at a family outing, mosquitoes can make life miserable. While there is no "silver bullet" available for combating this inevitable summer nuisance, this article provides information and management options available to homeowners.
WHERE DO THEY COME FROM?
Mosquitoes need quiet (non-flowing) water for their
development. In Kentucky there are two primary groups of
mosquitoes, Culex and Aedes. Mosquitoes of the Culex group
generally lay their eggs on the surface of water in rain
barrels, bird baths, tin cans, old tires, cisterns, roof
gutters and any other container that holds water.
Mosquitoes of the Aedes group lay their eggs at the base of
vegetation bordering streams or in low-lying areas subject
to flooding. Aedes mosquitoes can also deposit their eggs
above the water line in old tires and other water-holding
containers. These eggs hatch when inundated with rain
water.
Mosquitoes develop rapidly, transforming into biting adults in as little as one week. A neglected bird bath or boat bottom allowed to accumulate water can produce hundreds of new mosquitoes each day.
WHAT CAN I DO ABOUT THEM?
Eliminate Breeding Sites - The best way to control
mosquitoes is to find and eliminate their breeding sites.
Eliminating large areas of standing water such as swamps or
ditches may require community-wide effort. However,
homeowners can take several steps to prevent mosquitoes
from breeding on their property.
Controlling Adults - Some mosquitoes fly very long distances. It may be necessary to supplement elimination of breeding sites with control tactics directed against migrating adults.
Exclusion - Mosquitoes can be kept out of homes by securely screening windows, doors and porches. The occasional mosquito found indoors can be eliminated with a fly swatter or aerosol-type insecticide labeled for mosquitoes and other flying insects.
Topically-Applied Repellents - When spending time outdoors, repellents will help prevent bites. Use mosquito repellents containing ingredients such as diethyl toluamide (DEET). In general, the higher the percentage of DEET in the ingredients, the longer the protection. Low - percentage formulations are available for use with young children. Non-DEET containing repellents (e.g. Avon Skin- So-Soft ; citronella) may also provide relief, although generally of shorter duration. It is often desirable to apply repellent on outer clothing as well as the skin. Always read and follow directions on the container. Mosquito repellent should not be applied to the hands of young children, and treated skin should be washed with soap and water after returning indoors.
Vegetation Management - Adult mosquitoes prefer to rest in dense vegetation during the day. Consequently, homeowners should remove tall weeds and grass in their yard. To further reduce intolerable populations of adult mosquitoes around structures, insecticides can be applied to the lower limbs of shade trees, shrubs, and shaded areas adjacent to the foundation. Products containing carbaryl, chlorpyrifos, malathion or synthetic pyrethroids (e.g., permethrin, cyfluthrin, cypermethrin, deltamethrin) are effective, and may be applied using a compressed air or hose-end sprayer.
Bug Zappers, Citronella Candles, Ultrasonics, etc. - Many consumer products claim to attract, repel or kill outdoor infestations of mosquitoes. Most of these devices do not work, or are only marginally effective. "Bug zappers" using ultraviolet light as an attractant are generally ineffective in reducing outdoor mosquito populations and their biting activity. Studies indicate that less that five percent of the mosquitoes killed by bug zappers are females -- the only ones that actually bite. The rest are nonbiting, male mosquitoes and other harmless night flying insects. Somewhat better results were obtained with citronella candles. In studies conducted in Canada, citronella-scented candles reduced mosquito bites by 42% when test subjects were seated between a pair of scented candles, stationed three feet away. Interestingly, unscented candles reduced the incidence of bites by 23%, apparently due to the disruptive effects of light, heat, and carbon dioxide alone.
Ultrasonic devices, mosquito-repellent plants and other "panaceas," routinely advertised in the mass media, are generally ineffective in repelling mosquitoes and preventing bites. If it sounds too good to be true, it probably is.
Diagnoses on agronomic crops last week included: Stewart's wilt and zinc deficiency of corn; Leptosphaerulina leaf spot of alfalfa; bacterial soft rot, blackleg, target spot and soreshin, black shank, nutritional problems (temp. phosphorus deficiency, Mn toxicity), and herbicide injurieson tobacco. The first case of blue mold of tobacco was diagnosed in Christian county last Friday.
Diseases of turf and ornamentals included: pink snow mold, red thread, brown patch, anthracnose and fairy ring on turfgrass; and numerous cases of powdery mildew (on begonia, dogwood and rose).
| Princeton | |
| Black Cutworm | 7 |
| True Armyworm | 3 |
| European Corn Borer | 1 |
| Corn Earworm | 0 |
| Allen Co. | |
| European Corn Borer | 0 |