UNIVERSITY OF KENTUCKY COLLEGE OF AGRICULTURE COOPERATIVE EXTENSION SERVICE Lexington, Kentucky 40546-0091 KENTUCKY PEST NEWS ENTOMOLOGY C PLANT PATHOLOGY C WEED SCIENCE On line at - http://www.uky.edu/Agriculture/kpn/kpnhome.htm Number 898 September 25, 2000 ANNOUNCEMENTS SHADE TREES & ORNAMENTALS TOBACCO • A Kentucky conference on tree roots and soil • Dealing with mold on curing tobacco health CORN • Bacterial leaf scorch is visible now • Diplodia ear rot update • Boxelder bugs • Widespread stalk rot problems means producers HOUSEHOLD should scout now • How to pest-proof your home • Corn borer advisory PESTICIDE NEWS & VIEWS WHEAT DIAGNOSTIC LAB-HIGHLIGHTS • Powdery mildew management: now is the time INSECT TRAP COUNTS for decision-making ANNOUNCEMENTS possess a copy of the state label when the pesticide is applied. In Kentucky, 24-c labels are valid for three DECEMBER KENTUCKIANA CROP calendar years. PRODUCTION PROGRAM When there is an existing or expected local or minor The annual Kentuckiana Crop Production Seminar pest problem, the Kentucky Department of will be held December 12 - 13, 2000 at the Radisson Agriculture will be permitted to register one or more Hotel, Evansville, IN. A CCA continuing education pesticide products if: program, three hours of continuing education credit ! in either cropping systems management or soil and there is no EPA-registered pesticide for the use in question. water management, starts at 8 am. The Crop ! Production Seminar runs from 1 pm to 5:10 pm on the EPA-registered pesticide is not available or cannot be obtained in sufficient quantity. December 12 and from 8 am until noon on December ! 13. The program will be submitted to the Division of there is a suitable EPA-registered pesticide which, if Pesticides Ky Department of Agriculture for used in accordance with the label, would not be safe continuing education credit for commercial pesticide or effective under the local conditions. applicators (Categories 1 and 12). States cannot register: CURRENT STATE LOCAL NEED (24-C) REGISTRATIONS FOR KENTUCKY < pesticides on food crops that do not have an established tolerance on that crop. By Kentucky Division of Pesticides < pesticides containing active or inert ingredients not contained in any EPA- registered products. Section 24 (c) of the Federal Insecticide Fungicide and < pesticide products or uses affected by suspension or Rodenticide Act (FIFRA) permits the Kentucky cancellation based on human health, environmental, Department of Agriculture to register federally or efficacy considerations. registered pesticides for some uses that are not on the < pesticide products and/or uses previously denied existing label. 24-c or State Local Need Labels, are registration by EPA. valid only in the state of issue. The applicator must Educational programs of the Kentucky Extension Service serve all people regardless of race, color, age, sex, religion, disability or national origin UNIVERSITY OF KENTUCKY, KENTUCKY STATE UNIVERSITY, U.S. DEPARTMENT OF AGRICULTURE, AND KENTUCKY COUNTIES, COOPERATING Special local needs registrations may be sought by commodity groups, university, industry or others. TOBACCO The pesticide manufacturer or formulator must, however, be willing to support the effort and to DEALING WITH MOLD ON CURING prepare the documentation needed to justify the TOBACCO request. The registration is not effective for more by William Nesmith*, George Duncan and Gary than 90 days if disapproved by the EPA Palmer Administrator within that time. Recently, some areas of Kentucky have experienced Product Name - Use SLN Expiration periods of hot, humid weather with heavy fog Number Date persisting from dark to mid-morning for several days running. Others have experienced several days of Command 4EC KY-930002 12/31/02 misty to heavy rain. Now reports are being received winter and summer of extensive molding of cured tobacco, especially in squash river valleys. The problem is generally not occurring on uncured tobacco. Rather, it is mainly associated Dithane DF* KY-940002 12/31/02 with tobacco harvested early and already cured, tobacco seedlings which in general was some of the best quality leaf for transplant from this year's crop. Command 4EC KY-960003 12/31/02 cabbage The frequent periods of protracted mild, wet weather during August and September have been providing Poast KY-970002 12/31/02 favorable conditions for mold development in curing tobacco tobacco, especially that housed early. With more wet weather in the forecast, growers should expect Dual Magnum* KY-990001 12/31/02 increased potential for mold development in mid to transplanted bell late harvests, as more of the tobacco cures and peppers becomes more susceptible to mold development. Let's Dual Magnum* KY-990002 12/31/02 all remember that a greater percentage of the 2000 cabbage crop is earlier than normal, so there is a higher percentage of this crop exposed to the mold threat. Acrobat MZ KY-990003 12/31/02 Thus far, County Extension Agents have indicated control of metalaxyl that most mold activity has been associated with / mefanoxam- tobacco housed in traditional barns, but tobacco resistant strains of housed early in out-door curing systems is also blue mold in developing mold. However, this pattern may be as tobacco much the result of the tobacco being further along in the curing process, because in general, growers filled Terrazole 35 WP KY-000001 12/31/02 the barns first. On some farms where out-door control of pythium structures were used in early August, significant root rot in tobacco mold has been reported, especially where the transplant float structures are located in low areas. For example, Mike beds Carter, Garrard County Extension Agents, reported considerable house burn and mold developing in Tracer* KY-000002 12/31/02 outdoor structures in his area. control of budworms and Some frequent questions are: Why does mold develop hornworms on some years and not others? How do you prevent tobacco mold development? Does mold harm the tobacco? And, how do you remove it from cured leaf? * Still within EPA’s 90-day period to revoke.European Hopefully, the discussion below will help growers and southwestern corn borer levels are high and agents with these questions. 2 However, it is important that enough air be moved Once the tobacco leaf is dead it becomes an excellent through the tobacco and not just in the gable ends or source of food for a number of fungi that could not at the ground level. With outdoor or field curing feed on it while it was alive. Thus, the pattern of the structures, plastic covers need to be in place to mold being mainly associated with early housed prevent direct wetting of the leaf, followed by proper tobacco relates to the fact that it has more dead leaf, manipulation of plastic to manage ventilation, while the later-housed plants are still alive. The followed by timely stripping of the crop from these colonization of the leaf by these fungi results in moldy structures. tobacco which is lower in quality and weight due to deterioration, off-colors, and residues from fungal When wet periods persist longer than 24-36 hours, metabolism. Consequently, moldy tobacco is of less especially when temperatures are warm, the inside air value. can become saturated even with ventilators closed. Supplemental heat, although costly and probably not A small amount of mold develops every year on economical at current prices, can be used to dry the cured tobacco, especially the stems (mid-ribs), but this air. If heat is being used, the ventilation system is not usually considered to be serious. However, should be partially opened to allow the warm moist when mold develops on the lamina of the leaf, there is air to escape the barn. Otherwise, the barn and concern. Problem levels of mold develop when moist tobacco will `sweat'. Once the favorable outside conditions prevail. Furthermore, the higher the drying conditions return the heat should be stopped temperature during the moist period, the more rapid and the barn opened. If heat is not used during these is the mold development. In general, the mold growth prolonged wet weather periods, the next best option rate doubles for every 18 degrees F in increased is to leave the barn open to take advantage of temperature. whatever air circulation and drying exist. Most of the mold problems thus far are associated Removing Mold from Tobacco with early crops in poorly managed curing situations, No chemical is labeled for preventing mold growth on such as tobacco hanging close to the ground or in tobacco in the curing barn. But there also is no areas where surface water is draining into the barn. If shortage of rumors of home remedies being tried. the humid weather being experienced continues to Most of those could result in serious and illegal persist, the mold problem could begin to plague residue problems that would destroy the usefulness tobacco housed under better curing conditions and of the tobacco to the industry. Spraying Ridomil on even crops housed later in the season. the barn floor, walls, and hanging tobacco does NOT prevent molding of tobacco based on properly Judicious management of the barn's ventilation conducted experimentation; besides, it is not labeled system is critical to preventing moldy tobacco. for such use. This fungicide does not even control the Basically, it boils down to controlling moisture in the group of fungi involved! dead leaf. The leaf absorbs water from the humid air around it, so the key is to minimize the time moisture- There is a badly out-of-date publication from back in laden air exists in the barn, especially when the 1960 or 70's that many have. It clearly indicates summer-like temperatures are occurring. that experiments were conducted several years ago in cooperation with the University of Kentucky which Generally, the moisture content of air is higher at demonstrated that mold could be removed to some night and during rainy periods than during the extent from cured tobacco with a variety of alcohols.