by William Nesmith
Often our Department is asked to determine the race of the black shank fungus associated with tobacco samples. The Kentucky Cooperative Extension Service does not offer or recommend a lab test for race determination because it could yield very misleading results relative to what could be actually happening in the field at large. This is not a new position, but has been our position since the early 1960's when race differential procedures became available for the black shank pathogen. The problem relates to the fact that damaging levels of Race I may be present, even though they are below what we can detect with affordable and reasonable sampling protocols. Such situations present serious legal issues, as well. Therefore, we recommend growers use the "stick-rows" method of monitoring the black shank race operating on their farm. Our rationale for this position follows.
Let's assume you submit a sample of several plants with black shank symptoms to our laboratory and request a confirmation of black shank and determination of the race(s) involved. More than one race can colonize the same plant, and often does, if a mixed population is present. Confirmation of black shank takes about 48 hrs in our laboratory, since the fungus is readily isolated and identified in our hands in most cases. To determine the race(s), however, requires several weeks or months and considerable greenhouse and lab space. It requires isolation from many areas of submitted materials, including roots, stems, leaves, and soil. Once the collection of isolates has been made and put into pure cultures, inoculation into a series of host plants is required to determine differences in pathogenicity, because morphological differences do not exist between the races. The pathogenicity assays are straight forward, but very consuming of laboratory space, greenhouse space, and time. Pure cultures of each isolated fungus are inoculated onto the root systems of a series of differential plants ( Ky 14, 14xL8, and Ky 17) in order to determine the disease reaction. Within 10 days after inoculation, Race 0 isolates will cause a severe reaction on Ky 14 (death of roots and extending up the plant into the stem), no symptoms on the roots of 14xL8 although the fungus colonizes the root surfaces, and root lesions on Ky 17; Race I will cause severe reactions on both Ky 14 and 14xL8 with root lesions on Ky 17. If infested soil is bioassayed directly, it may take up to six weeks to have results. So, it is not difficult to determine the race of any particular isolate, although it does require considerable space and time.
In any case, the main problem is not determining the race involved with the sample, but collecting a sample that actually relates to the real situation in the field. For example, a case from Powell County illustrates the problem. I sampled from the roots, stems, leaves, and soil from 128 plants of Virginia 509 collected from the site, plus four, 5-gallon buckets of soil collected about the field. Only Race 0 was recovered. Based on these results, it was recommended that 14xL8 could be safely planted. It was, and all went well until about layby when a few plants developed black shank in two low areas of the field. Lab testing confirmed race I affecting the plants. By harvest time, 31.8% of the 14xL8 plants had died of black shank, even with a layby, rescue treatment of Ridomil. What had happened? In all likelihood, our assays were not sufficiently sensitive to detect the low level of Race I present in the soil. Once the L8 was planted, the Race I fungus was able to compete and began to rapidly increase its numbers and be spread about the field through cultivation and running water. By the way, our bioassay subsequently detected the Race I fungus in a 5-gallon-bucket of soil which had been collected at random 6 days before the symptoms appeared in the field.
The only reason for determining race from the management standpoint is that the root systems of L8 hybrids are immune to race O. Knowing if Race I is present is very valuable information, if the information is reliable. Unfortunately, Race I can be present in the field at a low level, below which detection is difficult, or even at a very high level but confined to some small area of the field. Therefore, planting an L8 hybrid in a field where only race 0 was detected, but the field was also infested at below the detectable level with race 1, could result in a serious loss from black shank. The Powell County example illustrates that well.
Although this type of error is acceptable in testing for fertility disorders (a non-infectious agent) and infectious pathogens with slow reproductive rates, such as nematodes, they are not acceptable with black shank or other pathogens with very rapid rates of reproduction. We cannot forget that the black shank fungus has a very rapid rate of reproduction with many cycles possible during the same season, and is easily and rapidly disseminated about the field. A case in point occurred in 1982 in Daviess County, when a grower lost his entire tobacco crop of an L8 hybrid after he introduced the pathogen on about 50 transplants being used to finish out one row in the field.
Some crop consultants have offered the test on a limited scale at times, only to suddenly stop the service after the first legal action. I am not aware of any labs currently offering the test. There are labs that offer tests for Phytophthora, but these detect all Phytophthoras, not just the black shank fungus.
There is a proverb that fits this situation. It says: What is possible is not always prudent. We have elected not to offer race testing for black shank (which is possible) because in our opinion it is not prudent and would lead to increased problems with black shank rather than reducing losses form the disease; plus it could generate ill will towards the University and Extension Service, if not have legal ramifications.
Growers are not left without an option, because they can conduct tests themselves, in their own fields, which have greater relevance to the site than a lab test, but it must be done the growing season prior to using the information to make a decision. It involves planting across the field a few paired, stick-rows of a variety susceptible to all races (e.g. Ky 14) and the other an L8 hybrid, which is race 0-resistant and race 1-susceptible. The alternative to sick-rows is alternating Ky 14 and L8 hybrids in the same row, so that if only Race 0 is present yield is obtained from the space used to conduct the test. This test will be more meaningful the more replications used. It is very important to observe closely the reaction on L8 hybrids. If lesions are only involving the stem of L8, it is possible that only race 0 is present, because the stem of L8 hybrids are susceptible to both races. Be sure at least some of the rows cross through the wet areas and drainage paths of the field. This technique is not fool- proof, of course, because the fungus could be present in other areas of the field not planted to the test rows.
by Lee Townsend
Grasshoppers are active now and the large differential grasshopper is particularly noticeable as it makes short flights around field margins and crashes into foliage. Grasshoppers will cause some leaf loss to crops still in the field but control is probably justified only in extreme cases. Golden Leaf Tobacco Spray, Lannate, Orthene, or Thiodan can be used for grasshopper control on tobacco if significant feeding is underway and grasshoppers are remaining in the field for an extended period of time. Be sure that plant damage from leaf or stalk breakage during the application will not exceed harm by the insect.
Grasshopper control is best accomplished before they enter the tobacco field. Watch for activity along field margins and adjacent grasslands and treat the hoppers there. Malathion, Orthene, or Sevin can be used in these situations. Be careful that mowing operations do not force grasshoppers into the crop.
by by Doug Johnson - Extension Entomologist
It is time again to begin thinking about insect control in our wheat crop. In many cases you have probably already given consideration to such items as variety selection, seeding rates and tillage. Certainly pest control should also have your attention because decisions made before planting will have an effect on insect populations for the entire growing season.
One of the most important decisions you will make is that of planting date. This choice will shape all of the pest decisions you will have in the fall and may even impact your spring season so do not treat it lightly. Planting date will directly affect all three of Kentucky's possible fall pests.
Fall armyworm - an unusual but certainly possible fall foliage feeder on small grains. Fall armyworm (FAW) is already in the area, having lived on corn, sorghum, and wild grass hosts since about July. Early planting and a late, mild fall will favor this pest. FAW could survive until heavy frost. FAW feeds on the above ground portions of the plant but normally does little lasting damage. There are no thresholds for control of this pest in small grains. Control should not be difficult, but the decision as to whether or not to make a spray is not at all clear. Most plants will come back, even if all the above ground parts are eaten. Producers are advised not to replant without considerable evidence that the original stand is damaged. Replanting usually results in a "double stand", which in turn results in severe lodging and other problems.
Hessian Fly - has not traditionally been considered a major pest of Kentucky's small grains. Unfortunately, that may be because we have never looked very hard. To get a better idea of how this insect affects Kentucky's crops, see Entfact-101. However, from an practical standpoint there are only a few things you can do to manage this insect. Again, the most important is planting date. This is the insect for which the term "Fly Free Date" was coined. In general, crops planted after this date will not be infested with Hessian fly. In Kentucky, the date varies from about Oct 10 in the northern wheat-growing counties to Oct 15 in the southern tier of counties (See Entfact-101 , ENT-56). In addition, it is important to pay strict attention to all agronomic practices and to select a variety that will produce strong, vigorous plants that stand well. Although resistant varieties will help, (and should be used if other plant characteristics are appropriate for your management plan) the populations of this pest found in Kentucky are able to break all the deployed resistance.
Aphid Complex and Barley Yellow Dwarf - This is without doubt the most contentious problem we have to face. While sap removal by feeding aphids is unimportant, the transfer of Barley Yellow Dwarf Virus (BYDV) by them is extremely important. Once again however, you have a very good management tool for avoiding the problem -- planting date. Though it is not absolute, the later one plants, the lower the chances of a problem with of BYDV. Though there is no definable calendar date for avoiding BYDV, the "Hessian Fly Free" makes a good compromise.
Beyond planting date, the fall weather will be the next most important factor in decisions concerning aphids and BYDV. Certainly, we would like to see the fall cool down to reduce the survival of incoming aphids and to slow the movement of aphids in the field. Producers/consultants should be on the lookout for aphids especially in the first 30 days after planting. The earlier aphids appear the more problem one would expect from BYDV.
You are likely to hear the continuing discussion about how many aphids should be present before there is a need to spray. In the past, scientific literature has suggested about 10 aphids per row foot. Many consultants think that 5 aphids per row foot is more appropriate. Additionally, there is some new research (not yet published) from Georgia that suggests (at least in the Deep South during the first 30 days post plant) that three aphids per row foot is the appropriate number. Though I will be very interested to see the work from Georgia in its entirety, I think that for Kentucky right now, that number is too low. Additionally, none of these numbers will matter much unless you do a VERY GOOD job of sampling the crop. Variation from poor sampling or too little sampling will completely wipe out any precision gained by having a more refined threshold, - AND - this will still not address whether or not the aphids are carrying the virus!
Fall control of aphids designed to reduce the incidence of BYDV will remain a difficult decision for awhile yet. However, I think the following factors still deserve your consideration.
A. Factors to consider when deciding on insecticide intervention.
by Don Hershman
Many of us in Extension and private industries, who develop educational programs, have come to realize the importance of obtaining Certified Crop Adviser Continuing Education Credits (CEU's) for our programs. In fact, many of us have found out that offering CCA CEU's can be a major boost to meeting attendance. The fact is that CCA's must consistently attend meetings offering CEU's in order to remain certified. This is good for the agricultural industry,since those in consulting and educational roles, will remain current. Likewise, it is good for those planning meetings, since attendance at our meetings has increased. Basically, offering CCA CEU's is a win-win situation all around.
The process of applying for CCA CEU's is quite simple and involves simply filling out the appropriate CEU Application Form and submitting it to the Chairman of the KY CCA Continuing Education Committee. The committee reviews the request and grants the CEU's if: 1) the application is filled out correctly, and 2) the program agenda meets specific criteria as to content (does the training apply to CCA performance objectives) and quality (are the presenters qualified instructors). Once CCA CEU's are granted, all the meeting organizer needs to do is record the name and CCA certification number of CCA's that completed the training, and send the list to CCA headquarters in Madison, WI. All in all, it is a fairly painless process, except that you must leave a substantial buffer of time between applications for CEU's and the program date. At least 1 month is recommended, which gives the Continuing Education Committee enough time to review and act on your application.
If you need CEU's Application Forms, contact Ann Marberry at the following address:
Ann Marberry
CCA Program
677 S. Segoe Road
Madison, WI 53711
Phone: 608/273-8080
Fax: 608/273-2081
Send completed CEU Application Forms to:
Jesse Whitehouse, Chairman
KY CCA Continuing Education Committee
104 Carolyn Lane
Nicholasville, KY 40356
by John Hartman
Oaks are among the most important trees planted along and in Kentucky streets and home landscapes. They are perceived to be durable and long-lived, and because of their size, often occupy a prominent place in the landscape. Unfortunately, many of these oaks are not in good condition from a variety of disease and stress related problems.
Bacterial Leaf Scorch. Symptoms of bacterial leaf scorch are now becoming noticeable from a distance, especially on street-side pin oaks statewide. Affected pin oaks show premature browning of the foliage and premature leaf fall. Healthy trees nearby are still green and have begun to drop their leaves. These contrasting conditions will be quite visible for the next several weeks, until the leaves of healthy trees also begin to turn their normal brown color and drop.
Leaves of diseased trees show symptoms of scorch, in which the leaf tissue between the veins and at the edges of the leaves turns brown while the leaf tissue nearest the veins remains green. Some of the fallen leaves still show the near-veinal green color pattern. The premature browning of affected trees is repeated each year and after several years affected trees begin to show symptoms of twig and branch dieback. Finally, after many years, affected trees decline and die. Bacterial leaf scorch appears to affect mainly older trees, but young trees can also die from this disease.
The causal agent, Xylella fastidiosa, a xylem inhabiting bacterium, is thought to be transmitted from tree to tree by xylem-feeding leafhoppers. Since the disease seems to spread slowly from one tree to another, the insects may not be very efficient carriers of the disease. In any case, once inside, the bacteria grow systemically and are probably impossible to control with the technology we have now. If a tree is showing bacterial leaf scorch symptoms, be prepared to lose it a few years hence. Plant another tree nearby as a future replacement.
Red oak leaf spot and lower branch dieback. Red oaks in several central Kentucky landscapes are showing severe leaf spot due to springtime anthracnose infections caused by the fungus Apiosporina quercina or Discula quercina, and by late season spotting by the fungus Tubakia (Actinopelte). Severely affected leaves have turned brown and dropped. In some cases, twigs and entire lower branches have died, possibly from the effects of previous seasons' defoliation, or possibly due to twig and branch canker infections. It is possible that other factors not yet known could be contributing to the poor condition of some of these trees.
Almost all the cases of leaf spot and lower branch dieback observed in the past two weeks have involved young, well established trees 6 - 10 inches in diameter. This rather severe condition seems to be confined just to red oaks for the present. In groups of red oaks, some appear to be more tolerant to the problem than others nearby. Providing good growing conditions may help to maintain the health of these trees.
by Monte P. Johnson
EPA RELEASES PESTICIDE SALES AND USE REPORT
EPA is releasing its latest estimate of pesticide use in a report "Pesticide Industry Sales and Usage -- l994 and l995 Market Estimates." The report indicates a continuation of recent trends in pesticide use, i.e., agricultural pesticide use remaining stable with year to year variations resulting from changes in acreage planted and weather conditions. The use of herbicides to control weeds in the United States for agricultural purposes has increased slightly over the previous three years. The increase is due primarily to more acres planted to pesticide-using crops including corn, soybeans, cotton, rice and sunflowers. At the same time, the report shows that the use of conventional pesticides for non-agricultural use (commercial, government and industry and homeowners) has declined over the same period of time. An average of nearly $4,200 per farm was expended in l995 on pesticides. Conventional pesticides account for about 27 percent of all pesticides used annually in the United States and total an estimated 1.2 billion pounds. Wood preservatives account for 16 percent of all pesticides used and total about .72 billion pounds; specialty biocides (such as those used to control bacterial growth in cooling towers, etc.) are about six percent of all pesticides and total .26 billion pounds; and chlorine/hypochlorites (used in water purifying plants and swimming pools) represent 51 percent of all pesticides used and total 2.32 billion pounds. To obtain a copy of the 35-page report write or call: U.S. EPA, NCEPI, P.O. Box 42419, Cincinnati, Ohio 45242-2419; (telephone - 513-489-8190). Only single copies will be available. The report will soon be available on the Internet at www.epa.gov/pesticides. (EPA Press Release, September 5, 1997)
MAINTENANCE FEES FOR PESTICIDE REGISTRATIONS INCREASED
EPA's Office of Pesticide Programs has announced that the annual maintenance fee paid by pesticide registrants will be increased as authorized by the l996 Food Quality Protection Act. Initially authorized by 1988 amendments to the Federal Insecticide, Fungicide and Rodenticide Act, the maintenance fees will be increased to $950 for the first product registration and $1,900 for each subsequent product registration with the following caps. No registrant will pay more than $55,000 for the first 50 products, and no registrant will pay more than $95,000 total. Small businesses will pay no more than $38,500 for the first 50 products and no more than $66,500 total. The maintenance fee levels were previously $700 for the first product and $1400 for each subsequent product. The fee was increased to permit the Office of Pesticide Programs to collect an additional $2 million per year in l998, 1999 and 2000 as authorized by the Food Quality Protection Act, which was passed in August l996. This act authorizes the EPA Administrator to adjust the fee to a level that will result in the collection of the additional $2 million. The l998 maintenance fee is due on Jan. 15, l998. In late November, EPA will send maintenance fee notices and instructions for submitting payment to all firms holding active pesticide registrations. (EPA News Release, September 5, 1997)
USDA ANNOUNCES NEW OFFICE OF PEST MANAGEMENT
On September 8, 1997, Deputy Agriculture Secretary Richard Rominger today announced the creation of the Office of Pest Management that will serve as USDA's focal point for pesticide regulatory issues. This is part of a new, coordinated approach to minor use pesticides issues that builds on existing programs at USDA and the U.S. Environmental Protection Agency (EPA). The new office is charged with integrating and coordinating pesticide issues within USDA along with improving communications with and strengthening the existing network of grower organizations and crop specialists at land grant institutions. This will help make available accurate, high quality data on pesticide use practices for regulatory decision making. EPA's Assistant Administrator for Prevention, Pesticides, and Toxic Substances Lynn Goldman also announced the agency's newly created Minor Use Program Team. It will work closely with growers organizations, USDA, registrants and other stakeholders to obtain and use the best available data, to facilitate an open dialogue with the minor use community, and to promote the development of safer pesticides for minor uses. EPA and USDA have been working together in recent months to secure funding for the collection of additional data on children's food consumption patterns and to collect pesticide residue information through the Pesticide Data Program. These efforts are in compliance with the Food Quality Protection Act of 1996 that requires minor use issues be handled more efficiently in a coordinated, cross-agency effort. (USDA News Release via AAPSE Notice, September 8, 1997)
EPA PROPOSES CHANGES IN WPS GLOVE REQUIREMENTS
The Worker Protection Standard (WPS) generally prohibits
glove liners made of absorbent material from being used
under chemical-resistant gloves unless specifically
permitted by a pesticide label. This existing prohibition,
though intended mainly to stop the use of flocked gloves
(where the liner material is an integral part of the
glove), has applied to separable liners as well.
Recognizing that its previous stance against any and all
glove liners was too broad, EPA has changed its
determination. EPA now proposes to allow all agricultural
workers, including pesticide handlers, to wear separable
liners beneath chemical-resistant gloves, *provided that*
used liners are discarded after the earliest of: (1) a
total of 8 hours of use, (2) the end of a 24-hour period
during which they were used, or (3) immediately if directly
contacted by a pesticide. So the liners could be worn
several times during a 24-hour period, up to a total of 8
hours, but they would have to be disposed of 24 hours after
first worn and immediately if a pesiticide is directly
splashed or poured on them. Further, EPA also proposes
that the liners may be no longer than the
chemical-resistant glove under which they are worn, and
that they may not protrude beyond the edge of the glove.
The complete notice of this proposed rule revision, as
published in the Federal Register yesterday [September 9,
1997 (Volume 62, Number 174), pp. 47543-47550] is in the
EPA website, at
http://www.epa.gov/fedrgstr/EPA-PEST/1997/September/Day-09
/p23833.htm.
A second revision that EPA is proposing in this notice is
to delete the requirement that pilots wear
chemical-resistant gloves when entering and exiting
aircraft used to apply pesticides. The deadline for
written comments on the proposal is October 9, 1997.
Comments, identified by docket control number OPP- 250120,
may be sent to:
Public Information and Records Integrity Branch,
Information Resources and Services Division (7506C),
Office of Pesticides Programs,
Environmental Protection Agency,
401 M St. SW.,
Washington, DC 20460.
(WPS Forum, September 10, 1997)
CHEMINOVA PRODUCES PUBLIC SERVICE ANNOUNCEMENT ON PESTICIDE
MISUSE
As a result of an agreement with EPA, Cheminova Agro of Denmark, the sole U.S. manufacturer and principal registrant of methyl parathion, has produced a public service announcement warning people of the hazards associated with misusing pesticides. The illegal spraying of methyl parathion has resulted in the relocation of more than 1,000 residents since the Fall of 1996. More than 700 homes need decontamination and more than 5,000 homes require testing in five states including: Mississippi, Louisiana, Tennessee, Arkansas and Illinois. Methyl parathion can pose imminent health hazards. Effects of severe poisoning include convulsions, cardiac arrest and death. The only legal uses of methyl parathion are for agricultural crops under restricted conditions. If used indoors, the pesticide can cause nausea, vomiting, headaches and diarrhea. Copies of the PSA can be obtained from Michelle Mention, John Adams Associates, 202-737-8400.
EPA REQUIRING NEW INFORMATION FROM MANUFACTURERS ON HARMFUL
HUMAN EXPOSURE TO PESTICIDES
EPA is strengthening its reporting requirements under which manufacturers disclose information to the Agency about unreasonable adverse effects of their products on human health or the environment. In addition to information on adverse health effects presently required, the new reporting rule requires pesticide manufacturers, for the first time, to provide EPA with information about: pesticides found in food above approved levels, pesticides detected in surface, ground and drinking water above safety standards, newly identified types of ingredients which may be of toxicological or environmental concern, specific details about incidents causing adverse effects, and occurrence of products no longer effective because of resistance developed by the pests. (EPA Press Release, September 18, 1997)
by Julie Beale and Paul Bachi
In the last two weeks we have seen a number of cases of stem canker, sudden death syndrome, and cyst nematode on soybean. The late tobacco is showing considerable damage in some areas from blue mold, as well as other leaf spots -- brown spot, frogeye and target spot. We have diagnosed Diplodia stalk rot in corn.
Among ornamentals, we have seen Pythium and Rhizoctonia root rots and bacterial leaf spot in chysanthemum; Macrophoma canker in boxwood; bleeding canker(Botryosphaeria) in sweetgum; and plenty of Actinopelte leaf spot in oaks.
Vegetable diseases have included rust, common blight(Xanthomonas), and Cercospora leaf spot in bean; watermelon mosaic virus and downy mildew in pumpkin; and bacterial spot in pepper.
Lee Townsend
Extension Entomologist