During last summer's blue mold epidemic, growers reported mixed results with the performance of their fungicide programs against blue mold. We, too, were evaluating fungicides during the epidemic and encountered mixed performance in some tests. Poor control was usually associated with poor coverage, poor timing, or too much reliance on induced resistance.
Below are the results of a test where we know the materials were applied accurately, and well. It was conducted at the University of Kentucky, Robinson Substation, Quicksand, Kentucky during the 2003 season. This test site is a foggy creek bottom field where we have evaluated blue mold controls for the past 20 years. The 2003 season was cooler and wetter than normal with moderate to strong blue mold and other foliar disease pressures from late July through 10 days post-topping. However, blue mold was the most serious disease problem impacting yield in this test.
We compared two regimes of the plant inducer Actigard 50 WP: Actigard 50W @ 0.5 oz/A in 30 gallons of water delivered with a broadcast boom starting at 18" in plant height, on August 11 and again August 21; verses, Actigard 50 W @ 0.5 oz/A in 30 gallons of water starting at first appearance of blue mold (July 17 with plants about 10" tall) and repeated July 28 (plants about 15" tall). Contrary to labeling, we made no attempt to control blue mold in Actigard plots with other fungicides. Our grower- advisory committee had asked that we determine how well Actigard could stand-on-its own, as that was how most planned to use it due to having inadequate spray equipment to apply foliar fungicides. Another treatment was a full-season (six applications), fungicide spray program applied on a 7 to 10-day interval between July 10 (when the advisory was issued) through August 28 (topping stage), using Acrobat MZ @ 2.5 lbs/100 gallons, with 20-100 gallons/A depending upon growth stage as per label directions ( the current standard). A gas- pressurized sprayer operating at 80 psi and equipped with one to nine hollow-cone nozzles per row was used for the first two and last applications of Acrobat MZ but a motorized-mist blower was used for the other applications of Acrobat MZ. The check treatment was untreated.
Plots of burley tobacco consisted of three rows, with only the center row receiving the fungicide treatment. Consequently, the disease pressure was probably much stronger than growers would encounter where the whole field is being treated, so we may be underestimating the actual control potential of the product. Each treatments was replicated six times in a randomized complete block. Except for these experimental fungicide treatments, this burley tobacco was maintained as a commercial crop: transplanted on June 25, topped and sucker control applied August 28, harvested September 18, housed September 20 and traditionally aired-cured, stripped and graded in January 2004 with the marketable weights collected for all plants in the treated row.
Blue mold was first found in the plots on July 17 as a few lesions per plant in small areas of the test plot, and it developed slowly until early August. Blue mold severity was evaluated by estimating the percentage leaf area damaged by blue mold at three locations within each plot on the date indicated. The percentage of systemic blue mold was determined at harvest time by cutting the lower stem of all plants in the treated row followed by examination for symptoms of systemic blue mold in the lower portions of the stem.
A study of the data presented in Table 1 should point out the value of a well applied, full-season spray program with Acrobat MZ in controlling blue mold and preventing yield losses from the disease. Moreover, that study should also uncover the limitations of Actigard 50 W as a stand-alone control for blue mold under high disease pressure. These findings are consistent with most of our studies under prolonged disease pressure where these materials were applied correctly.
Funding for this study was provided by the University of Kentucky Cooperative Extension Service, Kentucky Agricultural Experiment Station, and the Council for Burley Tobacco. To improve grower confidence in our findings, no funding was obtained from any of the chemical manufacturers, with the test products purchased locally in 2003 from commercial supplies.
|Effects of fungicide regime on the % leaf area damage by blue mold on various dates, % systemic blue mold in the lower stem, and the marketable yield of|
|Fungicide regime||% leaf area with blue mold||% Systemic Blue mold||Marketable Yield/A (lbs)***|
|Aug14||Aug 21||Sep 5|
|Acrobat MZ||7.8 b*||10.8 c||17.5 c||1.7 b||2966 a|
|Actigard 50 W, 1st||28.7 ab||19.5 bc||33.3 b||20.0 b||1830 b|
|Actigard 50 W, 18"**||42.5 a||25.7 b||37.5 b||18.3 b||2029 b|
|Check||46.7 a||47.5 a||59.2 a||50.0 a||1719 b|
¹Ed Dixon is a Research Analyst, Plant Pathology Department, University of Kentucky.
²Wade Turner is an Extension Associate, located at the Robinson Station, University of Kentucky.
For the latest blue mold status and other tobacco disease information, check the KY Blue Mold Warning System online.
For more information about tobacco pests, visit "Insect Management Recommendations".
An online soybean pest survey has been developed from a Pest Management Strategic Planning meeting held in August 2003. This is survey is intended for producers and others involved with soybean production in Kentucky, Tennessee, southern Illinois, and southern Indiana.
You can access this survey at: http://www.sripmc.org/KY/SoybeanPMSPSurvey/
The purpose of this survey is to demonstrate producer input on critical pest issues relative to soybean production in this region of the county. This information will be used by the United States Department of Agriculture (USDA) and the Environmental Protection Agency (EPA) in making decisions about pesticide registration issues and prioritization for the funding of extension and land-grant/government research projects.
This survey was developed through the Kentucky Pest Management Center (KPMC). The KPMC is a grant-funded program in the UK Entomology Department. We develop Crop Profiles and Pest Management Strategic Plan documents for commodities in Kentucky and the region. These documents were designed as a method for producers and those with first-hand or hands-on knowledge to provide input on what pest management tools are most critical for the production of Kentucky commodities. More information can be found at http://www.uky.edu/Agriculture/KPMC/KPMC.htm.
This is your chance to collectively provide "first-hand" information to the USDA and EPA on current troublesome pests and the potential impact of emerging pests. We encourage those involved with soybean production in this region (producers, industry, and extension) to take 10 to 20 minutes out of your day to provide your input on these critical pest management issues.
In the last issue of the Kentucky Pest News we reported the spring survey results for Henderson and Daviess counties, We now have the results for Caldwell county. Other information about how these results can be used was included in the article in the last issue.
|2004 SWCB Spring Survey Results|
|Damaged plants||Live SWCB recovered|
|Farm #1||8 / 100||0 / 50|
|Farm #2||2 / 100||3 / 50|
|Farm #3||1 / 100||3 / 50|
|Farm #4||23 / 100||1 / 50|
The additional information from Daviess county did not change values for overall survival per stalk. In Caldwell county, there were high levels of what appeared as bird predation on the larvae.
|Year||Girdled stalks (%)||Survival/girdled stalk (%)||Overall Survival/stalk (%)|
So for the spring of 2004, we can conclude:
For information about corn pests, visit
"Insect Management Recommendations".
The alfalfa weevil is the key pest of the first cutting of alfalfa each year. Degree day accumulations as of 23 March at Princeton (243) and Glasgow (249) are at the level at which early signs of tip feeding might be expected in the field. Accumulations are predicted to reach the "first check" level as follows Quicksand - 1 April, Lexington 8 April, and Covington 14 April.
The best alfalfa weevil management decisions are based on stem sampling. Information on this method is available in Insecticide Recommendations for Alfalfa, Clover, and Pasture - 2004, available from your county extension office. An average of 25% to 50% damaged tips in a field with 2 or more larvae per stem provides a satisfactory treatment guideline. Cold temperatures this winter will probably result in mostly spring-laid eggs this year so continue weekly field checks for feeding damage.
Pea aphids and spittlebugs are common spring insects in alfalfa fields. They are sap feeders so they will produce no feeding holes in leaves. Sap removal by these insects is very unlikely to affect alfalfa growth and they may even serve as food for beneficial insects.
Aphids will be found clustered at the tops of alfalfa plants. Spittlebug masses will be found on stems. A light green spittlebug can be found inside the frothy mass.
See Insect Recommendations
for more alfalfa pest recommendations.
Brood X of the periodical cicada (sometimes called locusts) will emerge over much of Kentucky during late April or early May. They will appear as soil temperatures climb above 64 F. Cicada emergence holes and chimneys will appear in the ground a few weeks before emergence and may be of some help in determining how abundant the insects will be. The intensity of cicada infestations will vary widely, ranging from virtually none to very heavy within different parts of the same county. The insects will remain active for about 6 weeks. Egg-laying damage will begin to appear about 2 weeks after emergence of the adults.
Egg laying activity should be greatest along forest edges and decrease rapidly with distance away from the source of the insects. Periodical cicadas are weak, clumsy fliers. Studies indicate relatively limited movement from emergence sites often in the range of 100 to 200 yards or less across open fields - but distances of about 0.5 mile have been seen around heavy outbreaks.
Cicadas neither bite nor sting so they pose no threat to people or animals. They may be attracted to vibrations from equipment mowers, weed eaters, etc. but are not swarming to attack the operator. This may not appear to be the case to the operator at the time, however. Cicadas generally will try to escape if approached and males will emit a loud alarm buzz if handled but that is the best that they can do. Males are responsible for the "din" associated with cicadas as they join sound in a chorus of calling songs that attract both males and females on high sunlit branches of trees.
Female cicadas use blade-like ovipositors to slit the bark of 2- to 3-year old stems of twigs of many deciduous woody plants to provide egg-laying sites. Oaks, hickory, apple, peach, pear, dogwood, and grapevines are commonly listed as being damaged but many other species can be attacked. Conifers should be relatively unscathed by these insects.
Twigs weakened by egg-laying slits will break causing "flagging" or browning of the tips of the branches. Pruning may be needed to compensate for damage to branch architecture on small landscape trees. There may be subsequent stress in future years to landscape trees on poor sites if many eggs are inserted into twigs. The nymphs hatching from these eggs will begin to remove sap from roots. Any appearance of this injury may be subtle and appear so long after this brood disappears that they area forgotten as a potential cause of the problem.
Plants can be protected in three ways: covering, spraying and pruning.
Birds and small mammals will eat many cicadas during the summer but where the insects are abundant, the impact of this natural control will be minor. There are some other organisms that will attach developing stages in the soil over the next 17 years but effects probably will be too subtle for us to notice.
A generalized map of the brood is available at http://insects.ummz.lsa.umich.edu/fauna/Michigan_Cicadas/Michigan/Index.html as part of an extensive cicada website that has many cicada pictures and sounds.
Crown gall is caused by the soilborne bacterium Agrobacterium tumefaciens. Grown gall disease affects a very broad range of landscape shrubs and trees and also many kinds of tree fruits and small fruits. In addition to many woody host plants, the disease also affects many herbaceous hosts.
Symptoms. Infected roots and stems develop galls, often at the root collar. New galls are greenish white or light brown but darken with age. Galls may be lumpy or spherical and rough-surfaced ranging in size from 1/4 inch to a foot in diameter. Plants with crown gall disease are generally stunted, less productive and more prone to drought or winter cold especially if galls are large and numerous or where galls girdle the base of the plant. Although galls by themselves are not likely to kill the infected plant, opportunistic pathogens may attack the stressed plant or enter through decaying galls and eventually kill it. Nevertheless, mature trees can sometimes bear large galls with little damage. Nursery plants with galls are not suitable for sale.
Crown gall infection is unique. Crown gall bacteria can only enter the target plant through a wound. Wounds caused by freezing temperatures, insect feeding, nematode punctures or by cultural practices such as cultivation, grafting, or pruning are all possible locations for infection. Crown gall bacteria enter live plant cells in the wound and cause a genetic transformation of the plant cell. Transformed plant cells produce high levels of plant hormones which induce gall formation. Once plant cells are transformed, gall formation continues with plant growth even if the bacteria are no longer present.
Disease spread. Crown gall can spread within the plant. Aerial galls may occur on highly susceptible plants such as spreading euonymus, willow, poplar, or rose. Crown gall also can be spread from one plant to another via pruning tools. Indeed, it is not unusual for the disease to appear throughout hedgerows of Euonymus kiautschovicus (formerly E. patens), the spreading euonymus, following pruning events. This can occur after an extremely cold winter where the hedge died back to the snow line. If one plant in the hedge has crown gall, pruning out the dead stems in spring could spread crown gall to the others. Crown gall can be spread long distances on nursery stock.
Crown gall management.
|UKREC-Princeton, KY, March 12 - 19, 2004||Black cutworm
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.
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