Ornamental Crops IPM E-newsletter, 2007

Alternative Fungicides for Reduction of Rhabdocline Needle-cast on Douglas Fir

Gary Couch, NYSIPM, gjc15@cornell.edu

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Douglas-Fir is a major component of the Christmas Tree and Nursery industries in NY State.  Unfortunately during some recent growing seasons weather conditions lead to severe cases of Rhabdocline needle-cast. The infections are sometimes so severe that affected trees' appearance becomes unacceptable and the trees are lost.  One grower estimated losses of approximately $10,000 per year due to a recent outbreak of  this needle-cast disease.

Fungicides currently labeled for controlling Rhabdocline on Douglas-fir are perceived as costly and require repeated application. Also, over-use of these labeled products is suspected to have potential for adverse environmental effects and pest resistance. Certainly, organic alternatives are being sought in nearly all phases of agriculture, and they are increasingly demanded by homeowners with children and pets.  Even the perception of a hazard can influence farm neighbors and customers, particularly at Cut-Your-Own operations.

Current IPM strategies recommended to control Rhabdocline include: weed control (mowing), lower branch removal, selecting plant sites with good air drainage, and removal of severely infected trees.  However there have been problems with IPM implementation involving lack of growers time to perform the labor-intensive tasks involved and a lack of efficacy information on possible alternative products.

This problem prompted the implementation of an alternative Rhabdocline needlecast control study sponsored by the New York State Integrated Pest Management Program. The project was conducted on two farms in Wayne County, New York. At each site 20 trees exhibiting Rhabdocline needle-cast were selected per treatment.  Treatments included:potassium bicarbonate, lime-sulfur,active compost-tea, copper sulfate, with chlorothalonil for comparison.  Rates and frequency of application were from the label or manufacturers recommendations.  In general, it was a relatively low infection season in the study area, probably due to the lack of rainfall events during the sporulation period.  This, along with several other factors, makes definitive conclusions problematic. However some indications can be mentioned.

The standard, chlorothalonil, was lowest in terms of both product cost ($.12 per tree per season) and labor cost (3 applications) and gave acceptable control (0-2% infected needles).  Of the alternatives, potassium bicarbonate was least costly ($.80 per tree per season, 4 applications) but did not provide acceptable protection (7% infected).  The copper sulfate pentahydrate product cost was $2.24 per tree per season, had the highest number of applications (7) and thus the highest labor costs and required personal protective equipment (PPE). Control was acceptable (1% infected). The compost-tea did not give an acceptable level of control (3% infected), left a black residue similar to sooty mold and had the highest product costs ($5.04 per tree per season, 4 applications).  The lime-sulfur gave excellent protection but at $1.28 per tree per season and high labor cost (5 applications, requiring PPE) it may not be economically viable.  The double rate dormant application of lime-sulfur left a noticeable white residue on older foliage that persisted into the following season.  If acceptable control can be achieved without the dormant application, and with fewer seasonal applications, the costs may be brought within reason.

While the economic information on material and labor costs should give growers useful guidelines when selecting a treatment approach, none of the treatments, as tested, gave us a clearly superior alternative to chlorothalonil. The inability to predict infection periods or detect the early stages of infection are both areas requiring further research. Further testing of lime-sulfur may yield an acceptable solution for those growers seeking an organic approach.

New Greenhouse Miticide/Insecticide has Potential for Use with Biological Control

Betsy Lamb, NYS IPM  eml38@cornell.edu
(with thanks to Dan Gilrein for additional information)

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The New York State Department of Environmental Conservation has granted a Special Local Needs label for the Miticide/Insecticide Judo (EPA Reg. No. 432-1280-59807) for greenhouse use on ornamental plants, flowers, and foliage plants only. The Special Local Needs labeling is assigned SLN No. NY-070001.  Judo is allowed for use in Nassau and Suffolk Counties.  Outdoor use is prohibited pending data concerning impact on honeybees by the active ingredient, spiromesifen.   Applicators should have a copy of the SLN label when applying Judo.

Judo is labeled for spider mites, Tarsonemid mites (broad and cyclamen) and Tenuipalpid mites, and greenhouse, silverleaf and sweetpotato whiteflies (see label for specific species). It is reported to be active on all mite development stages, with juvenile stages more susceptible than adults, and to be most active against whitefly nymphs and pupae.  Dan Gilrein has found Judo to be effective against the Q-biotype of silverleaf whitefly (Bemisia argentifolii), which is less susceptible to many of the insecticides currently used to manage the A and B biotypes of silverleaf whitefly in the greenhouse, and has the potential to become an increasing pest in New York State greenhouses.

Judo is reported by the manufacturer to be soft on beneficial insects used for biological control.  Based on the Koppert Biological Systems website on side effects (check for Side Effects in the left sidebar), it would be appropriate for use with some of the common biological control agents for whitefly or spider mites.  Spiromesefin is listed as harmless to Encarsia formosa adults and Amblyseius swirskii adults and eggs.  However, it is slightly to moderately harmful to adult Phytoseiulus persimilis.  There is no information concerning impact on other life stages of these beneficial insects or on Eretmocerus eremicus or Amblyseius californicus. While Judo has a reported residual control of 20-30 days, depending on the pest species, it has only short residual effects (low persistence) on some of the beneficial species.  Persistence is 2-3 weeks for P. persimilis and 0 weeks for A. swirskii and E. formosa, but has not been determined for A. californicus or E. eremicus.

Spiromesefin is a lipid biosynthesis inhibitor in the class tetronic acids and can be rotated with all other labeled miticides for resistance management purposes.  It affects water balance in the insect, resulting in desiccation.  Feeding stops after 1-2 days and death occurs 4 -10 days after treatment. While no injury has been reported on poinsetia, there is an expanded list (not yet on the label) of plants that show sensitivity to Judo.  Other crops require the use of lower rates.  Both lists are included on the Judo Product Information Bulletin.   Growers are advised to check for phytotoxicity on other crops, as not all crops have been included in the manufacturer's tests.

Whitefly Update Q & A (Biotype B too)

Betsy Lamb NYS IPM eml38@cornell.edu
(Information from Dan Gilrein and John Sanderson)

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The Q biotype whitefly is a new variant of the common A and B biotypes of Bemisia whiteflies, the silverleaf whitefly and sweet potato whitefly.  (Biotypes are genetically distinct strains of a species, similar to varieties of plant species, although some have been given species designation.)  Q and B biotypes are visually indistinguishable and require lab tests for accurate identification. Growers' first indication that they have Q biotype is that the usual  insecticides are less effective on what appears to be silverleaf whiteflies (not greenhouse white fly).  However, it is possible to have mixed populations of B and Q so lack of efficacy may not be clear-cut.

There were at least 6 cases of Q biotype reported from New York State greenhouses in 2006, on poinsettia and hibiscus.  If you suspect that you have Q biotype whiteflies, contact your local Extension personnel and they can help you get the necessary lab analysis and treatment options.

Following are some suggestions to growers on managing whiteflies, particularly the Q-biotype whitefly:

• Carefully check plant shipments for even low levels of whiteflies.

• Use good non-chemical controls.

• Correctly identify the whitefly species present!

• Monitor whitefly population levels as the crop is growing.

• Use sentinel plants to check for pesticide performance.

• Consider using biological control right from the start.

• For unusual silverleaf whitefly control problems, contact a regional Extension specialist for more information on preparing and shipping samples.

Survey Respondents Needed!

Betsy Lamb

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Frustrated by the lack of management options for ornamental crops you grow?  You can help by providing information on the types of pests you need help controlling!

For over forty years, the USDAs IR-4 Project has been the major resource for supplying pest management tools for specialty crops by developing research data to support crop protection registration clearances.. The Ornamental Horticulture Program was started in 1977 to address the disease, insect, and weed management tool and plant growth regulator needs of growers. Over time this program has expanded to cover not only ornamental horticulture plants grown in greenhouses and nurseries, but also landscape plantings, Christmas tree farms, sod farms and interiorscapes.

Research activities start with an identified need, an area where current management tools are not sufficient, such as for a newly introduced pest or for crops where little phytotoxicity information is available.  Each year, high priority projects are chosen to generate sufficient research to add uses to labels. In order to determine which projects are of most importance, IR-4 invites growers, and Extension and research personnel, to help focus the research by answering a few questions about the diseases, insects, and weeds that most impact them.

Help the Northeast Region be represented in this national survey.  In addition to determining national needs, regional information is also useful to researchers and Extension Educators within the state.

The survey can be completed on-line at 2007 Ornamental Horticulture Survey

Paper copies for individual use, or in larger numbers for use at CCE programs, are available from Betsy Lamb at eml38@cornell.edu (607-254-8800).

Completed paper copies can be mailed or faxed to:

Edith Lurvey
IR-4 Region Field Coordinator
Cornell University - NYSAES
Dept. of Food Science & Technology
630 W. North Street
Geneva, NY 14456-0462
Phone 315-787-2308
FAX 315-787-2397

More information on the IR-4 project can be found at Rutgers IR-4 project Ornamental Program Information

CCE personnel are encouraged to provide growers with information on the survey through individual contacts or at programs that relate to ornamental producers.

Tour Greenhouses in Canada
Learn from Growers in Canada about Greenhouse Biological Control

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The NYS IPM Program in collaboration with NYS Flower Industries and the NY Farm Viability Institute will be offering a tour to Canada where participants will visit growers using biological control in their operations.  This will offer a unique opportunity to learn from the experts at a very reasonable price.  The tour will start in Ithaca, make a quick stop in Buffalo to pick up participants, and continue on to Canada for a 2-night stay.  Over the 3 days participants will meet with biological control suppliers, research experts, and growers in Canada.

Extension Educators and Specialists Have Access to Plant Management Network

Brian Eshenaur, bce1@cornell.edu (with thanks to John Hartman)

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Cornell Extension Educators have access to the on-line Plant Management Network (PMN) and its resources because Cornell is a University partner.  Applied research articles presented in the journal Plant Health Progress is one of the PMN resources available to Cornell employees.

Listed below are some the titles published in this journal during the last 18 months. There are some that could be of interest to educators who work with ornamentals.

• Biology and Distribution of Pryeria sinica, a New Pest of Euonymus Found in Virginia and Maryland.

• First Report of Powdery Mildew of Mahonia aquifolium (Pursh.) Nutt. Caused by Erysiphe (Microsphaera) berberidis (DC.)  in Canada.

• Comparing Diagnostic Protocols for Phytophthora ramorum in Rhododendron Leaves.

• Phytophthora Root Rot and Stem Canker Found on Nordmann and Subalpine Fir in Norwegian Christmas Tree Plantations.

• Control of Phytophthora Root Rot in Field Plantings of Fraser Fir with Fosetyl-Al and Mefenoxam.

• Effects of Azoxystrobin Rate and Treatment Interval on the Control of Rhabdocline pseudotsugae on Douglas-fir Christmas Trees.

• Rhabdocline Needlecast Increases Needle Loss of Douglas-fir Christmas Trees.

• Abnormal Leaf Development on White Oaks Linked to Drift of Chloroacetamide Herbicides.

These articles listed are from only one journal, Plant Health Progress.  The PMN includes other on-line journals, all with color photographs to help illustrate research results. In addition, PMN offers resources such as the image database and the Arthropod Management Reports publications and  Biological and Cultural Tests for Control of Plant Diseases and Plant Disease Management.

Cornell Educators and Specialists can easily subscribe to the Plant Management Network for free by going to Plant Management Network.  Click on subscribe, then personal subscriptions, then complimentary personal subscriptions, then Cornell, and take it from there.