Ornamental Crops IPM E-newsletter

Chrysanthemum White Rust

Brian Eshenaur bce1@cornell.edu

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As fall approaches and chrysanthemum crops mature, growers should be aware of a disease that can devastate a crop: chrysanthemum white rust caused by the fungus Puccinia horiana. This disease is not known to overwinter in the US, however it has appeared here occasionally over the past few years, apparently as the result of importation.

It is important to scout your crop and also check mums near the greenhouse in the landscape including Montauk daisy. Look for any small yellow spots – especially those less than ¼” in diameter. The best place to look for the spots is on the upper surfaces of the young leaves and flower bracts. A characteristic feature that helps separate these spots from other spots is the tiny brown speck in the center. Raised tan to pink colored pustules develop on the opposite side of the leaf, under the yellow spots. These pustules, from which spores are released, fade to white with age – hence the name white rust.

To help prevent this disease from occurring at your operation, carefully inspect incoming mums. Imported cut flowers should never be handled in or near a mum growing facility—a particular challenge for greenhouse/florist operations. Cool humid conditions favor this disease (temperature range from 63 – 75 F).

Since chrysanthemum white rust is a federal quarantine pest, growers are obligated to report it. If you are not sure if you have white rust, contact your extension office or NY Ag and Markets to get a confirmation and required control information.

Managing Thrips

John Sanderson, Assoc. Prof., Dept. of Entomology, Cornell University, Ithaca, NY

Dan Gilrein, Extension Entomologist, Cornell Cooperative Extension of Suffolk Co., Riverhead, NY

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Western flower thrips (WFT) are one of the most serious pests for most growers of greenhouse flowers and bedding plants. Feeding by these tiny insects causes plant cells to collapse, resulting in scarred patches on mature growth and distortion of young leaves or flowers. The thrips' feeding can also transmit incurable tospoviruses, including Impatiens Necrotic Spot Virus (INSV) (most common) and Tomato Spotted Wilt Virus (TSWV), that can severely damage or kill greenhouse plants. Both the thrips and the viruses have a very wide host range including common flowers, vegetables, and many weeds. Following is a review of suggestions for managing western flower thrips:

Thrips control should start at the end of the previous crop or season. Eliminate all sources of thrips at the end of each crop or growing season to avoid harboring a small population ready to infest an incoming or spring crop.

Eliminate weeds inside and around the greenhouse perimeter, which may harbor thrips and/or the virus (plants don't always show symptoms of virus infection).

Keep older plants segregated from newer crops and avoid moving clean new plants into thrips-infested areas. Older stock plants and long-term flowering pot plant crops such as cyclamen or holiday cactus can carry the thrips (and the virus) over from the fall to the following bedding plant season.

Inspect incoming plant material for signs of thrips damage. Look for light scarred patches with irregular outlines on upper leaf surfaces - tiny black fecal specks from the thrips are also diagnostic. Insist on good thrips control from your plant suppliers.

Don’t neglect hanging plants which can be an overlooked source of trouble. Hanging baskets of infested crops can spread a thrips infestation (and possibly virus) to other plants below.

Discard heavily infested plants, which may be easier and more effective than treating.

Pinch off and bag unneeded flowers, which removes a large part of the thrips population. Thrips lay up to four times as many eggs when pollen is present, compared to when only leaf tissue is available. While impractical in large ranges and for crops being sold in flower, this has worked on a small scale for some growers.

Consider screening vents if outdoor sources are important. The National Greenhouse Manufacturers Association (NGMA) has compiled useful research data into its publication, “Helpful Hints: Insect Screening”.

Use yellow or blue sticky traps to monitor for WFT.Count and change cards weekly, noting increasing populations that signal the need for treatment. One 3 x 5-inch yellow or blue sticky card is spaced every 1,000 sq. ft. and positioned vertically just above the top of the plant canopy. The sticky cards may also be useful to detect when and where the thrips are entering placing some traps near doors vents. Also locate sticky cards near crops that are known to be susceptible to thrips. Flowers can also be checked for thrips by tapping a blossom over a white tray or sheet of paper and looking for the adults and tiny nymphs.

If insecticides are needed, refer to the current copy of the Guidelines for the Integrated Management of Greenhouse Floral Crops. Thrips can become tolerant or resistant to most insecticides and are difficult to control at best; therefore emphasis must be placed on sanitation and other non-chemical preventive measures.

Resistance to spinosad, the active ingredient in Conserve, has been reported and may explain why some growers are not seeing the same results observed when the product was new, although the complaints of poor control are still relatively few.

Follow label directions for each insecticide used. If allowed on the label, a five-day treatment interval with two to three applications may be needed to control thrips that hatch from eggs or emerge from pupae.

Use an application technique and equipment delivering small droplets that will give good pesticide coverage. As much as possible, insecticide should penetrate into thrips’ hiding places such as buds and terminals, so tiny spray droplets are important. Pump-up sprayers may not be adequate.

Consider biological controls. Beauveria bassiana materials may be used while the thrips infestation is still low. They have not performed well against serious infestations. Other options include weekly preventative releases of tiny predaceous mites, Neoseiulus cucumeris or Amblyseius swirskii, to the foliage and flowers, or soil applications of Hypoaspis mites or insect-killing nematodes, Steinernema feltiae, to attack thrips pupae in the soil. (A. swirskii has the added benefit of attacking whitefly eggs). These natural enemies should be used preventatively before thrips are noticed or when the populations are very low, rather than in an attempt to reduce a serious infestation. Chances of success improve when releases of natural enemies are made to both the foliage and the soil.

Growers get In-Depth IPM Experience

Elizabeth Lamb
eml38@cornell.edu

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Twenty-six growers attended the first IPM In-depth Hands-On workshop July 21, 2008.The half-day program covered thrips management, water and nutrient testing, and the management of botrytis and other diseases. Growers got their hands dirty learning how to read pH and electrical conductivity meters and what the results mean. They got an up-close example of biocontrol by feeding unsuspecting thrips to minute pirate bugs (Orius spp.), a thrips predator. And they ground up plant material to test for impatiens necrotic spot virus with a virus indicator test. Several brought plant materials of their own to test the soil or identify disease and insect problems.

In order to make the IPM Indepth Workshop as relevant as possible, the attending growers answered a survey to find out more about them and what they did and didn’t like in the program. The majority attending have a retail greenhouse as their primary business, but others have nurseries, wholesale greenhouses, garden centers and even apple orchards. For most, thrips are a moderate problem but they do plan to change their thrips management plan based on what they learned. Many thought improving their monitoring system would help; others thought they might try other chemical means or biocontrol.

Diseases are also considered a moderate problem, with botrytis, root diseases and mildews most commonly mentioned as being most troublesome. For botrytis and root diseases, in particular, a wide variety of crops were listed as being common hosts – including geraniums, petunias, vinca, callibrachoa and nemesia. Many growers plan on changing their disease management system. Better identification, more scouting, and improved sanitation are the top choices for improvement.

Almost everyone wanted to try the media monitoring methods they learned once they returned to their greenhouses. And most thought that using the monitoring would help them adjust their fertilization practices.

Planning for the 2009 IPM In-depth program is going on now! Topics were the reason most people attended, so help identify those areas most important to you – identification and management of specific insects and diseases, techniques you would like to learn about, etc. Contact Elizabeth Lamb at eml38@cornell.edu or your local Extension Educator if you have suggestions. And stay tuned for the announcement of next year’s IPM In-depth program!

Upcoming Biological Control Learning Opportunities

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Insect and Disease Control in the Greenhouse

Learn more about biological control at a NY greenhouse near you during these on-farm workshops!

Two DEC pesticide recertification credits have been issued in3a, 3c, 10, 24, 25 for each workshop.

6 locations around the state. Only $10/person.

These workshops are partially funded by a grant received from the New York Farm Viability Institute.

September 24, 2008 - Long Island

LOCATION: C.J. VanBourgondien, Inc.39395 Main Road, Peconic NY

TIME:9:00am-12:00pm

To register: Contact Linda Holm, 631-727-7850 x341 or lml10@cornell.edu

Make checks out to: CCE of Suffolk County, or call to charge credit card (MC or VISA)

Mail to: CCE , 423 Griffing Ave. Suite 100, Riverhead, NY 11901

Please include: Your business, # attendees, address, and contact information.

September 30, 2008 - Buffalo

LOCATION: Mischler’s Florist, 118 So. Forest Rd. Williamsville, NY 14221

TIME:2:30pm – 5pm

To register: Contact Sharon Webber, CCE 71-652-5400 ext 142

Make checks out to: CCE Erie County

Mail to:21 South Grove Street East Aurora, NY 14052

Please include: Your business, # attendees, address, and contact information.

October 6, 2008 – Albany Area

Greenhouse BioControl, Fall Mum Trials and Ground Cover Session

LOCATION: Becker’s Farm,420 Columbia Tpk. Rensselaer, NY 12144

TIME:1:30pm – 4pm

To register: Call Chris Logue, CCE Schenectady County.518-372-1622 ext. 265

Make checks out to: CCE – Schenectady County

Mail to: CCE, 107 Nott Terr. Suite 301, Schenectady, NY 12308

Please include: Your business, # attendees, address, and contact information.

October 8, 2008 – Hudson Valley

LOCATION: Techni-Growers Greenhouses, 177 Sanfordville Rd. Warwick, NY 10990

TIME:9:30am – 12pm

To register: Contact Cathy Hughes, Cornell Cooperative Extension 845-344-1234, cah94@cornell.edu

Questions: Contact Rose Baglia, Cornell Cooperative Extension 845-344-1234

Make checks out to: CCE – Orange County

Mail to: CCE, 18 Seward Ave. Suite 300 Middletown, NY 10940

Please include: Your business, # attendees, address, contact information

October 29, 2008 – Syracuse

LOCATION: Barone’s Gardens, 6200 South Bay Rd. Cicero, NY 13039

TIME:9:30am – 12pm

To register: Contact Karen Hall, NYSFI at 716-941-3502 or mrskdhall@aol.com

Make checks out to: Cornell University

Mail to :NYSFI, PO Box 1243, Orchard Park, NY 14127

Please include: Your business, # attendees, address, contact information

October 30, 2008

LOCATION: Rivermede Farm, Beede Rd. Keene Valley, NY 12943

TIME: 9:30am – 12pm

To register: Contact Amy Ivy, CCE518-561-7450 or adi2@cornell.edu

Make checks out to: CCE – Clinton County

If you have any questions on the above programs, please call NYSFI, Karen Hall at 716-941-3502 or by email mrskdhall@aol.com or Betsy Lamb, NYS IPM Program at 607-254-8800 or by email eml38@cornell.edu.

Betsy Lamb, NYS IPM eml38@cornell.edu

Biological Control in Greenhouses

Sponsored by: University of Massachusetts-Amherst Extension, University of Connecticut Extension, University of Rhode Island and Northeast SARE

More growers and retailers are using natural enemies to manage common greenhouse pests. Come learn from two leading experts and a panel of wholesale growers and grower retailers about the "nuts and bolts" of implementing a biological control program to manage thrips, aphids, fungus gnats and spider mites in greenhouse crops. There will also be examples of live specimens.

September 18, 2008. Sturbridge Host Hotel and Conference Center. Sturbridge, MA. 4 pesticide recertification credits. Contact: Leanne Pundt, 860-626-6240, leanne.pundt@uconn.edu

Full program here.