Greenhouse TPM/IPM Bi-Weekly ReportCentral Maryland Research and Education CenterEllicott City, Maryland

February 17, 2012From: Stanton Gill, Extension Specialist – IPM for Greenhouse and Nurseries, Central Maryland Research and Education Center, University of Maryland ExtensionKaren Rane, Extension Specialist, Director of the Plant Diagnostic Clinic, University of Maryland ExtensionAndrew Ristvey, Extension Specialist, Wye Research and Education Center, University of Maryland ExtensionSuzanne Klick, Technician, CMREC, University of Maryland Extension

Marketing TipYou’ve heard about Facebook and Twitter, but what about Pinterest? Ellen Frost, Local Color Flowers, showed what this on-line bulletin board site is about at the February 7th cut flower growers meeting in Annapolis. Ellen does floral arranging for a variety of events including weddings and mentioned that she has not had a bride recently who does not have a pinterest site. It is a way for whoever is providing the flowers to see the color scheme of a bride or another type of event. Pinterest.com is a way for growers to show photos of what they are likely to have in bloom in what month, show examples of arrangements and vases or containers used, and other items they have to promote. For an example of a pinterest board, go to http://pinterest.com/locoflo/

Tuliptree scale, 2nd instars, on star magnolia

White peach scale on yellow stick dogwood (left) and curly willow (right)

Scales of Cut Woody PlantsMany cut flower and stem growers are moving into woody plant production. Recently, I received samples from a cut flower grower of willow, plum, quince, yellow stick dogwood, curly willow, lilac and star magnolia. Each sample was infested with soft or armored scale. Horticulturists often overlook scale insects since their covers, for most species, blend in with the color of the bark of the plant and often look like part of the plant. The scale are pretty sneaky in how they have adapted to survive. Because they are hard to spot they build up over several years until you either see the mass build-up of covers or the plant stops producing all of the vigorous growth it used to produce because these plant parasites are covering the stems and feeding on the plant.

The landscape industry in Maryland requested that I develop a factsheet to help professionals identify the different scale insects. We posted this publication at http://ipmnet.umd.edu/landscape/lndscp_pubs.htm. As a cut stem producer you might want to access this publication and use it to help identify the scales that may be building up on your woody cut stem plants.

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Control: The least expensive control for soft and armored scale is applications of 3 – 4% horticultural oil applied when temperatures reach 50 - 55 °F for at least 4 or 5 days. Scale insects reduce their respiration in cold weather, but when temperatures reach 50 - 55 °F then respiration increases. The oil applications act as suffocant, so you want the insect respiration rate to be up to obtain successful suffocation. The application should coat the woody plant stems and trunk with a fine mist.

The other method is to apply an insect growth regulator during the crawler period. To be successful with this treatment, you need to identify the scale species in order to determine when crawlers will be active. The two best insect growth regulators that have minimal impact on beneficial insects are Distance and Talus. They are great products but rather expensive. You may have to go this route if you really let the scale population build up and the oil applications are just not sufficiently reducing the population.

Downy Mildew In ImpatiensSevere outbreaks of downy mildew in garden impatiens (Impatiens walleriana) were reported last fall on landscape plantings in Europe as well as in the US (Northeast, Midwest). Just this month, the disease has been reported in Florida landscapes and nurseries. If you grow garden impatiens, it is important to be on the lookout for this disease. All varieties of garden impatiens (seed or cutting propagated) are susceptible to downy mildew. New Guinea impatiens (Impatiens x hawkeri) are reported to be tolerant of the disease. SunPatiens, a hybrid impatiens developed by Sakata Seeds, is reported to be resistant. The impatiens downy mildew pathogen (Plasmopara obducens) does not infect any hosts other than impatiens.

Symptoms of this downy mildew can be very subtle – slight chlorosis (yellowing) or mottling of leaves, leaf edges curling downward, and plant stunting are early symptoms, followed by leaf drop. Look for the white to grayish white fuzzy growth on the undersides of the yellow or curled leaves as the key sign of downy mildew infection. If you are in doubt, send a sample to the UMD Plant Diagnostic Lab for diagnosis.

Management: Early detection and sanitation are critical parts of a management plan – inspect all new shipments of impatiens for downy mildew symptoms. Discard any symptomatic plants promptly, as well as nearby plants. (put plants in plastic bags right at the bench, before carrying them out of the greenhouse, to keep from spreading the spores through the facility). Do not compost diseased plants. Fungicides effective in controlling downy mildew in impatiens include mancozeb (a protectant), and systemics such as mefenoxam (Subdue Maxx), dimethomorph (Stature), fosetyl al (Aliette), fluopicolide (Adorn, must be tank-mixed with another downy mildew product according to label), and the combination product Pageant (pyraclostrobin+ boscalid). Make sure to alternate products with different modes of action (Group or FRAC codes). Ball Horticulture has released a fact sheet on impatiens downy mildew with detailed information on the disease cycle and management, which can be found at the following link: http://www.ballhort.com/pdf/ImpatiensDownyMildewGrowerGuidelines.pdf

White growth of impatiens downy mildew pathogen on lower leaf surface Photo: M. Hausbeck, Michigan State University

Stunting and yellowing, curled leaves of impatiens plant infected with downy mildew Photo: M. Hausbeck, Michigan State University

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Biological Control Options for Interiorscapes and GreenhousesAt the Chesapeake Green conference on February 9th, Carol Glenister, IPM Labs Inc., covered the top 7 ben-eficials for controlling pests in interiorscapes. These organisms work in production greenhouses as well. The following are the top three on the list.

On Carol’s list, beneficial nematodes for fungus gnat control were number one. Often, the nematodes are applied using watering cans. Small sprayers can be used in both interiorscapes and production greenhouses. Be sure to remove the screen on the sprayer to prevent clogging the nozzle. Keep the solution agitated because the nematodes tend to clump and will fall to the bottom of the watering can or tank within minutes. Use cold water since beneficial nematodes do not do well in heat (>90 °F). The nematodes will drown if the solution is not agitated for over an hour. Do not use if nematode solution sits overnight. If treating after an outbreak of fungus gnats, make 2 – 3 weekly applications.

The next two beneficials on the list are the predaceous mites, Neoseiulus californicus and Mesoseiulus longipes, which tolerate low humidity levels and high temperatures. N. californicus tolerates the highest temperatures of the available predaceous mites. It is a slow acting (long lasting) mite. These two predaceous mites are also sold for spider mite control as a combination so releases do not need to be made each week. The recommendation is to release again after 2 – 6 weeks or when necessary. Monitor plants for the presence of predaceous mites (look for mites with long legs that are fast moving). Predaceous mite eggs are 3 – 4 times larger than pest mites and are long, not round. Reapply predators if there are more than 30 pest mites to one beneficial mite. Washing plants in interiorscapes often wipes out the predator population. Both species reproduce in interiorscapes. The predaceous mite, Phytoseiulus persimilis, does not reproduce in interiorscapes because the environment is too dry.

Factors To Consider Before Releasing Beneficial Organisms• Identify the pest in order to choose the correct beneficial for control.• Avoid pesticides that are toxic to the beneficials (it might be necessary to knock down the pest population to

increase the effectiveness of the beneficals which do not reproduce as quickly as the pests).• Know when the beneficials will arrive and be ready to release them immediately. • Check the viability of the shipment.• Beneficial nematodes are the only beneficial organism that requires refrigeration. For the others, check the

shipping package for the temperature. If warm, predator survival could be low. Predators can be stored at about 50 °F (which is the temperature in packaging with a cold ice pack).

• It is best not to hold overnight if at all possible. Do not hold over the weekend before releasing.

Twospotted spider mites, including orange-red overwintering females

Fungus gnat larvae on pansy stem

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Perennial Manual (revised edition) is now available!

Cost: $25 (includes shipping)

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The information given herein is supplied with the understanding that no discrimination is intended and no endorsement by University of Maryland Extension is implied.

Read labels carefully before applying any pesticides.

Photographs are by Suzanne Klick, Shannon Wilhelm and Stanton Gill unless stated otherwise.

University of Maryland Extension programs are open to all citizens without regard to race, color, gender, disability, religion, age, sexual orientation, marital or parental status, or national origin.

Invasive Species ProgramMarch 21, 2012Location: Carroll Community College, Westminster, MDContact: Suzanne Klick, 301-596-9413ipmnet.umd.edu

ASCFG Mid-Atlantic Regional MeetingJune 18, 2012Roost Flowers and DesignLocation: Virginia Beach, Virginiaascfg.org

2012 Perennial Plant SymposiumJuly 4 - 10, 2012Location: Boston, Massachusettsperennialplant.org

OFA Short CourseJuly 14 - 17, 2012Location: Columbus, Ohioofa.org

OFA Perennial Production ConferenceSeptember 10 - 12, 2012Location: Grand Rapids, Michiganofa.org

ASCFG National ConferenceNovember 12 - 14, 2012Location: Tacoma, Washingtonascfg.org

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