Scouting Notes - December 2007

Deer can be picky. A Maryland cut flower grower has learned deer can be as picky as humans when it comes to which plants they prefer. With hydrangeas, ‘Endless Summer’ and ‘Limelight’ are the varieties of choice rather than ‘PeeGee’. Deer at the same location also fed on Hydrangea arborescens, Eryngium ‘Blue Glitter’ and Ilex verticillata ‘Winter Red.’ Other deer delectables include ornamental cabbage and kale and lilies. When it comes to pansies, yellow- and white-flowered plants are eaten before other colors.

For more: University of Maryland Cooperative Extension, (301) 596-9413; www.agnr.umd.edu/ipmnet.

Minimize growth regulator overdose. During the cold, cloudy weather of winter, there is a chance that growers could encounter a plant growth regulator overdose. University of Connecticut extension specialist Rich McAvoy said if an overdose spray of Cycocel or B-Nine (or a generic equivalent) is applied and the mistake is discovered before the spray dries (usually within 30 minutes of application), the material can be washed off with water and the damage avoided.

Diluting the chemical is not an option with products like Bonzi, Sumagic, Topflor or A-Rest. If the overdose is modestly high (25-50 percent too high a rate), environmental conditions that minimize stress may be enough to allow the plant to recover without further action. Adequate light levels, increased temperatures, increased fertilization and reduced water stress favor rapid growth, enabling plants to outgrow the adverse overdose effects. In situations where the dose is too high to correct in this way, a gibberellic acid treatment can be used to reverse the effect of the growth regulator.

For more: Rich McAvoy, University of Connecticut, Department of Plant Science; (860) 486-0627; www.negreenhouseupdate.info.

Screening detects Xanthomonas on geraniums. Bacterial blight caused by Xanthomonas campetris pv. pelargonii is one of the most destructive diseases of geraniums. Zonal geraniums are particularly susceptible to infection by this bacterium.

Researchers at University of Toledo devised a screening technique using polymerase chain reaction (PCR) to rapidly detect the presence of the pathogen before onset of symptoms. The resolution of this test is high and as few as 10 cells of the bacterium indicate a confirmation.

The researchers used PCR to screen 17 geranium species/cultivars for the presence of Xanthomonas and found that PCR could detect the bacterium as early as before the symptoms became visible. Efforts will now be made to design a workable, sampling protocol to screen incoming plugs. The specific objective, said University of Toledo professor emeritus Stephen Goldman, is to collect samples in an accountable manner, enabling a definitive diagnosis for infection at selected, expert testing laboratories.

For more: Stephen Goldman, University of Toledo, Department of Environmental Sciences, (419) 277-0290; www.eeescience.utoledo.edu.

Bandedwinged whitefly migrating into Maryland greenhouses. Some growers were seeing bandedwinged whitefly (Trialeurodes abutiloneus) migrating earlier into greenhouses from surrounding agricultural field crops, University of Maryland Cooperative Extension reported. The whitefly entered earlier than usual this year from weeds and field crops, including soybeans, killed by drought conditions. This usually occurs in late-September to mid-October after crops and weeds dry down.

Bandedwinged whitefly feeds on ornamental crops like cabbage, kale, asters and poinsettia. In previous years, this whitefly has also been found on petunia, geranium and hibiscus during the spring.

University of Florida entomologist Lance Osborne said bandedwinged whitefly were present in very high numbers on cole and cotton crops in Florida and Georgia during September, but that the silverleaf whitefly (Bemisia tabaci) was the main one being found there.

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For more: University of Maryland Cooperative Extension, Central Maryland Research and Education Center, (301) 596-9413; www.agnr.umd.edu/ipmnet.