Ornamental Crops IPM E-newsletter, 2006
|Welcome||Indicator plants, Trap crops, and Banker plants: Tools for Greenhouse IPM|
|Hosta Virus X||Links and Contacts|
Welcome to our first e-newsletter, the purpose of which is to provide regular integrated pest management updates to commercial horticulture educators in the Cornell Extension system and others that are in the position to disseminate information. It is our intent that the content from theses updates will be used in newsletters and programs that reach New York growers.
At this point we plan to send these updates out on a quarterly schedule (March, June, September and December). We welcome your feedback on the content or format of the information. We would appreciate it if you would let us know when and where you are using the content. This will help us determine the types of information that are useful for you and your programs. To subscribe to the email version of this newsletter, contact Brian Eshenaur firstname.lastname@example.org.
Thanks and Best Wishes for 2007!
Indicator Plants: The diversity of plant species in an area can be used to indicate something about the environment: ground ivy in shady lawns, rhododendrons in acid soil, etc. In the same way, species or varieties that are more susceptible to an insect or disease than the desired crop can be used to indicate when that pest has appeared in the greenhouse. Some common greenhouse examples are potato chunks used to check for fungus gnat larvae (not quite an indicator plant, but the same principle) or specific cultivars of petunias grown as indicator plants for impatiens necrotic virus or tomato spotted wilt virus on a variety of ornamentals. Tomato or eggplant can be used as an indicator of whitefly infestation in poinsettia crops. It is important that the disease or insect be identified rapidly on the indicator plant, before it moves onto the crop, so scouting is still essential when using indicator plants.
Trap crops are also species or cultivars that are more attractive to a pest than the crop, but in trap cropping, the pest is controlled on the trap crop. This system has most often been used in field crops for insect control, where the trap crop is planted around the perimeter of the crop plant to attract insects moving in from outside the field. Some examples are: collards as a trap crop for diamond back moth in cabbage, Hubbard squash for cucumber beetles in other Cucurbitaceous plants, and cherry peppers for pepper weevil in bell peppers. Once the insect is found on the trap crop, only those plants are treated, reducing the amount of chemical pesticide needed. Perimeter trap crops can be used in the greenhouse, but it is more useful to intersperse the trap crop in the desired crop, as it is less likely that insects will be coming into the crop from outside. A set of plants could be positioned near wall vents to monitor insects coming in from outside the greenhouse, however. In addition to tomato or eggplant in poinsettia, gerbera or verbena or a more susceptible cultivar of chrysanthemum have been used to protect chrysanthemum from western flower thrips. The trap crop can be treated before or after it goes into the greenhouse, depending on the chemicals available for use.
Banker plants take the same concept one step further for biological control in greenhouse crops. In this case, the banker plant is used to rear insects that act as an alternative food source for the biocontrol agent, to reduce dramatic changes in its population. The most commonly used banker plant system is a grass, such as wheat or barley, infested with a grass-preferring aphid species, such as bird cherry or corn leaf aphid, to control melon or green peach aphid in ornamental or vegetable crops. The predators or parasitoids are very mobile and can use either the pest population on the crop or on the banker plant as host. There is interest in using the pest population itself as part of a banker plant system, by using the more susceptible cultivar or species, like the indicator or trap crop, as a banker plant. Because the banker plant is infested earlier, predators and parasitoids could colonize it and the population of biocontrol agents would increase before the crop was infested.
For more information, contact Betsy Lamb at 607-254-8800, email@example.com
PowerPoint Presentation: Trap crops, indicator plants, and banker plants: Tools for IPM in greenhouse production. Download 1 MB file
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Hosta virus X was prevalent on hostas from wholesalers and retail establishments throughout NY and much of the nation over the past two years. Unfortunately, retail customers who purchase infected plants will likely be disappointed in their performance and the virus may spread to healthy hostas in their landscape. This could lead to the loss of a market for this popular perennial. To help avoid problems, look closely at stock before accepting new plants from suppliers. Below is information on this virus in fact sheet format.
Host Plants: Hostas are the only known plant to be infected by this virus.
Pathogen: The disease causing organism is a virus particle in the potex group. (That's where the X comes from.) The virus particles are so small they only can be seen with an electron microscope. This virus can only reproduce inside living hosta cells and once inside the plant it remains there for the life of the plant, but it can make plants unsalable.
Symptoms: Stunted growth, leaf distortion and various patterns of leaf discoloration are common symptoms of this disease. The symptoms vary among different cultivars. Rarely will Hosta Virus X kill a plant, but it can make plants unsalable.
Spread: Unlike many plant viruses, insects are not known to spread this disease. Any type of a mechanical injury that moves plant fluids, however, can transmit this virus. Thus, virus spread can occur from pruning tools when cutting off old leaves or removing flower scapes. Other possible means of spread in the landscape include string trimmers, shovels and even manual transmission, if hands become contaminated with sap from infected plants.
Control: There is no cure for infected plants. The best means for avoiding this disease is to carefully inspect all plants before they enter the nursery or landscape. Unfortunately in recent years a large percentage of certain varieties of hostas available from wholesalers were infected with this virus. Check with your source of plants and see if they have a testing program - or consider having suspect plants tested yourself. A test for hosta viruses will cost at least $25, so testing will be most appropriate when deciding weather to discard a large number of plants.
Some of the hosta cultivars that are most often found to be infected in nurseries and garden centers include Gold Edger, Gold Standard, Golden Tiara and Sum and Substance. Watch these cultivars especially carefully for virus symptoms, and discard suspicious plants.
For more information, contact Brian Eshenaur at 585-461-1000, firstname.lastname@example.org
(Photos by Margery Daughtrey, Plant Pathologist, Cornell University, Long Island Research and Extension Center.)
Cornell IPM Team for Production Ornamentals:
State Coordinator for Ornamental Crops IPM
Ithaca, NY, email@example.com
Eastern New York Specialist
Western New York Specialist
Rochester NY firstname.lastname@example.org