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FACT SHEETS >PEST MANAGEMENT > PEST MANAGEMENT IN RETAIL GREENHOUSES Pest Management in Retail Greenhouses Choices for greenhouse pest management vary depending on the size of a greenhouse and how a greenhouse is used. Basic integrated pest management practices such as inspecting incoming plants, weekly monitoring, sound cultural practices, pest identification and problem diagnosis are similar, whether a greenhouse is used for production or for retail sales, or whether the greenhouse is 3,000 sq. ft. or 30,000 sq. ft. in size. However, choices for management once pests are detected, can be very different depending on whether a greenhouse is used for small scale or large scale retail sales, or small scale or large scale production. Retail greenhouses have many challenges for managing pests that are different from production greenhouses. Retail greenhouses are open to the public, usually for long hours and often 7 days a week, making the timing of pesticide treatments difficult. These greenhouses contain a variety of mature plants ready for sale, often with delicate blooms. Plants arrive regularly from many different sources increasing the likelihood that pests will be brought into the greenhouse. Some plants are quickly sold while others remain in the greenhouse for long periods of time. The longer that plants stay in the greenhouse, the probability increases that insects will migrate to these plants. Another challenge is that many retailers now showcase gifts and other hard goods like wind chimes, knick-knacks and stuffed toys in their retail greenhouse and must be considered when treating plants for pests. Many retail greenhouses have a high rate of employee turnover and employees with little experience in basic plant care or pest management. Providing basic training to employees on insect and disease identification will prevent major outbreaks and save time and money. Training is especially important for employees receiving incoming plants. Also, basic training on the proper care and maintenance of plants will help to prevent cultural problems and conditions favoring disease outbreaks Incoming Plants Seasonal retailers open for the spring season, should monitor incoming plants carefully for aphids, whiteflies and thrips. They should also carefully inspect incoming plants for diseases such as powdery mildews, downy mildews, Botrytis blight, crown and root rots, and symptoms of virus infection or foliar nematodes. Greenhouses open year-round will have continuous incoming shipments of plants that need to be carefully inspected for a wider range of pests including aphids, whiteflies, thrips, mites, scale, mealybug, root mealybugs, fungus gnats and shore flies in addition to diseases previously mentioned. Both types of businesses should also have a weekly monitoring program in place. Year-round businesses will need to address pest problems on foliage plants, holiday crops and plants that remain in the greenhouse for extended periods of time. Incoming shipments of holiday plants will need to be inspected and monitored closely for specific pests, for example, whiteflies and Botrytis blight on poinsettias or aphids and root rots on lilies. Both types of businesses will need to inspect all incoming shipments of plants and reject those with pest problems. Conduct random sampling when plants arrive, taking plants out of the containers when possible and inspecting roots. When opening boxes, be able to recognize flying insects such as adult whiteflies, fungus gnats and shore flies. Adult whiteflies may be a sign that there are additional whiteflies on plants in immature stages. If adult fungus gnats are observed, inspect the plant stems at the soil line and roots for any damage. Observe new growth on plants for signs of thrips or aphids. Signs of thrips activity include distorted new growth or curled leaves. Signs of aphid infestation include empty white skins, curled new growth and shiny honeydew. If only a few incoming plants have aphids, you can try a forceful jet of water to hose off the aphids. Caterpillars will chew holes in the leaves, and are found primarily on perennials. If you notice a few caterpillars, they can be quickly handpicked and destroyed. Adult black vine weevils, also a pest on perennials, will notch the edges of leaves and will feed at night or on cloudy days. These can also be handpicked and destroyed before they overwinter at the garden center and become a persistant problem. On shipments of foliage plants, inspect stems, petioles and under leaves for scale and mealybug. Look for stippling on foliage for signs of mites. Inspect the underside of leaves along the leaf veins for adult mites, their eggs and any white, empty egg shells. If only a few incoming plants have mites, you can try washing off the underside of the leaves to wash off the mites. Knock plants out of containers and inspect the root systems for insect activity such as root mealybug or root aphids, or root diseases that cause root rot. If you find insect activity and decide to keep the shipment, quarantine the plants from others in the greenhouse and treat immediately. Plants with root rot diseases will unlikely recover in a reasonable length of time for retail sale even after treatment. Plants with viral or bacterial diseases or foliar nematodes will not recover and should not be accepted. Plants infected with viral diseases may show symptoms such as a mosaic pattern (a pattern of yellow and green, healthy tissue on the same leaf), leaf distortion, yellow streaking, ring spots, or unusual line patterns. Plants infected with bacterial diseases may show a greasy or water-soaked appearance to the leaves. Plants infected with foliar nematodes can have off color leaves with brown angular spots with a distinct margin. You may see a patch-like symptom that resembles a fungal leaf spot disease. Monitoring Retail greenhouses should have a weekly, integrated pest management (IPM) program in place to detect problems early. A regular monitoring program using sticky cards and plant inspection is the basis of all pest management programs. Early detection and treatment will result in better pest control, while pest populations are low and before pests move throughout the greenhouse. Retailers will find through experience that some plants will need to be monitored more carefully than others throughout the course of a year. Using Sticky Cards Yellow sticky cards are recommended to detect adult stages of fungus gnats, shore flies, thrips and whiteflies. Use small, 3" X 5" cards and change them each week to keep track of hot spots and to prevent them from becoming unsightly. Attach cards to a bamboo stake and place the stake in an empty pot of soil, or wood block with a hole drilled in it to hold it upright. This will keep sticky cards separate from plants for sale. Place cards horizontally throughout the greenhouse at a rate of at least one card per 1000 sq. ft. Place some cards just above the plant canopy (to detect thrips and whiteflies) and some cards at pot rim level to detect fungus gnats. An explanation displayed to customers would be helpful and a good marketing too, something as simple as a sign saying, "The yellow sticky cards you see help us to trap pests, use fewer pesticides and keep plants healthy". Plant Inspection Plant inspection is needed to assess general plant health and to detect diseases, mites, scale, mealybug and aphids plus any hot spots of immature whiteflies. Since most retail greenhouses are hand-watered, general observations can be made while watering, in addition to a regular weekly inspection. To conduct a weekly inspection, randomly select plants at ten locations in an area of 1,000 sq. ft., examining plants on each side of the aisle. Start this pattern at a slightly different location each week, walking through the greenhouse in a zigzag pattern down the walkway. Use a 10x handlens to examine the underside of leaves for insect pests and inspect root systems to determine plant health. Record-keeping Record information collected from sticky card counts and plant inspection including the pest numbers and their location, root health, overall plant health and the numbers and species of plants inspected. Records of pest numbers and locations will help to identify sources of pests and indicate whether treatment is needed or if control measures were successful or need repeating. Monitoring and record keeping will help to determine if the pest population decreased, increased or stayed the same since treatment has begun, if treatments need to continue and where pests coming from. Are insects established in the greenhouse on weeds, or on a specific plant or group of plants, or did they arrive with a new shipment? Decision Making Diagnosis Know specifically what pest you are treating. Accurate diagnosis is key to management whether you choose pesticides or biological control. Many pesticides and most natural enemies are often specific to just one pest or group of pests. If you are having trouble diagnosing a problem, visit the University of Massachusetts Extension website: www.umass.edu/umext/floriculture and click diagnostics. Cultural control Improper cultural practices can encourage disease development. For example, most varieties of phlox and bee balm when placed in the shade will develop powdery mildew. Retailers can prevent powdery mildew and other diseases by choosing varieties of plants that are disease resistant whenever possible and by using proper cultural practices. Plants that are overwatered will promote root diseases. Plants that have wet foliage for extended periods of time will develop foliar diseases. Space plants so that they are both attractive to the customer and sufficient to promote good air circulation. This will help prevent Botrytis and other foliar diseases. Promptly rogue out any plants that show signs of diseases. Train workers to regularly clean and groom plants so they are attractive and free of disease. Aprons with pockets are useful to hold debris from groomed plants until it can be disposed of properly. Train employees to properly water plants to avoid overwatering and be sure plants are watered early in the day so that the leaves dry quickly. It is difficult to control pests in a year-round greenhouse, once pest populations are established. To prevent establishing populations, it is important to discard leftover plants whenever possible, monitor and treat any plants that are held over each year. Retail greenhouses will sometimes hold over plants that do not sell during a holiday period which will serve as a source for pests. Choosing Pesticides There are many pesticides available for greenhouse use. See table1 and table 2 for selected pesticides labeled for greenhouse use. Additional pesticides and more detailed information is available in the 2005-2006 New England Floriculture Guide, A Management Guide for Insects, Diseases, Weeds and Growth Regulators.. Consider the pesticide container size and recommended application rates with regard to storage, shelf life and purchase price. Some pesticides sold as water soluble packets for safe handling, may have recommended application rates of 1 packet per 100 gallon of water. Other pesticides are sold in large quantities relative to small, recommended application rates. This is not a problem for large greenhouses, however, small retailers will not use enough pesticide to justify the expense. Greenhouses open year-round may invest in a wider selection of pesticides because they are used more often than a seasonal business. For best results, it is recommended that pesticides be used within one or two years. When choosing a pesticide, also consider how many different crops are listed on the label, the restricted entry interval (REI), pesticide residue and plant and blossom safety. See the websites at the end of this article to review pesticide labels, before purchasing a product. The REI is located on the pesticide label and is the length of time between treatment and when the treated area or the greenhouse can be re-entered, depending up the pesticide's label. Most pesticides for greenhouse use will have a re-entry period of 4-24 hours. A few will have 48 hour REI. During busy times of the year, the REI may influence which material to choose. When REI is a concern, and only a few plants are infested, some retailers remove plants from the greenhouse to treat them. This is also the best option if gifts and other hard goods are displayed in the greenhouse. Plants can be brought outdoors to treat, if weather is favorable, or to a production greenhouse, if available. Some pesticides will leave an unsightly residue or burn blooms and some pesticides will specifically be labeled, safe for blooms. Check the label, the 2005-2006 New England Greenhouse Floriculture Guide or with a technical representative for the pesticide before purchasing a pesticide for information on plant and bloom safety. Worker Protection Standards In addition to REIs, there will be reference to the Worker Protection Standard (WPS) in the "Agricultural Use Requirement" section on the label. The WPS contains requirements for training, decontamination, notification, and emergency assistance. It also contains specific information about personal protective equipment and REIs. Horticultural employers who use pesticides and who have one or more employees must comply with all of the provisions of the WPS. Owners of agricultural establishments and members of their immediate family are exempt from some WPS requirements. However, they must observe the appropriate REIs and must use the proper personal protective equipment listed on the pesticide label. Every retail greenhouse manager should have a copy of the following publications to explain responsibilities and comply with WPS, including the training of employees. These publications are available from: Gemplers - 1-800-382-8473, www.gemplers.com
Questions pertaining to Worker Protection Standards can be answered by your state Department of Agriculture or Extension Specialist. In Massachusetts , questions pertaining to WPS can be answered by contacting one of the following individuals:
Pesticide application methods for small retail greenhouses Pesticide application methods will vary according to the size of the greenhouse. Hand-pump sprayers are used in many small greenhouses for pesticide applications. This method is adequate for spot treatments but is not the best choice for treating an entire greenhouse. It is difficult to maintain continuous pressure and the spray coverage is likely to be uneven as the pressure changes when using a hand-pump sprayer. For some greenhouses a better choice would be a small generator sprayer that provides constant pressure for uniform application. This equipment is likely to be more expensive than hand-pump sprayers, but will result in better pest management. Some small retail greenhouses may also choose total release pesticides that are safe for blooms and require no special application equipment. Coverage will be inadequate on large mature plants and has limited effectiveness against many pests, such as immature whiteflies. Total release pesticides should not be used in retail greenhouses that contain hard good gift items. Biological control Biological control is an option on plants that will remain in a greenhouse for an extended period of time. Natural enemies are living organisms that need to be released when pest populations are low and are not effective for clean-up, once high populations of pests are established. They can be used for aphids, fungus gnats, mealybugs, mites, thrips, scale, and whiteflies. Choosing natural enemies and a release schedule will need to be customized according to the specific pests and populations, size of the greenhouse, size and number of plants in the greenhouse, and how long plants will be in the greenhouse. As suggested with the use of sticky cards, retail greenhouses using natural enemies may also want to display information to their customers about their use of natural enemies. Information on using natural enemies can be obtained from the floriculture website, www.umass.edu/umext/floriculture and from the 2005-2006 New England Greenhouse Floriculture Guide . References: Websites for Companies, Pesticide Labels and MSDS listed in this article.
2005-2006 New England Greenhouse Floriculture Guide . Make check for $25 payable to University of Massachusetts and send to P. Lopes, Cranberry Experiment Station, Glen Charlie Rd. , East Wareham , MA 02538-0569 . Distributors for Pesticides and Other Pest Management Products
Distributors for Biological Control Products
For contact information for additional commercial suppliers, see Suppliers of Beneficial Organisms in North America by Charles Hunter, available from the California Environmental Protection Agency, available online at http://www.cdpr.ca.gov/docs/ipminov/bensuppl.htm TABLE 1. SELECTED INSECTICIDES LABELED FOR GREENHOUSES
TABLE 2. SELECTED FUNGICIDES LABELED FOR GREENHOUSES
*Consider the recommended application rate and the available container sizes to help choose a pesticide for small greenhouses. Prepared by: |
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