Scouting and Decision Making

A regular monitoring program is the basis of integrated crop management (ICM) decision making, regardless of the control strategies used. By regular monitoring, a scout is able to gather current information on the identity and location of problems and to evaluate treatment effectiveness. The following are the basics for an effective greenhouse scouting program.

Tools.
Essential monitoring tools include:

• Trained personnel
• Handlens with 10X power and/or optivisor (headset with magnifying glass)
• Yellow sticky cards, clothes pins, bamboo stakes
• Flagging tape or colored flags
• Record keeping system, ie. clipboard and pen or small notebook
• Individual maps of all greenhouses
• Support labs and on-site diagnostic kits for disease diagnosis
• Support labs and solubridge for soil tests
• Resource information such as pesticide labels, pictures and life cycles of key pests

Optional tools include:

• Soil thermometer
• Field microscope (30X)
• Potato chunks (to monitor fungus gnat larvae)
• Waterproof magic marker to label sticky cards

Pre-Crop site evaluation.
Prior to the introduction of a crop, evaluate the entire greenhouse, inside and out. Note the presence of weeds in and around the greenhouse, drainage problems, algae build-up, pet plants, stock plants and debris under benches. Crops growing in adjacent greenhouses, or outdoors should be recorded. Previous pest problems in the greenhouse and current pesticide application methods should be reviewed. A plan of action may then be developed to eliminate these problems prior to the arrival of the crop. Prevention of key pest problems may be more easily accomplished if the grower and scout take the time to identify, analyze and correct problems before crops are introduced. Also, consider how the variety of plants to be grown in the same area may influence ease of pesticide applications and spread of disease. For example, keep seedling and cutting geraniums separate to help minimize spreading bacterial blight. Keep propagation houses separate from other growing areas, and vegetable transplants separate from ornamentals to help reduce the incidence of impatiens necrotic spot virus when western flower thrips are present. Note that most pesticides labeled for ornamentals are not labeled for vegetable and herb plants.

Inspection of incoming plants.
At the time of arrival or soon after, the scout should inspect one-third or more of the plants. Thoroughly examine the plants for signs of insects and diseases. (See chart.) Early detection and prompt action can minimize the spread of insects and diseases and save pesticide applications.

Using sticky cards.
Sticky cards are used to detect infestations of adult flying insects. Yellow colored cards will attract fungus gnats, shore flies, whiteflies, thrips, leafminer flies and winged aphids. Blue colored traps are more attractive to thrips, although it is more difficult to see the thrips against the blue background. Attach each card to a wire or wood stake using a clothespin. Using two clothespins glued back-to-back will allow you to move the card upwards as the plant matures. Attach one end of the clothespin to a stake and clip the card to the other clothespin.

Each yellow sticky card should be numbered and placed in the greenhouse at the minimum rate of one card per 1,000 sq.ft.. Space the cards equally throughout the entire range in a grid pattern. Place cards near all entryways and vents. Small greenhouses (<4,000 sq.ft.) can be scouted as one unit. Larger greenhouses should be divided into 2,000 to 3,000 sq.ft. sections for ease of scouting.

Change the cards weekly, and place new cards in the same areas of the greenhouse to track pest trends. Brief, concise and accurate information is one of the best tools available to make a pest management decision. Identify and record pest numbers in a notebook or clipboard. Over time, population trends will emerge and provide direction for your pest management program.

Scouting and Monitoring.
Scouting and monitoring should be performed weekly or, preferable, twice weekly during the entire production season. Scouting procedures should be performed as routinely as any other crop management task. Maps should be made of the greenhouse and scouting should follow the same pattern every time. Scouting must be intensive; the more plants monitored the better. Scouting should always start at the major doorway, which is usually an entry point of pests. Special attention should be paid to plants around any openings in the greenhouse.

Scouts should walk every aisle and move from bench to bench in a snake-like manner. At least 10 minutes should be spent inspecting 20 or more plants for every 1,000 square feet of production area. Three or more randomly chosen plants on every bench should be inspected. Inspection starts at the bottom of the plant by checking the soil for insect, mite or disease pests and proceeds upwards, looking at older leaves, young leaves and new growth. Pots should be tipped sideways for inspection of the underside of the leaves. Hanging pots and baskets should also be inspected. The first plant showing symptoms on a bench becomes an indicator plant. This plant is tagged to allow the scout to easily recognize it from a distance.

Indicator plants.
Indicator plants can be used in three ways:

1. to examine the pest's development cycle
2. to monitor the effectiveness of a treatment
3. to detect the early presence of Impatiens Necrotic Spot Virus (INSV) and thrips on petunias or fava beans.

Indicator plants should be marked and numbered with a colored flag or flagging tape so the scout can identify them quickly each week.

Making pest management decisions.
Each week, the grower and scout should review the scouting information. Pest numbers recorded from sticky card counts and foliar inspections, the use of indicator plants, and located reservoirs of pests and diseases will help to prioritize a pest management strategy. Once this information is analyzed, a decision must be made that will include; the choice of pesticide or biological control, the rate, method and site of application; and any other management techniques that may help solve the problem. Every pest management action should be recorded. Monitoring is an ongoing part of the management strategy.

Early detection will result in better pest management than a pest population that is "out of control". If problems are detected early, better pesticide coverage may be achieved due to a smaller canopy, and problem areas can be identified and treated reducing the need for blanket pesticide applications. In addition, "green pesticides" and biological controls may be more successfully incorporated into the pest management program. Over time, growers will determine their individual threshold for a given pest. One grower may accept 10-15 thrips per sticky card per week, while another grower with a history of Impatiens Necrotic Spot Virus will not accept 5 thrips per card per week.

Another important aspect of integrated crop management is crop culture. Crop culture involves plant nutrition, crop scheduling, height management, watering practices, temperature and light management.

At the end of each season, the grower and scout should examine their records to identify trends in pest populations and to review their management strategies. The weekly scouting reports and action taken is the basis for decisions about current and future pest management strategies and for judging the efficacy and cost of any management action.

Resources for Greenhouse Pest Management:

2003-2004 New England Greenhouse Floriculture Guide, $20 available from UMass Cranberry Station, PO Box 569, E. Wareham, MA 02538.

New England Integrated Pest Management Scouting Guide for Poinsettias, $10 available from: Univ. of Conn., Office of Communication and Information Technology, U-35, 1376 Storrs Rd, Storrs, CT 06269-4035.

Integrated Pest Management for Bedding Plants, A Scouting and Pest Management Guide, IPM No. 407, available from: Cornell University, NY State Ag. Exp. Station, Geneva, NY 14456.

KEY PEST	MONITORING GUIDELINES	WHERE TO LOOK/COMMENTS
Melon Aphid (Aphis gossypii)	Rely on plant inspection, not sticky cards. Scout weekly, beginning early in the cropping cycle. Aphids are 1/16 inch long with dark cornicles. Melon aphids are less likely to form winged adults than green peach aphids.	Inspect incoming plant material, on underside of leaves and stems. Most likely found along the plant stem then on the growing tip.
Green Peach Aphid (Myzus persicae)	Monitor weekly. Rely on plant inspection, not sticky cards. Winged adults are found on cards when aphid colonies on weeds and crops become overcrowded.	Look on tips of new growth for 1/14 inch long green to pinkish aphids. Look for signs of aphid activity: shed white skins, honeydew, and presence of ants. Inspect and remove weeds.
Western Flower Thrips (Frankliniella occidentalis)	Rely on sticky cards for population trends and to evaluate treatments. Use cards at floor level to detect overwintering thrips in Feb. Place cards at bench level, just above crop canopy in March before damage is observed.	Inspect incoming plant material for adults and larvae by tapping tender new growth and flowers over a white sheet of paper. Keep plants isolated for 4-5 days to detect thrips emerging from eggs and pupae. Inspect and control weeds, particularly white clover flowers outside greenhouses.
Whiteflies (Bemisia tabaci, Trialeurodes vaporariorum)	Rely on plant inspection to detect immature stages, esp. on cuttings and young plants. Use indicator plants to assess treatment effectiveness esp. if using insect growth regulators. Use sticky cards to monitor adults.	Older (3rd and 4th) instar immatures are found on lowermost leaves, egg laying adults on the uppermost leaves. Inspect and remove weeds and “pet plants”.
Fungus Gnats (Bradysia sp.) Shore flies (Scatella stagnalis)	Use yellow sticky cards to monitor for adults. Place some cards flat on rim of pot and others, horizontally just above soil surface to capture adults. Use potato chunks (pealed side inserted in soil) to monitor larvae. Examine daily.	Favorable habitats include areas with standing pools of water, mud floors and weeds. Potting mixes high in organic matter tend to attract fungus gnat activity. Adult shore flies spread pathogens and thrive in the same wet conditions that are attractive to fungus gnats.
Two spotted mites (Tetranychus bumaculatas)	Rely on plant inspection. Look for light stippling, discolored foliage, and webbing if high populations have developed.	Inspect incoming plants for mites, esp. on undersides of leaves by tapping leaves over a white sheet of paper. Monitor closely near hot, dry areas in greenhouse (ie. near steam pipes)
Pythium root and stem rots (Pythium sp.)	Visually examine roots for cortex that “sloughs off” leaving central core. Healthy roots are generally white and firm; decayed roots may be water-soaked and/or darkened in appearance. Stem cankers are brown to black.	Monitor incoming plants and plants that may have been stressed by high salt levels, wounding, and transplant shock especially if fungus gnats or shore flies are present.
Rhizoctonia root rot, stem canker and web blight (Rhizoctonia solani)	Monitor seed flats of slow growing plants for post emergence damping off. Look for cobwebby growth encouraged by high humidity and wet foliage.	Unlike pythium, drier soil is more favorable for disease development and therefore it is found in the upper portion of the soil.
Botrytis Blight (Botrytis cineraria)	Monitor closely during favorable conditions, ie. cool temperatures, free moisture and presence of fuzzy gray to brown fungal spores. Flowers may fade early and then mat together.	Plants may be attacked at any stage but new tender growth, freshly injured tissues and senescing or dead tissues are preferred. Look for tan to brown dead areas, and gray fungal growth. Monitor areas with poor air circulation, and crowded plants.
Powdery Mildew (Erysiphe sp. Oidium sp.)	Look for white powdery growth esp. on upper leaf surface of roses, begonias, viola, phlox, chrysanthemums. On poinsettias, look for white or yellow spots on upper leaf surface.	Monitor closely in areas with poor air circulation, high humidity, or drafty places with more temperature fluctuations between day and night temperatures.
Bacterial Blight (Xanthamonas pelargonii)	Inspect geraniums more closely during warm weather. Look for isolated leaf wilting, V or wedge shaped yellowing between veins, and 1/8 round, brown spots. Look for vascular discoloration. Plants may wilt and die.	All geraniums are susceptible. Do not place ivy geraniums over geraniums. When infected, ivies often do not show any distinct symptoms, perhaps only loss of vigor, and will serve as inoculum source. Monitor areas closely with geraniums from different suppliers.

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Tina M. Smith, Floriculture Program, University of Massachusetts Extension
Leanne Pundt, Cooperative Extension System, University of Connecticut

Information on our site was developed for conditions in the Northeast. Use in other geographical areas may be inappropriate.

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