Monitoring

A regular monitoring program is the basis of all pest management programs. Conduct a regular, weekly scouting program to detect problems early. This early detection and treatment will result in better pest control since plant canopies are smaller and better spray coverage can be achieved.

Yellow Sticky Cards

Use yellow sticky cards to trap and detect adult stages of fungus gnats, thrips and whiteflies. Place one to four cards per 1,000 square feet. The cards should be spaced equally throughout the greenhouse in a grid pattern with additional cards located near doorways and vents. Place some cards just above the plant canopy (to detect thrips and whiteflies) and some of the cards on the rim of the flats or pots to detect fungus gnats. Inspect and replace the cards weekly to keep track of population trends.

Plant Inspection

Plant inspection is needed to assess general plant health and to detect diseases, mites and aphids plus any hot spots of immature whiteflies. Randomly select plants at ten locations in an area of 1,000 square feet, 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. Examine the underside of leaves for insect pests and inspect root systems to determine whether they are healthy.

Key Plants and Indicator Plants

Focus on scouting key plants and indicator plants. Key plants are those plants or cultivars that have serious, persistent problems every year. For example, peppers and eggplants are prone to aphid infestations. Look for aphids on the young leaves and for shiny honeydew on the upper leaf surface. If grown near flowering plants, peppers and eggplant will also indicate an early thrips population. Look for distorted, young leaves with silvery flecked scars that are signs of thrips feeding damage.

Fava beans and certain cultivars of petunia are used as indicator plants to detect the presence of thrips carrying INSV and TSWV. These plants will develop viral symptoms within one week if fed on by the infected thrips. The petunia cultivar 'Summer Madness' and several varieties of fava bean have been successfully used to detect tospoviruses. To use petunias and fava beans as indicator plants:

• Remove flowers from indicator plants to encourage feeding on foliage where symptoms can be observed.
• Place a blue non-sticky card in each pot at plant height. The blue card will attract thrips to the indicator plant. Blue plastic picnic plates work well.
• Place petunia plants throughout the greenhouse among the crop at a rate of one plant every 20-30 feet and fava bean plants at the rate of 12 pots per 1,000 sq. ft.
• Remove symptomatic leaves on petunia plants and continue to use the plants. The virus is not systemic in these plants. Thrips feeding injury leaves distinct white feeding scars on the foliage. Virus symptoms appear as a brown rim around the feeding scars.
• Remove entire plants of fava beans if symptoms are observed, because the virus is systemic in these plants. Viral symptoms appear as dark brown angular lesions on leaves or yellow to light green ring spots. Dark necrotic areas can also be seen on the stem. Fava beans have dark black spots on their stipules that should not be confused with viral symptoms.
• Replace with new plants, planting 1 to 2 bean seeds per 4" pot.
  

Record Keeping and Decision-Making

Each time the crop is scouted, record the pest numbers, their location and the number of plants inspected. Records on pest numbers and locations will help you identify population trends. Population trends will also indicate if initial control measures were successful or if they need to be repeated. Once this information is collected each week, a pest management decision can then be made. Monitoring and record keeping will answer the following questions and help you make the necessary treatment decisions. Is the population decreasing, increasing or remaining stable over the growing season? Do you need to spray? Are insects migrating from weeds under the benches to your crops? Is the treatment from last week working? Tables 21 and 22 (pages 63 and 65)provide a list of selected materials labeled for managing insects, mites and diseases on greenhouse-grown vegetable transplants. Follow label instructions before using the material on vegetable bedding plants. The product must be used only for crops for which the compound is registered.

Biological Control for Insects and Mites

Biological control may be an option for aphids, mites, fungus gnats, thrips and whiteflies. Natural enemies are living organisms that need to be released when pest populations are low. They do not act as quickly as pesticides so cannot be used as a rescue treatment. Natural enemies (parasites, predators or pathogens) are best used early in the cropping cycle when plants are small, pest numbers are low and damage is not yet observed. A detailed plan of action is needed to insure success. Accurately identify the key pests in your production system. Natural enemies, especially parasites, are often very specific to a particular pest. Many insecticide residues can adversely affect natural enemies for up to 3 months after their application. Koppert Biological Systems has compiled a list of insecticides and their effects on natural enemies. This list is available from Koppert Biological Systems, Inc., 2856 South Main St., Ann Arbor, Michigan 48103 or through their website www.koppert.com. Biobest Biological Systems also has a searchable pesticide side effects database on its website: www.biobest.be. Become familiar with using insecticides that are compatible with natural enemies such as insecticidal soap, horticultural oil, certain insect growth regulators and neem-based materials (azadirachtin products, see Table 23) and have a sprayer dedicated for their use.

Start in a small trial area to become familiar with releasing, monitoring and evaluating the effectiveness of natural enemies. A separate greenhouse is best. With help from your supplier and university specialist, establish a schedule for introducing the natural enemies. Release rates and timing will vary depending upon the crop and its size, the degree of infestation, effectiveness and type of natural enemies, plus the time of year. Starting a biological control program will involve some trial and error, as release rates have not been scientifically evaluated for vegetable bedding plants. Vegetable bedding plants with only one or two key insect pests or with a longer production schedule may be logical candidates for biological control. Be sure that natural enemies are received from your supplier quickly (2-4 days), and that they are kept cool during shipment. Inspect natural enemies for viability and quality when they are received. Table 23 (page 72) provides information on scouting for key pests and biological control options.