Chapter 26

Integrated Pest Management in Greenhouses

Physical Pest Control in Greenhouses

Physical control strategies are those methods that reduce pest infestations by preventing pest access to the host or area, or, if the pests are already present, physically removing them by some means. For example, this could mean using barriers such as insect screens, traps, or quanantine, depending upon the pest and situation.

Sanitation

Sanitation can take many forms, including the use footbaths between greenhouse compartments, particularly between propagation and stock plant areas will minimize the transmission of diseases. Employees can rogue dead and dying seedlings from beds and containers to reduce the spread of disease. Do not leave diseased plants under benches. Place rogued plants with difficult-to-control diseases in commercial garbage containers and dispose of them to reduce potential sources of inoculum. Dedicate wheel barrows or soil carts used to discard diseased material strictly for disposal purposes. Have employees wear disposable gloves when handling diseased or infested plant material. Otherwise, employees should wash their hands thoroughly with soap or bactericidal hand lotion before performing another function.

Disinfectants and Cleaners of Greenhouse Surfaces

Disinfectants and cleaners play an important role in the prevention and control of fungal and viral pathogens and algae within the greenhouse. They should routinely be used as a pre-crop clean-up and during the cropping cycle to sanitize greenhouse structural surfaces and equipment. Disinfectants include solutions of sodium hypochlorite solution (Clorox), chlorine dioxide (Selectrocide), benzylkonium chloride (e.g., Physan 20, Green-shield), or pine disinfectant—diluted according to directions.

Greenhouse Insect Screening

Most greenhouses are equipped with ventilation openings to provide good microclimate conditions for plant growth. Unfortunately, these vents serve also as a major port of entry for pests and, as a consequence, growers are forced to cover the vents completely and permanently with fine mesh screens to prevent pest invasion. Screening greatly reduces the entrance of common greenhouse pests such as thrips, aphids, and whiteflies, as well as some less common pests such as tarnished plant bugs and European corn borers. Some growers have reported reducing pesticide use by 90 percent by using proper screening in combination with insect-free stock and good sanitation.

Ventilation

A major concern of growers considering screening is the reduction in air flow. Air flow resistance, primarily a function of hole or mesh size, varies widely among screen products. Reduced air flow can lead to overheating of the greenhouse, and stress on the fans (in the case of fan-ventilated greenhouses) that have to work harder to pull the same amount of air through the partially-blocked vent. To provide adequate airflow for ventilation, the area of the screen that covers the vent/shutter opening must to be increased. This is usually done by providing a frame or structure over the intake that will support additional material.

Positive Air Pressure

Winged insect pests can be prevented from entering a greenhouse from the outside if they are met with resistance in the form of air pressure as they try to enter through the vents and doors. Swamp coolers installed around the perimeter of the greenhouse will provide the needed resistance as they coolor ventilate the greenhouse.

Airlock Entrance

Walk-in doorways provide an easy entrance for many pests; growers need to evaluate strategies to reduce the likelihood of pest entrance. In greenhouses with fan and pad ventilation, an airlock entrance room is essential: attached to the exterior of the greenhouse and enclosing the entry doorway, its double-door system allows workers to enter the airlock room and close the outside door behind them before entering the greenhouse production area.

Quarantine

Reducing pest entry through quarantine is a good management strategy. Checking and quarantining plants that are being brought into the greenhouse for pest infestations is important to ensure that no infested plants are introduced into the greenhouse.

Click on the following topics for more information on integrated pest management in greenhouses.