IPM

What is it?

Integrated pest management (IPM) is an ecosystem-based strategy that focuses on long-term prevention of pests or their damage through a combination of techniques such as biological control, habitat manipulation, modification of cultural practices, and use of resistant varieties. Pesticides are used only after monitoring indicates they are needed according to established guidelines, and treatments are made with the goal of removing only the target organism. Pest control materials are selected and applied in a manner that minimizes risks to human health, beneficial and non-target organisms, and the environment.

Through regular scouting the PGF staff will make decisions when to spray or apply biologicals based on pest thresholds and treatment plans for each growing area. Users are expected to keep their areas (including floors and benches) clean of unwanted plant material and debris. Only greenhouse staff are allowed to apply pesticides to plants in the PGF facilities.

Cultural controls are practices that reduce pest establishment, reproduction,
dispersal, and survival. For example, changing irrigation practices can reduce pest
problems, since too much water can increase root disease and weeds.
Proper fertilization can help plants defend themselves from diseases and make
them less desirable to pests. For example, too much fertilizer can make plants
leggy and more susceptible to mite and aphid infestations. Whereas too little
fertilizer can stress plants and makes them more prone to insect attacks.

Mechanical and physical controls kill a pest directly or make the environment
unsuitable for it. Sticky card traps are examples of mechanical controls.
Physical controls include: Sweeping floors and benches to inhibit breeding
grounds for pests and diseases, proper order entry of growing areas (i.e. move
from clean to dirty or new to old plant material first), steam sterilization of the
soil for disease management, or barriers such as screens to keep birds or insects
out.

Biological control is the use of natural enemies—predators, parasites, pathogens,
and competitors—to control pests and their damage. Biologicals can be used in
the form of natural predators and parasites or as sprays to inhibit the growth of
pathogens or cause death to the pest. Fungal spores that attack insects are an
example of biochemical control.

Common Greenhouse Pests

Western Flower Thrips

Thrips feed by using their mouth parts to pierce plant cells and suck out their contents. Damage appears as small scars or silvered patches. Most plants can outgrow mild thrips infestations but seedlings can be severely damaged in heavy populations. Thrips also vector plant viruses such as impatiens necrotic spot and the tomato spotted wilt virus.
Control of thrips in greenhouses can be difficult due to pesticide resistance, but with proper crop rotation and sanitation along with good IPM procedures populations can be kept at a minimum. Breaking up the pest population by cleaning out greenhouse rooms and avoiding growing multiple stages of plants is key to keeping populations at a minimum. Biological control consists of predatory bugs, mites and nematodes that search out and kill thrips as well as biochemical sprays.

Aphids

Aphids are small, soft-bodied insects with piercing mouth parts that they use to suck out fluids from the plant. There are many different species of aphid that feed on a variety of different plants. Aphids can cause stunting, leaf curling and transmit viruses from plant to plant. They also produce a sticky exudate called honeydew that can attract other pest such as ants and can develop into a growth of sooty mold fungus.
There are a number of natural predators of aphids including parasitic wasps, and lady bird beetles. Keeping surrounding areas clean of debris and weeds is also an important part of pest management.

Spider Mites

Mites can cause leaf damage by sucking the cell contents. Mites are very tiny and difficult to see with the naked eye. Plant damage usually first appears as stippled or yellow leaves. As the pest becomes established you will see webbing on the leaves.
Spider mites have many natural enemies, including predator mites, and certain lady beetles which naturally limit their numbers in many yards and gardens, especially when undisturbed by pesticide sprays. Keeping debris and weeds clear of growing sites and proper crop rotation can be critical in breaking up existing pest populations. Chemical controls with oils and soaps are also good at keeping pest populations down.

Whitefly

Whitefly, like aphids, have piercing mouth parts and can cause some leaf distortion. They also create honeydew and can attract ants as well. Small populations do not usually cause damage and most plants can withstand moderate populations.
Whitefly populations can be kept in check with natural predators and a clean environment. Natural predators include, parasitic wasps, mites and some true bugs. Chemical sprays can be effective if caught early enough and all life stages are targeted.

Fungus Gnats and Shore Flies

Fungus gnats are small flies that are found in moist soil and potting mix. They are more of a nuisance then a pest, but in high numbers can cause problems. The adults do not feed on plants but their larvae will feed on fungi and organic matter in the soil including plant roots.
Eliminating excess moisture and debris in the planting media and around the plants is an effective control of the larval stage.

Shore Flies are found in over-watered conditions where algae is present. Neither the adults nor the larvae feed on plants and are only considered to be a nuisance. Controlling excess moisture and algae growth in and around the plants will help keep populations down.

Adult fungus gnat (left) and shore fly (right).

Powdery Mildew

There are many different species of
powdery mildew fungi and each species
only attacks specific plants. Powdery
mildew first appears as white, powdery
spots that may form on leaf and shoot
surfaces. Powdery mildew spores are
carried by wind. Humidity
requirements vary but all powdery
mildew species can germinate and infect in the absence of free water.
Temperatures between 60° to 80°F and shady conditions are the most favorable
for powdery mildew development. Spores and fungal growth are sensitive to
extreme heat (above 90°F) and direct sunlight. The best method of control is
prevention, planting resistant varieties, and following good cultural practices.