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Common Insect and Mite Pests of the Greenhouse

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Kara Bates

on 1 February 2012

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Transcript of Common Insect and Mite Pests of the Greenhouse

Common Insect and Mite Pests of the Greenhouse
Control Measures?
A greenhouse provides the perfect environment: warm, humid conditions and abundant food supply with few (if any) predators.
We are going to take a closer look at the following:
Spider Mites
Fungus Gnats
There are many, many more pests - but these are the most common/problematic in a greenhouse.
Silverleaf WF
Greenhouse WF
Plants attacked
Feed on > 500 species of plants
Ex: poinsettia, hibiscus, gerbera daisy, verbena, garden mum, salvia
Damage Symptoms
Feed by injecting enzymes and sucking out the sap;
Feed on underside of leaves;
Reduce plant vigor (stunted growth);
Chlorotic spots (yellowing);
Honeydew (excrement) causes sooty mold, which interferes with photosynthesis
Biological Controls
2 parasitic wasps
Encarsia formosa
(develops within the W.F. nymph)
Adult feeds on blood from the wound
(more effective against silverleaf W.F.)
It is important to control W.F. populations very early - once they are established, they are very hard to control.
Plants attacked
Aphids will attack nearly all greenhouse plants
Damage Symptoms
Young leaves are stunted, curled;
Honeydew, sooty mold;
Cast skins;
Virus vector
Biological Controls
Parasitic Wasps
Green lacewing
Lady beetle
Pirate bug
Genus Aphidius
Beauvaria bassiana - an insect-pathogenic fungi (AKA: Entomopathogen)
Spider Mites
Damage Symptoms
Leaves of affected plants show this distinct spotted effect, known as "stippling"
This happens when the spider mites tear into the plant tissue to feed on the sap - this causes the leaf cells to rupture
Spider mites can also spin webbing
The easiest way to sample for spider mites:
- Sharply tap suspected leaves over white paper
- Look for green, red, or yellow specks the size of a grain of pepper
Biological Controls
Pirate bugs are also effective
Mites in the family Phytoseiidae (orange) are predators of spider mites.
Damage Symptoms
White spots
Distortion of leaves and flowers
Early flower maturity
Flower discoloration
Virus transmission (Impatiens Necrotic Spot Virus - INSV)
In addition to sucking the plant's juices, adults and larvae scrape plant tissues to induce the flow of juices. This causes the tissue to dry out and enlarge to form silvery patches.
Biological Controls
There are a lot of options, but there isn't 1 method that works completely. Predators, such as the pirate bug and predatory mites must be fast moving if they are going to feed on thrips. Pathogens, such as B. bassiana, can also work.
Fungus Gnats
Damage Symptoms
They thrive on overwatering
Larvae feed on roots, which lead to less root vigor and increased disease incidences
Because this equates to reduced H2O and nutrient uptake, the plant will show signs of stunted growth and yellowing
Adults spread detrimental fungal spores throughout the greenhouse through defecation
Biological Controls
Beneficial Nematodes (genus Steinernema)
Also, predatory mites are effective.
Damage Symptoms
Adults: puncture leaf and feed on juices
Larvae: feed on interveinal tissues
The mines themselves are the primary damage: unslightly and reduce overall plant health.
Biological Controls
These parasitic wasps find larvae in the mines, penetrate the leaf tissue, and lay an egg directly on the larvae.
Dacnusa sibirica
Diglyphus isaea
In addition to sucking the plant's juices, adults and larvae scrape plant tissues to induce the flow of juices. This causes the tissue to dry out and enlarge to form silvery patches.
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.
Physical controls kill a pest directly or make the environment unsuitable for it. Examples include mulches for weed management, steam sterilization of the soil for disease management, or barriers such as screens to keep birds or insects out.
The easiest way to sample for thrips:
- Use blue sticky cards/insect traps (thrips are attracted to the blue color; most other insects are attracted to yellow)
Now it's your turn to identify these common greenhouse and agricultural pests!
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