Each crop grown has a few common crop or garden pests that growers will need to deal with. In most cases they can effectively be managed with beneficial insects such as predatory mites, parasitoid wasps, and nematodes. The advantages of biological pest control are that the crop pests are managed throughout the season with minimal effort and that no sprays (that affect plant health and often result in marginal pest control) are required.
Aphids
Identification
Many different species of aphids occur in the greenhouse, varying in size and morphology; (0.5- 6.5 mm long). They can be green to black, yellow, brown, purple, pink, grey or white in colour. They have piercing, sucking mouthparts. They can often be identified by the cornicles (tubes) extending from the end of the abdomen. They are sometimes present in a winged (alate) form, but are usually found in the wingless form (apterous).
Damage They Cause:
-plant sap is removed by the stylet, causing deformed leafs and shoots -excretion of honeydew, reducing photosynthesis and causing sooty mold to colonize on the leaves -often a disease vector for viruses
Beneficial Insects for Control:
Aphidius spp. (Hymenoptera: Braconidae) -parasitoid wasps -lays eggs in individual aphids
Fungus Gnats
Identification
This is a narrow, black fly with large wings (2.5 mm long) and long antennae. The larvae are almost transparent with a black head (6 mm long). Characterized by Y-shaped venation on transparent wings.
Damage They Cause:
-larvae feed on the young roots causing plant stunting and wilt -larvae can spread mites, nematodes, and fungi -adults can encourage pathogens such as; Pythium, Botrytis, Fusarium, Verticillium
Beneficial Insects for Control
Strateolaelaps scimitis (Mesostigmata: Laelapidae) -generalist predatory mite
Gaeolaelaps gillespiei (Mesostigmata: Laelapidae) -generalist predatory mite Dalotia (Atheta) coriaria (Coleoptera: Staphylinidae) -generalist predatory beetle
Spider Mites
Identification
Spider mite larvae are transparent and have 6 legs. Two-spotted spider mite are the most common. The adults are yellow-green to dark red with two dark spots on back. With eight legs (arachnid, not insect), they are 0.75 mm long and show bright orange-red colour when entering diapause. Fine webbing on leaves is evident in large infestations.
Damage They Cause:
-feeding on plant tissue and sap causing yellow speckling of the leaves -distortion of young leaves and loss of chlorophyll -leaf drop and shriveling of leaves -much damage can be caused by small populations of spider mites.
Beneficial Insects for Control:
Phytoseiulus persimilis (Mesostigmata: Phytoseiidae) -predatory mite for (Tetranychus urticae) Two-spotted Spidermite
Neoseiulus (Amblyseius) fallacis (Mesostigmata: Phytoseiidae) -predatory mite for all types of spider mite Neoseiulus (Amblyseius) californicus (Mesostigmata: Phytoseiidae) -predatory mite for all types of spider mite Stethorus punctillum (Coleoptera: Coccinellidae) -predatory beetle for all types of spider mite Micromus variegatus (Neuroptera: Hemerobiidae) -generalist predatory adults & larvae
Thrips
Identification
Thrips posses piercing-sucking mouthparts. The larvae are tiny crawlers, pointed at both ends while the adults are tiny winged insects (0.5- 1.4 mm) displaying fringes along both edges of their wing. They range from light tan to brown to black in colour depending on the species (some are striped on their backs).
Damage They Cause:
-often feeding is on young leaves and flowers causing distortion in plant growth -piercing mouthparts damage leaves, fruit, and flowers leaving silvery/ grey patches on the leaves -black fecal pellets called frass is often left in the damaged area -frass can be a problem, causing sooty mold to occur
Beneficial Insects for control:
Neoseiulus (Amblyseius) cucumeris (Mesostigmata: Phytoseiidae) -predatory mite -primarily feed on the first larval stage of thrips
Neoseiulus (Amblyseius) swirzkii (Mesostigmata: Phytoseiidae) -predatory mite -primarily feed on the first larval stage of thrips Strateolaelaps scimitis (Mesostigmata: Laelapidae) -generalist predatory mite Dalotia (Atheta) coriaria (Coleoptera: Staphylinidae) -generalist predatory beetle Orius insidiosus (Hemiptera: Anthrocoridae) -generalist predatory beetle Micromus variegatus (Neuroptera: Hemerobiidae) -generalist predatory adults & larvae
Whitefly
Identification
Adults whiteflies are winged fly-looking insects, usually found on undersides of leaves. They are grey to white in colour and 1.25- 2 mm long.
Damage They Cause:
-plant sap is removed from the leaves and young shoots causing plant stunting and leaf drop -excretion of honeydew, reducing photosynthesis and causing sooty mold to colonize on the leaves -often a disease vector, ingesting virus particles when feeding and spreading them to other plants
Beneficial Insects for Control:
Encarsia formosa (Hymenoptera: Aphelinidae) -parasitoid wasp -excellent control of greenhouse whitefly -lays eggs in pupae of Trialeurodes vaporariorum (Greenhouse Whitefly)
Delphastus catalinae (Coleoptera: Coccinellidae) -predatory beetle Micromus variegatus (Neuroptera: Hemerobiidae) -generalist predatory adults & larvae
