Pests and Diseases
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Pests ď Ž A pest
is any organism that causes harm to the crop
- Insects -
Diseases Weeds Birds/animals/man
How to limit damage caused by plant pests and diseases • • •
Early identification of symptoms Quick response to diagnosis Preventative action •
•
Prevention is always better than cure!!!
Biological curve
Identification of pests
Where to look
Leaves
Top and bottom
Shoot tips Stem Roots Fruit
Insects Pests
4 Groups Chewing Pests Sucking Pests Stinging Pests Soil Pests
Chewing Pests
Snails, Slugs, Grasshoppers, leaf miners, caterpillars, beetles. Snails & slugs create havoc seedlings and “leafies”. Baits & coffee grounds. Usually use Stomach poisons. Thin deposit on leaf surface.
Slugs and Snails
Grasshoppers
Leaf miner
Diamond Back Moth
Swallowtail Caterpillar
Heliothis/Bollworm
Stalk Borer
Sucking Pests
Aphids, Thrips, White Fly, Red spider mite Under leaves. Not visible until bad infestation. Symptoms – back curling of leaves, Silvering or bronzing of foliage. Reproduce quickly. Rapid response. Contact not stomach poison. Systemics. Mites dust with sulphur. Aphids – Sooty mould. Fungus on Honeydew.
Aphids
White Fly
Thrips
Stinging Pests.
Cucurbits main veg troubled by this Pumpkin fly Baiting (15g Malathion, 500g sugar, 5L water). Control from first flowering.
Pumpkin Fly
Soils Pests
Cutworms, wire worms, white grubs, millipedes & Nematodes. Cutworms severe seedlings at night. Browse shoulders of root crops. Bait. Nematodes – “eelworms”. Unthrifty plants but well cared for. Lift plant see disfigured roots.
Cutworm
Nematodes
Rhizobium
Diseases
Fungal Diseases Bacterial Diseases Viral Diseases
Fungal Diseases
Parasitic/Saprophytic organisms that attack foliage, stems, flowers and fruit. Problem in low light intensity and high humidity. Attack plant family. Others wide range. Reproduce using spores (Wind, water, seed coats and contact) Germinate in free surface water
Fungal Diseases (cont’d)
Problem with “overcrowding”. Clean in dry conditions but outbreak in humid. Adequate space plants dry off quickly. Only Group which can be effectively controlled by sprays and dusting (early detection). ‘Wilt’ causing not controlled by spraying – remove infected plants and destroy. Use long rotations.
Damping off
Rhizoctonia
Fusarium
Fusarium Wilt
Alternaria
Powdery Mildew
Early Blight
Late Blight
Rust
Bacterial Diseases Bacteria - Microscopic single celled organisms which parasitize host plant (Pathogenic). Many forms, wilting, spotting, cankers on stems, root rots Normally attack vascular systems. Spraying little value. Black Rot – seedcoat & seedlings. Control – Sanitation.
Verticilium Wilt
Bacterial Lesionses
Viral Diseases Virus – very tiny infectious agent. ID’ed by symptoms produced. Symptoms mottling, stunting, crinklings and distortion of foliage. “Colour breaks” flowers. Mainly spread by pests. Sucking and Chewing. Weeds can act as ‘hosts’
Streak Virus
Mosaic Virus.
Possible Control Measures • • • •
Cultural Biological Physical Chemical
Cultural • • •
Healthy Plant – Nutrition, Season. Healthy Soil - Rotation Good agricultural practices • •
•
Irrigation Stress management
Good sanitation – residues, weeds, ‘volunteer’ growth.
Biological Control ď Ž Predators
Other insects or organisms which eat/consume the problem pest.
Birds (Insect Eaters)
Assassin Bug
Orius spp (Minute Pirate Bug)
Mason Wasp
Praying Mantis
Ladybirds
Spiders
Lacewings
Hover Flies
Biological Control ď Ž Parasites
Other insects or organisms that parasitize and eventually kill the host or problem pest.
Tachnid Egg
Tachnid Eggs
Tachnid Fly
Braconid Wasp
Braconid Wasp
Braconid Wasp
Braconid Wasp
Braconid Wasp
Physical Control Roguing Soap Removal
of pests by hand Water – humidity/dryness
Chemical Control Read
the label Correct dose and technique Calibration Nozzles
Safe
handling and application