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Quick Problem Solver
This table provides a quick checklist of common garden pests and diseases, their characteristic symptoms and some basic control strategies. 

(This text is an edited version of text that appears in my book 'Organic Vegetable Gardening'
published by ABC Books, plus additional information) See
[Books]

Problem  Symptoms  Control Strategies 

Chewing Insects

Caterpillars
see PestID
Holes in flowers, leaves and fruit. Pick off by hand, encourage birds.  On cabbages, broccoli and other brassica plants, check planting time.  Use molasses, Derris dust, diatomaceous earth or Dipel.
Grasshoppers Holes on growth tips and on the edges of leaves. Snip large ones in half with secateurs during early morning garden patrols. Plant sacrificial trap crops like acalypha. Apply diatomaceous earth or use molasses or oil as a contact spray.
Beetles
see PestID
Chewed holes in flower, leaves and fruit. Suck off with the vacuum cleaner. Use Derris or diatomaceous earth. Check roots for beetle larvae.
Cut Worm Seedlings cut off at ground level. Place physical barriers around young seedlings such as plastic sleeves cut from soft drink bottles.
Leaf Miner
see PestID
Silvery tracings on leaves marking internal tunnels made by caterpillars.     Locate the insect and squash the leaf and the insect between your fingers. Oil acts as a repellent. Problem is largely cosmetic on established trees.

Piercing & Sucking Pests

Aphids
see PestID
Tiny green, yellow, red or black insects on the new growth of plants. Hose off or squash them.  Sprinkle ash, lime, Derris or diatomaceous earth to dehydrate them.  Spray with soap or oil. Wait for ladybirds and their larvae to control them.
Green Vegetable Bugs Tiny pale green bugs that cause tips to die and cause spots and dimples on fruit. Pick off by hand. Vacuum them up. Spray with pyrethrum. Cover plants such as capsicum and tomatoes to keep them free from attack - also prevents fruit fly infestation.
Mealy Bugs
see PestID
White fluff covered insect on roots, stems of flowers or fruit. Dispose of plants where roots are infested.  Squash where visible on stems. Spray with diatomaceous earth, oil or soap spray.
Scale
see PestID
Flat disc-like insects stuck to plants often associated with black soot and ants. Spray with oil or pyrethrum. Sprinkle chilli powder around plant stems to deter ants. Use horticultural glues or barrier paints. Scrub heavy infestations with soap and water and a soft nail brush, then respray with oil.
Fruit Fly
see PestID
homemade remedies
more info.... (pdf)
Premature fruit drop with white maggots present in fruit. Grow susceptible crops when fruit fly population is low. Place bags over individual fruit.  Cover entire vegetable gardens with white shade cloth or exclusion fabric. Use baits to monitor populations and act as traps. Place these baits away from the targeted fruit as you do not want to attract the fruit fly to the fruit.
White Fly Clouds of white flying insects when plants are disturbed. Overhead water to drown them. Use repellent sprays and oils. Apply soap sprays regularly.

Other Pests

Ants
see PestID
Ants visible on plant stems and fruit often with sticky black soot and scale insects present. Torch-light expeditions especially after rain or watering.  Buy some ducks. Place containerised baits or barriers around plants. Iron based based are safe for the environment and pets.
Snails and Slugs
see PestID
Holes and silver trails.  Seedlings disappearing completely. Torch-light expeditions especially after rain or watering.  Buy some ducks. Place containerised baits or barriers around plants. Iron based based are safe for the environment and pets.
Slaters Mini armadillos that role into a ball when disturbed. Large populations occur where habitat is provided such as newspaper mulch, decomposing wood or other organic debris. No real damage occurs.  Buy some chickens.
Mites
see PestID
Silvery appearance on undersides of leaves.  Loss of green colour on top. Outbreaks occur in hot, dry weather when plants are stressed. Water, mulch, use sulphur, soap and oil sprays.
Root Nematodes
see PestID
Plants wilt in hot weather even though well watered.  Knotted, distorted roots. Incorporate organic matter.  Rotate crops.  Grow and dig in natural repellents such as cobbler’s pegs (Bidens pilosa). Water molasses around susceptible crops like tomatoes and capsicum

Diseases

Anthracnose
see DiseaseID
Failure to set fruit, premature fruit fall, black spots on flowers, fruit and leaves. Plant resistant varieties, prune to improve air circulation, increase potassium. Spray copper or casuarina tea prior to flowering and at fruit set.
Mildews and Black Spot
see DiseaseID
White powdery and then burnt look to leaves or black sunken spots. Plant resistant varieties, check planting season, improve air circulation, reduce nitrogen, increase potassium. Use seaweed on a regular basis. Spray with Condies crystal, sulphur, copper or milk. Use bicarbonate soda based sprays like Ecocarb or Eco Rose.
Root Rot Poor growth and soft, brown odorous roots on plants. Decrease watering, incorporate organic matter and improve drainage.
Viruses
see DiseaseID
Poor growth, distortion, uncharacteristic stripes and mosaic patterns on leaves. Remove and destroy infected plants.  Obtain clean seed. Avoid propagating from infected plants. Control aphids that transfer many viruses between plants.

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