Insect Pests of Vegetable, Ornamental and Spice Crops (2+1)

Mites, Thrips and Scale

4. Phytophagous mites. : Tetranychus urticae

• Common name: Two spotted spider mite
• Scientific name: Tetranychus urticae
• Family: Tetranychidae
• Order: Acarina

Damage:

• Suck the cell sap from under side of leaves, flower buds and flowers.
• Bronzing and curling of leaves and discoloration of flowers and leaves.
• Webbing of leaves, sepals and petals occur which give untidy look to the plant.
• The infestation is more severe under poly house conditions.
• More severe in dry conditions

Identification:

• Eggs are Spherical, shiny white and transluscent
• Newly emerged larva is dirty white in colour and possesses three pairs of legs
• Protonymphs possess four pairs of legs and is slightly green in colour.
• The male deutonymph is smaller than the female.
• Adults are bigger than deutonymphs.
• Adults are orange coloured mites with two black spots on their body.

Life cycle:

• • Eggs are laid mostly along the midrib and side margins on the lower surface of the leaves.
• • Eggs hatch is about 2-4 days
• • Larva becomes protonymphs in about 2 days
• • Protonymph after under going a quiescent stage develops into deutonymph.
• • At this stage sexes are determined.
• • Deutonymph stage lasts for 1-3 days and develops into an adult.
• • Male longevity is 9-13 days and females live for 14-20 days.
• • Weather factors play an important role
• • Under dry and hot conditions the multiplication of these mites is very high and the infestation is also severe.

Management:

• • Remove the old and infested leaves and burn them
• • Try to avoid dry conditions and spray frequently with plain water at least twice a week with sprinkler.
• • Observe the plants regularly for mite population
• • If incidence is noticed spray with profenofos (0.05%) or fenazaquin (0.0025%) or propargite (0.057%) or dicofol 0.04%.

5. Greenhouse whitefly, Trialeurodes vaporariorum

• Discussed earlier

6. Thrips, Thrips flavus (Thripidae: Thysanoptera)

Identification:

• • These are very small, slender insects.
• • Adults are brown
• • Nymphs are reddish in colour.

Damage:

• • Their attack coincides with the appearance of new flush.
• • Both nymphs and adults scrap the surface and suck the oozing cell sap from leaves, tender shoots, apical buds and flowers.
• • Tip of the leaves get mottled and crumbled.
• • Brown scars and burnt margins occur on petals of infested flowers.
• • Severely attacked flowers remain unopened or half opened and ultimately dries away.

Management:

• • For monitoring of thrips, blue sticky cards should be placed 1-2" above the crop canopy at the rate of 2 per 1000 ft2.
• • Spray of oxy- demeton methyl (0.025%) or dimethoate (0.03%) at 10 days interval is affective.
• • Soil application of phorate granules @ 1.0 kg/ ha or drenching with chlorphyriphos (0.04%) helps to kill the pupae of thrips

7. Armoured scale, Aonidiella aurantii

Damage:

• • Suck the cell sap from the tender shoots.
• • Affected plants loose vitality become weak and bear less and small sized flowers.
• • In case of severe infestation the twigs get dried and disfiguring of plant takes place.
• • Whole of the plant may also scumb to severe attack.
• • Attack is more sever during summer.

Identification:

• • Female scales are reddish brown with hard waxy scale covering on the body and are without legs and having vestigial antennae.
• • Scales are mostly found on the tender shoots

Management:

• • Prune and destroy the infested leaves and twigs.
• • Scrap the scale and destroy the same by rubbing the affected stems with swab of cotton soaked in methylated sprit.
• • Spray the crop with chlorpyriphos (0.04%) or dimethoate (0.03%).

8. Digger wasp, Crabro sp

• • Brown yellow wasps which make nest in the pruned twigs.
• • The attacked twigs can be spotted by the presence of round hole.
• • Attack the branches soon after the pruning
• • Wasps tunnel through the pith and build their nests within.
• • They usually prey upon flies and don’t feed on rose
• • Attacked branches dry from top to down wards.
• • These branches also become susceptible to fungal attack causing die back diseases.

Management

• Soon after pruning, paint the pruned ends of branches with fungicidal pastes so as to prevent the entry of these wasps into the stem.

9. Bud borer, Helicoverpa armigera (Noctuidae: Lepidoptera)