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

Exercise - 9

Exercise: Identification of Insect Pests of Rose and their Damage Symptoms
1. Rose aphid, Macrosiphum rosaeformis (Aphididae: Hemiplera)

• Identification: These are small (about 2.5 mm long) wingless aphids having large red eyes, black cornicles and a yellowish green tip of abdomen.
• Damage: The aphids suck the sap from the tender leaves, buds and twigs. It is particularly injurious to tender buds, resulting in the disfigurement and withering of flowers there by reducing the quality of the flowers significantly. A black fungus also develops on the honey dew excreted by the aphids, giving an ugly appearance to the plant which further deteriorates the market value the produce.

2. Ground nut aphid, Aphis craccivora (Aphididae: Hemiptera)

• Identification: Adults are black or brown with variable size.
• Damage: Both nymphs and adults suck the cell sap from flowers, tender leaves and terminal portion of the plant. Damage results in downward cupping of leaves and premature drop of flowers.

3. Rose sawfly, Arge fumipennis (Argidae: Hymenoptera)

• This saw fly is an important pest of rose. The larvae feed voraciously on the leaves of rose and may cause complete defoliation of the plant. The pest appears during first week of July with the onset of monsoon and remains active through out the rainy season causing severe damage to roses in mid hills of Himachal Pradesh. Female makes an ovipositional slit on the stem and side branches with the help of saw like ovipositor and lay eggs.
• Eggs: Eggs are oval shaped and transparent creamy white and turn dirty white to black before hatching.
• Larvae: Newly emerged larvae which are green in colour with black head and thoracic legs move upward and firmly hold the leaves with them and start feeding on leaves in groups from their margins
• Adults: The adults on emergence are dull in colour which soon changed into shining black orange in colour. Males are lightly smaller in size than females.

4. Phytophagous mites. : Tetranychus urticae (Tetranychidae: Acarina)

• Damage: Damaged is caused by the larvae, nymphs and adults by sucking the cell sap from under side of leaves, flower buds and flowers. When population is high it results in 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.
• Eggs: Eggs are spherical shiny white and translucent which are laid mostly along the midrib and side margins on the lower surface of the leaves.
• Larvae: Newly emerged larva is dirty white in colour and possesses three pairs of legs.
• Protonymphs: Protonymphs possesses four pairs of legs and is slightly green in colour. Deutonymphs: The male deutonymph is smaller than the female. Deutonymph
• Adults: Adults are bigger than deutonymphs, orange in colour with two black spots on their body.

5. Greenhouse whitefly, Trialeurodes vaporariorum (Aleyrodidae: Hemipera)

• Discussed under tomato

6. Thrips, Thrips flavus (Thripidae: Thysanoptera)

• These are very small, slender insects. Adults are brown where and nymphs are reddish in colour. 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. Due to feeding the 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.

7. Armoured scale, Aonidiella aurantii

• Damage is caused by sucking 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 succumb to severe attack. Attack is more sever during summer. 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 and there are several overlapping generation is a year.

8. Digger wasp, Crabro sp

• The adults are brown yellow which make nest in the pruned twigs. The attacked pruned twigs can be spotted out in the field by the presence of round hole. Soon after the pruning of the rose plant, the cut branches are attacked by digger wasp. These wasps enter from cut ends, tunnel through the pith and burrow down words to build their nests within. They usually prey upon flies and small spiders which are paralyzed and taken into the cavity inside the branch and stored as food for their young ones. As a result of their attack the branch dries from top to down wards. These branches also become susceptible to fungal attack causing die back diseases.