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

Exercise - 11

Exercise: IDENTIFICATION OF INSECT PESTS OF CARNATION, CHRYSANTHEMUM, GLADIOLUS AND OTHER ORNAMENTALS AND THEIR DAMAGE SYMPTOMS
Carnation:

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

• Damage: Damage is caused by the caterpillars by boring into the developing buds and feeding on petals inside them. Infested buds never open and dry as such. Partially damaged buds open into deformed flowers. The infestation coincides with the bud initiation and peak activity is between March and June.
• Adult moths are stoutly built and are yellowish brown. There is a darker area near the outer margins of the forewing. The forewings are marked with grayish wavy lines and black spots of varying sizes on the upper side. The hind wings are whitish and lighter in colour with a broad blackish band along the outer margins. Caterpillars are grayish to green with broken grey or green lines on lateral sides depending upon the host on which they feed. Pupae are dark brown in colour.

2. Phytophagous mites, Tetranychus sp.

• Discussed under the pests of rose.

3. Blister beetles, Mylabris spp. (Meloidae: Coleoptera)

• The pest is widely distributed in Africa and south-east Asia. Blister beetles feed on various hosts like cucurbits, okra, cotton, carnation, rose, groundnut, beans, millet etc.
• Damage is caused by the adults only by feeding on the floral buds and flowers, thus causing direct damage by disfigurement of the flowers. Attacked flowers become brownish and unattractive.
• Full grown grubs are coarctate and form pseudopupae, which become pupae later. Beetles have three black and three yellowish orange bands running transversely and alternatively on elytra. Among different species of Mylabris the beetles of M. pustulata are the biggest (22-26 mm in length), the beetles of M. phalerata are slightly smaller in size (20-24 mm in length) than M. pustulata and has its yellowish red bonds narrower than black bands. Beetles of M. mecilenta and M. tiflensis are relatively smaller in size than the earlier two species.

Chrysanthemum:

1. Chrysanthemum aphid, Macrosiphoniella sanborni (Aphididae: Hemiptera)

• These are soft bodied, generally sluggish insects with piercing and sucking type month parts. Nymphs are greenish black where as adults are chocolate brown which feed in groups. Damage in caused by the nymphs and adults by sucking the cell sap from growing shoots and apical leaves especially from the lower surface of the leaves. Feeding results in the loss of vigour, yellowing of leaves, premature leaf fall and stunted growth of plants. Flowers also dry up prematurely. Aphids also excrete honey dew on which sooty mould develops and interferes with the photosynthesis. This pest is also responsible for transmitting viral disease. Adult aphids can be winged or wingless. Winged aphids appear with the environment changes (day length, temperature, etc), when aphid become over crowded or the plants begins to deteriorate and they need migration. Reproduction is both parthenogenetic vivipary as well as sexual.

2. Serpentine leaf miner, Liriomyza trifolii

• Eggs: Female flies lay eggs by embedding them into the leaf tissue, singly in close proximity to one another. Newly laid eggs are white and translucent and turn opaque as the development advances.
• Larvae: The larvae are orange yellow without legs and move through peristaltic action between the two epidermis of the leaf
• Pupae: Pupae are orange yellow initially which turns dark brown on maturity.
• Adults: The adults are minute grayish black flies with plum red eyes and a yellow spot on the scutellum. The female are bigger than male.
• Damage: Damage is caused of the larvae, which feed on the palisade mesophyll tissue in between the two epidermis of the leaf. Affected leaves give transparent papery appearance in the mined area, thereby reducing the photosynthesis. The attack appears during April and is more pronounced from June onwards.
• (Also see under insect pests of tomato)

3. Pea leaf miner, Chromatomyia horticola (Agromyzidae: Diptera)

• Damage: Larva is the destructive stage. Adult females also puncture the leaves. Two types of punctures are made on leaves one is ovipositional punctures in which egg is laid and second is feeding puncture from which sap oozes and both male and female adults feed on it. Larvae feed by making the prominent tunnels between lower and upper epidermis of leaves which interfere with the photosynthetic activity and ultimately the proper growth of the plants is reduced. Tunnels make the leaf unattractive and give yellowish look thereby reducing the quality and market value of the cut flowers.
• The adults are small (2-2.5 mm in length) flies having a pair of transparent and shining wings with grayish black mesonotum and yellowish frons. Females are slightly bigger than males with pointed ovipositor.

4. Cabbage semilooper, Thysanoplusia orichalcea (Noctuidae: Lepidotptera)

• This pest attacks many vegetable and ornamental plants through out the North western India. Damage is caused by the larvae by biting round holes in the leaves. Under severe infestation the entire leaf and flower may be eaten.
• Larvae: The larvae are plump and pale green in colour.
• Adults: Adults are light pale brown moths with a golden patch on each fore wing.
• (See under the insect pests of cole crops)

5. Leaf folder, Hedylepta sp. (Pyraustidae: Lepidoptera)

• Adult moths lay pale white eggs singly or in small batches on leaves and tender shoots. On hatching larvae roll the leaves up wards and feed within on chlorophyll. Attacked leaves get skeletonized and ultimately get dried. The damage is more sever if the growing tip in attacked. The larvae are green is colour, about 10-12 mm in length and remain hidden inside the leaves by folding them.

6. Thrips, Microcephalothrips abdominalis
Gladiolus:

1. Gladiolus thrips, Taeniothrips simplex (Thripidae: Thysanoptera)

• The nymphs are light yellow, while adults are black in colour with wings having hairs which are arranged like the parts of the feather.
• Damage: Both nymphs and adults damage leaves and spikes by rasping the tissue and sucking the oozing sap. Affected leaves and spikes develop silvery streaks which later on turn brown, get deformed and ultimately dries up. If young plants are attacked, there is a reduction in flower production and quality. Thrips also attack corms under storage and the infested corms become sticky, shrivel and produce weak plants when planted.

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

• Damage: Adult females lay small yellow round eggs on the underside of leaves. Larvae on hatching feed on leaves by eating leaf lamina. These caterpillars then enter into the developing spikes and feed inside by damaging the flowers.
• Other details have been described under carnation

3. Tobacco caterpillar, Spodoptera litura (Noctuidae : Lepidotera)

• Damage: Damage is caused by the caterpillars by feeding gregariously during early instars by scrapping the chlorophyll content from the leaves and skelotonising them. Later on these caterpillars get scattered and feed voraciously and the whole of the leaf may be eaten away.
• Moths are active at night and lay eggs in cluster covered with brown hairs. Newly emerged larvae feed gregariously for few days and then disperse to feed individually on the foliage.

4. Cutworms, Agrotis segetum and A. ipsilon (Noctuidae: Lepidoptera)

• Damage: Damage is caused by the caterpillars which attack mainly the newly grown gladiolus plants. Larvae feed during night on emerging shoots mainly up to third leaf stage. They also attack the under ground corms thus causing the yellowing of leaves
• Other characters have been described in earlier topics