The importance of ornamental plants from aesthetic, environmental and economic points of view has been realized since quite recently. India has made a noticeable advancement in the production of flowers, particularly the cut flowers, which have a high potential for export. During 2012-13, floriculture covered an area of 0.23 million ha with a production of 1.73 million tons of loose flowers and 76.73 million tons of cut flowers.
The leading cut flower producing states are West Bengal (33.1%), followed by Karnataka (12.3%), Maharashtra (10.3%), Andhra Pradesh (9.07%) and Orissa (7.9%). The leading loose flower producing states are Tamil Nadu (18.1%), followed by Andhra Pradesh (12.98%), Karnataka (12.0%), Madhya Pradesh (11.16%) and Gujarat (8.63%).
Ornamental plants are attacked by insects, mites, nematodes, millipedes, molluscs, earthworms and rodents. The insects eat away or bore into the leaves, flowers, buds, fruits and roots. They may suck the sap, making the plant look pale and unhealthy. The growth and the beauty of the ornamental plants receive a set-back.
Various species of thrips, aphids, leafhoppers, scale insects, mealy-bugs, leaf-miners, caterpillars, cutworms and chaffer beetles attack the common ornamental plants including rose, chrysanthemum, hibiscus, hollyhock, sunflower, iris, jasmine, etc. As many as 33 species of mites have been recorded feeding on ornamental plants in India. The nematodes cause the swelling of stems, deformation of the leaves, and suppression of the blossoms and production of galls in roots.
In the case of severe attack, the plants remain stunted or even die. The millipedes, molluscs and earthworms are harmful, when their population becomes very high. The rodents, including field rats, do not spare the ornamental plants and they may spoil the plants as well as the lawns while making their burrows.
1. Rose Aphid, Macrosiphum Rosaeiformis Das (Hemiptera: Aphididae):
The rose aphid, has been found infesting roses from November to April in northern India. The population of the aphids often increases to pest level. This insect is generally neglected by the garden owners owing to its minute size and the absence of the visible signs of its attack at the early stages.
The vigour of the plant is reduced and the quality of flowers deteriorates. This aphid has been recorded in Punjab, Delhi, Mysore, Andhra Pradesh and the Nilgiri Hills. In addition to this species, the cotton aphid, Aphis gossypii Glover, also infests rose plants from September to December in northern India.
Life-Cycle:
The non-winged rose aphid has an elongated body measuring 2.5-2.6 mm, large red eyes, black cornicles and a yellowish green tip of the abdomen. The form of species occurring in southern India has a purple abdomen, yellow head and dark legs. Nymphal development is completed in 11-14 days of the non-winged forms and 14-19 days of the winged forms, the growth being the quickest in March. In northern India, the insect appears in the middle of November.
The population increases progressively and is the highest in March, declining early in April as the season warms up. The winged forms are present throughout the period from November to April, but there is an increase in their number from December onwards, reaching the peak in March, when about 90 per cent of the adults become winged. The aphid multiplies most rapidly in late spring but cannot withstand the summer heat. Consequently, its population declines.
Damage:
The aphid sucks cell sap from the tender leaves, buds and twigs. It is particularly injurious to tender buds, resulting in the disfigurement and withering of flowers. Each aphid makes several punctures, producing wounds, which leave their mark as the flower opens. A black fungus may also develop on the honey-dew excreted by these insects, giving an ugly appearance to the plant. Some varieties are most susceptible than others, e.g. Damask is susceptible whereas Hawaii is comparatively resistant.
Control:
Spray 500 ml of malathion 50EC or methyl demeton 25EC or 200 ml of phosphamidon 85WSC in 500 litres of water per ha. The treatment may be repeated at the reappearance of the pest.
2. Red Scale, Lindigaspis Rossi (Maskel) (Hemiptera: Aphididae):
The tiny insects look like reddish brown waxy scales. Reddish brown encrustations are seen on the lower portion of the old stems and at times on the younger shoots also. The tiny specks in scurvy like patches on the affected stems appear like spots of pox. The affected plant parts become disfigured, dry and wither away. In case of severe infestation, the entire plant dies.
Control:
(i) The affected part should be rubbed with a piece of rough cloth soaked in methylated spirit.
(ii) Spray 500 ml of dimethoate 30EC or endosulfan 35EC in 500 litres of water per ha.
3. Milk Weed Bug, Lygaeus Civilies Wolff (Hemiptera: Lygaeidae):
It is a red bug with black spots on corium and clavus, and three white spots on the black membrane of the hemelytra. The adults of this species are found feeding on plant sap of Hibiscus rosa-sinensis Linn., Asclepias curassavica Linn., Carissa carandas (Linn.), Dombeya spectabilis Cav. and D. natalensis Sind. throughout the year. The maximum population is observed in May-June on its most preferred host plant, A. curassavica.
Control:
Spray 500 ml of malathion 50EC in 500 litres of water per ha.
4. Hollyhock Tingid Bug, Urentius Euonymus Fabricius (Hemiptera: Tingidae):
The tingid bug infests the garden hollyhock, Althaea rosea (Linn.), Abutilon indicum Sweet, Sida cardifolia Linn, and Chrozophora rottleri A. Juss. The bugs are easily recognized by their densely reticulate body and wings, and measure about 5-6 mm in length. The nymphs are spiny in appearance.
Life-Cycle:
The hollylock tingid bug appears on hollylock plants from March to June. The adult female lays eggs on the upper surface of leaves. The incubation period of the eggs is 8-10 days. There are five nymphal instars and development is completed in 15-27 days. The full developmental cycle is completed on a single leaf. The pest overwinters in egg stage.
Damage:
Both adults and nymphs suck plant sap from the under-surface of leaves. The infested leaves become pale-yellow and turn brown. Ultimately they shrivel and dry up.
Control:
Spray 500 ml of dimethoate 30EC in 500 litres of water per ha.
5. Sunflower Lacewing Bug, Cadmilos Retiarius Distant (Hemiptera: Tingidae):
The sunflower lacewing bug is a small insect measuring about 4 mm, with transparent, shiny, reticulated wings and black body. Both adults and nymphs cause damage to many garden plants like sunflower, Gaillardia, daisy, Chrysanthemum, marigold, vernonia, launea and the weed, Argemone mexicana Linn.
Life-Cycle:
The pest appears during July and remains active upto September. The adult female bugs lay eggs mainly on the upper surface of leaves of the host plants. The eggs are inserted slantingly into plant tissue leaving the opercula exposed, which appear like white or brown dots. The eggs hatch in 5-7 days and the young nymphs moult five times during nymphal period of 2- 3 weeks. Then they become adults.
The eggs are parasitized by Trichogramma sp. (Trichogrammatidae). A mite, Leptus sp. (Erythraeidae) is parasitic both on nymphs and adults.
Damage:
The nymphs and adults suck plant sap and the infested leaves turn yellowish-brown and finally dry up.
Control:
Spray 500 ml of malathion 50EC in 500 litres of water per ha.
6. Ak Butterfly, Danais Chrysippus Linnaeus (Lepidoptera: Nymphalidae):
Ak butterfly (also called plain tiger or African monarch) is widerspread in Asia and Africa. It is a medium sized butterfly with a wingspan of about 7- 8 cm. The apical half of the forewing is black with a white band. The hind wing has three black spots around the centre.
The body of caterpillars is covered with bands of black and white intersegmented with thick, yellow dorsolateral spots. There are three pairs of long and black tentacle-like appendages on third, sixth and twelfth segments. The larval host plants are from several families, most importantly Asciepiadoideae (Apocynaceae).
The caterpillars of the Ak butterfly feed on Asclepias curassavica Linn, from September to December. Their population becomes high during the months of October and November. The larvae feed on the leaves and flowers of this plant, and in many cases, the entire leaves are eaten up.
Control:
Spray one litre of methyl parathion 50EC in 625 litres of water per ha.
7. Jasmine Leaf Webworm, Nausinoe Geomecralis (Guenee) (Lepidoptera: Pyraustidae):
The larvae of this moth attack the terminal portion of the jasmine plants. This pest is widely distributed in West Africa, India, Pakistan, Sri Lanka, Myanmar, Java, Formosa, China and Australia.
The moths are brown with hyaline patches on the wings. Their abdomen is purplish brown, which is interspersed with lateral patches of lighter shades on each segment. The young caterpillars are light yellow in colour but as they grow they become darker.
Life-Cycle:
This pest is most active during the rainy season. The moths are seen resting on the lower surface of leaves on the periphery of the plants, thus avoiding the inner shaded portions. The female lays 15-20 eggs singly on the leaf lamina. The eggs are greenish yellow in colour which hatches in 3-4 days.
The larvae become full grown in 12-15 days after passing through five instars. The larvae spin extensive webbings in the shaded portion of the plant around the leaves on which they feed and pupate within that area. The pupal stage lasts 6-7 days and the life-cycle is completed in 22-24 days during July-August.
Damage:
During the rainy season, the caterpillars attack leaves of the plant mostly in the lower bushy and shaded portions. During the dry and sunny weather the terminal shoots are attacked. The leaves are webbed in an open and loose manner. The silk threads are seen as a cobweb on the surface of leaves.
The larvae skeletonize the leaves by eating away the parenchyma. As a result of the gregarious attack of the caterpillars, the vitality of the plant is reduced which tells upon its further growth and the production of buds, which are so important for getting a good commercial crop of jasmine flowers?
Control:
Spray 500 ml of dimethoate 30EC in 500 litres of water per ha.
8. Jasmine Budworm, Hendecasis Duplifascialis Hampson (Lepidoptera: Pyraustidae):
The larva is yellowish green in colour with a distinct black head and prothoracic shield. The moth is pale white.
Life-Cycle:
The freshly laid eggs are round, creamy and glued to the flower buds. The eggs hatch in 2.6-3.5 days and the larva passes through five instars. The total larval duration varies from 11.5 to 17.0 days depending on the jasmine species. The pupal stage lasts 6.5-9.0 days and the life cycle is completed in 21-29 days.
Damage:
The larva bores into immature bud and feeds on the internal contents. The larva feeds voraciously on the corolla leaving only the corolla tube in mature buds. In the case of younger buds, the larva remains outside the buds and feeds on the inner floral whorl through a small hole in the corolla tube. The infested flower turns violet and eventually dries out. A single larva may damage upto 6 flower buds. During heavy infestation, the adjacent buds along the inflorescence are webbed together by silken thread.
Control:
Spray 500 ml of dimethoate 30EC or 200 ml of cypermethrin 25EC in 500 litres of water per ha.
9. Lily Moth, Polytela Gloriosae Fabricius (Lepidoptera: Noctuidae):
The lily moth is a sporadic and specific pest of lilies in India and Sri Lanka. The larvae have chocolate brown head and they defoliate the lily plants. The full-grown larva measures 39-42 mm and possesses black, white and red mosaic patterns on the body. The moth has mosaic patterns of red, yellow and black on fore wings, with a row of black and yellow dots on the apical margins. The hind wings are black.
Life-Cycle:
The adult moths emerge from the hibernating pupae after the first heavy shower during July. The female moth lays round, yellowish eggs on the apical portion of the undersurface of leaves in clusters of 13-42 eggs. The larvae emerge from eggs after 3-6 days and they feed on leaves for 16-20 days. When full fed, they pupate in the soil in an earthen cocoon and the adults emerge within 15-20 days. The insect has two generations in a year and the pupae of second generation hibernate.
Damage:
The larvae feed on green matter of leaves which may result in complete defoliation of the lily plants.
The other noctuid caterpillars namely Brithys crini (F.) and Spodoptera litura (Fabricius) occasionally defoliate the lily plants.
Control:
Spray 500 ml of malathion 50EC in 500 litres of water per ha.
10. Blister Beetle, Mylabris Pustulata (Thunberg) (Coleoptera: Meloidae):
This prominent large beetle has six alternating, bright orange and black bands, against the general dark background of the body. It is 3 cm in length. The adult beetles attack the flowers of Hibiscus rosa-sinensis and Ruellia indica and other plants from July to September, and devour them completely. In August, the population becomes high and they appear to be more prominent than the flowers.
Control:
(i) Handpick and destroy the beetles.
(ii) Spray 1.25 kg of carbaryl 50WP in 625 litres of water per ha.
11. Citrus Red Scale, Aonidiella Aurantii (Maskell) (Hemiptera: Diaspididae):
Scales mainly infest the matured shoots of rose and spread to young shoots in case of severe infestation. Infested shoots bear reddish-brown encrustations. Both young and adult stages suck the sap. The damaged shoots lose vigour, produce small and few flowers, and dry in case of severe attack.
Control:
(i) Select scale-free planting material.
(ii) Cut and burn heavily infested shoots.
(iii) Apply carbofuran 3G @ 20 kg/ha at 5 cm depth to soil after digging.
(iv) Apply Pongamia oil (1%) to pruned shoots soon after pruning.
12. Gerbera Leafminer, Liriomyza Trifolii (Burgess) (Diptera: Agromyzidae):
This is a devastating pest on gerbera inside polyhouse. Infestation starts when plants are at 3-4 leaf stage. Adult flies lay eggs in the leaves by puncturing. Larvae feed inside leaves by making characteristic mines. Damaged leaves turn brown and dry while plants get stunted and produce small flowers in case of severe attack.
Control:
(i) Pluck and burn severely infested older leaves.
(ii) Spray one litre of dimethoate 30EC in 250 litres of water per ha.
13. Eriophyid Mite, Aceria Jasmini Chanana (Acarina: Eriophyidae):
It is a serious pest of various jasmine species in South India. The female is cylindrical and 150-160 µ long and 44 µ thick. The males are rare and generally 95 µ long. These mites make webs which look like felt and appear to be white hairy outgrowth on the leaf surface, tender stems and flower buds. As a result of this activity, growth of plants is reduced and the production of flowers is suppressed.
Control:
Spray 625 ml of dimethoate 30EC or malathion 50EC in 375 litres of water per ha.
14. Red Spider Mite, Tetranychus Urticae Koch (Acari: Tetranychidae):
Red spider mite is a serious pest of carnation inside polyhouse. Heavy infestation of the mite is observed during summer (March-June). Colonies of mite are mainly seen on leaves and young buds covered with dirty coloured webs. Mite spreads to the entire plant in case of heavy infestation. Attacked leaves look dirty, discoloured and dry. Damaged plants lose vigour, become stunted and dry in severe cases.
Control:
(i) Cut and burn the severely infested and dried shoots.
(ii) Wash plants with force to dislodge webs and reduce mite population.
(iii) Watering of polyhouse and providing proper ventilation during summer is essential to reduce mite population.
(iv) Spray 500 ml of dimethoate 30EC or oxydemeton methyl 25EC in 250 litres of water/ha.
15. Snails and Slugs:
Snails and slugs are soft-bodied animals belonging to class Gastropoda of the phylum Mollusca. Their body is asymmetrical, spirally coiled and enclosed in a shell. They have a large flat foot which is used for creeping and they do not have separate sexes.
The common snails found in Himachal Pradesh, Uttar Pradesh, Andhra Pradesh, Bihar, Maharashtra and Orissa are Helix spp. Another phytophagous species, Achatina fulica Ferussae, the giant African snail, has been reported as a serious pest of fruits, vegetables and ornamental plants in coastal areas of Orissa, West Bengal, Assam, Tamil Nadu and Kerala.
The common garden slug, Laevicantis alte Ferussae, in Punjab and Himachal Pradesh, has been observed feeding on a number of ornamental plants, including balsam, portulaca, pot- marigold, verbena, dahlia, cosmos, narcissus and lily. Another slug, Limax sp., occurs all over India.
Life-History:
The common snail breeds in the spring and the summer. It makes a hole of 1.24 cm in diameter and 3 cm in depth in damp soil, in which it lays eggs in a loose mass of about 60. The eggs hatch within two weeks and the young snails start feeding upon tender plants.
The shell increases in size with age and the snail is full-grown in about two years. Snails are seen at all hours, except during mid-day when it is hot and dry. In winter, they stay in colonies and are found among rockeries, loose boards of fences, at the bottom of hedges, in rubbish heaps, etc.
The slugs feed at night in damp places and destroy young shoots of various plants. Under dry conditions, their population is reduced considerably.
Damage:
Snails and slugs appear as sporadic pests in those places where damp conditions prevail. They may also appear in large number on roads and runways, creating problems during the taking- off or the landing of the aircraft. The slugs are known to feed on celery, lettuce, cabbage and a number of ornamental plants. When their population in high, they may do serious damage.
Control:
(i) Low population can be collected and destroyed.
(ii) Dust 15 per cent metaldehyde dust or spray 20 per cent metaldehyde liquid or sprinkle 5 per cent metaldhyde pellets around infested fields.
16. Root-Lesion Nematodes, Pratylenchus Spp. (Tylenchoidea: Tylenchidae):
Of the various ornamental plants, roses are the most affected by parasitic nematodes. More than a dozen species have been recorded from the roots of rose plants in India. Out of these, the more important are three species of the root-lesion nematodes, belonging mainly to the genus Pratylenchus and some to the genera Tylenchorynchus, Hoplolaimus, Xiphinema and Trichodorus. These root-lesion nematodes are vagrant parasites of plant roots and inhabit the aboveground portions only in rare cases. All these groups of nematodes have world-wide distribution.
Life-Cycle:
Both adults and larvae go in and out of the roots. The penetration usually occurs in the mature region of the rootlets and not from the root-tips. A female usually lays one egg per day. The egg stage lasts 16-20 days. The development and reproduction are rather slow in P. pratensis taking 54 days to complete the life-cycle.
In other species, like P. zeae, the life-cycle is completed in 35-40 days. During periods of drought, these nematodes lie quiescent, but they resume growth as soon as free moisture is available. The population of the root-lesion nematodes is high in October, whereas the infestation of Tylenchorynchus and Hoplolaimus occurs more frequently in the rainy season.
Damage:
Lesion nematodes feed on the parenchyma of the root and cause lesions, especially when a large number of them feed together. The root injury results in decreased growth of the aboveground portions. The plants bear small or no flowers at all.
Control:
(i) The roots of several varieties of French and African marigold and of sesame are known to release nematicidal compounds in rootlets, which are left in the soil and are effective against nematodes. The cultivation of marigold in rotation or as an intercrop is a useful practice.
(ii) Mix phorate 10G @ 10 kg/ha or carbofuran 3G @ 30 kg/ha in soil at the time of planting.
(iii) Apply Nemagon @ 25 litres per ha, sprinkle thoroughly chemical on soil followed by flood irrigation.