STEM & BARK BORERS

1. Yellow Stem Borer, Scirpophaga incertulas (Walker): (Lepidoptera: Pyralidae)

Distribution: S. incertulas is distributed primarily in tropical Asia. , Nepal, , Pakistan, Afghanistan, Nepal, Bangladesh, Myanmar, Vietnam, Thailand, Malaysia, Indonesia, Philippines, China, Japan and are the main habitat of the pest. Host Range: Cultivated rice is the primary host of S. incertulas. However, wild rice species, Oryza rufipogon, O. nivara and O. latifolia, and African cultivated rice, Oryza glaberrima, are potential alternative hosts of S. incertulas. Nature of Damage: Newly hatched larva enters into the leaf sheath, feeds voraciously for 2–3 days and then bores into the stem and, staying in the pith, feeds on the inner surface of the walls. When this occurs during the vegetative phase of the plant, the central leaf whorl does not unfold, but turns brownish and dries off, although the lower leaves remain green and healthy. This condition is known as dead heart, and the affected tillers dry out without bearing panicles. Larval feeding and internodal penetration at reproductive stage of plant cause development of empty or partially filled grain distinguished by its white colour and known as whiteheads.

2. White Stem Borer, Scirpophaga innotata (Walker): (Lepidoptera: Pyralidae)

Distribution: India, Australia, Malaysia, Indonesia, New Guinea, Indonesia, Philippines and Iran. Host Range: Rice is the main host for S. innotata, but it is reported on sugarcane, Cyperus rotundus, Cynodon dactylon, Oryza australiensis and Oryza rufipogon. Nature of Damage: The larvae feed by boring inside the leaf sheath. During vegetative stage central growing point of plant becomes yellow and finally dies producing dead heart symptom. During vegetative stage one larva may require about six tillers till pupation. During reproductive stage the larval feeding can cause development of white ear heads.

3. Striped Stem Borer, Chilo suppressalis (Meyrick): (Lepidoptera: Pyralidae)

Distribution: Striped stem borer also known as pale-headed stem borer is a pest of rice in India, Philippines, China, Korea, Japan, Vietnam, Taiwan, Cambodia, Iran, Myanmar, Bangladesh, Indonesia, Nepal, Pakistan, Thailand, Malaysia, Hawaii and Australia. Host Range: Rice and wheat are the main host plants for Chilo suppressalis; however, it has been reported to feed on maize, kodo, pearl millet, sugarcane, sorghum, broad bean, water oat, Sorghum sudanense, Vetiver zizanioides and other grassy weeds with low survivability. Nature of Damage: The larvae bore inside the leaf sheath and cause damage by feeding inside it. The larval feeding causes yellowing and drying of the central leaf known as dead heart. These affected tillers fail to bear panicle. In later stage of plant growth, feeding by larvae causes white ear heads, i.e. panicle with empty or half-filled grains.

4. Pink Stem Borer, Sesamia inferens (Walker): (Lepidoptera: Noctuidae)

Distribution: India, Pakistan, Bangladesh, Malaysia, China, Taiwan, Japan, Indonesia, Philippines, Sri Lanka, Thailand, Vietnam, Kenya and Myanmar. Host Range: Pink stem borer is polyphagous and reported on rice, wheat, finger millet, sorghum, bulrush millet, oat, barley, maize, kodo, sugarcane, foxtail millet, minogome, Sudan grass, Cyperus japonicus, Scirpus maritimus, Cymbopogon nardus, Echinochloa spp., Eleusine indica and Saccharum arundinaceum. Nature of Damage: Larvae bore into the plant and feed the central shoot. The central shoot becomes yellow and dries after some time showing the dead heart symptoms. Infestation during panicle initiation and milky grain stage leads to production of partially filled or empty grains. These affected panicles appear white and called white ear heads.

5. Mango Stem Borers: (Coleoptera: Cerambycidae)

Distribution: The species recorded in India include Batocera rufomaculata (De Geer), B. rubus (Linnaeus), B. roylei (Hope), B. numitor (Newmann) and B. titana (Thomson). Of them, Batocera rufomaculata De Geer is the most destructive. Besides B. rufomaculata, mango is also attacked by two other cerambycids, viz. Glenea multiguttata Guerin-Meneville and aedificator (Fabricius), and one buprestid in Karnataka. In Pakistan, the scolytid, H. mangiferae, was reported to be associated with sudden death disease of mango. Host range: Beside mango, they attack fig, jackfruit, mango, mulberry, papaya, apple, etc. Nature of Damage: After hatching from the egg, the neonate larva initially feeds under the bark. The larvae tunnel through the sapwood and make tunnels of about 2–3 cm width, which interfere with sap flow and affect foliage and production. The tunnels may either be in the peripheral region or may go deep down into the core of the tree. The damage in the early stage is not perceptible, but it can be noticed by the oozing of sticky fluid from several places of the tree trunk and branches. The damage results in yellowing of branches followed by drying and dieback of terminal shoots and branches ultimately leading to the death of the whole tree.

6. Apple Stem Borer, Aeolesthes sarta (Solsky): (Coleoptera: Cerambycidae)

Distribution: It spreads in all fruit-growing regions of temperate India. Host range: This pest infests fruit and forest trees besides apple. Nature of Damage: The grub is more destructive than adult. The grub makes a tunnel and reaches close to the trunk of the tree. Vitality and productivity of plant is greatly impaired.

7. Guava Stem Borer, Aristobia testudo Voet: (Coleoptera: Cerambycidae)

Distribution: Guava stem borer is introduced into India through North-Eastern Hill region. Host range: apart from gua va it also infests litchi, Hibiscus syriacus and Cajanus cajan. Nature of Damage: The damage symptom of stem borer on guava can be identified by the presence of small exit holes at the 20–30 cm interval with straw-coloured faecal matter in the form of pellets accumulated at the base of the plant. Severe incidence of this pest leads to leaf fall, drying of twigs and death of the plant.

8. Grapevine Stem Borer, Celosterna scabrator Fab.: (Coleoptera: Cerambycidae)

Distribution: In India, grapevine stem borer was reported for the first time at Pune in 1968. Nature of Damage: Affected leaves look yellow in colour and resemble micronutrient deficiency, which later dry and drop down. Adult emerge out by making a round hole and cause damage to the tender shoots by scraping and tunnelling inside the trunk. As a result, the affected vines get weakened and growth of the vine is reduced leading to decrease in the yield.

9. Bark borer, Indarbela tetraonis Moore: (Lepidoptera: Metarbelidae)

Distribution: In India it occurs mostly in areas having rice-wheat cropping system. Host Plants: Pomegranate, Aonla Nature of Damage: It is identified by the presence of irregular tunnels and patches covered with silken web consisting of excreta and chewed up wood particles, on the shots, branches and trunk. Shelter holes may be seen particularly at the joints of shoots and branches. The young shoots dry and die, giving sickly look to the tree. The pest has been reported to infest 70 plant species across fruits, forests and avenue plantations.

DEFOLIATORS/ LEAF FEEDERS

1. Leaf Folder, Cnaphalocrocis medinalis (Guenee): (Lepidoptera: Pyralidae)

Distribution: India, Sri Lanka, Pakistan, Nepal, Philippines, Fiji, Bangladesh, Korea, China, Malaysia, Japan, Vietnam, Afghanistan, Bhutan, Indonesia, Myanmar, Nepal, Taiwan and Australia. Host Range: Rice, maize, sorghum and wheat are the main host plants, while it has also been reported from barley, oats, pearl millet, tobacco, Echinochloa colona and Saccharum spontaneum. Nature of Damage: Leaf folder larvae cause damage to rice plant by folding leaf with the help of salivary secretions and feeding inside it by scrapping the upper epidermis. The lower epidermis becomes dry and falls off. During higher infestation growth of whole plant gets affected. The total photosynthetic area of plant gets reduced, and it affects the yield of the plant. The faecal matter of inside the folded leaf can cause development of fungal and bacterial infections. The economic injury level for leaf folder varies from 3 to 6% damaged leaf. When leaf folder attacks at boot leaf stage, it may cause partially filled grains.

2. Rice Hispa, Dicladispa armigera (Olivier): (Coleoptera: Chrysomelidae)

Distribution: India, China, Taiwan, Bangladesh, Myanmar, Japan, Nepal, Malaysia, Pakistan, Indonesia and Thailand. In India this pest is reported from West Bengal, Assam, Tripura, Meghalaya, Andhra Pradesh, Punjab and Himachal Pradesh. Host Range: Rice, sugarcane, Andropogon gayanus, Chrysopogon sp., Carex sp., Sorghum halepense, Imperata cylindrica and Themeda anathera. Nature of Damage Grubs mine the rice leaves from leaf tip (which is the ovipositional site) and feed on the chlorophyll content. The affected leaf shows blotched or burned appearance. During severe infestation the photosynthetic activity of leaves gets affected and the leaves dry. Adults cause damage by scrapping the upper and lower surfaces of leaves. The leaves damaged by adults show characteristic feeding symptoms of white streaks parallel to the midrib of leaves. The damage due to hispa is more when it attacks crop at nursery stage. The crop loss due to rice hispa has been reported from 28 to 100% in India.

3. Caseworm, Nymphula depunctalis (Guenee): (Lepidoptera: Crambidae)

Distribution: Asia, Australia, America and Africa. Host Range: Rice, millets and grasses like Panicum, Eragrostis and Paspalum. Nature of Damage: Larvae make a case with the help of leaves and feed inside it. Larvae feed by scrapping the leave tissues. The leaves damaged by larvae show characteristic white patches on it. The larvae along with cases float on water and move from one plant to another. The total photosynthetic area of the plant is reduced and ultimately yield is reduced.

4. Armyworm, Spodoptera mauritia (Boisid): (Lepidoptera: Noctuidae)

Distribution: It is distributed in Australia and South and South East Asian regions. Host Range: S. mauritia is a polyphagous pest and reported from rice, sugarcane, maize, barley, millet, wheat, tobacco, legumes, vegetables, cotton, ragi, Bermuda grass, Pennisetum typhoideum, Paspalum dilatatum, Paspalum scrobiculatum, Panicum setigerum, Agropyron repens, Digitaria ciliaris and other grasses. Nature of Damage: The newly hatched larvae of armyworm feed by scrapping the leaf tissue. Later on larvae feed by nibbling leaves voraciously. They feed in groups during night. They cause severe damage at seeding stage of plant. The field damaged by armyworm appears as if grazed by .

MANAGEMENT OF BORERS AND LEAF FEEDERS 1. Cultural Methods (a) Many varieties are resistant to borers and leaf feeders (e.g. Karjat 5, Anjali, Karnataka hill Paddy 9, Mahananda, Surya). For cultivation, select the rice varieties resistant to major insect pests. If multiple resistant varieties are not available, select the local variety resistant or tolerant to most severe pest of the area. (b) In absence of resistant or tolerant varieties, select early-maturing variety for cultivation. It may escape the damage of late-coming pests such as the stem borers. (c) Grassy and other weeds or alternate hosts of pest should be removed from seedbed, paddy field or surrounding area especially in localities inhabited by armyworm, cutworm, leaf folder, rice hispa and rice bug. (d) Cut the stubbles at ground; remove, burn or plough the stubbles; and leave the ground fallow for 3–4 weeks to reduce the population buildup of stem borers and leaf feeders.

2. Mechanical Control (a) Pheromone traps are used for monitoring and mass trapping and disrupt the mating of yellow stem borer male moths (male annihilation technique). Controlled release formulation of sex pheromone of yellow stem borer consisting of (Z)-9-hexadecenal and (Z)-11-hexadecenal at a ratio of 1:3 has been found to disrupt mating up to 98% when used at the rate of 40 g a.i./ha in 625 dispensers spaced at 4 metre.

3. Natural Biological Control (a) All the insect pests of rice are attacked by a large number of parasitoids, predators and pathogens under natural conditions which reduce the population of insect pests depending upon their population and weather conditions.

4. Chemical Control (a) Insecticides should be used only when pest population reaches economic threshold level. (b) Late afternoon spray has been found more effective against armyworms and cutworms.

(c) After crop reaches maximum tillering, granules are not much effective against stem borers, and spray formulation should be used. (d) While selecting the insecticides, preference should be given to those which are more effective and safe to natural enemies. (e) Soil application of carbofuran before sowing or transplanting of rain-fed lowland rice followed by need-based spray of quinalphos or monocrotophos has been found effective against stem borers and defoliators. (f) Fipronil 0.3 GR, Carbofuran 3 CG, Carbosulfan 6 GR, Monocrotophos 36 SL, Chlorpyrifos 20 EC are other effective chemical insecticides against borers and leaf feeders.

References 1. Bhatt, N., Joshi, S. and Tiwari, S.N. (2018). Pests of Rice. In: Pests and their management (Ed: Omkar), Springer Nature, Singapore. 2. Tripathi, A.K. (2018). Pests of Medicinal and Aromatic plants. In: Pests and their management (Ed: Omkar), Springer Nature, Singapore. 3. Reddy, P.V.R., Gundappa, B. and Chakravarthy, A.K. (2018). Pests of Mango. In: Pests and their management (Ed: Omkar), Springer Nature, Singapore. 4. Khan, A.A., Wani, A.R., Zaki, F.A., Nehru, R.K. and Pathania, S.S. (2018). Pests of Apple. In: Pests and their management (Ed: Omkar), Springer Nature, Singapore. 5. Gundappa, B., Rajkumar, M.B., Singh, S. and Rajan, S. (2018). Pests of Guava. In: Pests and their management (Ed: Omkar), Springer Nature, Singapore. 6. Kulkarni, N.S. (2018). Pests of Grapes. In: Pests and their management (Ed: Omkar), Springer Nature, Singapore. 7. Rajendra Singh (2018). Elements of Entomology, Rastogi Publications, India. 8. Images (https://www.google.com/imghp?hl=en)