Domain:                  Eukaryota
Kingdom:                Animalia
Phylum:                   Arthropoda
Class:                       Insecta
Order:                       Hemiptera
Suborder:                 Auchenorrhyncha
Family:                     Cicadellidae
Genus:                      Nephotettix
Species:                   N. virescens
Binomial Name:      Nephotettix virescens (Distant, 1908)

Worldwide. Widely distributed in Asia. Known from Malaysia, Indonesia, Burma, South Vietnam, Thailand, India, Pakistan, Sri Lanka, China, Hong Kong, Philippines and Laos (Ghauri, 1971). Also found in the southern part of Japan.This species is known from Japan, Ryukyu Islands, Formosa, India, and the Philippines (Ishihara 1964 [390]). (Nielson,1968)

পোষক পরিসীমা
Restricted to rice.

ডিমঃ Greenish transparent eggs are deposited in the midrib of leaf blade or sheath of rice or green grass. They are laid in batches of 10 to 15 arranged in a single row.

নিম্ফঃ Nymph are soft bodied, pale green/yellow with small spines on the dorsal surface of abdominal segments, with small, dark-brown or black markings on the dorsal surface.

প্রাপ্তবয়স্কঃ Medium size, slightly robust species. Length of male 4.30-4.50 mm., female 4.90-5.50 mm. (Nielson, 1968) General color light yellowish green to green. Crown and pronotum light yellowish green, immaculate; elytra green with small brown or black spot at middle, brown or black band on apex in male, female unmarked. Vertex usually unmarked with distinct furrow, and longer in middle than next to eye, appearing quite pointed in most specimens. Head, pronotum and scutellum are usually green but some males have black markings adjacent to ocelli. Forewing with a distinct spot that does not touch claval suture, but this spot may be absent or only partially represented. Apical third of tegmen black in males; females with unmarked head, pronotum and clavus.(Nielson, 1968)Male genitalia: Subgenital plate off- white or partly black. Corners of male pygofer rounded , with 1 long and 4 smaller spines. Aedeagus with 3-5 pairs of spines located in the middle of the shaft. (Nielson, 1968) N. virescens is usually one of the easiest Nephotettix species to identify, with its unmarked vertex and distinctly pointed head. Occasionally males are found with a partial submarginal band present on the vertex. These may be distinguished by the genitalia; in particular the number of spines on the aedeagus, which is far less than in N. nigropictus.(Wilson & Claridge 1991).

Head, pronotum and scutellum are usually green, but some males have black markings adjacent to ocelli. Forewing with a distinct spot that does not touch claval suture, but this spot may be absent or only partially represented. Apical third of tegmen black in males; females have unmarked head, pronotum and clavus.
Adults are 3-5 mm long, bright green with variable black markings, wedge shaped with a characteristic diagonal movement. Male insect has a black spot in the middle of the forewings that is absent in females. The insect is active from July to September.

The species can be differentiated from other species of Nephotettix known from Australia by the relatively longer vertex and the complete absence of dark markings from the vertex. Confirmation of identification requires an examination of the male genitalia.

[NO INFORMATION AVAILABLE]

The insects feed on rice fields/ wild grasses in the absence of rice fields. Eggs are laid in rows inserted into leaf sheaths. The egg stage last from 5 to 10 days and the nymphal period from 13 to 18 days. There are five nymphal instars. (Nielson, 1968)

Very important vector of tungro disease in tropical Asia.(Wilson & Claridge 1991)This species is a vector of the rice yellow dwarf virus in Japan and rice tungro disease in the Philippines. Nasu (558) first reported this species as a vector in 1963 under the name of ‘Nephotettix sp. (B) [2].
Economic losses due to direct feeding damage by N. virescens may sometimes be masked by losses caused by the viruses it transmits. Although N. virescens is a phloem feeder on susceptible rice varieties, it does less damage than planthoppers such as Nilaparvata lugens and Sogatella furcifera. Blockage of the vascular system has not been demonstrated for cicadellids such as N. virescens, though feeding by large numbers of insects can cause wilting and drying of rice plants through excessive removal of assimilates.

Numbers of N. virescens are sometimes very high on irrigated rice crops in South India, with large numbers attracted to lights even in urban areas (Anjaneyulu et al., 1994). It has been estimated that in five states in southern India between 17 and 23 kg/ha of grain yield was lost to N. virescens in 1990-1991 and an additional 15 to 24 kg/ha to tungro (Ramasamy et al., 1996). In rainfed lowland areas in East India, an estimated 15 kg/ha of grain yield was lost due to direct feeding by N. virescens in 1990-91 (Ramasamy and Jatileksono, 1996). The same authors reported that yield losses of 12 kg/ha occurred in Thailand. Setboonsarng (1996) reproduced data from the Department of Agricultural Extension in Thailand in which the average area damaged by N. virescens feeding in 1986-1991was shown as 12,997 and 19,554 ha in rainfed and irrigated areas, respectively.

However, all these figures on production losses due to direct feeding by N. virescens should be treated with caution. Some appear to be based on estimates linked to economic thresholds for the insect. One such threshold used as a basis for insecticide recommendations by a government research institute in eastern India is two insects per rice plant (Chancellor et al., 1997). This number of leafhoppers would have a negligible effect on the rice plant through direct feeding but could spread tungro rapidly through a field if there was a strong source of virus inoculum present (Shukla and Anjaneyulu, 1982; Chancellor et al., 1996). Most economic thresholds, such as the one for eastern India, do not take into account the presence or absence of virus inoculum, perhaps because of the difficulties in identifying inoculum sources. An exception, is the threshold developed for tungro control in Bali, Indonesia which relates insect numbers to the proportion of diseased plants in fields at a particular growth stage (Suzuki et al., 1992).

The major economic impact of N. virescens is through the rice viruses it transmits. The most important of the diseases caused by N. virescens-mediated virus transmission is rice tungro. Tungro is a composite disease caused by Rice tungro bacilliform virus (RTBV) and Rice tungro spherical virus (RTSV) (see respective data sheets for each virus) and has a complex epidemiology (Hibino et al., 1978). Yield losses due to tungro are primarily due to infection with RTBV. The disease has a high profile because of its ability to cause total loss of both grain and straw yield and because there are no effective control measures once rice plants have become infected. Irrigated areas are most at risk, although tungro may also occur in rainfed lowland rice.

A commonly cited figure for annual economic losses due to tungro throughout Asia is US$ 1500 million (Herdt, 1988). However, this is likely to be an overestimate as the frequency and extent of large-scale outbreaks of tungro has declined since the period of peak occurrence in the 1960s and 1970s (Chancellor and Thresh, 1997). In a recent multiple pest and disease survey conducted in four Asian countries, tungro incidence was low, illustrating the sporadic nature of the occurrence of the disease (Savary et al., 2000). However, the production loss in affected areas due to tungro was estimated to be 2.6 tonnes/ha, which was the highest value of any of these stresses.

Although major epidemics of tungro are less common than in previous decades, major outbreaks still occur. In 1990-1991, an outbreak occurred in India in which a total of 134,000 ha of rice in Andhra Pradesh and 49,000 ha in Orissa were affected by tungro (Ramasamy and Jatileksono, 1996). In 1995, an epidemic was reported from Central Java in Indonesia where 12,340 ha of rice were affected causing an estimated loss of US$ 1.87 million (Daradjat et al., 1999). In 1998, 40,000 ha of rice in Punjab, India were damaged by an outbreak of yellow stunt syndrome that has similar symptoms to tungro (Azzam et al., 1999). This outbreak, in which yield losses were estimated at 30-100% in the affected area illustrates one of the difficulties associated with assessing the economic impact of tungro. Symptoms of tungro may be confused with other plant disorders and in some regions appropriate diagnostic techniques are not readily available to confirm the cause of the problem.

In some areas, tungro is endemic and regularly causes economic losses. In certain districts in Bali, Indonesia tungro is a problem in most years even though the total area damaged may not exceed a few hundred hectares (Astika, 1999). On Mindanao in the Philippines, between 900 and 2700 ha were affected annually by tungro during 1993-1998 with the disease occurring every year in the North Cotabato district (Truong et al., 1999). Disease incidence on this scale may not represent significant economic loss when viewed on a national basis. Teng and Revila (1996) cited a study in Malaysia covering the period 1981-1984 when outbreaks of tungro occurred in the Muda irrigation scheme and caused much concern amongst policy makers. These authors pointed out that surveys revealed that when losses were averaged across all rice-producing areas in Malaysia the mean yield loss was less than 1% (Heong and Ho, 1986). However, this perspective does not take into account the serious effects on the livelihoods of those farming communities affected. Many Asian rice farmers rely on credit to purchase inputs such as fertiliser and to pay for labour costs. One crop failure can very seriously affect the economic security of a farm household.

Other virus and phytoplasma diseases transmitted by N. virescens include Phytoplasma oryzae, Rice bunchy stunt virus, Rice gall virus and Rice yellow stunt virus. However, each of these pathogens is transmitted by other cicadellid vectors and with a greater degree of efficiency than by N. virescens (Ou, 1985). Experimental field data on rice yellow dwarf disease in Taiwan showed that 93% yield loss was possible when rice plants were infected at the seedling stage and losses declined to 4% when infection occurred at 50 days after sowing (Chen and Ko, 1975). A similar association between age of infection and yield loss was also demonstrated for rice transitory yellowing which caused significant crop losses in Taiwan in the early 1960s (Ou, 1985).

Plants/Leaves/abnormal colours
Plants/Leaves/abnormal forms
Plants/Leaves/honeydew or sooty mould
Plants/Leaves/necrotic areas

Small numbers of insects may not visibly damage the plant. Virus-diseased plants may show various symptoms, such as stunted, deformed leaves, increased tillering, gall formation, or yellowing, depending on the virus (for further details, see virus datasheets and Brunt et al., 1990) [3].

1. Yellowing of leaves from tip to downwards
2. Vector for the diseases viz., Rice tungro virus, rice yellow & transitory yellowing cause direct damage to the rice plant
3. Retarded vigorous and stunted growth
4. Drying up of plant due to sucking up of the leaf

[NO INFORMATION AVAILABLE]

INTEGRATED PEST MANAGEMENT
IPM programmes for the control of N. virescens and some other rice pests are increasingly advocated to reduce the use of pesticides (for a review, see Way and Heong, 1994). The manipulation and encouragement of predators and parasitoids is likely to be of considerable importance in most countries where tungro disease is important. The tungro viruses (RTBV and RTSV) transmitted by N. virescens are more damaging than the insect itself.

ETL: 60/25 net sweeps or 5/hill at vegetative stage or 10/hill at flowering or 2/hill in tungro endemic area
Nursery should not be located near the street lamps
Spray any one of the following insecticides:
Phosphamidon 40 SL 50 ml, Phosalone 35 EC 120 ml
Maintain 2.5 cm of water in the nursery and broadcast anyone of the following in 20 cents:
Carbofuran 3 G 3.5 kg, Phorate 10 G 1.0 kg

Ratoon rice may serve as a reservoir for both insects and virus diseases. Grass weed species may also harbour viruses. Sanitation in and around seedbeds and fields, covering wet seedbeds with nylon screens at a height of 60 cm, and simultaneous cropping are used against N. virescens (Mochida et al., 1986). Tungro outbreaks can be triggered by the presence of early infected paddy fields in asynchronously transplanted areas. For the control of Rice bunchy stunt virus in China, since the disease attacks rice plants most easily in the seedling stage and green recovering tiller stage, control was affected by regulating sowing and transplanting times to escape the migrant peak of the vectors (Xie et al., 1984). The vectors should also be controlled at the time of sowing and transplanting.

Kiritani et al. (1983) concluded that changes in cropping practices in Japan, such as an increase in the cultivation of early rice and the earlier planting of some mid-season rice, facilitated disease spread and led to serious epidemics. However, the duration and frequency of these epidemics have been reduced by subsequent changes in cultural practices, including the decreased cultivation of wheat and barley, the use of new rice cultivars and insecticides, and winter and spring ploughing of fallow ricefields.

FIELD MONITORING/ECONOMIC THRESHOLD LEVELS
Thresholds are employed as part of the strategy to control tungro disease. Suzuki et al. (1992) investigated the build-up of rice tungro disease infection in paddy fields in Bali, Indonesia and found that practical control thresholds could be established for monitoring 2-5 weeks after transplanting, on the basis of percentage of diseased hills. The areas which might be infected in the first half of the wet season could be predicted from the number of infected locations during the second half of the dry season. Increase in virus infection was preceded by population build-up of the vector. Increased migration in the first-generation adults accounted for population build-up of the vector. Conditions for severe outbreaks were: tungro intensity in paddy fields that are under young plants reaches over four times the economic control threshold; and, at the time of transplanting, the mean infective vector index in migrant-producing fields in the area exceeds (15 insects per 25 strokes) per 100 hills.

HOST-PLANT RESISTANCE
Resistant varieties are used as part of an integrated control programme (see, for example, Heinrichs et al., 1986; Myint et al. 1986). Current breeding programmes include screening for resistance to N. virescens (Pathak and Khan, 1994). Myint et al. (1986) investigated the levels of resistance to N. virescens of nine rice varieties in greenhouse and insectary trials in the Philippines. On the basis of seedbox screening, survival and oviposition, and feeding and population growth tests, IR29 and IR56 were resistant, IR8, IR36 and IR42 moderately resistant, and IR22, IR46, Utri Rajapan and TN1 susceptible. The degree of predation of leafhopper by Lycosa pseudoannulata and Cyrtorhinus lividipennis was the same on all varieties, regardless of the level of varietal resistance to N. virescens. Mortality of N. virescens was highest and populations lowest in treatments where the resistant varieties IR29 and IR56 were combined with predators. A study showed that IR28, IR29 and IR34, which all have the variety Gam Pai as one of the resistant parents, were the most resistant to N. virescens [5].

CONTROL BY FUNGAL PATHOGENS
The use of fungal pathogens for control is at a preliminary stage of investigation; fungi are more prevalent at times of high humidity (Nayak and Srivastava 1979; Li 1988). In the Changsha region of China, Entomophthora delphacis generally infected from 37 to 64% in Nilaparvata lugens and the same fungus also attacked N. virescens (Li, 1988; Ambethgar, 1997). Beauveria bassiana spores were found on nymphs and adults of N. virescens in the ricefields of Cuttack, India (Nayak and Srivastava, 1979). Hirashima et al. (1979) found the same fungus in Thailand. In India, Beauveria bassiana attacks N. virescens and N. nigropictus during September-November (Gupta and Pawar, 1989).

Due to the variable regulations around (de-)registration of pesticides, we are for the moment not including any specific chemical control recommendations. For further information, we recommend you visit the following resources:

EU pesticides database (http://ec.europa.eu/food/plant/pesticides/eu-pesticides-database/)
PAN pesticide database (www.pesticideinfo.org)
Your national pesticide guide

The results obtained from a recent study showed that both the shoot and leaves extract of Bambusa vulgaris and the shoot extract of Bambusa malingensis have potential insecticidal activity against Nephotettix virescens [6].

তথ্য পাওয়া যায়নি।

তথ্য পাওয়া যায়নি।

https://academic.oup.com/ee/article-abstract/14/3/297/2393277

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https://plantwiseplusknowledgebank.org/doi/full/10.1079/pwkb.species.36198

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https://ph02.tci-thaijo.org/index.php/MIJEEC/article/view/245179