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The initial symptoms of leafhopper damage in all crops are yellowing of leaves, followed by crinkling around the margins and upward curling of leaves. The leaf tips and margins develop necrotic areas. At later stages, bronzing of entire leaves can be seen. This may or may not be associated with leaf fall. Severely affected plants have stunted growth.
Sowing of cotton between mid-April and June may minimise A. biguttula biguttula damage in Northern India (Joginder Singh et al., 1978). A. biguttula biguttula incidence was significantly lower on cotton intercropped with sunflower, green gram (Vigna radiata) and black gram (Vigna mungo) than cotton alone (Venkatesan et al., 1987), although Singh et al. (1993) observed high incidence of A. biguttula biguttula in sunflower (Helianthus annus) and okra, when intercropped with cotton.
In glasshouse experiments Bernardo and Taylo (1990) observed a pronounced preference by A. biguttula biguttula for feeding and oviposition on okra compared to aubergine. They indicated the possibility of using okra as a trap crop to save aubergine germplasm from leafhopper damage.
After rice harvest, sowing cowpeas by minimum tillage methods among standing stubble reduced colonization by leafhoppers during the first 2 weeks of crop growth (Litsinger and Ruhendi, 1984).
A number of reports are available from India on screening of cotton (Dhawan, 1991), okra (Mahal et al., 1993), aubergine (Gaikward et al. 1991), sunflower (Deshmukh and Akhare, 1979) and cowpea (Sagar and Mehta, 1982) germplasm for resistance to A. biguttula biguttula. Several of these reports are based on repeated field screenings. Few reports also pertain to laboratory screening for confirmation. Statistics, however, are not available whether these resistant varieties are cultivated or not.
Leafhoppers show less preference for varieties of Gossypium arboreum than G. hirsutum (Balraj Singh et al., 1976; Yein, 1983; Khan and Agarwal, 1984; Malik and Nandal, 1986). Among the G. hirsutum types resistance is associated with long hair length and tough leaf lamina on the ventral surface of leaves (Khan and Agarwal, 1984; Premsekhar, 1985). Balasubramanian (1979) reported long internodes in variety HB 69 contributing to resistance to leafhopper attack.
The varieties/lines Sel 6-2, AE 30, White Velvet, Clemson Spineless, Early Long Green, AE 27, IC 75, HB 45, HB 39, HB 43, IC 7194, Punjab Padmini and New Selection have been reported to have resistance to leafhoppers (Uthamasamy et al., 1975; Patil et al., 1977; Teli and Dalaya, 1981; Kishore et al., 1983; Mahal et al., 1993). A wild species, Abelmoschus moschatus, has also been found to offer resistance to leafhoppers (Hooda and Dhankar, 1992).
Field screening of aubergine germplasm against A. biguttula biguttula in India has led to identification of Manjari Kota, Vaishali, Mukta Keshi, Round Green and Kalyanpur T 3 possessing resistance. The resistance was associated with increased length and density of hairs and trichomes (Mote, 1982; Gaikwad et al., 1991). In studies conducted in the Philippines, the aubergine varieties PI 381272-2 and PI 386257-11 have been found to be less preferred for feeding by leafhoppers in greenhouse conditions. Both these varieties exhibited the antixenosis mechanism of resistance (Caasi-Lit and Bernardo, 1990).
Brar and Sandhu (1974) recorded low leafhopper infestation in two spring varieties, EC 15527 and EC 27501, and a summer variety, EC 68415, during screening studies. Early and dwarf varieties, Morden and Cerianka 66, have been found to be less preferred for leafhopper infestation (Deshmukh and Akhare, 1979).
Sagar and Mehta (1982) screened 14 cowpea varieties and isolated Vita 4 as possessing resistance to leafhoppers.
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:
A. biguttula biguttula causes heavy losses particularly in cotton and okra during the summer months in the Indian subcontinent. In cotton it can cause yield loss greater than 100-114 kg of lint per hectare (Sukhija et al., 1987; Dhawan et al., 1988). The combined losses due to leafhoppers and whitefly on sunflower is estimated to be 9.2% (Balasubramanian and Chelliah, 1985). In the absence of effective natural enemies, this pest requires insecticide intervention for its control in the entire Indian subcontinent.