Biological Control of Insect Pests: Southeast Asian Prospects - EcoPort

Biology
Damage
4.12
Nezara viridula
199
The entirely green colour form smaragdula of N. viridula is the one that
occurs widely in the Pacific area. In other areas of the world it is
accompanied by several other colour forms (Yukawa and Kiritani 1965).
The barrel-shaped eggs are usually laid at night in neat rafts, commonly of
80 to 120 or more eggs and they are cemented firmly to one another and to
the sheltered surface of a leaf. The eggs hatch in 4 to 9 days, and the newly
emerged nymphs remain together near the eggshells for a day or two, a
degree of gregariousness persisting also in the next instar or two. There are
five nymphal stages before the adult emerges, 24 to 60 days after hatching,
depending on temperature. At 25Ð28¡C, 55Ð65% RH and 14 hours daylight
the development periods (in days) were: egg, 4.8; 1st instar nymph, 3.8; 2nd
instar, 5.2; 3rd instar, 4.5; 4th instar, 6.4; 5th instar, 11.9 (Harris and Todd
1980). The nymphal stages are multicoloured, but the adults are a uniform
green in the form smaragdula.
The adults can fly strongly. There may be
four generations in a year in coastal New South Wales, and perhaps more in
areas with no perceptible winter.
The adult bugs live up to 3 weeks in hot weather. In regions with a cold
winter those of the autumn generation may live much longer, hibernating in
debris, under bark, or in buildings, inactive and non-reproductive. Such
hibernating bugs change colour from green to brown. In areas with a less
severe winter the still-green adults may remain active, although nonreproductive.
Waite (1980) showed that the adults and nymphs tend to bask
exposed on the surface of the plant canopy in the early daylight
hoursÑbehaviour that can be availed of in applying chemical control
measures (Kamal 1937; Clausen 1978; Hely et al. 1982; Singh and Rawat
1982; Todd 1989).
When not controlled by chemicals or natural enemies, this bug can be a
serious pest of a very wide range of crops and ornamental plants. In Australia
there are recommendations for its chemical control on beans, cucurbits,
peas, potatoes, tomatoes, passionfruit, groundnuts, sorghum, soybeans,
sunflowers and tobacco (Anon. 1967, 1979b; Miller et al. 1977), but it also
attacks maize, crucifers, spinach, lucerne and many other legumes, grapes,
oranges and many other fruits and seeds, and macadamia (Ironside 1979; La
Croix 1986) and pecan nuts (Seymour and Sands 1992). Undoubtedly there
would be recommendations for a much wider range of cultivated plants were
it not for the fact that biological control is effective now in many situations