6
Rice Brown Planthopper
(Krishnaiah etal., 2002; 2006; 2007).
Feeding preference among insect species and life stages:
There are differences in feeding preference among these species and feeding capability
of different stages in their life cycle. Among the three species, BPH is capable of causing
maximum damage per individual insect and together with its very high fecundity it
causes very high damage under field conditions in a given time. Among different life
stages in BPH third and fourth instar nymphs have been reported to be more devastating
than younger nymphs or adults. WBPH generally prefers to feed and develops relatively
faster on younger rice plants in nursery or up to 30-35 days after planting. BPH prefers
to feed on 45-50 day old plants.
Field Distribution and Sampling:
“If you go to field and observe, plants can speak to you, If you remain behind the desk
or at home, Plants cannot cry to you.” Says Norman E. Borlaug, “Father of Green
Revolution” and the Nobel Laureate. This is fundamental for agriculture and agricultural
research. This is equally and more importantly applicable in case of BPH when it comes
to observing the incidence in the field. Farmer or researcher has not only to go to rice
field and observe the plants, he must also enter inside the field and bend and observe at
the basal portion of rice plants to really see where the insects are?
Field settling of BPH occurs in newly transplanted crop, in about 15 days after planting
either by short range travel or long range migration depending on source area of the
insect. At the time of initial settling, population is very low ranging from 1-5 insects
per100 hills or to a maximum of 30 insects per 100 hills. At this stage macropterous
adults are randomly distributed in the field. They lay eggs on the same plants they settle
or shift slightly to nearby plants after laying some eggs on original plant. Usually the
nymphs that emerge are not uniformly distributed in a field or even in a small area of the
field. Later, they move to nearby plants and become mainly brachypterous adults. By
the end of second generation populations reach damaging levels if unchecked. During
the third generation damage starts appearing in the field in circular patches and if
unchecked may spread to whole field causing total “hopper-burn”.
