18
Rice Brown Planthopper
easily moves forward along the winds even with slight macroclimatic disturbance due
to winds. WBPH rarely settles to the extent that it can multiply to the population levels
that can cause economic damage to rice crop. Hence, it could settle early in Punjab and
Haryana, which are the final destination points of south-west monsoon. On the contrary,
BPH is more sedentary and does not move forward unless the situation demands in
terms of exhaustion of food sources by way of harvest of the crop. Hence, BPH was
confined only to eastern parts of India apart from its southern strong hold. However,
with large-scale cultivation of rice in boro season in the states of West Bengal, Bihar,
Jharkhand and Eastern Uttar Pradesh, rice crop is available to BPH in these areas up to
April-May. More favorable climate exists in these states for the multiplication of BPH
from February to May. Hence, BPH might have become one of the pests for “boro” rice
in these areas similar to that of Bangladesh (Islam &Haque, 2009). Further, “boro” rice
in these states might be serving as a temporary shelter for BPH migrating from Orissa
and coastal areas of West Bengal up to the harvest of rice in April-May. Immediately
after harvest of “boro” rice the time is also ripe for southwest monsoon which can take
BPH up to Punjab and Haryana quite early in the kharif, i.e. in June, or early parts of
July. This allows sufficient time for completion of 3 generations for BPH before the
kharif rice is harvested in October end or first fortnight of November. Thus, “boro” rice
might be helping for wide spread occurrence and damage by BPH in Punjab, Haryana
and Western Uttar Pradesh.
After the harvest of kharif rice in September end or first fortnight of October, winter
starts setting in the entire northern sates of Punjab, Haryana, Uttaranchal, Uttar
Pradesh, Bihar, Jharkhand etc. Then it is most likely that BPH migrates back to either
eastern states of West Bengal and Orissa or even to the southern states of Andhra
Pradesh, Karnataka, Tamil Nadu and even Kerala. Usually during this period, North-
East monsoon starts and it might be helping the migration of BPH from northern states
to eastern and southern states where it can have year round multiplication. North-East
monsoon rains can take BPH only up to southern tip of Indian Peninsula and up to Sri
Lanka. BPH cannot move further south of Sri Lanka as it has to cross the mighty Indian
Ocean. There are no land areas or islands where rice is cultivated in the south beyond
Sri Lanka. The monsoon winds move mainly in North-South direction from one area to
another area and not in East-West direction. This might also be responsible for isolating
South-Asian biotype from South-East Asian biotype. All this is hypothetical till date.
No studies have been carried out at the ground level (Krishnaiah et al.2011; Krishnaiah
