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Cotton (Gossypium spp.), being an important commercial crop of the world, plays a
significant role in the economy and employment. In India, cotton is cultivated in an area
of over 9 million ha, which is almost 25% of the world area (35 million ha) under the crop.
However, the average yield of cotton (440 kg/ha) is far below the world average(677 kg/ha) and the production is only about 16% (4.13 million tons) of the world production
of 26.19 million tons. Thus, India ranks first in area and fourth in cotton production in
the world. The main cause for its poor productivity is its susceptibility to insect pests
and a number of diseases. Among the cordial factors, complex pest spectrums associated
at all stages of crop growth are of prime importance. Cotton is the highest insecticideconsuming
crop (Siayed et al., 1999) because of bollworms (Thimmaiaha et al., 1990),
which are responsible for the reduction in yield. Insect and noninsect pests of 1,326
species across the world and 162 at national level (Hargreaves, 1948) are known to cause
damage to cotton crop. In India, about a dozen of insect pests (Agarwal et al., 1984) cause
major losses to the extent of 52 to 60% in cotton production. Bollworms are the most
serious pests of cotton in India causing an annual loss to the tune of 1,200 cr. Among
these bollworms, viz., spiny boll worm, Earias insulana (Boisdual), spotted bollworm,
Earias vittella (Fabricius), American bollworm, Helicoverpa armigera (Hubner) and pink
bollworm, Pectinophora gossypiella (Saunders) pose greater threat to cotton production.
Since time immemorial, pink bollworm has been a regular occurrence in cotton and has
become a threat to cotton production due to changed agroecosystem.
Squares and bolls are extensively damaged by bollworms. Pink bollworm is the most
destructive pest of cotton in the later stages of the crop growth. However, the larva
feeds on anther and pollens of flowers by living in a sort of thin web leading to characteristic
rosette formation. Affected flowers may dry and fall off. Later, the larva bores into the
bolls and penetrates into immature seeds. The larva keeps on feeding the seeds by tunneling
across the locules. Unnoticeable small pinhead-sized hole on the affected bolls is the only
doubtful symptom for identifying pink bollworm infestations. Here the affected bolls
may shed off, while those retained on plants open partially before maturity, resulting in
stained immature fiber (Agarwal et al., 1984).
Cultivation of high-yielding varieties/hybrids susceptible to insect pest under the
insecticide umbrella failed to give economic returns due to the development of resistance.
Continuous cultivation of hybrid cotton in large areas increases vulnerability to pests.
Insect pest management in cotton has traditionally relied upon synthetic insecticides
(Graves et al., 1999). Reaction of bollworms varies with group of chemicals and also the
site at which the bollworm lives. However, a single spray is not sufficient to combat the
bollworm menance in cotton.
As many as 10 to 16 spray applications of synthetic insecticides are required to manage
bollworms in cotton (Henneberry and Narango, 1998). On an average, farmers apply 6 to
18 rounds of insecticides in different situations to manage the insect pests menace on
cotton (Kulkarni et al., 2003). Sole reliance on and continuous use of broad spectrum and
sub-lethal dose of insecticides not only reduce the efficacy, but lead to uneconomical and
undesirable ecological changes, viz., resurgence, resistance and residue buildup to insect
pests. The three R’s, Resurgence, Resistance and Residue, are the most potential problems
associated with indiscriminate use of insecticides in cotton agroecosystem and have
made cotton cultivation nonprofitable. Development of resistance to synthetic pyrethroids against pink bollworm (Kranthi et al., 2002) has reached an alarming stage. Heavy reliance
on broad spectrum chemicals neither provided sustainable pest control nor maintained
the ecological balance, but killed the natural enemies and disrupted the ecological balance
and urged the farmers into a crisis in the changed agroecosystem. Given the exorbidant
price of insecticides and their adverse effects on environment, the entry of new products
has become imperative to work out their efficacy, so as to give better choices to the
farmers/growers and quality lint to the spinners, weavers/textile industry. Search for newer
and safer group of chemicals either by unilateral sprays or by alternate use of different
groups of chemicals is the need of the hour in cotton pest management.
Pest management in cotton has always been a challenge. Adverse effect of chemicals
on nontarget organisms, decline of cry proteins in Bt cotton will lead to evaluate the
newer molecules of pesticides for adoption in changed agroecosystem.
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