Page 7 - Vol.38-No.6

CROP PROTECTION

staying on the under surface during the day,
run around on the upper surface at night
where they pick up contact insecticide.
This problem can be overcome by always
spraying up and into the cotton plant by
holding the lance with the nozzle project-
ed upwards under the leaf canopy. Alter-
natively growers should use a systemic
insecticide which enters the leaves and Split cotton bolls with lint exposed and
poisons the pests as they feed. ready for harvest
Insect pest control of large areas (Picture courtesy Omex)
of cotton can carried out by aerial The other option is to use a knapsack
application of insecticide (Picture mistblower, a unit not widely used for of these insect pests, which are larvae of
courtesy Dr Roderick Robinson)
applying insecticides to cotton in Africa moths, can in certain circumstances attack
and a good shower of rain can seal the but extensively used in Asia on the Indian very young plants. They do considerable
insects in the soil and thereby offer sig- sub-continent and in South East Asia with damage by either severing the growing
nificant natural control. good effect. The leading edge of the air point (Helicoverpa) or boring into the shoot
Applications of contact insecticide using blast, which reaches the leaves momen- tip (Earias). Plants are not killed, but the
knapsack sprayers may give disappointing tarily before the spray, flips the leaves and damage caused destroys the ability of af-
results against many sucking pests because exposes the undersides to incoming spray. fected plants to develop a normal shape.
these sprayers, fitted with hollow-cone Bollworm pests such the African cotton This in turn affects the ability of farmers
nozzles and held in the standard mode, bollworm and spiny/spotted bollworms to move easily and comfortably up and
will deposit most spray on the upper leaf (Earias sp) is regarded as mid-season down the rows. Be that as it may the real
surface, while the insects like aphids and pests of the cotton plant’s reproductive onslaught from bollworms comes later in
whitefly larvae are on the under-surface. period (45 days onwards) when the plants the day when cotton flowers and fruits
Better results are achieved against jassids are bearing fruiting bodies as flower buds (bolls) are in abundance, but that is an-
because both adults and nymphs, while (squares), open flowers and bolls. But both other story.
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Vol. 38 No. 6 5