Contents - Faperta

Pest Management and the Environment 9
S. graminum, in sorghum (Schweissing and Wilde, 1979). Increase in nitrogen in potato
leaves increased the development and survival of serpentine leaf miner, Liriomyza trifolii
Burgess (Facknath and Lalljee, 2005). Potassium and phosphorus, on the other hand,
decreased the host suitability of potato plants to L. trifolii, and were detrimental to the pest.
Intercropping and Crop Rotations
Crop rotation is another means of reducing insect infestation. It breaks the continuity of the
food chain of oligophagous pests. Sorghum is generally rotated with cotton, groundnut,
sunfl ower, or sugarcane to reduce the damage by A. soccata, S. sorghicola, and C. angustatus.
A carefully selected cropping system (intercropping or mixed cropping) can be used to
reduce pest incidence, and minimize the risks involved in monocultures. Sorghum shoofl
y, A. soccata, and midge, S. sorghicola, damage is reduced when sorghum is intercropped
with leguminous crops. Intercropping sorghum with cowpea or lablab reduced the damage
by spotted stem borer, C. partellus by 50%, and increased the grain yield by 10% to 12% over
a single crop of sorghum (Mahadevan and Chelliah, 1986). Intercropping sorghum with
pigeonpea reduces the damage by H. armigera in pigeonpea (Hegde and Lingappa, 1996).
Intercropping chickpea with mustard or linseed (Das, 1998) reduces the damage by H.
armigera. Sesame, sunfl ower, marigold, and carrot can be used as trap crops for H. armigera
(Sharma, 2001, 2005). Carrot intercropped with lucerne has been shown to suffer less damage
by the rust fl y, Psila rosae F. (Ramert, 1993). Intercropping bean with collards decreases
fl ea beetle, Phyllotreta cruciferae Goeze densities on the collards and minimizes the leaf
damage (Altieri, van Schoonhoven, and Doll, 1977). Intercropping red clover with maize
also reduces the damage by the European corn borer, Ostrinia nubilalis (Hubner) (Lambert
et al., 1987).
Field Sanitation and Tillage
Collecting and burning of stubbles and chaffy panicles reduces the carryover of spotted
stem borer, C. partellus, and midge, S. sorghicola, in sorghum. Stalks from the previous season
should be fed to cattle or burnt before the onset of monsoon rains to reduce the carryover of
C. partellus (Gahukar and Jotwani, 1980). Piling and burning of trash at dusk in the fi eld
attracts the adults of white grubs, Holotrichia consanguinea (Blanchard), and the red hairy
caterpillar, Amsacta moorei Butler, and kills them. This helps to reduce the oviposition and
damage by these insects. Ploughing the fi elds after crop harvest and before planting
reduces the abundance and carryover of white grubs, grasshoppers, hairy caterpillars, and
stem borers by exposing them to parasites, predators, and adverse weather conditions
(Gahukar and Jotwani, 1980). Timely weeding reduces the extent of damage by some
insects (Sharma et al., 2004). Many common weeds also act as hosts for oviposition, and
provide a better ecological niche for the insects to hide, thus shielding them from natural
enemies and insecticide sprays. However, many weed hosts also sustain the natural enemies
of insect pests, and thus may help in increasing the effi ciency of natural enemies in
population suppression of insect pests. Flooding of the fi elds at the time of pupation
reduces the survival of H. armigera (Murray and Zalucki, 1990).
Chemical Control
Insecticides are the most powerful tool in pest management. Insecticides are highly effective,
rapid in action, adaptable to most situations, fl exible enough to meet the changing