Environmental Engineering Reference
In-Depth Information
is also an important component. Most insecticides kill only by direct
contact with the insect, so bringing insects closer to the surface may be
important. Extensive irrigation usually makes insects crawl toward the
soil surface. Root-feeding insects must be treated with insecticides that
move downward through the soil to the place of the greatest insect
activity. The best results are obtained when the two movements are
combined: when insecticides penetrate the soil and at the same time
insects move upward toward its greatest concentration. This combination
would normally require at least 10-15 mm of irrigation water after ap-
plication of the insecticide. Watering should follow insecticide applica-
tion quickly, because in addition to encouraging increased contact with
insects, immediate drenching reduces insecticide losses associated with
foliar adherence, volatilization and photodecomposition.
On the other hand, shoot-feeding insects ingest mainly insecticide
that adheres to the foliage. If these insects are the main targets, irrigation
should be delayed as long as possible after application of the insecticide.
Because many shoot-feeding insects feed at night, the insecticide should
be applied late in the day.
Insect control is a complex issue requiring extensive knowledge of
both biology of insects and chemistry of insecticides. Turf-grass man-
agers in a particular tropical location are usually confronted with only a
few species of insects that seriously damage turf. A discussion of all
harmful tropical insects and methods for their control is beyond the
scope of this topic. Up-to-date information on particular pests in specific
locations is frequently released by research institutions and chemical
companies. It is typically published in professional magazines as well
as on the Internet, two excellent sources of information that should be
used to the fullest advantage.
