and Integrated Pest Management - part - usaid

IM ACI'IV1IS OF1TI III 111.1 11NI t-GIMAN CO'ITON PROJECt' 163
weevils are attracted to okra and the cotton gains up to three weeks in which
bolls can be set without flower weevil influence. Later on A. lata apparently
overcomes the okra barrier and colonizes tie cotton fields.
MANAGEMENT OF COTTON BOLLWORM
The previously described technologies against two key pests of cotton lead
to a considerable delay in the need to apply pesticides. This contributes to a
more favorable environment for arthropod predators capable of limiting cotton
bollworm to low population levels. I lowcver, these predators are commonly
absent or present only in low numbers, making it necessary to develop integrated
control strategies for this most destructive of all the Philippine cotton pests.
Cultural Control Strategies
11. armigera is a highly polyphigous insect known as a pest to such diverse
crops as maize, sorghun, ton.:.to, tobacco, and cotton. It was observed that
given a choice, iIliothis wofuld prefer some host plants over others. Cotton
does not secm to be its favorite crop. Tobacco and maize appeared to be
considerably more attractive.
TRAP CROPS Single rows of Irap crops can be intcrcropped at intervals of
15-20 rows of cotton. Ileliothis females seirching for suitable host plants are
then diverted away front the main crop. On some trap crops, e.g., maize,
bollworn larvae cannibalize each other in the major feeding site at the tip of the
corn car. On trap rows of tobacco the larvae are easily spotted through their
feeding damage. They canl be handpickcd as the farmcr inspects the few tobacco
rows. Figure 4 demonstrates the high attractivity of tobacco rows within a
cotton field.
In the tobacco-cotton intercrop, three times the number of eggs were
deposited on tobacco terminals than on comparable sampling areas on the cotton
plants. Ilowevcr, the total number of leliothis eggs per season found in the
intercrop was not si~,nificnntly diffCrent from those found in cotton monoculture.
It was noted tht all host plants were generally more attractive to lleliothis
females in the early reproductive stages. Some crops such as maize and sorghum
lose their appeal abruptly after flowering. It is therefore vital to time the
planting dates of the different crops so that they enter their respective
reproductive plmse simultaneously. Only then can cotton be expected to benefit
through a delay il the nccd for pesticide a lplication. In the example given in
Figure 4, tobacco seedlings were transplanted right after planting cotton. The
first pesticide application in the intercrop was delayed by two weeks as compared
to the first treatment of the monoculture. On average, the tobacco-cotton system
receivcd 2.5 sprays per season versus 6.5 sprays on cotton alone.