and Integrated Pest Management - part - usaid

no.&%
60
50
40
1PM ACTIVrI1S OF "I'I[L P ILI)IpNI--GEI2MAN COT'ON PROJIECr 161
bolls/m 2 %infest. flowers
130 000 plants/ha 0-­
85,000 plants/ha
0--4
.. 0
30 i , _ .- 1.500 4 3 gr. kg/ha /boll at
0
10
--41
50 60 70 80 90 100 110 120 130 140 DAE
Figure 3. Yield development in relation to planting density under cotton flower
weevil infestation.
susceptibility to flower weevil attack in individual fields. Figure 3 demonstrates
the advantages of this technology in an area where flower weevil continuously
migrated from nearby areas of heavily infested older cotton, thereby obscuring
true generation cycles.
The data suggest that at about 90 days after emergence, all bolls which later
contributed to the yields of 1,780 kg and 880 kg respectively had been set. Bolls
developing after that (late were subject to shedding due to flower weevil
infcstation.
WATER MANAGEMENT In areas prone to flower weevil attack, a cessation
of irrirltion for up to four weeks aftcr the onset of flowering can reduce yield
losses in three ways. Firstly, the reduced water supply forces the cotton plant
toward maturation as flowers are initiated more rapidly, giving the "rose garden"
effect. Irrigation should resume as soon as sufficient bolls are set. Secondly,
dry soil surface conditions greatly decrease pupal survival, with 100% pupal
mortality at moisture contents of 8-10% in clay soil. Thirdly, dry soil surfaces
favor the activity of Solenopsis geminata L., a red fire ant which is the main
predator of A. lata larvae and pupae in the Philippines. Table 3 shows an
assessment of mortality factors affecting the flower weevil under dry season
conditions in the field.