and Integrated Pest Management - part - usaid

164 PESI1CIDE MANAGEM12vwr AND IPM INSOUTH1EAST ASIA
NO. Bollworm eggs
17 per 10 terminals
16 - / Tobacco in intercrop
15.
14 LJ Cotton in intercrop
14
Cotton in monoculture
12
11
10.
9
8
8 7­
:t *t_,.
4 i
6..
"
lit
Figurc 4. 1-liothis cgg distribution in a cotton-tobacco intercrop as comparcd
to cotton alone.
Biological Control Strategies
Ileliothis eggs in Philippine cotton areas were generally found to have a low
rate of natural parasitization. However, laboratory studies confirmed the
potential of Trichogramntaspp. as biocontrol agents against leliothis armigera
(Torreno & Cadapan 1984). Moreover, a simple low-technology mass rearing
procedure for Trichograinnaspp. had been developed in the Philippines (Medina
& Cadapan 1982). Several field trials were conducted to evaluate the use of
TrichograminaaustralicuinGirault against cotton bollworm as a substitute for
chemical control methods (Table 5).
Table 5. Ilcliothis egg-parasitization after inundative release of Trichogramma
australicwn.a
e
Crop year ]Q83184 b
Crop year 1984 /85b No. of eggsC % No. of eggsd %
While eggs 70 100.0 90 100.0
Parasitized eggs f
53 75.7 67 74.4
Lost eggs 11 15.7 4 4.5
IHlatched eggs 6 8.6 19 21.1
'40,000 parasitoids per hectare in 3- and 4-day intervals, bno natural parasitization was
detected during these years in the control fields, Cover 20 sampling occfasions, dover 9
sampling occasions, efound and marked prior to release of parasitoids, bla,k eggs recovered
indicating successful parasitization.