and Integrated Pest Management - part - usaid

132 PES'I1CIDE NIANAGE,\mLENT AND 1PM IN SOUVHEAST ASIA
Bustamante (1986) reported astrong reduction of exit holes and the larvae or
pupae of corn stalk borer, in corn fields treated with '. evanescens. This in turn
resulted in a remarkable increase in the yield and quality of the marketable corn
ears (sweet corn) against the untreated control plot (Table 2).
Between 1985 and 1986, surveys (Leyza et al. 1986, Tran et al. 1986)
revealed that '. evanescens had established in the areas where the parasitoid had
been released. Leyza (1986) observed in an economic threshold level-corn stalk
borer trial that there were 3.7 parasitized eggmasses per corn plant at 50 DAP
(July 1985). In his survey in Sultan Kudarat, he further found significant
increases in parasitxm at later growth stages of the plant, especially at high corn
borer incidence: ,'.g., at Tuk 1, !agumbayan, 33% para.itisni occuired on
Pioneer White Hybrid 3224 at growth stage 6, with a total of 3-15 corn borer
eggmasses per flant, 1 but 10 days later at growth stage 7-8, 94.07% parasitism
was recorded. There was a record of 42 parasitized eggmasses and two with
Trichogranmain action on one plant.
Table 1. Percent of parasitism of corn borer eggmasses by Trichogramma
released at different locations and years.
Location
Region II
Isabela
Region IV
Calauan, Laguna
Cavite
1983
73.8
41.8
-
Average % parasitism
1984
1985
44.56
74.6
76.0
65.5
-
78.2
1986
-
-
76.8
Region V
Pili, Camarines Sur 46.5 53.2 - -
Region IX
Molave - 72.4 - 60.0
Region X
Malaybalay, Bukidnon - 65.7 77.2 -
Region XI
Bansalan, Davao 44.7 62.1 -
Region XII
Koronadal
54.2
-­
Tacurong.
51.3 60.1 78.9 32.2
Sources of data: Regional Crop Protection Centers and Biolab, Crop Protection
Division, Bureau of Plant Industry, Manila, Philippines. - = No data available.