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Management of Arthropod Pests Affecting Soybean (Glycine max (L) Merrill) with Emphasis on the Soybean Pod Borer (Etlella zlnckenella Treitschke)
Dissertation Abstract:
Insect pest colonization and succession were studied and the most susceptible stage to insect damage of soybean was determined. Evaluation of the different insect control strategies in soybean was conducted at the Experimental Area of the Research and Extension Office, Central Luzon State University, Munoz, Nueva Ecija, Philippines from January 1987 to May 1988.
The crop was colonized as early as five days after planting (DAP) by Phaneroptera furcifera Stal., Attractamorpha psittacina de Haan, and Epilachna philippinensis Dieke. Two days later, Ophiomyia phaseoli Tyron appeared. On the second week, lepidopterans like Lamprosema indicata Fabricius, Homona coffearia Nietner, Spodoptera litura Fabricius, Chrysodeixis chalcites Esper, Catachrysops onejus Fabricius, and Stomopteryx subsecievella (Zeller) were noted. At 32 DAP, Etiella zinckenella Tre itschke was noted.
The most critical stages when insects damaged the crop were during the pod filling (53 DAP) and beginning of seed formation (60 DAP). Plants that were defoliated during the late vegetative and reproductive stages had a higher percent yield reduction than those which were defoliated at early stage. The highest effect of defoliation on yield was at the beginning of seed formation stage. As the degree of defoliation increased, yield Joss correspondingly increased.
Levels of simulated pod injury s ignificantly affected yield as manifested by increased y ield loss from 0 to 100 percent pod injury level. Damage at podding, pod filling, and seeding showed significantly higher yield losses than damage at full seeding.
Monocrotophos at the rate of 500 g ai/ha plus deltamethrin at 20 g ai/ha (recommended in secticides) outyielded all other insecticide treatments but proved inferior in terms of return on investment (ROI) over the application of deltamethrin at I 0 g ai/ha. Dipel (Bacillus thuringiensis var. kurstaki) at the rate of 20 g/16 liters water was the most profitable of all treatments.
Trichogramma chilones Ishii most effectively controlled Jepidopterous insect pests of soybeans. Increased rate of T. chilones Ishii significantly increased pod number and yield. The release of 100,000 parasites per hectare was the most economical.
Tillage and mulching practices adversely affected damage and insect density of Empoasca ricei Devorakowska and P. furc!fera Stal. Higher plant density increased hoppers and leafholder populations. Unfertilized plants had fewer colonizers than inoculated and fertilized plants.
In the integrated insect pest control study, zero tillage plus mulching and T. chilones Ishii application was the best combination for suppressing both pre- and post-flowering insect pests of soybean.