The effects of the infestation ratio of spiny bollworm (Earias insulana) and pink bollworm (Pectinophora gossypiella) on cotton yield grown in semi‐arid region of Turkey

Abstract: Field studies were conducted in Harran Plain, Turkey, to investigate the infestation of spiny bollworm (SBW) and pink bollworm (PBW) in cotton blind bolls during the period 1999–2001. Blind bolls left on the cotton plants after the harvest were collected, and the PBW and SBW larvae, which are the causes of infection were counted in the laboratory by splitting the bolls. The statistical methods reveal that the infestation ratio variable plays an important role in reducing cotton yield. The infestation ratio variable was found to be statistically significant in all models used. Different soil types may have little effects on yield. We also estimate elasticity of yield with respect to infestation ratio variable. A 1% increase in infestation ratio would reduce about 2.5–6% of cotton yield. Although the infestation ratio of cotton yield is inelastic, which means that the yield is less responsive to the infestation ratio, the elasticity is however an economically important indication because additional cost spent on pests will increase total cost thereby increasing the level where marginal revenue equals the marginal cost.