Summer Temperatures of the Soil Surface and Their Effect on Survival of Boll Weevils in Fallen Cotton Squares

Mortality in populations of immature boll weevils, Anthonomus grandis Boheman, in fallen cotton squares on the soil surface commenced when the summation of the index of time (1-hour period) × temperature >38°C reached 60. All the weevils died when the summation reached 550. Soil surface in Arizona cotton fields attains a mean temperature of 38°C when the mean air temperatures are 30°C. Soil surface temperatures of 38°C are com mon when air temperatures are lower than 30°C and may reach 60°C when air temperatures are at maximums. Frequent and prolonged periods with temperatures >38°C impose a strong bioclimatic control on the boll weevils until late season, when shading by maturing cotton plants enables the survival of the immature weevils in the squares on the soil surface.