The white grub, Phyllophaga crinita (Burmeister) (Coleoptera: Scarabaeidae), is an important soil insect pest in Texas, U.S.A., and Tamaulipas, Mexico. The objectives of this study were to estimate biometric parameters and develop a simulation model to determine the factors associated with interannual fluctuations of P. crinita adults captured with blacklight traps at Rio Bravo (irrigated area) from 1979 to 2008 and San Fernando (dryland area) during 1979–1980 and 1990–1993, in Northern Tamaulipas, Mexico. More males were captured at both Rio Bravo (89%) and San Fernando (76%). Flight activity occurred from March to September, although 97% of total captures were concentrated from April to June, with peak emergence during 1–15 May at Rio Bravo and 16–31 May at San Fernando. Protandry was observed only at Río Bravo, where males emerged 5 days before females at 50% cumulative emergence. Multiple regression analysis for testing the association between yearly captures of P. crinita (y) and independent variables (x_n) resulted in best-fit model: y = -6143.5 1.75 x₁² 3676.8 x₂ 0.087 x₂*x₃ (R²= 0.7026), where x₁ = precipitation (mm) in January, x₂ = number of rainfall events (>20 mm) number of irrigations from April to July, and x₃ = total captures of P. crinita the previous year.