The role of rainfall in Sternechus subsignatus (Coleoptera: Curculionidae) adult emergence from the soil after its winter dormant period

VAN NIEUWENHOVE, GUIDO A.; LILJESTHRÖM, GERARDO G.; SOCIAS, M. GUILLERMINA; WILLINK, EDUARDO; CASMUZ, AUGUSTO S.

ENVIRONMENTAL ENTOMOLOGY

ENTOMOLOGICAL SOC AMER

Lugar: Lanham; Año: 2016 vol. 45 p. 1049 - 1057

0046-225X

In this work, we report the effect of rainfall on Sternechus subsignatus adult emergence after winter dormancy. This weevil is a univoltine soybean pest found in Northwestern Argentina, a subtropical region with dry winters and rainy summers. Before harvest, fully-grown larvae burrow into the soil where they overwinter. In the spring they emerge as adults and recolonize the crop during its planting and early vegetative stages.Our study examines the seasonal timing of adult emergence with the aim of improving chemical control strategies and avoiding unnecessary pesticide applications. To do so, we developed a regression model to predict adult emergence onset as a function of acumulated rainfall after November 1st. The regression with the highest coefficient of determination between cumulated rainfall and adult emergence onset was: Emergence onset (Julian day) = -7.98 Ln(cumulative rainfall) + 65.7 (r = 0.77; n= 8; F (1, 6 df) = 20.6; P < 0.004). The negative relationship showed that adults emerged earlier in wet years than in dry years. Also it was observed that adults emerged from late November to mid-March, in pulses following periods of rainfall. Males were more abundant than females at first, but then the reverse was true towards the end of the period. In most cases, there was a suggestion of relationship (though not significantly) between peaks of adults emergence with peaks of rainfall 15 days prior to adult emergence. These results revealthat rainfall has a significant impact on the beginning and dynamics of adult emergence from the soil.