Population Study of Diabrotica speciosa (Ger.) (Coleoptera: Chrysomelidae) in Fall / Winter Season

Population studies of D. speciosa on fall / winter crops were conducted. Larvae were monitored on maize (Zea mays L.), wheat (Triticum aestivum L.) and black oats (Avena strigosa Schreb.) and beetles on soybeans (Glycine max (L.) Mill., maize, common beans (Phaseolus vulgaris L.), wheat and black oats from March 23, 2001 to August 24, 2001. Soybean, maize, common beans, wheat and oats were sown on December 28, 2000; February 9, 2001; March 2, 2001; April 26, 2001 and May 11, 2001, respectively. Maize and common beans were grown on latter growing season. Adult beetles of D. speciosa were collected throughout the sampling period. Greatest beetles population peak occurred on wheat in August 3, 2001 which coincided with flowering period. Population dynamics of males and females was similar on common beans and soybeans. Females on maize predominate mostly after the first 30 days after the plant emergence (dae) (before were not detected) until about 45 dae. Males appeared to predominate during the flowering period. Similar population dynamics of males and females were found on wheat and black oats. Greatest peak of larvae occurred on maize roots. The growing season corn farm system was recently introduced, what probably explains the reports of increasing populations of adults during almost the whole year. Probable applications of the results are discussed.