Aspectos biológicos e parasitismo de Trichogramma atopovirilia Oatman & Platner, 1983 (Hym.:Trichogrammatidae), em ovos de Helicoverpa zea (Boddie, 1850) (Lep.: Noctuidae)

Abstract

The present research work was carried out in order to study the biological aspects and parasitism of Trichogramma atopovirilia in Helicoverpa zea (Boddie, 1850) eggs to obtain information for the biological control of this insect pest. Biological studies were conducted under four constant temperatures (15, 20, 25 e 30°C) and six patterns (D = day; N = night) of variable temperatures as follows (30°C D - 25°C N, 30°C D - 20°C'N, 30°C D - 15°C N, 25°C D - 20°C N, 25°C D - 15°C N e 20°C D - 15°C N). The duration of the egg-adult period and the longevity of the adults were significantly affected by temperature. The increase of temperature determined a decrease of the egg-adult period; the greater longevity was observed at 20 C (14,67 days). The average number of parasitized eggs per female was greater at 25°C D - 15°C N (51,63 eggs/female) followed by 30°C D - 15°C N (45,68 eggs/female) and 25°C (45,22 eggs/female). The average number of adults emerged per egg was 1,86+0,08. The number of parasitised eggs was higher during the first 24 hours, with oviposition concentraded up to the fourth day. The finite rate of increase and the net reprodution ratio were greater at 30 and 25°C respectively. The threshold temperature and thermal constant in the egg-adult period were 11,4°C and 130,7 degree-days, respectively. Taking in account the H. zea thermal requeriments for its life cycle, it was found that for each generation of this insect, there will be 4,30 generations of T. atopovirilia.