Species of Trichogramma parasitoid of Alabama argillacea. II. Determinaton of thermal requirement of three strains.

Abstract

The biology of Trichogramma sp. (Piracicaba ,strain) and Trichogramma pretiosum Riley, 1879 (Iguatu and Goiânia strains) (Hym.: Trichogrammatidae), parasitoids of Alabama argillacea Hübner, 1818 (Lep.: Noctuidae), reared on Anagasta kuehniella (Zeiler, 1879) (Lep.: Pyralidae) was studied under five constant temperatures (18, 20, 25,30 and 32ºC) in order to determine thermal requirements of the parasitoid. A chance was given to the parasite to parasitise eggs for five hours. The eggs were then set at the preestablished temperatures. When the eggs turned black (sign of parasitism) they were individually isolated in 50 replicates par temperature. The observations were done early in the morning and at the end of the day recording the egg-adult period. The threshold temperature and thermal constant value were done by using the hyperbole method. The threshold temperature and thermal constant for insects from Piracicaba, Iguatu and Goiânia in the egg-adult period were: 13.99 ºC and 123.25 degrees/day; 12.81 ºC and 133.25 degrees/day and 11.89 ºC and 131.95 degrees/day, respectively. Taking in account the A. argillacea life cycle which has 353.62 degrees/day, it was found that for each generation of this insect, there would be 2.65, 2.68 and 2.8/generations of the parasitoid from Iguatu, Goiânia and Piracicaba, respectively.