Trichogramma pretiosum: 1 Development in Two Hosts in Relation to Constant and Fluctuating Temperatures23

Abstract

The time of development of Trichogramma pretiosum Riley Hym.: (Trichogrammatidae) in Sitotroga cerealella (Olivier) (Lep.: Gelechiidae) and Trichoplusia ni (Hübner) (Lep.: Noctuidae) eggs was determined at 10 constant and 6 fluctuating temperatures. Development in S. cerealella eggs took ca. 1.5 and 0.3 days longer at 17 and 32°C, respectively, than in T. ni eggs. At constant temperatures, development times varied from 32 days at 15°C to 6.6 days at 32°C in T. ni eggs, but at temperatures >32°C, development times were slightly longer than at 32°C. Development times were similar between tests at constant temperatures and tests at fluctuating temperatures in which average temperatures equalled comparable constant temperatures and maximal temperatures were >32°C. Development times of 3 strains were similar at temperatures between 20 and 30°C. Development required 128.7 heat units above 12.2°C in S. cerealella and 131.5 heat units above 11.3°C in T. ni eggs.