ARTIFICIAL INFESTATION OF THE TOMATO WITH EGGS OF THE TOMATO FRUITWORM (LEPIDOPTERA, NOCTUIDAE)

Field-grown tomatoes [Lycopersicon esculentum Mill.] were artificially infested with Heliothis zea (Boddie) by applying a suspension of eggs in a 0.2% agar solution to the top surface of randomly located leaves. Degree of infestation depended largely upon the number of eggs applied. Fruit damage due to natural H. zea populations ranged from 6-10% and that due to the natural populations plus the maximal numbers of eggs tested, 3000-3200 eggs/plant, ranged from 51-54%. There was a curvilinear relationship between number of eggs and degree of fruit damage; damage increased as egg dosage increased but at a decreasing rate. Application of eggs was most effective approximately 1 mo. before 1st harvest. Multiple or repeated applications were no more efficient than a single application of an equivalent number of eggs. Practical aspects of the choice of an appropriate damage rating criterion are discussed. The method seems satisfactory for use in screening tomatoes for resistance to H. zea.