BIOLOGICAL AND TOXICOLOGICAL EFFECTS OF FOUR MINOR NUTRIENTS ELEMENTS ON THE FOURTH INSTAR LARVAE OF THE BLACK CUTWORM, AGROT1S IPSILOIV (HOFNAGEL) : LEPIDOPTERA: NOCTUIDAE

The toxic effect of four micro- nutrient elements, zinc (Zn), Iron (Fe) Copper (Cu) and Manganese (Mn) against the fourth instar larvae of Agrotis ipsilon was evaluated in laboratory tests. The fourth instar larvae were fed for 48h on castor leaves Rkinus communis dipped in a solution of each mineral element of the four elements at different concentrations (1'^t test) ,hence on a mixture consists of the four elements at the LC_w values (2^°1 test). Manganese (Mn) was the most toxic element against the fourth instar larvae (LO_A value was 250 ppm). While, zinc (Zn) was the least toxic one (LC,₀ value was 1400 ppm). The biological activities of the treated larvae with each of the four elements (1" test) were affected. Only Mangenese or Mangenese and copper treatments showed a higher effect than other treatments. However, the larval and pupal duration were prolonged, the pupation and adult emergence percentages were depressed, the pupal weight was decreased ,and pupal malformations percentage were produced. .Also, the sex ratio of the emerged adult was more affected. as compared to control. Whereas, Iron treatment had a stronger effect on some biological parameters .This led to an inhibition in both fecundity and fertility, shorten in the adult longevity and caused adult malformations. While the larval treatment with a mixture of the four elements at the LC_w values had the most suppressive effect on the above mentioned biological activities.