| Detection of larvae feeding on Puccinia recondita
(Rob. ex. Desm. f. sp. tritici) uredospores.* S.D. KHANZADA, S.M. VASTI and Z.H. KHAN Atomic Energy Agricultural Research Centre Tandojam, Sind, Pakistan. During screening of wheat varieties towards their response to rust, on our Experimental Farm, some minute brick colour bodies were observed on the leaves of rust infested plants. They resembled rust pustule at a cursory glance and on macroscopic examination it was found that the minute objects were larvae of some insect (tentatively identified as belonging to the order Diptera). Detailed microscopic studies revealed that the original colour of the larvae was creamy white but due to feeding on rust spores they assumed brick red colour. It was further observed that their midgut was full with rust uredospores. This observation provided further support that the larvae were exclusively feeding on rust spores and thus resembled rust pustules. Reports regarding insects feeding on rust are already available in the literature. COBB (1890-94), COBB & OLLIFF (1891), and WEBSTER (1890) suspected some species of genus Diplosis and Sminthurus feeding on leaf rust spores in Kenya, Egypt and India respectively. They further pointed out that in addition to feeding exclusively on rust spores, the larvae were active disseminators of the rust fungus. According to CHESTER (1946), some workers in 40'ies, reported species of thrips feeding on rust spores. Therefore, when they are abundent and scattered all over the leaf surface the plants may be rated as susceptible on the basis of present technique of screening. As a result of this "deception factor" being reported for the first time from Pakistan, the workers screening for rust resistant varieties are cautioned not to discard their material without carefully differentiating between the larvae and pustules. References CHESTER, K.S. 1946. The Nature and Prevention of Cereal Rusts (as examplified in the) Leaf Rust of wheat. Waltham, Mass., U.S.A. pp. 164-165. COBB, N.A., 1890-94. Contributions to an economic knowledge of the Australian rusts (uredineas). Agrl. Gaz. N.S. Wales 1 : 185-214; 3 : 44-68 : 181-212 ; 5 : 239-252. COBB, N.A. and OLLIFF, A.S. 1891. Insect larvae (Cecidomyia sp.) eating rust on wheat anf flax. Agri. Gaz. A.S. Wales 2 : 67-70. WEBSTER, F.M., 1890. A podurid which destroys the red rust of Wheat. Insect Life 2 : 259-260. |