Foi verificado haver correlação entre a manifestação de sintomas nas plantas indicadoras intercaladas no batatal para semente e a disseminação, nêle, do vírus do enrolamento das fôlhas. Médias de 12 ensaios realizados em vários pontos do Estado de São Paulo deram os seguintes valores: 49,6% em Datura stramonium, 34,0% em Physalis sp. e 28,5% em tomateiro Santa Cruz. Somente 0,9% das plantas de batata mostraram sintomas de infecção primária pelo vírus, embora a infecção no campo tenha realmente sido de 23,6%. É sugerida a introdução do uso de plantas indicadoras na legislação que regulamenta a produção de batata-semente certificada como método auxiliar para estimativa do teor do vírus do enrolamento nos tubérculos produzidos.
Leaf roll infection on the interplanted indicator plants, jimson weed, tomato, and a non-identified Physalis species is correlated to spread of the disease in the seed potato field. Result from twelve tests carried out at several localities gave the following infection averages: jimson weed, 49.6%; Physalissp., 34.0%; tomato plants, 28.5%. Potato plants showed an average of 0.9% primary leaf roll, but tuber tests indicated that field spread had been 23.6%. Potato virus Y infected 45.1% of the tobacco plants, 37.3% of Physalissp., and 18.1% of the tomato plants. Potato plants were not infected with this virus because the Ycomplex present was the one that infects tomato and pepper plants and very seldom potato plants in the field. The viruses of tomato curly top and Brazilian tobacco streak infected jimson weed at the average rates of 16.1% and 2.7%, respectively. Tomato plants showed an average of 4.1% of curly top, but no infection with the Brazilian tobacco streak virus. Potato plants were not affected by these viruses. Tomato spotted wilt virus infected several of the indicator species and also the potato plants, but there was no perpetuation of the virus through the tubers. Interplanting indicator plants in the certified seed potato fields is suggested as a means to estimate the extent of leaf roll spread in the crop.