THE RELATION BETWEEN POTATO BLIGHT AND TOMATO BLIGHT

Abstract

SUMMARY AND CONCLUSIONS.1. In Jersey, potato and tomato crops are grown in close proximity in the open, and both suffer from severe attacks of blight (Phytophthora infestans). The disease appears first on the potatoes, and most growers assume that it passes from this crop to the tomatoes. To test this assumption, potato and tomato plants have been inoculated, using blight from either host plant.2. In four out of five experiments, ordinary blight lesions developed on tomatoes inoculated with blight from glasshouse potatoes in January, February and March. The result suggests that tomato plants for the outdoor crop are liable to contract blight, if, as is often done, they are raised in glasshouses where diseased potatoes have just been, or are being, grown.3. Blight from the early outdoor potato crop often failed to infect tomatoes. Where infection did occur typical symptoms of blight were not produced. When, under field conditions, early potatoes were interplanted with tomatoes, the former were quickly killed by blight while the latter remained almost healthy. The evidence indicates that early potato crops affected with blight are not so dangerous to neighbouring tomato crops as is commonly assumed.4. Successful infection was established on all tomatoes inoculated with blight taken from outdoor potatoes in autumn, but ordinary blight lesions were not produced except in one experiment.5. Blight taken from the leaves, stems, or fruits of the tomato infected the potato, and the disease so produced in the latter passed back readily to the tomato. This indicates that diseased tomato crops may be a serious menace to neighbouring potato crops.6. The results of numerous inoculation experiments support the view that more than one strain of Phytophthora infestans exists.