Late blight symptoms on tomato

• Organs attacked :

• Symptoms : 
  • Pale green to brownish green spots on the leaflets at first wet (figure 1). These spots are frequently surrounded by a livid, ill-defined tissue margin (Figure 2).
  • large sectors of the lamina browning and becoming necrotic (figure 3).
  • Brown cankerous lesions on apex, stems and petioles,  more or less extensive, and with irregular outline (figures 4 to 6).
  • Browning of floral bouquets and drop of many flowers.
  • Brown mottling on fruits which are often more or less bumpy. The latter remain relatively firm regardless of the precocity of the attack (FIGS. 7 to 9).
  • Diseased plants are distributed in clusters in the plots; When the conditions are favourable, the progression of the symptoms on the plants and in the culture is dazzling: leaves, twigs, even plants end up necrosing and drying out completely.
     

• Signs : presence of a discreet and fleeting white down on the affected organs: the underside of the blade of the leaf lesions (figures 10 to 13), the stem, the fruits (figures 9 and 14); this is made up of the sporocystophores and sporocysts of P. infestans.

• Production areas affected