Main symptoms
All the aerial organs of the tomato can be affected at any time during its development. Botrytis cinerea can be rampant in nurseries , causing failure to emerge or damping off (figure 1). Senescent cotyledons often allow it to settle on young stems; stem cankers can then develop (Figure 2) and penalize the development of young plants in the weeks following planting.
The leaflets frequently show spots rather circular and moist at first (Figures 3 and 4). Hue beigeâtre to light brown , they also reveal an aspect parchment and reveal the concentric arabesques (Figure 5). They evolve rapidly and cause the drying out of important sectors of the blade (figure 6). These alterations can give rise to rot which then spreads and eventually injures entire leaves, with the tissues collapsing and necrosis gradually . Having gained the petioles (figure 7), this rot will be able to settle on the stem (figure 8).
Once the stem is affected, whether on a young plant as explained above or on an older subject, it reveals one or more canker lesions beginning mainly from pruning and disbudding wounds. These cankers are initially wet (Figure 9) and tend to dry out as they evolve. With well-defined contours, they take on a beige to brown tint (figure 10); they end up altering the stems several centimeters long and girdling them. Subsequently, the leaves of the distal parts turn yellow, wilt, dry out and then die.
The senescent petals are particularly vulnerable. They allow B. cinerea to settle on the inflorescences (figure 11) and cause them to rot, but also to use them as a nutritive base initially, in order to ensure subsequent infections on leaflets and on fruits in particular.
The green fruit , and more rarely mature tomatoes, have thin whitish rings, 2 to 10 mm in diameter, encircling a central tiny necrotic lesion. These rings, known as "ghost spots" ( ghost spot ) are rather yellowish in mature fruits (Figures 12 and 13). They are due to a reaction of very young fruits following aborted infections, after the spores have germinated and then the germinal filaments have entered the tissues.
Whatever organs are affected, dying tissue becomes covered with a very characteristic dense gray mold, consisting of the conidiophores and conidia of the fungus. B. cinerea can produce black sclerotia 2-5 mm in diameter, rarely visible on lesions.