Survey Instruction Details:
In Geranium: Collect stems from symptomatic plants (wilting; yellowing of lower leaves). Check for bacterial exudation by placing a piece of stem from a symptomatic plant into water, look for viscous streaming.
In Potatoes: Slice tubers and look for ooze, vascular discoloration (can incubate at 30oC 86oF for 3-4 weeks).
On potatoes and other solanaceous hosts: the first visible symptoms are wilting of the youngest leaves during the hottest part of the day, often on just one side of a leaflet or on a single branch. Another common symptom associated with bacterial wilt in the field is plant stunting.
The entire plant may wilt quickly, leading to general wilting and yellowing of foliage and eventually plant death.
A longitudinal slice of infected stems or stolons will reveal vascular browning, visible as long, narrow, dark brown streaks. In succulent young plants of highly susceptible varieties, the stem can collapse, and gray-white bacterial ooze may be visible on stem surfaces.
In geranium: symptoms of Southern wilt can be subtle and easily overlooked. Symptoms usually begin with chlorosis and wilting of the lower leaves, then progress to an upward curling of leaf margins that is very characteristic.
Under favorable conditions, the disease develops rapidly on geraniums and wilting may move upwards from older to younger leaves.
Wilted leaves often develop wedge-shaped areas of chlorosis that become necrotic. The leaf margins may also become chlorotic, then necrotic, and the whole plant may desiccate and die. In late stages of disease, stems may collapse. Vascular discoloration is visible in stems (especially at the root crown) and roots; these can blacken and eventually become necrotic.
In the early stages of disease in potato and geranium, the infected plants may appear to recover at night.