Angular leaf spot in strawberries

Conditions have been good for the development of bacterial angular leaf spot in strawberries, caused by Xanthomonas fragariea. Conditions which favour this disease include cool temperatures, irrigation for frost protection, and splashing rain. Sound familiar?

Symptoms of angular leaf spot develop on the leaves and the fruit calyx. Tiny angular spots are first evident on the lower leaf surface. The spots look wet when viewed from above but are translucent when held up to the light. Bacteria ooze out of these spots in humid weather. When the ooze dries up, it leaves white flaky residue. Infected sepals turn black and make the fruit unmarketable. Infected leaves turn yellow with green or brown blotches. Although rare, this disease can be systemic on the plant, causing plant collapse. The most serious damage is when calyces are infected. Blackened calyces caused by angular leaf spot make the fruit less attractive and sometimes unmarketable.

Because it is a bacterial disease, angular leaf spot is not affected by most fungicides. The disease will not spread much now in fruiting fields. In new plantings, use the following management practices to reduce the risk for next year:

• Avoid excessive nitrogen because young leaf tissue and leaves on very vigorous plants are more susceptible.
  
• Clean up crop debris, especially on plastic-mulched beds.
  
• Avoid work in fields when they are wet.
  
• Avoid excessive irrigation for frost protection.

Cavendish, Annapolis, Kent seems especially susceptible to this disease, but it infects most varieties.

Figure 1. Angular leaf spot symptoms on lower leaves, turning the leaf yellow

Figure 2. Angular leaf spot on calyces

Figure 3. Angular leaf spot causes small water soaked spots on lower leaf surface.