• a. rapid (1 to 7 days) collapse
• lightning damage (Fig. 12) 
•  
• FACTSHEET: http://edis.ifas.ufl.edu/EP263
• 
  b. moderately fast (more than 2 weeks) to slow collapse of crown (months)

• 1) longitudinal-section through crown area shows crumbly trunk tissue (actually insect frass) and possibly ¾ to 1 inch long gray caterpillars

• Opogona (banana moth) larvae damage (Fig. 13)

• FACTSHEET: IP-24.pdf

2) longitudinal-section through crown reveals galleries packed with frass, sometimes with creamy white grubs, cocoons or pupae; most common in Sabal palmetto or Phoenix canariensis, especially if stressed

palmetto weevil damage
 

FACTSHEET: http://edis.ifas.ufl.edu/IN139