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Inside the world of the red ring nematode

The red ring nematodeBursaphelenchus cocophilus, causes the red ring disease that can kill palm and coconut trees. This nematode gets its name from the red lesion, around 3-5 cm wide, that forms on the trunks of infected palms (See Figure 1 below). A cross-section of the trunk will reveal the almost perfect bright red band (ring). The color of the lesion may vary depending on the age of the infection.

Figure 1: A cross-section of a palm showing the typical by red ring symptom of Bursaphelenchus cocophilus. Photograph by Society of Nematologists slide collection.

On the outside, leaves of infected palms gradually change color, starting from the tips of older leaves, and can quickly spread to other parts. The leaves eventually dry up and die, and if infected trees are young, they may not live up to the sixth week after infection.

In some cases, infected trees can remain standing for many weeks, months, or even years, before finally dying.

 

 

 

The nematode needs a ‘shuttle’ to move to healthy trees

Interestingly, the nematode hitches a free ride on an unlikely friend, the palm weevil (Rhynchophorus palmarum). Nematodes are introduced into healthy trees when the palm weevil lays eggs. Apart from the harm the nematode causes, the larvae of the beetle also cause serious injury to the trees by digging through the center of the tree.

Figure 2: Rhynchoporus palmarum in a Rhyncolure pheromone. Credit: Oswaldo Brito, Independent Consultant, Bugwood.org.

The maturing weevil would pick up the nematodes by the time they are ready to take the first flight to explore newer trees. So, they carry the nematode with them wherever they go.

The good news is that both the red ring nematode and the vector, the palm weevil, have not been reported in Florida.

Please check out the University of Florida Department of Entomology and Nematology Featured Creature article for more information on the red ring nematode.