Staff August 4, 2016
Ficus encounters new pest
Photos: Donald R. Hodel
Ficus microcarpa (Chinese banyan; Indian laurel) is among the most widely planted and widely favored landscape trees in California, and it’s not unusual for the plant to battle a number of pests. There’s a new bug in town, however, and it has thus far affected trees in Los Angeles, Orange, Ventura, San Diego, San Bernardino and Riverside counties.
First detected south of Los Angeles in February, the invader has been identified as the ficus leaf-rolling psyllid (FLRP) and confirmed by a Swiss psyllid specialist as Trioza brevigenae, a native of India about which very little is known. Researchers Donald R. Hodel, Gevork Arakelian, Linda M. Ohara, Cheryl Wilen and Surenda K. Dara have produced a fascinating paper on their study (see the link below), and it is well-worth the read.
One rolled margin eventually overtakes the other, forming a cylinder with two distinct tubes.
Briefly, however, they have observed FLRP only on F. microcarpa, which is a good thing for other plants, but not so good for the Ficus. The most telltale sign of an infestation is distinctly rolled leaves, some of which are so tightly compacted that the resulting leaf “cylinder” is only about 5 millimeters in diameter. Leaf rolling may be unilateral, in which only one margin appears to be curled, or bilateral, in which both margins have been rolled toward the midrib.
According to the research team, “The FLRP appears to be nearly exclusively attracted to the newest developing leaves, which are softer, more pliable, and easier to roll, rather than simply the leaves’ position on the canopy periphery where they would be first encountered. If further study shows this observation to be true, it will impact how this pest can be managed culturally and mechanically.”
The psyllid is a tricky little devil to identify because they tend to disintegrate over time. But if a fresh infestation is detected, one might be able to unroll the leaves to find varying developmental stages of tiny FLRP nymphs. Adults may be spotted on the outside of the leaf and are nearly as difficult to see: They range between 2.6 to 2.8 millimeters long with somewhat translucent wings that extend to about 3 millimeters long.
Ficus leaves are so tightly rolled that they sometimes can be compressed into a diameter of 5 millimeters.
Because this pest has been newly discovered, nothing yet is known about its long-term effect on tree health. Minimal leaf rolling may result only in aesthetic damage, but heavily infested trees could suffer from decline due to reduced photosynthesis.
Vigilant scouting and immediate removal and disposal of affected shoot tips is recommended, as is periodic pruning. Insecticides have not yet been tested.
To learn more: http://ucanr.edu/sites/HodelPalmsTrees/files/242336.pdf.