[From the August 2016 issue of the UC IPM Green Bulletin]
A new psyllid pest that causes a distinctive, tight, typically complete rolling of leaves (Figure 1), has been found on Ficus microcarpa (Chinese banyan, Indian laurel fig) in Los Angeles, Orange, San Bernardino, Ventura, San Diego, and Riverside counties. This species of Ficus is one of our most common, useful, and widespread ornamental landscape trees. Incidentally, it has also long been a target for numerous exotic pests.
The psyllid, identified as Trioza brevigenae and tentatively named the Ficus Leaf-Rolling Psyllid (FLRP), was discovered in February 2016 south of Los Angeles in Carson, California and appears to have spread rapidly among the six counties listed above. It has only been observed on Ficus microcarpa (sometimes incorrectly called F. nitida or F. retusa).
Damage
Rolled leaves, though brittle, remain green throughout, although other pests, such as Josephiella microcarpae (the leaf gall wasp) and various mealybug species, might be present and may discolor or further deform them.
The rolled leaves could be mistaken initially for damage from Gynaikothrips ficorum (the Cuban laurel thrips), which creates a gall by folding the leaf blade adaxially (upper surface) along the rachis. However, careful observation will quickly show the distinct difference between the rolled leaf (caused by the FLRP) and folded leaf (caused by Cuban laurel thrips).
Description and Identification
Peeling back the rolled leaf blades typically reveals various developmental stages of FLRP nymphs (Figure 4). Early instars are 1–2.5 mm long, oblong, dark grayish-tan initially, changing to brownish and then brownish-green.
Advanced nymphal instars have skirts of long, white, waxy filaments at cranial and caudal parts of their bodies (Figure 5). Wing pads are typically visible in later developmental stages.
Cast skins of the final instar FLRP nymphs from which the adults have emerged are often seen attached to the leaves. Also, small, oval, mostly orange-colored nymphs embedded in leaf tissue on the outside of the roll and observable to the naked eye are likely very early instars of the FLRP, although we have not confirmed this possibility.
The FLRP exhibits two peculiar behaviors. In one (the more common of the two observed), an individual psyllid sits on a leaf blade or perches on the margin of a rolled leaf, raises its abdomen until it is at about a 45-degree angle (Figure 8), and then moves it from side to side like a dog wagging its tail. In another, it extends one wing until it is at a right angle to the body, then waves it back and forth while walking.
Management
One management strategy likely warranting evaluation includes vigilant scouting followed by judicious and immediate removal, bagging, and disposal of shoot tips with infested leaves.
Frequent, periodic pruning, as is done for hedges and topiary, might also be an effective management technique by constantly removing infested leaves. Such regularly pruned Ficus specimens have frequently been observed with less damage from foliar pests such as the leaf gall wasp, Indian laurel thrips, and the FLRP. Timing of such pruning, though, might be critical; if possible and practical, time pruning so that resulting new growth appears at a time when FLRP activity is low, typically during the cooler months.
The practices listed above could be combined with insecticidal treatment for noteworthy and valuable tree specimens, although no pesticides have yet been tested specifically for FLRP. In these special cases, soil applications of imidacloprid or similar materials applied to the soil might be beneficial.
—Gevork Arakelian, Entomologist, Los Angeles County Agricultural Commissioner/Weights & Measures, garakelian@acwm.lacounty.gov
—Linda M. Ohara, Biology Sciences Lab Technician, El Camino College, lohara@elcamino.edu
—Cheryl Wilen Wilen, Area IPM Advisor, UCCE San Diego, Orange, and Los Angeles counties, cawilen@ucanr.edu
—Surendra K. Dara, Affiliated IPM Advisor and Strawberry and Vegetable Crops Advisor for UCCE, Ventura, Santa Barbara, and San Luis Obispo counties, skdara@ucanr.edu
Read the full article, originally published in the eJournal PalmArbor at http://ucanr.edu/sites/HodelPalmsTrees/files/242336.pdf.
/h3>/h3>/h3>/span>- Author: Donald R. Hodel
- Author: Gevork Arakelian
- Author: Linda M. Ohara
- Author: Cheryl A. Wilen
- View More...
A psyllid, perhaps new to the Western Hemisphere and that causes a distinctive, tight, typically complete leaf rolling , has been found on Ficus microcarpa (Chinese banyan, Indian laurel fig) in Los Angeles, Orange, San Bernardino, Ventura, San Diego,and Riverside counties.
So far we have observed the FLRP only on Ficus microcarpa. Damage is fairly obvious and unusually conspicuous on heavily infested trees. Leaves at the branch and twig tips are tightly and typically completely rolled into a narrow cylinder. One rolled margin eventually overtakes the other, actually forming a cylinder with two tubes. In some instances only one margin rolls, in which case the rolling stops at the leaf blade midrib. The rolled leaf is brittle and remains green throughout
The rolled leaves could be mistaken initially for damage from Gynaikothrips ficorum (the Cuban laurel thrips). However, careful observation will quickly show the distinct difference between the rolled leaf (cause by the FLRP) and folded leaf (caused by Cuban laurel thrips). Indeed, the FLRPs shape the leaf to look more like the Mexican food taquito (tightly rolled tortilla) while the Cuban laurel thrips cause the leaf to look more like a taco (folded tortilla).
Because the FLRP is likely a new arrival, we know nothing about its long-term impact on tree health. If damage is mostly restricted to few or several leaves, long-term health would likely not be significantly affected; in such cases it could be considered simply a nuisance esthetic issue. On the other hand, if most or every new leaf is infested and rolled, as it appears it is going to be on at least one of the trees we saw, esthetic damage would be significant and tree health would likely decline because of reduced photosynthesis.
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.
To see the entire article with photos and more details go to
http://ucanr.edu/sites/HodelPalmsTrees/files/242336.pdf
If you see this kind of damage, please let one of the authors know as we are trying to describe its current range in California.