The Ficus Leaf-Rolling Psyllid: A New Pest of Ficus microcarpa

[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

The FLRP appears to be almost exclusively attracted to the newest developing leaves, which are softer, more pliable, and easier to roll. Damage is fairly obvious and conspicuous on heavily infested trees. Leaves at the branch and twig tips are typically rolled tightly and completely into narrow cylinders (Figures 1 and 2), sometimes eventually compressed to only about 3–5 mm in diameter (Figure 3).

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).

Also, the folded leaf gall from the Cuban laurel thrips typically has dark or purplish flecking or stippling on the abaxial (lower) leaf surface.

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.

Adult FLRPs are typically found outside and adjacent to rolled leaves (Figure 6); apparently they exit the confines of the rolled leaf immediately upon reaching adulthood. Adults are small (about 2.6–2.8 mm long). The head and thorax are brownish-green. The abdomen is green when young and brown when old. Wings are 3 mm long, transparent, with no color pattern, and extend beyond the posterior end of the abdomen. Eyes are red and protruding (Figure 7). Females are larger than males.

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

Unfortunately, nothing is known about the management of the FLRP, and additional work will likely be needed. The spectrum of natural enemies of FLRP has not been studied, although we have found lacewings, lady beetles, and pirate bugs among the leaves.

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.

Because the FLRP primarily attacks new, soft, pliable new growth as it unfurls, management techniques that suppress new growth, such as withholding or lowering irrigation and fertilizers, might also be effective techniques for reducing infestations. Indeed, we have observed neglected trees with little or no irrigation and much reduced new growth that have many fewer pests, including leaf gall wasps, Indian laurel thrips, and the FLRP.

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.

—Donald R. Hodel, Landscape Horticulture Advisor, UCCE Los Angeles County, drhodel@ucanr.edu
—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.