Cuban laurel thrips—Gynaikothrips ficorum and weeping fig thrips—Gynaikothrips uzeli
These thrips (family Phlaeothripidae) suck and feed on foliage of Ficus species and cause infested leaves to discolor and distort.
Identification
These Gynaikothrips species cause loose curling or folding of ficus leaves and discoloration of the galled foliage. Cuban laurel thrips mostly galls Indian laurel fig, Ficus microcarpa. Weeping laurel thrips mostly galls weeping fig, Ficus benjamina.
Adults, eggs, and larvae (or nymphs) of these Gynaikothrips closely resemble each other. They are distinguishable only by an expert examination of microscopic hairs (pronotal posteroangular setae), which in comparison with G. ficorum are longer on G. uzeli.
Gynaikothrips adults are 1/10 to 1/8 inch long and black to dark brown. Characteristic of thrips, the adults are narrow and have long fringes of tiny hairs (setae) along the margins of their wings.
The tiny eggs occur on foliage within galls. Eggs are beige to translucent white, cylindrical, and smooth and have rounded ends.
The first instar (larva) is translucent white and about 1/25 inch long. The second instar is pale yellow and about the length of adults. Second instars commonly hold the rear end pointing up. First and second instars have red eyes.
The prepupa (propupa) and pupa do not feed and are relatively inactive. Prepupae develop wing buds (pads) that are externally visible and have antennae that point forward. The pupa has longer wing buds and antennae that are folded back over the head.
Several other insects also gall ficus. These inadvertently introduced pests and their host plants are native to Southeast Asia.
Ficus gall wasp. Josephiella microcarpae infests only Indian laurel fig and causes leaves to curl or distort. The leaf deformation from feeding of each wasp larva is distinctly rounded and spherical, unlike the leaf curling or folding caused by Gynaikothrips. Leaves galled by the wasp remain uniformly green, unlike with the Gynaikothrips that cause brown, reddish, or purple scars on galled leaves.
Ficus eye-spot midge. Horidiplosis ficifolii causes elliptical to irregularly shaped blisters or swellings in leaves of Indian laurel fig. Each swelling is up to about 1/5 inch long and caused by a gall midge (fly) larva feeding inside leaf tissue. The swellings later turn brown and sunken with a tiny hole where the mature larva emerged to pupate. Weeping fig is not infested by this gall midge even when growing near heavily infested Indian laurel fig.
Ficus leaf-rolling psyllid. Trioza brevigenae is an aphidlike insect that causes Indian laurel fig leaves to become tightly rolled lengthwise into narrow cylinders about 1/6 inch in diameter. These pencil-like cylinders can harbor various nymphal stages of the psyllid. Infested leaves become dry and brittle but remain uniformly green. Feeding by abundant psyllids can cause premature leaf drop and result in a sparse canopy.
Life cycle
Thrips hatch from an egg that adult females deposit inside galled (rolled) leaves. They develop through two larval stages that feed, then a prepupal and pupal stage that do not feed before becoming an adult. After hatching the larvae remain feeding inside the gall. All thrips stages occur year-round in galled leaf terminals. Mating, egg laying, and a complete generation develop within a single gall. Gynaikothrips are most abundant from about October through December. Newly galled foliage is formed from midsummer through fall.
Only the adults occur outside of galls. Adults are active flyers when temperatures are warm. They readily spread with the wind and movement of infested plants. Adults commonly exit galls within a few days of emergence from the pupal stage. They migrate to other terminal leaves and start a new generation. Adults induce folded-leaf galls within 2 to 3 days of infesting a terminal.
The life cycle from egg to adult requires about 30 days during the growing season. Gynaikothrips have several generations per year.
Damage
Adult Gynaikothrips feed on new leaves, causing them to distort and deform. The leaf folds along the main vein and forms a permanent gall with dark brown, reddish, or purplish scarring. Prolonged feeding by high populations of adults and larvae can slow plant growth and cause premature drop of leaves.
Solutions
Except for aesthetic damage, Gynaikothrips do not seriously harm ficus, so no control is needed if distorted foliage can be tolerated. Replace F. benjamina and F. microcarpa with a resistant Ficus species if these thrips' galling is intolerable. Alternatives include creeping fig (F. pumila), Moreton Bay fig (F. macrophylla), and rubber plant (F. elastica). Where this problem occurs and Indian laurel fig will be planted, consider using F. microcarpa ‘Green Gem’, which is resistant to Cuban laurel thrips and weeping fig thrips.
Common predators of thrips in galls include larvae of green lacewings and adults and nymphs of a minute pirate bug, Macrotracheliella nigra, which is dark reddish brown to black and less than 1/8 inch long. To conserve natural enemies control ants, reduce dustiness (e.g., periodically hose off small plants), and avoid the use of persistent, broad-spectrum insecticides. See Protecting Natural Enemies and Pollinators for more information.
Prune and dispose of infested terminals to improve plant appearance and reduce the abundance of these thrips. Winter may be the best time to prune off tips because more galled tissue generally does not form until next summer and relatively few thrips can survive the winter outside of the protection provided by the rolled leaves.
Because they feed protected within galls, only a systemic insecticide (e.g., acephate, dinotefuran, imidacloprid) is likely to provide control and minimize the extent of future galling. These broad-spectrum, persistent insecticides are poisonous to natural enemies that have the potential to maintain populations of Gynaikothrips at relatively lower abundance. Because of their potential to poison adult natural enemies and pollinating insects that feed on nectar and pollen to which systemic insecticides can move, if used apply these insecticides shortly after the end of seasonal flowering.
For more information and photographs see Common Name: Leaf-gall Thrips of Ficus from the University of Florida and New Pests of Landscape Ficus in California (PDF) from the University of California.
Adapted from the publications above and Pests of Landscape Trees and Shrubs: An Integrated Pest Management Guide, University of California Statewide Integrated Pest Management Program (UC IPM). |
