White Flies

White Flies

Description:

Recently, a new pest was reported attacking ficus trees and hedges in Florida There is a new pest attacking ficus trees and hedges in Miami-Dade, Broward and Palm Beach Counties, Florida. This pest was identified as the fig (ficus) whitefly, Singhiella simplex, and is a new US continental record.

White flies are small, winged insects that belong to the Order Hemiptera which also includes aphids, scales, mealybugs, and bugs. These insects typically feed on the underside of leaves with their “needle-like” mouth parts. White flies can seriously injure host plants by sucking juices from them causing wilting, yellowing, stunting, leaf drop, or even death.

Damage:

The leaves of ficus trees infested with whiteflies begin to turn yellow before the leaves are dropped from the plant. Ficus trees without their leaves are one of the most obvious symptoms of a whitefly infestation. This whitefly has been most commonly found infesting weeping fig (Ficus benjamina) but has also been reported on Ficus. Altissima (lofty fig, false banyan tree), Bengalensis (also called “banyan tree”), Microcarpa (Cuban laurel), Aurea (strangler fig), lyrata (fiddle-leaf fig), and macllandii, binnendijkii) (banana-leaf fig). This whitefly may eventually be found on other species of ficus.

If the foliage is disturbed the small, white gnat-like adult whiteflies can be seen flying from the foliage. The adult whitefly resembles a very small moth with a yellow body and white wings with a faint grey band in the middle of the wings. Immature stages (eggs and nymphs) can be found primarily on the underside of the leaves. Prior to adult emergence, the nymphs are tan to light green discs with red eyes. The underside of infested leaves look like they are dotted with small, silver or white spots which are actually the empty “skin” of the pupae after the adult emerges. Leaf infested with Adult whitefly Immature whiteflies whitefly Red eyed stage

Biology:

The life cycle of the ficus whitefly is approximately one month. Eggs which are usually laid on the underside of leaves hatch into a crawler stage. The crawler wanders around the leaf until they begin to feed. From this point until they emerge as adults, they are immobile and remain in the same place on the plant. These feeding, non-mobile stages (nymphs) are usually oval flat, and simple in appearance. The early nymph stages can be very difficult to detect.

Management:

Although efforts to understand and control this pest are ongoing, there are several potential options for whitefly control. However, it is necessary to consider the site (landscape, hedge, large tree, container, production, etc), the size and number of trees, and the surrounding environment before taking steps to control this pest. For large trees, for example, a foliar spray may not be possible. In the landscape, several natural enemies have been observed attacking this whitefly which can play an important role in long term control.

Awareness of these natural enemies is very important so decisions for additional control measures can be made wisely so as not to also kill the natural enemies. The most commonly seen natural enemies include beetle predators, parasitoids, and lacewings. Beetle predator Beetle predator Parasitized whitefly Parasitic wasp monitor your ficus plants for early signs of an infestation because it will be easier to manage the pest before it builds to high populations and causes major damage. Defoliation usually occurs after the whiteflies have been there for several generations.

Also, if infested trees or hedges are trimmed, either leave the clippings on the property or if removing, bag the clippings to reduce the chance of spreading the insects. If clippings are being transported in a truck, be sure to either bag them or cover these clippings with a tarp. Although the eggs and early stages of the whitefly on fallen leaves will die, the last nymphal stage of the whitefly can likely survive, emerge into an adult and attack more ficus. Insecticidal soap or oil sprays may be an effective method of control for small trees or shrubs, but, thorough coverage of the undersides of the leaves is especially important.

It will also be necessary to repeat these applications every 7 to 10 days. The use of other insecticides may be necessary to control this pest. However, it is important to use products that will not be detrimental to the natural enemies. Protecting natural enemies may be a critical component in the long-term control of this pest. Insecticides with systemic properties may be very useful in whitefly control because they can be applied as a drench to the soil and provide longer lasting control.

Control in the Landscape:

The current recommendation is to drench the soil around the base of the tree or hedge with a product that contains a neonicotinoid compound (see below table). If applied appropriately, these products should provide sufficient control of the whitefly for 4-8 months (or perhaps longer) depending on the size of the tree or shrub. It is advisable to monitor your plants 3 months after application for the presence of live nymphs. Foliar sprays can also be applied to treat “hot spots” or get quick knockdown in addition to the soil applications. Products that can be considered for foliar applications are listed in the next section (Control in the Nursery), but it is important to only use those products that are allowed in the landscape. Also, the products (neonicotinoids) listed in the below table can also be Aug 2008 used as a foliar spray but it is not recommended that you use them as both a foliar and soil application and it is the soil application that will provide the longest control.