4. Whiteflies
The giant whitefly (Aleurodicus dugesii) and the mulberry whitefly (Tetraleurodes mori)
both are pests of mulberry trees. Whiteflies generally congregate on lower leaf
surfaces; adults have a white, waxy covering on their wings and body. All stages of the
whitefly life cycle suck plant juices from leaves and excrete a sticky, sweet substance
known as honeydew that attracts ants and hosts the development of sooty mold.
Heavy feeding can cause leaf yellowing and drop. The whitefly population grows
rapidly in warm weather or when natural predators are disrupted by dusty conditions
or broad-spectrum insecticides. Insecticides do not provide good whitefly control.
Instead, a whitefly infestation is best addressed by spraying small mulberry trees with
water to reduce dust, or by addressing ants that are protecting the whiteflies.
5. Scales
The California red scale, oleander scale and San Jose scale are armored scale
insects that feed on mulberry tree fluids. Scales appear as small, immobile bumps on
leaves or bark. Although armored scales do not usually seriously damage the hosting
mulberry tree, a heavy infestation can cause leaf wilting, yellowing and premature
drop. A large population on the trunk or branches can cause bark to crack and exude
gum. A scale infestation is best addressed by providing the mulberry with good cultural
care including adequate water, pruning off heavily infested portions of small trees, and
encouraging natural scale enemies such as small parasitic wasps and ladybugs. A
well-timed application of horticultural oil when the scales are in their mobile crawler
stage offers control.
6. Mealybugs
The Gill's and pink hibiscus mealybugs are potential pests of mulberry.
These insects have a grayish to pink body and are covered in a white waxy
material. They tend to form masses where they feed on the plant, producing
honeydew and impacting plant growth. Natural predators usually provide
adequate mealybug control unless interrupted by ants, dusty conditions or
insecticides. If necessary, a strong blast of water, narrow-range horticultural
oil or insecticidal soap will control mealybugs. Healthy mulberry trees can
tolerate moderate mealybug feeding.
7. Fall Webworm
The fall webworm, Hyphantrea cunea, is an inch-long, yellow or green caterpillar with
a broad, bumpy stripe, a dark head and tufts of long white hairs. The adult moth is
white with dark wing spots. These caterpillars create webs up to several feet in
diameter around their feeding sites, covering leaves or entire branches. In large
numbers, these nests can seriously impact a tree's appearance. On small trees where
there are few nests, pruning out nests may provide adequate control. There are
several naturally occurring webworm parasites and predators, so broad-spectrum
insecticides that harm beneficial insects should be avoided. Other control options
include Bacillus thuringiensis, applied thoroughly to foliage when the caterpillars are
young, and systemic insecticides.
8. Glassy-Winged Sharpshooter
The glassy-winged sharpshooter, Homalodisca vitripennis, is a 1/2-inch-long,
dark-brown leafhopper that feeds on plant sap. The females lay eggs in
masses covered with a white chalky material under the lower leaf surface.
Although glassy-winged sharpshooters rarely cause serious damage directly
from feeding, they excrete a large volume of liquid that makes foliage and
anything under the mulberry appear whitewashed. These pests also spread
the bacterium Xylella fastidiosa, the pathogen responsible for serious plant
diseases, including mulberry leaf scorch, oleander leaf scorch and Pierce's
disease on grapes. No cultural control methods address this pest, but
numerous natural parasites and predators offer biological control. Thorough,
repeat foliar applications of insecticidal soaps and oils is one chemical treatment
option.