The Hibiscus or Pink Mealybug
Plant Protection & Quarantine
July 1996
The hibiscus or pink mealybug, Maconellicoccus hirsutus (Green),
is a dangerous pest of many plants, trees, and shrubs. It infests
hibiscus, citrus, coffee, sugar cane, annonas, plums, guava, mango,
okra, sorrel, teak, mora, pigeon pea, peanut, grapevine, maize, asparagus,
chrysanthemum, beans, cotton, soybean, cocoa, and many other plants.
This pest occurs in most tropical areas of the world, including Asia,
the Middle East, Africa, Australia, and Oceania. The hibiscus mealybug
arrived in Egypt from India in 1912 and in Hawaii in 1984. Finally,
it appeared in Grenada, Trinidad, and St. Kitts in the 1990's.
It is now a very serious pest in the Caribbean where it attacks many
hosts of economic importance and disrupts Caribbean agricultural trade
and commerce.
The U.S. Department of Agriculture's (USDA) Animal and Plant Health
Inspection Service (APHIS) is charged with protecting American agriculture
from exotic plant pests like the hibiscus mealybug. With the pest's
recent arrival in the Caribbean, APHIS is increasing its vigilance
to prevent this pest from entering the United States.
The hibiscus mealybug is considered a pest of extremely serious quarantine
importance and has the potential to expand its geographical distribution
to North, Central, and South America.
Description and Life Cycle
The hibiscus mealybug is also known as the grape mealybug and the
grapevine mealybug. The pest forms colonies on the host plant, and
if left undisturbed, the colonies will grow into large masses of white
waxy coverings on branches, fruiting structures, leaves, and even
whole plants, including large trees.
Both female and male adult hibiscus mealybugs are about one-eighth
inch (3 mm) long. Female bodies are pink in color with a white waxy
covering. They are wingless and appear as ovoid shapes covered by
a mass of white mealy wax. Males have a pair of wings and two long
waxy tails and are capable of flight.
Observers have reported that reproduction may occur by means of parthenogenesis
in the absence of the male. In cool climates, the pest overwinters
in the soil or on the host plant, either in the egg stage or as an
adult.
Newly hatched nymphs are called crawlers and are very mobile. They
may disperse over the host, especially toward tender growing parts,
or be carried away by wind, man, or animals. The nymphal stages appear
much like the female in form, but the female nymphs have three instars,
while male nymphs have four instars. The last instar of the male is
an inactive stage with wing buds within a cocoon of mealy wax. The
nymphal stages may last for as long as 30 days.
Spread
The mature female lays eggs in an eggsack of white wax, usually in
clusters on the twigs, branches, and bark of the host plant, and also
on the plant's leaves and terminal ends. Eggs are initially orange
in color but turn pink on maturity. Egg development takes between
3 and 9 days. Eggs are minute, varying from 0.3 to 0.4 mm in length
and number as many as 654 eggs per sack. In its egg stage, the hibiscus
mealybug disperses most easily by wind. The wax, which sticks to each
egg, also facilitates passive transport by animals or man.
Wingless crawlers, nymphs, and females have been known to travel
short distances over the ground to get to other host plants in adjoining
fields. Agricultural commerce is also responsible for the pest's spread.
The hibiscus mealybug can complete its entire life cycle in 23 to
30 days. Under optimum laboratory conditions, there can be as many
as 15 generations a year. The pest can occur seasonally in colder
regions from infestations spread by wind currents.
The pest has some ability to adapt to cooler weather as shown by
nymphal movement to sheltered locations and the female's choice of
protected places for eggsacks.
Damage
As it feeds, the hibiscus mealybug injects into the plant a toxic
saliva that results in malformed leaf and shoot growth, stunting,
and occasional death. Leaves show a characteristic curling, similar
to damage caused by viruses. Heavily infested plants have shortened
internodes leading to resetting or a "bunchy top" appearance.
A heavy, black, sooty mold may develop on an infested plant's leaves
and stems as a result of the mealybug's heavy honey-dew secretions.
When fruits are infested, they can be entirely covered with the white
waxy coating of the mealybug. Infestation can lead to fruit drop,
or fruit may remain on the host in a dried and shriveled condition.
If flower blossoms are attacked, the fruit sets poorly. In plants
such as peanuts, potatoes, and some grasses, the pest has been reported
to attack the root systems.
The hibiscus mealybug has a wide range of hundreds of unrelated plant
hosts; the list is growing as the pest spreads into new geographical
areas. So far, the pest has been found on 215 genera of plants. Its
wide host range favors rapid spread and complicates effective control.
In spite of its wide distribution, the hibiscus mealybug was a major
pest only in India and Egypt prior to its discovery in the Caribbean.
In India, it is a major pest of grapes, reducing grape yields 50 to
100 percent. Yield losses on other crops such as sorrel, jute, mesta,
and roselle range up to 75 percent. In Egypt, the mealybug is an extremely
serious pest of shade trees, such as the lebbekh and the bauhinia,
and of mulberry, pigeon pea, and guava. Cotton is particularly susceptible
if it is planted near infested trees.
In Hawaii the hibiscus mealybug has not become an economically important
pest, probably because it is regulated by several natural enemies.
In Grenada the hibiscus mealybug infests cocoa, many types of fruit
and vegetables, and ornamental plants, such as hibiscus, oleander,
and croton. The worst effect has been on Grenada's forests, where
entire trees have been killed and whole groves are under threat of
extinction.
Control
Ways to control the hibiscus mealybug include the use of insecticides,
cultural practices, and biological control. Biological control is
the best long-term solution.
A number of natural enemies are known, including the coccinellid
predator Cryptolaemus montrouzieri and the parasite Anagyrus
kamali. In Egypt and India, biological controls have been quite
successful in controlling the hibiscus mealybug. Other coccinellid
predators have also been reported in India. At present, 21 parasites
and 41 predators are known to attack the hibiscus mealybug worldwide.
The U.S. Department of Agriculture (USDA) prohibits discrimination
in all its programs and activities on the basis of race, color, national
origin, sex, religion, age, disability, political beliefs, sexual
orientation, or marital or family status. (Not all prohibited
bases apply to all programs.) Persons with disabilities who
require alternative means for communication of program information
(Braille, large print, audiotape, etc.) should contact USDAís
TARGET Center at (202) 720-2600 (voice and TDD).
To file a complaint of discrimination, write USDA, Director, Office
of Civil Rights, Room 326-W, Whitten Building, 1400 Independence Avenue,
SW, Washington, DC 20250-9410 or call (202) 720-5964 (voice and TDD).
USDA is an equal opportunity provider and employer. ã
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