Curbing Pink Mealybug (1997, Vol. 20 No. 4) - SIA

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CURBING PINK MEALYBUG
by Trevor Falloon
The good news is that cane is not its favorite food.
Even better news is that it is hardly news anymore in a number of Caribbean islands where it was wreaking havoc only a short while ago. So, for the farmer growing multiple crops, anyone who enjoys puttering around the home garden or the lover of greenery there is now little cause to be despondent.
The startling revelation that the mealybug was attacking more than 125 different plants, later upgraded to over 200, though essentially correct, needs to be reviewed in light of current information.
The turn around from predictions of doom can be credited largely to another insect, the Australian ladybird, brought to the Caribbean and released to fight the mealybug. This ladybird beetle, (Cryptolaemus montrouzieri) released in Trinidad, Grenada and St. Kitts, just loves eating mealybugs and consumes many hundreds in a few weeks. As a consequence, guango trees and various hibiscus plants that were dying at one stage are today sprouting again. Indeed, one has to search to find any plant under serious attack by the mealybug.

NOT IN JAMAICA - YET
There were reports in September, 1996, that the mealybug was found in Jamaica. Happily, the experts have since determined that this was a false alarm. This only goes to show how difficult it is to distinguish between one mealybug and the next by physical appearance. Nonetheless, it may be just a matter of time before it is here. So vigilance must be maintained and preparations continued for possible entry.
So far, Grenada, where it seemed to have first entered the Caribbean, followed by Trinidad, St. Kitts, St. Lucia and more recently Guyana have borne the brunt of the attack. Initial reports from the islands were most disquieting. Multiplying at a rate much faster than customary in its countries of origin (Australia, Indonesia, Philippines, India and South East Asia, Middle East and Africa), it was ravaging agriculture and horticulture and even forestry leaving a trail of damage valued at over US $150 million in two years.


DON’T LOOK FOR PINK
Also known as the hibiscus mealybug, and the grape mealybug in various parts of the world, this sucking insect is perhaps more readily identifiable by the damage it does than by the colour “pink” that the name suggests. Sure, it is pink if the white waxy coating is removed from its 3 mm long, oval-shaped adult body. But then there is already a “pink mealybug” (Saccharicoccus sacchari) in sugar cane. This is however well controlled by natural enemies, though it may be occasionally found beneath leaf sheaths, at the cane joints, particularly in water-starved or partly abandoned fields. Here too, the pink is usually not visible under the coating of white wax.
It may take many painstaking hours of peering under a microscope for the trained expert to distinguish between one type of mealybug and the next. Even the layperson however will readily recognize that something unusual is afoot when faced with an attack by this new pest.

DAMAGE
As it feeds, the pink mealybug (Maconellicoccus hirsutus) injects toxic saliva, in reaction to which leaves curl and crinkle while stalk growth becomes stunted so that leaves appear bunched together. These symptoms are sometimes produced even where the mealybug merely pauses to sample a plant it may subsequently reject.
Where the bug comes across a plant it truly fancies the results are much more dramatic. Most Hibiscus species, including the popular ornamentals used to form hedges, the blue mahoe (the national flower), sorrel (Christmas favourite), as well as okra, will rapidly become almost totally covered - the tender tip of the stem, especially, and even exposed roots - by teeming masses of the bugs. With their constant sucking of the plant sap they pass out a sugary liquid called honeydew which coats the leaves encouraging growth of the black sooty mould fungus, often referred to as “blight.”
Despite its famed preference for plants of the Hibiscus species, it is hard to say whether it does not savour fruits most of all. Pictures of surfaces of fruits such as soursop, sweetsop, guava, pumpkin etc. completely covered, with literally not a centimeter of visible surface, tell the story. Fruits not directly attacked are so deformed, they become useless. The list of popular plants attacked given in Table 1 shows our potential vulnerability.
If it enters and is allowed to go unchecked the mealybug would have the capability of devastating watersheds and would threaten Jamaica’s mahoe forests and the magnificent century-old guango trees that dot the countryside. There would indeed be grave implications for water resources, food supplies, the treasured greenery and consequently even tourism.

WHY SO DEVASTATING?
Pink mealybug is of little importance in its countries of origin. Why then is it so damaging in the Caribbean?
The explanation is simple. In its homeland it is suppressed by a range of natural enemies - other insects mainly - that prey upon or parasitize it. Leaving those natural enemies behind, it arrived in the Caribbean unfettered and free to realize its full reproductive and damaging potential. Now that it has been rejoined by its natural enemies its capacity for devastation has been dramatically reduced.

SPREAD
Because females lack wings, spread would normally be relatively slow. Unfortunately, human beings are the most efficient agents of dispersal taking plant material, usually unknowingly infested, from place to place, sometimes from country to country.
In addition the mealybug can piggyback on clothing, packages of various sorts, and animals - including birds. It can be wind blown or washed to other sites in streams and may
infested material to the authorities for identification. You could be spreading the insect along the way. Call them for an on-site inspection. If you are a cane farmer your best bet would be to:
Call SIRI at 962 2241/ 962 1287 or the nearest RADA office.
When presence of the mealybug is confirmed, burn cuttings from infested plants as close as possible to the site. Don’t put them with garbage to be taken to the dump. Also avoid shaking or scattering infested material.

CONTROL
In instances of an insect outbreak it is customary to look to insecticides for an immediate solution. While there will indeed be a place for insecticides, the mealybug is not easily controlled by chemicals.
The waxy covering shields it from insecticidal sprays. Furthermore the bugs tend to congregate in cracks and crevices in the bark of trees, within curled up leaves, beneath the sepals of flowers and even under rocks on the ground. In such locations many will escape the best directed spray. In addition when the mealybugs attack full-grown mahoe or guango trees, only aerial spraying could potentially reach them.
The frequency with which such spraying would have to be conducted would not only prove harmful to our own health but more damaging in the long term as natural enemies would also be destroyed creating the possibility of even greater outbreaks of the mealybug and unpredictable secondary outbreaks of other pests.
Don’t start spraying every mealybug in sight. This could do more harm than good. Infestations of our native mealybugs may well be sustaining populations of natural enemies that could be helpful in fighting this expected invader. Spraying will kill these beneficial insects.
Insecticides may however be judiciously used in an effort to protect certain crops. Precise recommendations will depend on type of crop and should follow initial testing.
In the long run, the solution lies in the importation, rearing and release of natural enemies such as certain ladybird beetles and parasitic wasps (which pose no danger to humans or livestock) which will establish themselves to counter the buildup of the mealybug.

OUTLOOK
The mealybug ought not to be as devastating in Jamaica as it has been in Grenada. For one thing, we have had ample time for preparation. The Ministry of Agriculture and press have done an excellent job in alerting us to the danger. We need to maintain the vigilance and play our part in observing quarantine regulations and continue to immediately report sightings of suspected mealybugs.
Entry of the mealybug to Jamaica would have to be regarded as a national emergency requiring the full cooperation of all agencies. The goal must be to provide a welcoming party of so many of the mealybug’s natural enemies that it feels right at home in Jamaica.
That is why SIRI plans to join the national effort to rear natural enemies.
Total eradication after arrival is unlikely. It should however be possible to so integrate it into the local environment that after a while its presence becomes hardly noticeable.
 
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