April 2012. A request from the Ministry of Agriculture, St Lucia for the identification of a pest on seagrapes. This plant is a major ornamental on the beaches, and it is also used for landscaping at most of the hotels.
it was not clear to members what was on the seagrapes, but it seems that the plants are black because of sooty moulds; that means that there is an insect that secretes honeydew; this could be a whitefly (Hemiptera: ternorrhyncha: Aleyrodidae) or a mealybug (Hemiptera: Sternorrhyncha: Pseudococcidae).
It was thought likely that it was the giant whitefly, a species of Aleurodicus, but another photo of the undersurface of a leaf is needed. There are several species of Aleurodicus that are hosts of seagrapes. Identification would require study of slide-mounted specimens.
This was confirmed by another member who said that it was Aleudocus pulvinatus, which is found throughout the Caribbean. Periodically, populations of the whitefly increase in response to favourable weather conditions. A number of natural enemies – parasitoids belonging to Encarsiella and Encarsia species as well as small, black coccinellid beetles (ladybirds) – are usually associated with the whitefly. Other generalists, such as syrphids and chrysopids, also play a role in bringing down the populations. Therefore, with time, the populations should subside.
But an authoritative ID was needed. It could be a new introduction from South America!
Other comments were as follows:
- Another member mentioned that he had seen a whitefly on seagrape at Salt Cay island in the Turks and Caicos islands in April 2010.
- There was also a suggestion that it could be a species of mealybug, perhaps the Hibiscus mealybug (Maconellicoccus hirsutus) or papaya mealybug (Paracoccus marginatus). Seagrape is used as a host for these species for the production of their parasites and predators. If either of these are present in St Lucia and are problems, they may be the cause.
Later, the specimen was looked at under the microscope and mealybugs of all stages and Ensign coccids were found. The species needs to be determined.