April 2008. A request from the Cameroon for information on mealybugs on banana. The insects attack the fruits and cause a black fungus which reduces the aesthetic value of the fruits. What chemicals can be used when the fruits are washed to remove the mould?

A PDF file of a paper on mealybugs on banana and plantain in Africa for mealybug identification purposes was sent to the Cameroon. Sooty mould develops on the sugary honeydew excreted by mealybugs, so a simple cold water jet should be sufficient to dislodge and wash off most of the sooty mould fouling the fruit. It will also remove the mealybugs, which will reduce the likelihood of pest problems on exported fruit and increase the likelihood of quarantine compliance.

Other replies mentioned field control of mealybugs using the coccinellid predator Cryptolaemus montrouzieri (www.bugsforbugs.com.au/product/32) (see photo) and also Anagyrus spp. Mineral oil was also said to be effective. Members were reminded that often mealybugs are protection by ant, and that control of ants may be required rather than control of mealybugs, so that natural enemies can carried out their “beneficial acts”.

For scale insects (and possibly mealybugs, too), spraying a thin solution of starch is useful. When the starch dries and flakes away it will take the mould with it. See:
www.pestnet.org/Summaries/Crops/Fruitnuts/Guava/Sootymould/tabid/2399/Default

The following link has some information on starch dosage as well as other pesticides that can be used.
http://books.google.com/books?id=ZiY9ZDZ_QUUC&pg=PA612&lpg=PA612&dq=starch+for+sooty+mould&source=web&ots=bxfA8uyWej&sig=G8T_0R3OOe8mUnxofhNOCaxrfqs&hl=en&sa=X&oi=book_result&resnum=3&ct=result.

Horticultural oil (2%) timed for peak crawler activity can be tried. More than one spray might be needed, because the bodies of the adult scales are well protected by the wax coverings. The oil will soak through the wax to some degree, but this will depend on how thoroughly the scale is wetted. There is not likely to be phytotoxicity on mango or palms from a 2% solution of horticultural oil.