Pseudococcus calceolariae (scarlet mealybug)

P. calceolariae feeds on the phloem of deciduous and evergreen plants in warm, temperate climates. Under these conditions, populations of P. calceolariae seldom reach sufficiently high levels to debilitate the plant, and the symptoms of attack are usually restricted to visual sighting of mealybugs or sooty mould. When P. calceolariae (or other mealybugs) shelter in fruit, for example within the calyx (pipfruit), around the stalk (pipfruit) or under fruit sepals (citrus, persimmons) they are often hidden from view, and cannot be seen without cutting open the fruit. Sooty mould fungi growing around the calyx or sepals on excreted honeydew are a good indicator of the presence of mealybugs in the fruit. Sooty mould on foliage may result from mealybugs or other Sternorrhyncha.

P. calceolariae is an endemic pest throughout most of Australia, and is perhaps the most serious pest of citrus in South Australia (Altmann and Green, 1991). P. calceolariae is commonly found throughout the major fruit-growing regions in New Zealand, and may be very common locally on most fruit crops (Charles, 1993). It can be a severe pest, at least locally, in Italy (Laudonia and Viggiani, 1986). The introduction of natural enemies has reduced its importance in the Republic of Georgia (Yasnosh, 1995).Mealybugs are pests for several reasons. They may debilitate parts of the plant through sap depletion, transmit disease (Petersen and JG Charles, Horticulture and Food Research Institute of New Zealand Ltd, personal communication), or scar fruit, for example P. calceolariae feeding under the 'button' of citrus fruit causes a necrotic halo mark. A heavy infestation can cause fruit drop (Altmann and Green, 1991). More commonly, the presence of mealybugs in other perennial fruit crops leads to unacceptable growth of sooty mould fungi on honeydew deposits on the fruit, either as a deposit on the cheek (which is difficult to remove at packing) or around the stalk, calyx or sepals. For growers producing fresh fruit for export markets, the presence of mealybugs or sooty mould may be sufficient to limit the sale of that fruit to local markets at reduced prices. Some countries accept the fruit, but insist on fumigation, which is costly, and results in poorer quality fruit with a shorter shelf-life.P. calceolariae has recently been shown to be a vector of the closterovirus associated with grapevine leafroll disease, and is implicated in the spread of this disease in vineyards (Petersen and JG Charles, Horticulture and Food Research Institute of New Zealand Ltd, personal communication).The significance of mealybugs as pests thus varies among country, crop and grower. The pest status of P. calceolariae (and mealybugs in general) can only be evaluated on a case-by-case basis.