2012 Annual Report
1a.Objectives (from AD-416):
The Harrisia cactus mealybug is a severe pest of columnar cacti worldwide. It is native to Northern Argentina and Chile, westernmost Brazil, Paraguay and southern Perú. In native lands, H. pungens also affects Portulaca spp. (Portulacaceae), Acalypha (Euphorbiaceae) and Althernanthera spp. (Poligonaceae). This host plant preference indicates a tendency towards polyphagy. Little is known about its biology or natural controls.
In other parts of the world, H. pungens has been used as an effective biological control agent of cacti. In Australia and South Africa, where cacti have become rangeland nonnative invaders, the mealybug has been credited with clearing thousands of hectares of these plants.
Current distribution of this species in the Caribbean includes Florida, Puerto Rico and Barbados. This mealybug has also been intercepted at ports in southern Europe, but establishment has not been documented. It has also been reported in Hawaii.
Cacti are important members of the dry forests in Puerto Rico, being abundant in “seed rains.” There are 13 native and three endemic species; two columnar species are listed by the U.S. Fish & Wildlife Service as endangered: Harrisia portoricensis and Leptocereus grantianus. They are also important food sources for endemic bats, birds, moths and other pollinators, which predicts long-lasting damage to these organisms. H. pungens also presents potential negative impacts to agriculture, precluding the establishment of commercial productions of ‘dragon fruit’, Hylocereus undatus, an important crop for dry areas in the Caribbean. The mealybug is also a potential pest of ornamentals, such as Acalypha and Portulaca. The eventual expansion of H. pungens range will soon include offshore islands (Mona, Desecheo, Vieques and Culebra), which now harbor the last remaining wild populations of endangered cacti. The introduction of H. pungens to Puerto Rico poses a heightened extinction threat to these endemic cacti, and to the endemic organisms that depend on them.
1b.Approach (from AD-416):
Field surveys will start in October 2009, to find, select and evaluate the most appropriate candidates for the biological control of this pest in Puerto Rico, and eventually, in Florida and Hawaii. The minimum duration of this program should be three years to cover the following agenda of activities (the agenda might change according to the progress of the program):
Year 1: Field surveys to study (1) the distribution, mainly in Argentina, of H. pungens; (2) the presence and abundance of natural control organisms; and (3) the techniques to rear H. pungens under laboratory conditions at the South America Biological Control Lab.
Year 2: Field surveys continued. Pre-selection of the best candidates for biocontrol. Preliminary security tests with selected agent/s.
Year 3: Field surveys continued. Efficacy of selected agent/s on H. pungens control. Apply for exportation permits. Shipments of selected agent/s to quarantine conditions in the U.S.
Biological control of the Harrisia cactus mealybug in Puerto Rico. The mealybug is a severe pest of cacti. In its South American native land it also affects plants of other families. Current distribution in the Caribbean includes Florida, Puerto Rico and Barbados. Cacti are important members of the dry forests in Puerto Rico with native, endemic, and endangered species. It also presents negative impact to agriculture and will spread to offshore islands (Mona, Desecheo, Vieques and Culebra) which harbor wild populations of endangered cacti. At present, it has also been detected in California.
Samples of the mealybug collected in Argentina, Australia, California, Florida, and Puerto Rico were sent to specialists for taxonomic and genetic analysis. So far, taxonomic identification concurred with the genetic analysis. The studies indicated that the 3 haplotypes found in Argentina corresponded to two identified and one unidentified mealybug species. Tests with reciprocal crosses revealed no reproductive compatibility between these species; one species did not show parthenogenesis, and one species showed parthenogenesis. New evidence indicated that the mealybug present in Puerto Rico might not have entered from Argentina and might be a different new species.
A survey of parasitoids and predators in northern Argentina were conducted using sentinel nymphs and adults of one mealybug species, and by collecting wild populations of two mealybug species. The sentinel nymphs and adults were obtained by caging individuals on potted cacti. Potted plants with nymphs and adults were placed in 8 sites in north central Argentina. So far, 10 parasitoid and 2 predator species were collected. The materials are being identified.