Survey of papaya mealybug, Paracoccus marginatus and its introduced parasitoids on papaya plants in the low country dry zone of Sri Lanka

Papaya mealybug, Paracoccus marginatus Willams and Granara Willink, is an invasive hemipteran that attacks several genera of host plants, including economically important tropical fruits and ornamentals. It is an alien invasive species and was reported for the first time in Sri Lanka in 2008 and the biocontrol programme was implemented with the introduction of three natural enemies Acerophagus papayae, Anagyrus loeki, and Pseudleptomastix mexicana imported from Puerto Rico in some selected regions in 2008 and 2009. After a decade following the initial introduction it is essential to investigate the presence of the parasitoids for the management of papaya mealybug pests. Therefore a survey was conducted to study the pest status of papaya mealybugs and to check the availability and the abundance of their introduced parasitoids is some randomly selected locations of the low country dry zone of Sri Lanka during the period from January 2018 to December 2019. The survey revealed that P. marginatus is still spreading in Sri Lanka but is present at lower population levels than in previous years, probably due to the action of introduced hymenopteran parasitoids. Among the three parasitoids the A. papayae and P. mexicana were found to be established on the papaya plants infested with papaya mealybug. The parasitoid with the greatest impact on the mealybug is generally Acerophagus papayae , whereas A.  loeki was failed to establish. The finding would be very essential to tackle if there are any future threats caused by P.marginatus

Life cycle of the cotton mealybug Phenacoccus solenopsis in shoe flower plants under the Laboratory conditions

The cotton mealybug Phenacoccus solenopsis Tinsley (1989) is one of the invasive species recently introduced to Sri Lanka and nowadays it is wide spread among various parts of the country. The life cycle of P.solenopsis was studied under the laboratory conditions using Hibiscus rosa-sinenesis (Shoeflower) as host plant. This paper describes the lifecycle and discusses about the reproductive parameters of P.solenopsis under laboratory conditions relative to the appearance of symptoms on the host plant and the importance of making management interventions during the effective reproductive period of the insect

Anopheles culicifacies breeding in brackish waters in Sri Lanka and implications for malaria control

<p>Abstract</p> <p>Background</p> <p><it>Anopheles culicifacies </it>is the major vector of both falciparum and vivax malaria in Sri Lanka, while <it>Anopheles subpictus </it>and certain other species function as secondary vectors. In Sri Lanka, <it>An. culicifacies </it>is present as a species complex consisting of species B and E, while <it>An. subpictus </it>exists as a complex of species A-D. The freshwater breeding habit of <it>An. culicifacies </it>is well established. In order to further characterize the breeding sites of the major malaria vectors in Sri Lanka, a limited larval survey was carried out at a site in the Eastern province that was affected by the 2004 Asian tsunami.</p> <p>Methods</p> <p>Anopheline larvae were collected fortnightly for six months from a brackish water body near Batticaloa town using dippers. Collected larvae were reared in the laboratory and the emerged adults were identified using standard keys. Sibling species status was established based on Y-chromosome morphology for <it>An. culicifacies </it>larvae and morphometric characteristics for <it>An. subpictus </it>larvae and adults. Salinity, dissolved oxygen and pH were determined at the larval collection site.</p> <p>Results</p> <p>During a six month study covering dry and wet seasons, a total of 935 anopheline larvae were collected from this site that had salinity levels up to 4 parts per thousand at different times. Among the emerged adult mosquitoes, 661 were identified as <it>An. culicifacies s.l</it>. and 58 as <it>An. subpictus s.l</it>. Metaphase karyotyping of male larvae showed the presence of species E of the Culicifacies complex, and adult morphometric analysis the presence of species B of the Subpictus complex. Both species were able to breed in water with salinity levels up to 4 ppt.</p> <p>Conclusions</p> <p>The study demonstrates the ability of <it>An. culicifacies </it>species E, the major vector of falciparum and vivax malaria in Sri Lanka, to oviposit and breed in brackish water. The sibling species B in the <it>An. subpictus </it>complex, a well-known salt water breeder and a secondary malaria vector in the country, was also detected at the same site. Since global warming and the rise in sea levels will further increase of inland brackish water bodies, the findings have significant implications for the control of malaria in Sri Lanka and elsewhere.</p

Larval Development of Aedes aegypti and Aedes albopictus in Peri-Urban Brackish Water and Its Implications for Transmission of Arboviral Diseases

Aedes aegypti (Linnaeus) and Aedes albopictus Skuse mosquitoes transmit serious human arboviral diseases including yellow fever, dengue and chikungunya in many tropical and sub-tropical countries. Females of the two species have adapted to undergo preimaginal development in natural or artificial collections of freshwater near human habitations and feed on human blood. While there is an effective vaccine against yellow fever, the control of dengue and chikungunya is mainly dependent on reducing freshwater preimaginal development habitats of the two vectors. We show here that Ae. aegypti and Ae. albopictus lay eggs and their larvae survive to emerge as adults in brackish water (water with <0.5 ppt or parts per thousand, 0.5–30 ppt and >30 ppt salt are termed fresh, brackish and saline respectively). Brackish water with salinity of 2 to 15 ppt in discarded plastic and glass containers, abandoned fishing boats and unused wells in coastal peri-urban environment were found to contain Ae. aegypti and Ae. albopictus larvae. Relatively high incidence of dengue in Jaffna city, Sri Lanka was observed in the vicinity of brackish water habitats containing Ae. aegypti larvae. These observations raise the possibility that brackish water-adapted Ae. aegypti and Ae. albopictus may play a hitherto unrecognized role in transmitting dengue, chikungunya and yellow fever in coastal urban areas. National and international health authorities therefore need to take the findings into consideration and extend their vector control efforts, which are presently focused on urban freshwater habitats, to include brackish water larval development habitats