Colony of weevils safely in CABI Pakistan quarantine

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A colony of 200 Listronotus (Listronotus setosipennis) have been safely transported from South Africa to Pakistan. The stem mining weevil is a biological control agent against parthenium. CABI’s Dr Philip Weyl, with the help of Dr Lorraine Strathie (ARC-PPRI) successfully imported the weevils into the new quarantine facility at CABI’s Central and Western Asia (CWA) offices in Pakistan from South Africa.

The weevils arrived safely into their new home in Pakistan with “virtually no mortality” according to Dr Weyl. The insects have been put onto parthenium plants to start CABI’s own colony for host specificity testing of important plants in Pakistan.

CABI’s new facility allows scientists to investigate a range of biological control options such as listronotus. The weevils are being kept in locally-sourced cages made by Shani enterprises.

Listronotus is a natural enemy of parthenium, from the weed’s native range of Central America, and along with the leaf-feeding beetle, Zygogramma bicolorata, has been used as a biological control agent in several countries around the world including Australia, Ethiopia, India, South Africa and Uganda.

Parthenium is a highly destructive weed, crossing continents to invade around 48 countries. In Pakistan the weed is spreading rapidly in both rural and urban landscapes. Parthenium is highly-invasive due to its prolific seed production, flower production within four weeks of germination, tolerance of varying climatic conditions, and the production of allelochemicals which affect the growth of nearby plants.

Listronotus is a nocturnal weevil which lays its eggs primarily in the flowers of parthenium where newly hatched larvae tunnel into the stem and continue to feed, eventually exiting at the base of the stem to pupate in the soil. Several larvae feeding in the stem can kill parthenium rosettes and mature plants. In Australia, the weevils were found to provide additional control of parthenium particularly in areas with low rainfall and extended dry periods, where other biocontrol agents struggled to survive.

With this newly arrived colony, CABI is going to conduct host range testing on several species and varieties of important native and crop plants to ensure the weevils do not pose a risk to indigenous fauna. Once considered safe to use, which is likely take up to two years of testing, the plan is to release listronotus in Pakistan and contribute to the control of parthenium.

Alongside partners from Pakistan’s National Agricultural Research Centre (NARC), the work is being led by CABI’s Dr Kazam Ali, “the aim is to help all those affected by the scourge of parthenium in Pakistan; from farmers’ fields and livestock, to the parks and green spaces used by families.”

With parthenium weed invading fast, it’s vital to find sustainable management approaches such as biocontrol, which does not require the use of chemicals or machinery that can negatively impact the environment.

Further reading

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