A network that helps people worldwide obtain rapid advice and information on crop protection, including the identification and management of plant pests.
PestNet is a network that helps people worldwide obtain rapid advice and information on crop protection, including the identification and management of plant pests. It started in 1999. Anyone with an interest in plant protection is welcome to join. PestNet is free and is moderated, ensuring that messages are confined to plant protection.
June 2011. A message from the University of Fiji about an outbreak of the Kou leaf worm (Ethmianigroapicella) on Nanumea Atoll, Tuvalu. All the Cordia subcordata (known as Kanava in Tuvalu) trees have died. This is an important tree, culturally, and also a major protection against coastal erosion, climate change, and a windbreak. The caterpillars of the moth were reported to have destroyed extensive stands of C. subcordata in Hawaii in 1883, and it has also been reported recently from the Herald Islands in the Coral Sea, northeast Queensland. It was said that the caterpillars are most active at night, and early morning when large numbers can be seen hanging from webs.
The same caterpillar has also been found damaging Kou on Guam, see:
The moth is in the Family Tortricidae, subfamily Olthreutinae. The Tortricid.Net hostplant database: (www.tortricidae.com/foodplant_database.pdf) lists a few species reared from Cordia spp., all except one were from India, but none were reared specifically from C. subcordata. It was suggested that onr of the tortricid specialists be contacted (e.g., J Brown or T Gilligan) via the Tortricid.Net website (www.tortricidae.com/contact.asp). Emergency measures were suggested:
a severe cut back of the trees to allow a slow recovery
de-infest inter-island vessels
consider ways to prevent the moth being attracted to lights of vessels at ports
newspaper articles reporting the outbreak
spraying with Bt (Bacillus thuringiensis), which is non-toxic to humans, domestic animals, and the great majority of other fauna. It is not specific to moths, so it not appropriate to spray large areas; instead, it should be aimed at the affected trees
the idea that the epidemic should run its course, even if it meant the loss of all the Cordia, was not supported. An emergency response programme was required.
What is needed is the following:
ensure that the moth does not spread further
find out from Nanumea, if there are any surviving trees that could be sprayed with Bt
liaise with Hawaii to determine what parasitoids have been used there to protect their now limited numbers of trees
strengthen interisland biosecurity; particularly protect atolls from alien invasions carried by boats and planes originating where such potential invaders exist (there is circumstantial evidence that the moth may have been bought on a cruise ship traveling between FSM, Kiribati and Tuvalu the previous September; this was later thought to be incorrect)
strengthen awareness of the seriousness of invasive species to small island ecosystems and that they threaten common, ecologically and culturally important coastal trees, such as Cordia, Erythrina and Pisonia – trees that are often not included in biodiversity conservation programmes. [The CBD emphasises protecting ecosystem services, and that means, in part, coastal littoral trees must be given much greater priority. They are perhaps the most threatened trees, as they are the first line of defense again climate change and coast extreme events. Although they are not necessarily threatened with extinction, they are clearly under threrat, and that seriously undermines the resilience of local communities, nesting birds, crabs, sea turtles, etc. for which coastal littoral species are their main habitat.]
In time, the moth populations will decline, due to the effects of natural parastoids and predators. By then considerable damage may have been done to the Cordia trees, so it is important to protect them now.
There was also a suggestion that perhaps for the long term there should be diversification of trees on the atolls, for instance, planting of Terminalia or Casurina. Is it that there is a monoculture of Cordia that this problem reoccurs with such intensity? Perhaps a greater diversity of species would limit the ecological devastation that occurs. A note from Kiribati (July 2011): In Kiribati, kou is called kanawa. It is found naturally in the littoral zone, but also around residential areas. People grow the tree mainly for medicinal purposes and some plant it as an ornamental. There are two varieties, with light orange and dark orange flowers. The dark orange kanawa seems to be recently introduced, and infestations of the caterpillar appear to be less on this variety.