Tuesday, April 1, 2008

Hawai'i citrus crop under attack by new bug

An Asian sucking insect, capable of carrying a severe citrus disease, is established in the Islands.
(Photo: life stages of the Asian citrus psyllid. Credit:USDA.)
The Asian citrus psyllid is also a problem on the popular hedge plant known as mock orangte or orange jasmine—which has leaves smaller than most citrus leaves and bears clusters of fragrant white flowers.
The critter is known as Diaphorina citri, and was first found in the Islands on a navel orange branch that had been submitted to the state Department of Agriculture by a Waiakea resident wondering what was infesting his orange tree.
The psyllid sucks the sap out of its host plants, and can cause them to be misshapen and weakened.
But it's also a bigger potential problem, because it is the main carrier of an incurable citrus disease called citrus greening disease, or huanglongbing.
So far, the psyllid is in the Hawaiian Islands, but the disease is not.
The pest has spread over much of the Big Island, along the Hilo side, up to Volcano and other parts of the island, since its discovery in 2006. It is also found extensively on Maui from Pukalani to Lahaina and other areas.
The psyllid showed up in Florida in 1998. The disease showed up in 2005.
Last year, the psyllid was discovered in Guam. Agriculture officials in Guam issued this notice in a community pest alert:
“The citrus psyllid is found on the underside of young leaves and buds. The insect sucks the sap of plants, causing leaf distortion and curling. Affected leaves may be covered with honeydew and sooty mould. Adult psyllids are 3 to 4 mm in length, and have a yellowish-brown body and greyish-brown legs. Wings are clear and mottled with brown edges. Nymphs are smaller and generally yellowish-orange in colour. Psyllids are often confused with aphids, which are of similar size and are common on tender young citrus leaves. The main difference is that aphids move slowly, whereas adult psyllids are active insects that jump when disturbed and may fly a short distance. Adult psyllids also hold an unusual posture on the leaf head down, almost touching the surface, rear end pointing up at an angle. Like aphids, psyllids are often tended by ants, which are attracted to the honeydew they produce.”
The bacterial disease that the psyllid can carry causes discolored leaves and misshapen, green and bitter fruit. It can cause a plant's vascular system to collapse. There is no known treatment for infected trees, and agriculture officials recommend they be destroyed once infected.
There appear to be some predators of the psyllid present in the Islands, including certain ladybird beetles. The U.S. Department of Agriculture is working on a range of strategies for controlling the spread and impact of both the psyllid, and where it is present, the disease.
The main measure thus far seems to be to keep the disease under control by limiting the numbers of the bug— through biological control, chemical control and planting systems that limit its populations.
Information on the psyllid is available at:
© 2008 Jan W. TenBruggencate