Save Lanikai from CRB

Protecting Your Trees

Once CRB infests a tree, there is litte recourse: the tree, unless only lightly damaged and the CRB (somehow) removed, must be cut down to prevent further spread of CRB. Thus, it is important to protect trees proactively. Following are some traditional and emerging methods.

• Netting trees. Research conducted in India, plus real-world experience in Hawaii, indicates the effectiveness of netting trees to keep CRB out of the crowns of trees. Netting must be regularly adjusted or renewed due to the growth of the trees. The type of netting and how it is deployed is extremely important. If wrapped too tight, the beetle can eat right through it. The best netting is 1" diagonal nylon fishing net, wrapped relatively loosely, that the beetles get stuck in trying to go through one of the holes in the netting, causing them to die. One source of netting is Memphis Net & Twine. Select netting with these specifications: 1/2" SQ., 1" STR., 110 MD which means each hole is 1/2" square but diagonally it's 1" when stretched. This is the perfect size as the beetles will try to squeeze through the holes and get stuck. Another approach is to wrap netting around small rocks (~2") and form "bow ties" of netting that are then put between the fronds where the CRB enters. This approach, from the University of Guam, is documented in this Youtube Video on the Bow Tie Trap.
• Moth balls. Research from India has shown the moth balls (Naphthalene) are effective at repelling CRB. The researchers worked with relatively young trees (3.5 years old) and simply put the mothballs between the fronds and renewed them every 45 days. They compared the moth balls with insecticide and found the moth balls worked better.
• Ring Spray System. Recently developed by Oahu resident Brown Cannon Jr., this is a device mounted in the crown of each tree with a tube running down the trunk of the tree to the ground where it is hooked to a pump. Trees are periodically sprayed with a mixture containing basil oil, which UH has found is an excellent deterrent to CRB. Do-it-yourself instructions are included at the web site SaveHawaiianPalms.com. There's also great instructions on this website for building CRB traps.
• Regularly spraying the crown of the tree with insecticide. This is effective according to the Hawaii Invasive Species Council. Choice of insecticide is important, because some, like Permethrin, are UV sensitive and break down quickly. Others, like Lambda-cyhalothrin, are much less UV sensitive and can last for several months. Bees are very sensitive to these insecticides, so best practice is to trim the tree, apply insecticide, and then keep trimming and applying insecticide before coconut flowers emerge (every 2-3 months). Recommendation: Use other effective methods first to avoid the negative environmental impacts of these powerful insecticides.
• Injecting insecticide into the trunk of the tree. This is effective using chemicals such as Imidacloprid (Xytect) & Dinotefuran and must be repeated every 6-12 months or so. This is the method being used by the Honolulu Parks Department to save some of the coconut trees in urban Honolulu. It costs about $300/tree. Recommendation: Use other effective methods first to avoid the negative environmental impacts of these powerful insecticides. Coconuts eaten from trees poisoned in this manner have caused serious illness in humans.
• Spraying the crown of the tree with natural oils. Testing by Hawaii Invasive Species Council has shown that Neem oil is NOT very effective. However, Basil oil is effective as a repellant. In tests showing its effectiveness, Basil oil was applied every 3 weeks. Good info on Basil oil can be found at CRB Management Options for Landscape and Nurseries in Hawaii.
• Waxed ropes. Newly emerging, this method utilizes segments of 1" rope that are soaked in a hot wax-oil-essential oil bath and then tied into the crowns of coconut trees around and between the fronds. The wax-oil matrix gradually releases a potent essential oil blend the repels CRB for months.