By LISSA FOX
Even the largest wildfires start small. The 1988 Yellowstone fire started with a single lightning strike. The 2002 fires in Colorado and Utah started from burning love letters.The blaze now burning on Maui and the fire on the Kohala Coast of Hawaii island both started with a single spark in the early 1980s.
What fire, you ask? Fireweed is burning across the hills of Upcountry Maui, and pastures are ablaze with little yellow flames. Fireweed, or Senecio madagascarensis, is a small shrubby plant from South Africa with a reputation for spreading like wildfire.
On Maui, the yellow daisylike flowers carpet the pastures around Makawao and Kula, creeping south into Ulupalakua and Kanaio. A survey of alien-plant populations along Maui roadsides done in 2000 and repeated in 2009 shows an explosion of fireweed. Forest and Kim Starr, who conducted the surveys, say fireweed has spread faster than any other alien-plant species they monitored and now covers tens of thousands of Maui acres.
Like many alien plants in Hawaii, this annual (a plant that dies off every year) behaves like a perennial in the favorable Hawaiian climate. Drought-tolerant and lacking the natural enemies, the weed flourishes year after year. One plant produces an average of 30,000 seeds that blow on the wind, or hitchhike on passing animals or vehicles.
Fireweed is a nitrogen-loving plant and can outcompete most other plants for this valuable element. In turn, fireweed uses the nitrogen to produce the poisonous alkaloids reviled by livestock owners. The alkaloids are a chemical toxin that causes illness, liver malfunction and death in cattle and horses. Goats and sheep are less susceptible to the toxins in fireweed, but very young animals still can be affected. Livestock will avoid fireweed when other forage is available, but fireweed will continue to take over pastures. In Australia, where fireweed is a widespread problem, nearly $2 million is lost annually to livestock poisoning and depressed forage yield.
Fireweed has been so successful at invading pastures by outcompeting the notoriously aggressive pasture grass, kikuyu, there’s reason for concern about other impacts. There is no reason this drought-tolerant nutrient hog wouldn’t invade natural areas on the south slopes of Haleakala. As James Leary, specialist with the University of Hawaii’s College of Tropical Agriculture and Human Resources, stated, "Fireweed is not a ranchers’ problem anymore – it’s everyone’s problem."
Is Maui doomed to be carpeted in yellow? For many years ranchers have struggled to control this pest, and county funding has helped with fireweed control. But this noxious weed has continued to spread, and livestock owners and conservationists alike anxiously anticipate tools being developed by the Hawaii Department of Agriculture and UH College of Tropical Ag.
Leary is working on new ways of managing existing fireweed populations. He has developed an herbicide-application system tied into a large deck mower, a system he calls wet-blade technology. As the blade mows through fireweed, it coats the cut section of the plant with herbicide. Initial trials show this technique reduces the amount of herbicide used by 90 percent, and it can be used safely in windy or wet weather.
The downside to this technology is the cost. Leary says this will not be the solution across 70,000 acres of infested pasture. The best use of this technology may be for controlling small infestations.
Meanwhile, the Hawaii Department of Agriculture has been working to release a natural enemy of fireweed – a type of moth, Secusio extensa. Maui scientists will do pre-release monitoring of fireweed populations in anticipation of a release later this year. This information will be used to determine if the natural enemy has a significant impact on fireweed populations.
As extensive as the fireweed infestation is, it has yet to reach areas in Haiku and Hana, and is limited in West Maui. There are scattered populations on Lanai and no known populations on Molokai. Except for Hawaii island and Upcountry Maui, these yellow daisies are limited in the rest of the state. Nevertheless, it is better to keep a blaze in check than to fight a statewide inferno of fireweed.
Since it is unlikely we will be able to fully extinguish this destructive daisy, our best hope will require a two-pronged approach: use of a natural enemy, like the Secusio moth, in well-established, high-density areas; and development of more cost-effective options for smaller populations.
Those interested in a demonstration of Leary’s wet-blade technology, most suitable for pasture management situations, can contract him at (808) 352-8774 or e-mail him at leary@hawaii.edu.
