Posted August 6, 2015 by Rachel Smith
To wrap up the Integrated Pest Management (IPM) blog series, today’s topic is Biological Control, otherwise referred to as Bio Control. Bio control is a method of controlling pests where natural predators are used as tools to manage an invasive species. This method relies on active human management, and most often parasitic or herbivory species. It is usually used where widespread pests are causing massive crop degradation in agriculture or when extremely aggressive invasive species are rapidly reproducing and causing a major threat to delicate and native ecosystems.
Bio control is often considered a very valuable management method because it does not require grueling man-hours, heavy equipment, or use of herbicide. When considering management of a widespread pest, bio control is one of the most effective and cost-efficient methods. However, successful bio control can take years to develop. There is a demanding process that involves strict permitting and regulations to ensure that the biological control agent, or the chosen predator species will only benefit the Hawaiian ecosystem and not cause any adverse harm to the environment.
KISC does not currently use bio control on any of our target species. However, there is a plant species commonly known as Fireweed, in which Big Island Invasive Species Committee (BIISC) targets, and bio control has been chosen as the method of control. Fireweed is a pasture weed that spreads rapidly and when ingested by livestock can cause progressive liver disease, killing the animal with in weeks to a few months. Getting rid of this species has been a daunting task for some neighbor islands, as well as Australia where it costs the cattle industry $2 million annually in damages.
BIISC partners with the Hawaii Department of Agriculture (HDOA) for the bio control of Fireweed. Ultimately HDOA is in charge of the release of biological control, and is responsible for managing the species once released. The Invasive Species Committees (ISC’s) often work very closely with HDOA to manage pests, and frequently specific pests and their eradication, fall under the jurisdiction of HDOA, with the partnerships of the ISC’s. The last known population of Fireweed on Kauai was eradicated in 2005, however it was a small population and bio control was not needed. If Fireweed were to be detected again on Kauai in mass, KISC would strongly consider the use of bio control because of it’s success on Big Island and Maui.
So what IS it?? You must be asking…
Well, it’s a moth. A cute, little, moth. Actually, it’s the larval stage of the moth, commonly known as a caterpillar. The Madagascan Fireweed moth, Secusio extensa, was studied for over 13 months as a contender for bio control, and in February 2013, it was released on a ranch on Hawaii Island, where Fireweed had nearly taken over the entire pastureland. The fuzzy black Madagascan fireweed moth larva has a voracious appetite, and loves the taste of the leaves of fireweed. This process has not eradicated the populations of fireweed on Maui and Big Island, however it has drastically slowed the spread of the weed. It continues to be used as an effective part of IPM on this weed.
Biological control is more commonly being used in Hawaii as research progresses. It continues to be an extremely cost-effective and efficient management method that has the potential to last for years with out much human intervention. However, it remains to be a difficult task to introduce new species into the Hawaiian ecosystem. With so many of Hawaii’s endemic species listed as threatened and endangered, there is a fine line between introducing a helpful species and a harmful species. Luckily we have dedicated and well rounded researchers and scientists working across the state to ensure the biological control agents that are chosen will only benefit Hawaii. Looking back on some of the mistakes that were made here, one being, the failed predator introduction of the Indian Mongoose for rat control, it can be scary to consider bringing in new species. Although, it important to note that the introduction of mongoose was not a scientifically backed bio control strategy, and instead was simply a bad judgment call by a sugarcane landowner who was tired of rats in his cane fields. I think it is safe to blame them for not even considering that rats are nocturnal and mongoose are active during the day! Bio control uses scientific research to determine whether or not a new species should be introduced. As we progress with invasive species and conservation issues, it is safe to put our confidence in modern biological control as an effective Integrated Pest Management practice.
Moths are just one of the really cool insects that are used for biological control in Hawaii! To read more about other control agents used in Hawaii click here.