05-26-2008, 10:23 AM
The comments so far on Punaweb with respect to biological control of strawberry guava (SG) have been far ranging, but it seems we could use a few more pro-biocontrol essays here.
I think I need to start with a definition of Classical Biological control (the “mini-definition” here) which is the introduction of natural enemies to control a pest. Ideally those natural enemies should come from the native range of the pest so that the natural enemy is evolutionarily adapted to its host and specific to it, and the pest should be an alien species, but in the past, even some natives were targeted! So let’s explain a few more things about Classical Biocontrol.
You have already been told by Kim that the introduction of the mongoose predated any organized science-based biocontrol efforts. Biological control (BC) of arthropod pests is a different topic from BC of weeds, and also has a different historical record with respect to non-target effects. I don’t have space to review 100+ years of that BC work here, but it is true that there have been more non-target effects with arthropod BC than weed BC. This is mostly because many more natural enemies of arthropods have been released in Hawaii. Prior to the 70’s there were several that should not have been released, and native insects and even some intentionally released BC of weed natural enemies have taken hits. Since the 70’s, the record, I believe is unblemished. If any of you can think of an example then let me know. The testing and review procedures in Hawaii since the 70’s are probably now more stringent than all other States and most countries.
But that is classical biological control of arthropods not weeds, which is the topic at hand. The record of non-target attacks by intentionally released natural enemies of weeds in Hawaii is actually much better than that of arthropods. BC of weeds began in Hawaii in 1902 with the release of the lantana lace bug for biological control of lantana. Since then about 85 more natural enemies of weeds have been released for a variety of agricultural and natural area weeds, with some notable successes, as well as many that had little effect. A few of these prior to the 70’s did indeed attack non-target plants. However, these were closely related plants that could have been predicted as alternate hosts. But back then tests were not so thorough and people didn’t seem to mind if some native plants or other “unimportant” plants were chewed on! Such insect s would never be approved for release these days. Oddly enough, that first release, the lantana lace bug, did in fact cross to an unpredictable host! But that has not happened since, and safety testing now tries to include all possible alternate hosts. Certainly there are still some risks, but for Tectococcus ovatus, those risks are quite small.
I don’t see how strawberry guava invasion in native forest can be good for our watersheds, when it’s monospecific stands have no other understory plant species and the forest floor is all mud! Some of that mud probably ends up on our reefs. Personally, I am unwilling to give up Hawaii’s low to mid-elevation wet and mesic native forests to become a monoculture of one plant just because it makes a fruit that hardly gets used! Wild pigs fatten up on the fruit seasonally, increasing their numbers, then may invade crop lands when the SG fruit are gone. They then spread or facilitate spread of more SG and other weeds in our native forests.
Another “benefit” we get from SG is, the production of an alien nitidulid beetle, Lasiodactylus tibials, which increases seasonally breeding in the thousands of fallen fruit, then comes to indoor lights at night in large numbers in Mountain View and Glenwood annoying some residents there. Without biocontrol those cycles will not change. Speaking of fruting cycles, what about fruitflies?
I realize there are a few people that make some SG jam and sell it, but it is definitely not an important commercial “crop”. Sometimes the needs of the many (both us and ohia trees!) outweigh the needs of the few. “Farmerjohn” was correct about SG being a reservoir of fruit flies, that attack many other fruit crops that are economically important, and we need growers to expand acreage, not spend their money spraying pesticide to control all those fruitflies!
If you have not already read the letters to the editor (Hawaii Tribune Herald) sent on May23 by Geg Asner, JB Friday and Pat Hart, please do so. They are some of the most dedicated native forest researchers I know. Also, do visit the Forest Service website that Kim referred to previously that presents the rationale for classical biocontrol of weeds. And be sure the read the Environmental Assessment so you know what the actual risks and benefits are.
If any of you know another effective way besides classical biological control to save what is left of our heritage native Hawaiian forest, please attend the Conservation Conference in July in Honolulu and tell us all about it. Obviously pesticides are unpopular and if you think there are enough tax dollars to send out armies of workers with machetes (without spreading other weeds) over thousands of acres, you’re way more of a Liberal than I am. We have wrecked native ecosystems so bad with our pretty imported plants (and hitchhiking pests) that classical biocontrol really is the only hope. Without it, you can kiss goodbye to the last of what is truly the native Hawaiian landscape.
If I may borrow Farmerjohn’s style of rhetoric, this is Hawaii not Brazil. If you want to “live in harmony” with invasive alien weeds, just don’t oppose actions that will protect ka aina. If you must hug a tree (nothing wrong with that), hug an ohia, not a weed from Brazil!
Malama wao kanaka.