- Author: Chris McDonald
With apologies to Deborah Rabinowitz. (Seven Forms of Rarity, 1981)
There are many different ways of being a pest. Some of the easiest ways are to use large bulldozers next to an office building, or have a computer virus send spam to every person on earth with an email address. How classifying pests relates to weed management is relatively straightforward.
What I specifically mean is how many different types of weeds are there? Not the individual species but the general ways of being a weed. There are surprisingly only a few ways a weed can be a pest. There are infinite details (similar to being infinitely pestered) to add to the general framework that in sum makes every species unique. The broad picture remains the same, even as we add more details.
There are three general parameters to consider: the population size, the geographic range and the diversity of habitats the plant is found.
The first measure determines if the weed has a large or small population size. Yellow star thistle can occur in large populations, Mexican fan palm occurs in small numbers.
Next we determine if the weed has a large geographic range or a small one. Stinkwort is in a majority of counties in California. Canary island knapweed, is in one, maybe two counties (its near a county line).
The last thing to note is the variety of habitats it invades. Does the weed invade a wide variety of habitats, say from valley to mountain, or is it confined to a specific area, like a clay lens? Cheatgrass or ripgut brome can be found in mountains, coastal areas and deserts, rabbitfoot grass, in Southern California, occurs in wet areas or seasonally flooded canyons.
We combine all three categories and can create a simple classification of any weed and its potential effects. Thus, we have 8 different types of weeds. For example, cheatgrass can have a large population, has a widespread range and is locally abundant. It is a common weed. Yellow star thistle in Southern California has large populations, has a widespread range, but is (so far) abundant mainly in disturbed areas. It is different from cheatgrass. If it becomes established in a variety of habitats in Southern California it would be similar to cheatgrass, and useful to acknowledge when developing a management plan. A weed that is locally rare, found in one region and occupies one type of habitat is very different.
This then allows a practitioner to perform a simple prioritization of weeds, without having to compile too much information. There are of course very complex prioritization processes that are also very useful, but few that can be completed on a scrap of paper. If there should be no weeds on a property, and there is the funding to back that goal up, then there is no problem, they all go away. If there is not enough money to treat the entire property, then we have to prioritize. Is it better to treat something that is locally abundant with a large population? Or should we treat something that is locally rare, with few individuals in a restricted habitat and attempt eradication? Only the local practitioner can determine where its best to put their resources. My goal is to help practitioners classify the type of weed they have and use that information to create a slightly logical process (only on a scrap of paper of course!).
At this point we realize that the bulldozer has a small population, has a small geographic range and occupies a restricted habitat (construction sites). The virus has a large population size, a worldwide range and occupies a diverse set of habitats (every email inbox). I’d venture this helps explain why I can end the noise, but not stop my spam.