Part of what makes Japanese knotweed so difficult to deal with is its resilience- the plant is incredibly difficult to remove or control once it has established itself in an area. 

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In the past few decades, many methods of removal have been used against Japanese knotweed. Few, however, have been effective. The most obvious of these is to simply dig the plant out of the ground. Unfortunately, knotweed's extensive underground systems of roots and rhizomes make this very difficult to do. Entire plants can grow back from very small amounts of plant matter left in the soil, meaning that large areas must be excavated completely in order to ensure that the plant will not re-establish itself soon after its 'removal.' This can lead to massive habitat destruction for native plants and animals as once-vibrant ecosystems are reduced to large, open pits of exposed soil. To make things even more complicated, Japanese knotweed has become notorious for establishing itself in landiflls where it is taken after being removed from other areas. To put it differently, using excavation to get rid of knotweed often just moves the plant to another location, where it can freely grow once again.

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Traditionally, herbicides have been effective deterrents of unwanted plants. This is not true for knotweed. While herbicides can be effective in reducing the plant's growth, it has been found that large quantities must be applied very often to do so. The high amounts of expensive chemicals needed to effectively control the plant make using them economically infeasible for most individuals. Additionally, using such high amounts of herbicides in small areas can damage soil for decades and inhibit the development of native ecosystems, making herbicide use a less-than-ideal method of controlling knotweed growth.

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The failures of traditional measures to corral the plant have forced us to come up with new means of doing so. One of these is covering areas with asphalt or concrete to prevent the plant from sprouting and continuing its growth cycle, eventually killing it. This, of course, comes with quite a few downsides. Large areas need to be covered to successfully get rid of the plant, and, if the covering is not thick enough, the plant will be able to grow through it with little issue. All things considered, this method is best used when trying to eliminate the plant from an area that will be built on, and its applications outside of these scenarios are limited.

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Currently, the best methods of controlling Japanese knotweed involve using its natural predators and diseases against it. Certain species of beetles (such as the Japanese beetle shown to the right) and fungi (such as the Mycosphaerella leaf spot fungus, also shown to the right) are specialized in preying upon knotweed in its native range, and much speculation has occurred as to whether or not they would be effective deterrents of knotweed growth around the world. Small, controlled trials and experiments have provided promising results. Of course, there is also significant doubt about this approach. Some argue that combating invasive species with other invasive species will only serve to make current problems worse, while others are concerned by the fact that insects and fungi introduced to new areas could further damage them. However, it is possible that this is the best method of controlling knotweed growth available at this time, and it is likely that it will be put to the test across the globe fairly soon.

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