When you see the title, if you think of people like as Alexander, who created vast kingdoms by invading kingdoms far and wide, then you are out of luck. I’m talking here about invaders of a different kind. Bio-invaders.
I still remember the time in the late 1970’s when there was no Parthenium (Linn: Parthenium hysterophorus) in India. Apparently introduced to India through wheat imports from the United States, the weed has taken over large tracks of India that it is hard to find a place this does not grow. Parthenium is linked to many respiratory allergies and illnesses that have become more common after it was introduced into India.
When I visited the Nagara Hole national park in Karnataka a few years ago, I was surprised and shocked to see Parthenium becoming the major component of ground cover in the forest. It must have displaced manly local species of plants, and other organisms that depended on them. There is no better illustration of what an alien species can do to a new ecosystem than this.
(Click on the above picture to get a larger view. All the greenery, and the small white florets you see on the ground are Parthenium plants)
This year, when I came back to town after a few weeks of vacation, I was greeted with some icky, sticky, waxy stuff on some of the hibiscus plants in my front yard.
There were some small white moth like flies flying around these sticky spider-web like thread on leaves. I went to the local garden store, and described the symptoms. The person in the listened to my description, and said it might be an infestation of spider mites. I came home, washed the plants and sprayed them with the pesticide prescribed at the garden center, hoping that it would all be gone the next day.
It did not take too long for me to realize I was wrong. The insects, and the sticky threads came back each time I washed and sprayed the pesticide. Then I was sure that the diagnosis was wrong in the first place.
Some more on-line search, and help from Facebook friends pointed me in the right direction. This was an infestation of an insect called Giant Whitefly, which came in from Mexico to California sometime in the early 1990s, and came in to the Bay area much later – around 2005. And apparently it loves hibiscus plants, and is very hard to get rid of this pest.
One of the website said -“If you don’t care for your hibiscus plants in your garden, it is best to get rid of those plants rather than trying to get rid of the pest”. However, I do care about my hibiscus plants and the color they add to my front yard. So I’m doing other things such as using a systemic insecticide (which is slow to act, but hopefully keeps the insect population under control) and trimming branches (anyway, with winter around the corner, there won’t be many more blooms).
I’ve also come to terms with the fact that I can’t totally get rid of this pest from my yard. Oh fate!