rose bush

Example Sentences

• "If a rose bush is completely free of aphids, it is the equivalent of a deserted island. The only possible infection is allo-infection, and this requires a winged aphid. Once it arrives, this allo-infecting aphid, which is invariably a female, will feed on its host and begin to reproduce. Unlike most other insects, it will reproduce without sex, and with live births rather than the laying of eggs. The sexless reproduction is the equivalent of vegetative propagation in plants, and all the progeny are genetically identical to their mother. They constitute a clone. The loss of the egg stage saves time, because the young are born alive. They are also born without wings, because flying is not necessary for auto-infection. The young are all female, and they grow very rapidly as a result of sucking the rich juices of their host. Soon, they too start their own sexless and eggless reproduction. There is then a population explosion of aphids, all auto-infecting the same host plant. All rose growers know how quickly a rose bush can become crowded with aphids. Eventually, over-crowding stimulates the birth of winged individuals, which then fly away to allo-infect a rose bush somewhere else. Ecologists have a special term for this kind of reproduction. They call it r-strategy. An r-strategist species is one that reproduces very rapidly and cheaply, with large numbers of very small offspring. It is a quantity breeder. It can exploit an ephemeral food supply very effectively by producing a population explosion. This explosion is followed by a population extinction when the food supply disappears, usually with the onset of an adverse season. Only a very few individuals survive the winter, or the tropical dry season, but there are enough of them to produce another population explosion in the following favourable season. Most of the serious pests and diseases of our crops are r-strategists, and it is their population explosions that can be so alarming, so damaging, and so very difficult to control."