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Busier than ever

作者:蒯哚    发布时间:2019-03-07 07:16:00    

By Joanna Marchant HONEYBEES are being enlisted to tackle fire blight, a disease that can devastate apple and pear orchards. By spreading a harmless bacterium, the bees prevent plants becoming infected. Fire blight affects apples, pears and related species, and is caused by a bacterium called Erwinia amylovora. This infects the flowers in spring and spreads rapidly through the rest of the plant. Traditionally, infection has been prevented using either copper-based compounds, which are toxic to plants themselves, or the antibiotic streptomycin, which is banned for agricultural use in many European countries. “Once the pathogen is in the tissue there is nothing you can do,” says Joel Vanneste of the Ruakura Research Centre in New Zealand. “We wanted to prevent the infection by breaking the cycle early on in the spring.” More recently, researchers have been looking for biological controls. One close relative of the fire blight bacterium, Erwinia herbicola, is harmless to plants, but can check the growth of E. amylovora. By competing for space and nutrients on blossoms, and by producing a protein that inhibits the growth of its harmful cousin, it can prevent the disease spreading. The tricky part, however, is establishing E. herbicola populations on flowers. Rather than spraying the bacterium all over trees, Vanneste and his colleagues decided to use honeybees to carry E. herbicola directly to apple and pear blossoms in orchards. He asked growers to put powder containing the bacteria in a small trough just inside hives, where bees would walk through it as they were leaving. After 7 days, more than 95 per cent of the flowers harboured the bacteria, Vanneste announced at the International Symposium on Biological Control Agents in Crop and Animal Protection in Swansea last week. “The key is that honeybees are being used to distribute living organisms,” says Vanneste. “They bring a few bacteria and then the bacteria multiply.” So even if no more powder arrives, the bees continue to spread the bacteria. “Targeting the blossoms directly is more elegant than spraying bacteria around,” says Eve Billing, who previously worked on fire blight at the East Malling Research Station in Kent—now called Horticulture Research International (HRI). She hopes the method will help to eliminate antibiotic use in orchards. Fire blight is most serious in areas where spring temperatures are between 21 °C and 30 °C, such as the US, New Zealand and southern Europe. “In some places, fire blight absolutely devastates trees, ripping through orchards,

 

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