VIRTUAL plants crawling with simulated bugs are the latest weapon for
researchers waging war on crop pests.
Studying the shape of these virtual plants could help cut the use of
pesticides while keeping pests at bay, says David Skirvin of Horticulture
Research International in Wellesbourne, Warwickshire. Skirvin and his team are
studying the way pests and their natural predators move through a crop. They
hope to find the most effective predators to act as biological controls.
The researchers are focusing on the shape of the 鈥渃anopy鈥� formed by leaves of
a field full of plants, such as chrysanthemums. 鈥淎 more connected canopy should
lead to better biological control,鈥� explains Skirvin, 鈥渂ecause the predators
should be able to move more freely across the canopy and reach pests more
辩耻颈肠办濒测.鈥�
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Skirvin has developed a computer model that puts together large numbers of
plants in different arrangements to see how this affects the shape of the
canopy. He then uses the model to find out whether a particular crop is
connected enough for farmers to simply release their predators at one spot and
let them spread out themselves, or whether they need to scatter the predators
randomly.
To begin with, Skirvin鈥檚 model will assume that the pests don鈥檛 move through
the crop when the virtual predators attack. However, eventually it will model
the movement of both predator and pest. Doing both will be vital, says Helmut
van Emden, an applied entomologist at Reading University, as prey are often able
to stay one step ahead of predators.
鈥淭he pests tend to appear in crops in fairly random ways forming hot spots,鈥�
says van Emden. But because predators might rely upon smelling insect excrement
or the smell produced by a plant when it鈥檚 under attack, it is easy for the
predators to arrive after the pests have moved on.
Skirvin鈥檚 model is founded on the shapes of individual real plants, which he
measures using a sort of 3D plotter called a sonic digitiser. This consists of
an array of three microphones surrounding the plant鈥檚 stem, plus a probe which
emits a sharp noise. From the sounds picked up by the triangular array of
microphones the researchers can plot the position of the probe. First they plot
the position of the base of the stem, then they move the probe to the first
branch on the stem and so on until they have plotted the branching points of the
entire plant. 鈥淵ou start at the base and work your way up,鈥� explains Skirvin.
The 拢1.2 million project is part of a four-year programme that is
sponsored by Britain鈥檚 Ministry of Agriculture, Fisheries and Food.
