A common garden plant may hold the key to protecting brassica crops from a damaging pest without the need for insecticides, according to new research.
Brassicas, such as broccoli and cauliflower, are not just important horticultural crops but planted by many farmers to use as stock feed.
The Nysius huttoni wheat bug is a major pest of brassica seedlings, and is usually controlled by treating seeds with neonicotinoids and spraying with chlorpyrifos and pyrethroid insecticides.
However in a paper just published in the journal Agricultural and Forest Entomology, researcher Sundar Tiwari, outlined his study into protecting brassica seedlings from the wheat bug Nysius huttoni wheat bug.
It shows that the popular garden plant, alyssum planted around the perimeter of a brassica field protects the seedlings by "trapping" wheat bugs.
Trap cropping is a form of companion planting, using one plant to keep insect pests away from nearby plants and can help to reduce the need for insecticide.
"These practices can generate severe external costs, including to human health, the environment and biodiversity," Dr Tiwari and his co-authors wrote.
For his PhD research, Dr Tiwari tested alyssum, as well as wheat , coriander and clover for their ability to draw the wheat bug away from brassica crops.
While coriander and clover did not perform well, alyssum and, to a lesser extent, alyssum and wheat together did.
"To significantly reduce wheat bugs in brassica fields, first establish alyssum at its flowering stage or alyssum plus wheat at its seed-ripening stage around the perimeter of the brassica field,"
"This can prevent wheat bugs from migrating from outside the field into the brassica crop."
Once the bugs are established in the trap crop, and the brassica seedlings have matured past their vulnerable stage, the trap crops can either be removed (along with the wheat bugs) or treated with suitable insecticide, but making sure to not taint the brassica crop, the study said.
"Such a trap-cropping protocol potentially reduces pesticide use in brassicas, and can also deliver multiple ecosystem services such as biological control of insect pests."
Dr Tiwari has recently completed his PhD through the Bio-Protection Research Centre at Lincoln University.