Flowering Alyssum Can Help To Protect Brassica Crops

A common garden plant may hold the key to protecting brassica crops from the wheat bug, Nysius huttoni, a damaging pest.

In a paper just published in the journal Agricultural and Forest Entomology, Sundar Tiwari, who has just completed his PhD through the Bio-Protection Research Centre, outlines his research into protecting brassica seedlings from the wheat bug.

It shows that alyssum (Lobularia maritima L. Desvaux cv. Benthamii White) 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. It can help to reduce the need for insecticide.

Brassicas, such as broccoli and cauliflower, are not just important horticultural crops; many farmers also plant fields of brassicas as stock feed. The 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.

“These practices can generate severe external costs, including to human health, the environment and biodiversity,” Dr Tiwari and his co-authors wrote. “Trap cropping is one alternative option to protect brassica seedlings from N. huttoni.”

For his PhD research, Dr Tiwari tested alyssum, as well as wheat (Triticum aestivum L. cv. Morph), coriander (Coriandrum sativum L.cv. Santo) and clover (Trifolium repens L. cv. Nomad), 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,” Dr Tiwari says. “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.

“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 concludes.

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