Black Mustard Calls White Knight for Help When Attacked

It is known that plants release some sort of chemical signals to find help when they are attacked by pests and attract other insects to tackle the pests.

Earlier studies have also suggested that plants use the scent to warn other plants in order to take precautionary and defensive measures.

It seems the black mustard makes use of this interesting technique, as a new study finds that the plant produces a type of scent to fend off cabbage white butterflies, which lay their eggs on the plants.

A team of researchers from the Laboratory of Entomology of Wageningen University, Netherlands, and the Netherlands Institute of Ecology (NIOO-KNAW) led by researcher Nina Fatouros, performed experiments in a greenhouse setting to study how black mustard reacts to cabbage white butterflies known as the Pieris brassicae when they lay their eggs on the plants.

They found that the plants generate a chemical and adopt structural changes when the butterflies lay their eggs on them. They release a form of chemical signal that is capable of repelling the egg-laying butterflies as well as attracting two species of wasps known as Trichogramma brassicae and Cotesia glomerata, reported Live Science.

The plants try to defend themselves before facing the harmful effects of the pest attack which might sometimes result in the plants' death.

Wasps are a kind of insects that are natural enemies of butterflies. When plants attract them, they attack the eggs laid by the cabbage white butterflies and also the pregnant butterflies, thus preventing the pests on the plants. The wasps, then, parasitize these eggs.

However, experts noticed that the black mustard did not show any changes or release the scent when another less common pest, the cabbage moth (Mamestra brassicae), laid their eggs on them.

Experts are planning to further study the plant's reaction to the pest attack in more natural conditions.

The findings of the study are published in the Sept. 5 issue of the journal PLoS ONE.