Early rise can help you tackle garden weeds

GARDENERS may be able to cut the amount of weed killer they use by tackling invaders at specific times of day, such as dawn, a study suggests.

Researchers at the University of Bristol discovered that the circadian rhythms of plants make them more vulnerable to herbicides at different points in their 24-hour cycle.

The team found Arabidopsis plants were more sensitive to glyphosate herbicide around dawn, when a lower concentration was needed to kill them off.

A second species called proso millet (Panicum miliaceum) was also more sensitive to glyphosate at sunrise and dusk, but not in the middle of the day.

Researchers say the findings, published in the journal Nature Communications, could help farmers by reducing crop loss and improving harvests. Gardeners could benefit from knowing which weeds respond better at certain times of day.

Pesticides and herbicides have been implicated in the decline of pollinating insects such as bees.

Dr Antony Dodd, the study’s senior author, said: “This proof of concept re- search suggests that, in future, we might be able to refine the use of some chemicals that are used in agriculture by taking advantage of the biological clock in plants. Approaches of this type, combining biotechnology with precision agriculture, can provide economic and environmental benefits.

“It could be useful for gardeners ... if we knew about the daily rhythms in the responses of certain weeds. It could reduce the amount of herbicide needed or increase its effectiveness.”

Like humans, plants have evolved to take advantage of cycles of night and day, with certain biological processes turning on at different times of day.

Scientists have discovered that many drugs work much better in humans if they are given at specific hours. Aspirin, for example, has double the impact on thinning the blood if taken at night as opposed to the morning. The process is known as “chronotherapy” and researchers wanted to find out if the concept could be applied to plants.

Many gardeners already know that plants drink in more water in the morning because their stomata, or pores, are open to take advantage of early morning dew and water vapour. At the break of day, plants are also not busy producing food through photosynthesis.

The open pores could also be the reasons that chemicals are more effective at dawn and also at dusk.

The air is also likely to be stiller at dawn and dusk, meaning that pesticides or herbicides are less likely to blow away to places where they are not wanted.

Many insects are active early in the morning and around dusk, also making those times effective for insecticide.