Weeds may prove to be agricultural angels: study

Weeds - often thought to be a menace for farmers - may actually benefit agricultural crops and help reduce reliance on pesticides and herbicides, scientists have claimed.
"Managing crop pests without fully understanding the impacts of tactics - related to resistance and nontarget plants or insects - costs producers money," said lead author Antonio DiTommaso, professor at Cornell University in the US.
"We are taking a renewed look at a holistic, sustainable integrated pest management (IPM) approach," said DiTommaso.
In corn production, maintaining a few villainous milkweed plants in the middle of a cornfield may help minimise crop loss from the destructive European corn borer.

The milkweed plants can harbor aphids (destructive sap-sucking flies) that produce a nectar food source for beneficial parasitic wasps Trichogramma.
The wasps, in turn, lay eggs inside the eggs of the European corn borer, killing the corn borer eggs - reducing damage to the crop.

"Production management rarely considers the benefits of weeds in agricultural ecosystems. Let's look at the big picture. If we open our eyes - even if it is a weed growing in the cornfield - we show it could be beneficial," said DiTommaso.
"Integrating weed benefits will become increasingly important, as pest management is likely to move from total reliance on herbicides and transgenic crop traits for control, because of increasing resistance of weeds to these products," he said.

Another benefit of having a few milkweed plants in a field of corn is that it serves as a breeding place and food source for monarch butterflies.
As of late, monarch numbers are low, and the US Fish and Wildlife Service is evaluating a petition to have them protected under the Endangered Species Act, researchers said.
With increasing no-till production, producers will inevitably see rebounds in perennial weeds - such as milkweed, the researchers said.
Thus, some growers may be willing to tolerate a low milkweed population in favor of providing livable plant space for monarchs.
"Every organism in an agricultural system plays multiple roles. If management decisions are based solely on the negative aspects, yield and profit can be lost in the short term and broader problems can arise in the longer term," said John Losey, professor of entomology at Conell University.

Integration of the weed costs and advantages will become important.
The study appears in the journal Weed Science.