As biological controls become more viable as complements or replacements for pesticides and other chemicals, more growers are finding ways to keep these predatory insects happy.
According to a new study by researchers at the University of Copenhagen, predatory insects live longer when they have access to nectar and pollen. Flowers benefit both the insects and the farmers.
Until recently, it was believed predatory insects needed prey to survive. But in a review conducted at the University of Copenhagen’s Department of Plant and Environmental Sciences, researchers collected, compared and analyzed data from studies and concluded that most predators benefit greatly from flowers. They can even survive for extended periods of time on nectar and pollen alone. This means farmers can promote a consistent production of biocontrols by incorporating flowering strips and flowering margins in their fields.
“By planting flowering margins and strips alongside fields, one can ensure an ever-abundant supply of predatory insects such as hoverflies, lacewings, minute pirate bugs, phytoseiid mites and two-spot ladybugs,” said associate professor Lene Sigsgaard of the Department of Plant and Environmental Sciences. “By planting a wide variety of flowers that bloom both early and late in the season, one can ensure for an optimal effect that ensures the survival of predators throughout the growing season. On top of the that, the presence of more flowers improves pollination and biodiversity, as they attract more insects and pollinators into fields.”
In order for the biocontrol bugs to access flower nectar, easily accessible open flowers need to be planted, as predatory insects don’t possess the long feeding tubes that bees have. Examples of open and beneficial flowers are wild carrot, ox-eye daisy, dill and dandelion.
The researchers found that across all predatory insects, females survive 2.2 times longer with access to flowers, and males 1.7 times longer, compared to insects that only have access to water but no flowers. But not all predatory insects and flowers are the same. Some predators manage to lay eggs with access to flowers alone. Of the 17 predatory insect species tested with more than one species of flowers, nine (including lacewings, two-spot ladybugs and pirate bugs) lived significantly longer with flowers.
Differences among flowers were noted as well. Buckwheat, which has open flowers and is a cultivated crop, helped predator insects live an average of 8.6 times longer than on water alone. Mallow, yarrow and ox-eye daisy are also highly valuable flowers.
“It’s quite an elixir of life. Wisely planted flowers can contribute to robust crop production because predatory insects will live longer and better,” said Sigsgaard. “It pays to design tomorrow’s agriculture so as to accommodate wild flowering plants alongside fields. For the greatest impact, this needs to be done on an informed basis, which is why we are looking at how to design mixed flowering strips and flowering margins that benefit both predatory insects and pollinators.”
The researchers recommend planting native perennial flowers to create permanent habitats for predatory insects. It’s also important to have a wide variety of species that bloom at different times and that benefit different insects.
The research team is continuing to look at which flowers and flower combinations are particularly beneficial for predatory insects and their contribution to biological pest control and pollination.