Good news for green hands! Plant pests like aphids may soon be scared off thanks to scientists who managed to bottle the scent of predatory insects.
Researchers at Pennsylvania State University have identified the specific chemicals that ladybugs give off that aphids can catch and flee.
The discovery may provide an alternative to ordinary pesticides, to which many insects are increasingly resistant, while eliminating the risk of environmental contamination.
Insecticides can also accidentally kill predators that feed on pests like aphids, inadvertently making the problem worse in the long run.
Good news for green hands! Plant pests like aphids may soon be scared off thanks to scientists who managed to bottle the scent of predatory insects. Pictured: a ladybug eats an aphid, a common and very destructive pest
LADYBIRD, LADYBIRD, FLY HOME
Despite their common names, ladybugs (or ladybirds) are actually a family of small beetles.
Ladybugs can be found in almost all of the major crop-growing regions of temperate and tropical countries around the world.
They are generally considered beneficial insects by gardeners and farmers as they feed on various agricultural pests like aphids and mealybugs.
Many ladybugs lay their eggs in the midst of colonies of these parasites, ensuring that their larvae have prey to feast on as soon as they hatch.
However, there are certain species whose presence may present drawbacks.
Members of the ladybird subfamily Epilachninae, for example – like the Mexican bean beetle – are themselves herbivores.
The damage to crops they can cause is usually minor, but can become significant in years when their rows are growing due, for example, to a temporary lack of predation by enemies such as parasitoid wasps.
‘It is not uncommon [for us] to use our senses to avoid risky situations, ”said article author and entomologist Sara Hermann of Pennsylvania State University.
“If a building were on fire, we humans could use our senses of sight or smell to detect the threat,” she added, by way of example.
“There is evidence for such behavioral responses to risk across taxa which suggests that prey organisms can detect predation threats, but the detection mechanisms are not well understood, particularly with insects.”
“Insects rely on scent cues to find food, mates, and places to live, so this is a great opportunity to study how to use those scents to manipulate their behavior,” agreed Jessica Kansman, co. -Article author and fellow Penn State entomologist.
Small, sap-sucking insects, aphids (sometimes also known as “black flies” or “green flies”) are particularly destructive pests that can transport and spread plant diseases, but are often difficult for home gardeners to control. and farmers.
“Aphids are crazy insects,” Dr. Hermann told The Times.
“We always see the females and they reproduce asexually. This is why they are such bad parasites because they do not need males and can continuously have babies.
The tiny threats reproduce quickly, which means that when insecticides are used against them, populations can easily recover if even a small number is missed.
And aphids typically occupy the undersides of leaves or the space between plant petals where sprays may be unable to reach.
In addition to this, many aphid species have developed resistance to common classes of pesticides like carbamates, organophosphates, and pyrethroids.
However, aphids are also the favorite food of ladybugs (also known as ladybugs) – a family of small beetles that gardeners generally welcome as a source of sustainable pest management.
In their study, Dr Hermann and his colleagues demonstrated that aphids and other phytophagous insects, or “herbivores,” will avoid fields and gardens if they catch a whiff of predators like ladybugs in the air.
Additionally, it appears that aphids also slow down their reproductive rates and increase the frequency with which their young will sprout wings when exposed to the scents emitted by ladybugs.
Both responses are designed to help tiny parasites physically move away from threats.
Small, sap-sucking insects, aphids (sometimes also known as “black flies” or “green flies”) are particularly destructive pests that can transport and spread plant diseases, but are often difficult for home gardeners to control. and farmers. In the photo: aphids devour a leaf
Based on these observations, the team then set out to find out whether the scent of the ladybugs alone would be enough to put the wind in their tracks – and encourage them to find plants elsewhere to devour.
To do this, they first used what’s called “gas chromatography-mass spectrometry” to separate and identify the individual chemicals that make up the ladybug scent.
After isolating these compounds, the team exposed them one by one to living aphids to determine which chemicals the pests react to in nature.
The insect’s responses were measured by attaching an electro-antennogram to their antennae, which allowed the researchers to record the strength of the impulses each scent caused to be sent from the insect’s antennae to their brains.
The team then investigated whether the scent of the ladybugs alone would be enough to put the wind in their tracks – and encourage them to find plants elsewhere to devour. To do this, they first used what’s called “gas chromatography-mass spectrometry” to separate and identify the individual chemicals that make up the ladybug scent. In the photo: a female aphid and her young nymph
Dr Hermann and his colleagues found that among the many compounds that make up the scent emitted by ladybugs, aphids exhibited the strongest responses to so-called methoxypyrazines.
(Methoxypyrazines are also present in some wines, such as Cabernet Sauvignon and Sauvignon Blanc.)
After identifying the chemicals needed to scare off aphids, the team then combined them into a special mixture that they placed in essential oil diffusers, so that they could eventually be deployed in a garden or a garden. agricultural field.
When testing this mixture in the lab, the team found that green peach aphids (which feed on crops like broccoli, cabbage, and kale) preferably avoided roads that had been spattered with the odor.
Likewise, the team found that watering the plants with the chemical mixture discouraged aphids from settling there.
After their initial study is complete, the researchers are now looking to see if they can get the same kind of results in the field that they saw in their lab tests.
The team also wants to determine the effective dispersal area of their scent diffusers – and explore whether they could be used to control other pests on different crops by exploiting the scent of other predatory insects.
Finally, the team is also working with a manufacturing company to develop fragrance diffusers for the industrial agriculture and home gardening markets.
The full study results were presented at the American Chemical Society’s (ACS) National Meeting and Exhibition in the fall of 2021, to be held both in Atlanta and virtually August 22-26.
THE USE OF AGRICULTURAL PESTICIDES HARMFUL TO BEE POPULATIONS
The decline in the number and health of honey bees in recent months has sparked global concern due to the critical role of insects as major pollinators.
Bee health has been closely monitored in recent years as the nutritional sources available to honey bees have declined and pesticide contamination has increased.
In animal model studies, researchers found that combined exposure to pesticides and poor nutrition reduced bee health.
Bees use sugar to fuel their flights and work inside the nest, but pesticides lower their blood sugar levels in the hemolymph (“bee blood”) and therefore reduce their energy reserves.
When pesticides are combined with limited food supplies, bees lack the energy to function, causing survival rates to drop.