Take a stroll along one of Hawaii Island’s beaches in late summer and you’ll likely come across almond-shaped fruits sitting in the sand. Known as false kamani nuts, or tropical almondsthey fall high and shaded Terminalia catappa trees which line the island’s many picturesque ocean views.

But what may not be clear to the casual beachgoer is that a struggle for survival is taking place within the flesh of these unassuming fruits. Tropical almonds are one of many battlegrounds in a war between a global agricultural pest, a parasitic wasp and a beneficial virus.

As an entomologist who studies insect viruses, I want to unravel the complex interactions that insects have evolved with microbes. The findings could help researchers address global food security issues.

A global challenge against pests

At the center of this conflict are invasive fruit flies of the family Tephritidae, many of which have spread across the world and wreak havoc hundreds of commercial fruits and vegetables.

In Hawaii, several species of tephritid fruit flies overgrown, starting in the late 1800s. They caused major economic losses for fruit production across the islands. Scientists and fruit growers have undertaken enormous efforts have been controlling these flies since their initial introduction, but they remain a serious economic problem.

A reliable control method consisted of releasing tiny insects called parasitoid wasps in nature that can track down immature fruit flies and target them for annihilation. The term parasitoid describes an organism that spends its development as a parasite and eventually kills its host.

Parasitoid wasps use an elongated stinger, called an ovipositor, to pierce the fruit where flies develop and pierce the body of the fly to lay an egg. Wasp eggs hatch inside the fly host and gradually devour the entire fly from the inside out.

Human use of parasitoid wasps or other natural enemies to control pest populations is known as biological controlor biocontrol. It was so much success in Hawaii that several species of parasitoid wasps have established wild populations on the islands. They helped continually delete several fruit flies pests to date.

The release of non-native insects for biocontrol purposes could have unintended negative consequences on local ecosystems. That’s why federal agencies like the U.S. Department of Agriculture have strict regulations for new and existing biocontrol programs.

The enemy of my enemy is my friend

So how do wasps achieve the impressive feat of reducing fruit fly populations? Once seated inside a fly host, the wasp must face the the fly’s immune systemwho will try to smother the egg before it hatches.

This inhospitable environment forced the wasps to evolve arsenal of microscopic substancesalso called molecular factors, to combat defenses against flies. These include a cocktail of different molecules introduced by the mother wasp at the time of laying eggs.

It’s the story of an unlikely partnership that many species of parasitoid wasps formed with beneficial viruses.

The purpose of these factors is to manipulate the physiological processes of the fruit flysuch as its development from egg to adult and its immune response to invading parasites. By interacting with molecular components, such as proteins, that make up insect physiological pathways, parasitoid wasp factors can delay insect host development and suppress host immunity to allow offspring of the wasp to feed unharmed on the fly’s tissues.

This is the origin story of an unlikely partnership with which many species of parasitoid wasps formed beneficial viruses. Viral particles multiply in massive quantities in the reproductive organs of female wasps during their development. Wasp mothers then use their ovipositor like a hypodermic needle to inject viral particles into host insects during egg laying.

Viral particles transform into biological weapons which infect the cells of the wasp’s host. This infection disrupts processes such as the fly’s immune response. The developing wasps benefit from the virus’s activity and return the favor by transmitting the virus to future generations of wasps.

Not all heroes wear capes

Diachasmimorpha longicaudata is a small, bright orange wasp with a distinctly long ovipositor. The literal translation of longicaudata is “long-tailed” in Latin. But don’t let his charismatic appearance fool you.

D. longicaudata is fierce in its ability to feast several species of fruit flieslike the Mediterranean fruit fly, Ceratitis capitataand the oriental fruit fly, Bactrocera dorsalis. Due to D. longicaudata ability to attack a wide variety of fruit flies, pest control specialists around the world have released the wasps in agricultural ecosystems, where they reliably establish new populations and provide sustainable pest control.

Like many parasitoids, D. longicaudata was formed an alliance with a virus known as Diachasmimorpha longicaudata entomopoxvirus, or DlEPV.

DlEPV replicates in the venom gland of female wasps, which stores billions of viral particles. The virus particles are so dense there that they often cause the venom gland to appear. iridescent blue.

DlEPV particles are highly deadly when injected into flies in the laboratory. The virus freezes the development of the fly and replicates with abandon until its final disappearance.

On the other hand, the alliance between wasp and virus is so strong that heal D. longicaudata wasps Their resident DlEPV infection causes the death of the wasp’s offspring inside the host flies.

A potential new path forward

My colleagues and I published a study showing that DlEPV can play a vital role in helping D. longicaudata prepare a meal with so many different fruit flies. We found a link between D. longicaudata survival and lethality of DlEPV within different fruit fly host species.

When we infected C. capitata And B. dorsalis flies with DlEPV, the virus replicated and successfully killed large swaths of fly hosts. However, DlEPV was unable to replicate within the melon fly, Zeugodacus cucurbitaea species of fly that D. longicaudata wasps cannot be used as hosts.

These findings shed new light on the effect of viruses on host-parasite rivalries. The presence of these viruses could influence the usefulness of parasitoid wasps in eliminating harmful fruit flies. In the case of D. longicaudatathe virus associated with it could be responsible for decades of reliable help this wasp has contributed to fruit fly biocontrol programs around the world.

This work also revealed a new potential tool in the war against fruit flies. DlEPV is now known as a deadly enemy to many of the world’s most destructive pest species. If researchers can determine precisely how DlEPV exploits host flies at the molecular level, they could one day integrate the same strategies used by this virus into new methods of combating fruit flies.

This article is republished from The conversation under Creative Commons license. Read the original article.