Predatory Mexican Fly Drafted to Save Prickly Pear Cacti

Professor Zvika Mendel, an entomologist from the Volcani Agricultural Research Center, is leading the search for natural enemies of the cochineal scale insect, with the help of KKL-JNF and its Friends in Mexico.

“This fly will help to bolster our biological control campaign against the pest,” explained Prof. Zvika Mendel. “As it develops very quickly, producing a new generation within about six weeks, we hope that we shall soon be seeing it everywhere in nature.”

Prickly pear cacti afflicted by the cochineal scale insect become covered in what appears to be a white powder, then dry up and die. This phenomenon has been increasingly observed in northern Israel in recent years, and there are fears that it will spread throughout the country and destroy its prickly pears, which, although they arrived originally from Mexico, are regarded as an ultimate symbol of Israeliness.

The cochineal scale, the rapacious aphid that is attacking the cacti, is also Mexican in origin. Will the predatory Mexican fly prove capable of saving the situation? As it feeds exclusively on the troublesome aphids, there would certainly seem to be reason for optimism.

Professor Mendel explains that, as competition between the fly and the beetle is not too fierce, he believes that the two insects will be able to coexist and work together against the aphid. “The fly lays its eggs inside the cochineal scale colonies, and the larvae that hatch feed on the aphid during all the different stages of its development,” he said.

About three years ago an unsuccessful attempt was made in Israel to control the cochineal scale insect biologically with the help of an Australian beetle. The next stage was the use of a Mexican beetle belonging to the genus Hyperaspis, a natural enemy of the cochineal that was then released at different locations throughout northern Israel.

And, indeed, the Mexican beetle appears to be doing a good job. Dr. Alex Protasov, a researcher in the Volcani Agricultural Research Center’s entomology department, told us:
“We’ve seen a significant improvement in the prickly-pear cacti that have been treated with the beetles. In Moshav Amirim, for example, we recently revisited one of the affected plants and found it to be completely free of the pest.”

Only the remnants of the beetles’ pupae on this cactus at Amirim bear witness to the fierce battle waged there in recent months, with a most satisfactory outcome. The hope now is that the beetles will move on to other affected cacti and continue the biological warfare on their own.

In view of these positive results, the experiment has been extended to include another natural enemy imported from Mexico – a small fly from the Chamaemyiidae family called Leucopis bellula. On its arrival in Israel nine months ago it was placed in quarantine to ensure that it would not prove harmful to local fauna, and only after it had received full official authorization was it allowed to become operational.

An initial dose of almost two hundred flies has been released into Klil and Rakefet, two communities in northern Israel, and thousands more are due to be set free soon at different locations throughout the north.

These activities have been accompanied by Aviv Eisenband, the KKL-JNF Afforestation Division’s director of forestry and professional development, who told us: “KKL-JNF has decided to get involved in the campaign to save the prickly pear, and this entails cooperation between Israeli and Mexican researchers and the KKL-JNF office in Mexico, which helps all those involved to liaise successfully with one another.”

Klil was selected as the initial site for the fly-release trial mainly because it is an ecologically aware community in which there is no use of pesticides that could harm the flies. Klil was founded in the late 1970s and today it is home to some six hundred people. It has no electricity infrastructure, and all its electrical needs are met by solar power. The residents’ modest homes, which are scattered among attractive hills, are accessed by dirt roads.

Hayim Shenhar settled in Klil in the early 1990s, when he was still director general of Israel’s ministry for environmental protection. “We hope that we can use natural means to beat this disease affecting the prickly pear,” he said. “Flies are normally a nuisance, but we welcome the arrival of this particular fly and hope to see our prickly pear cactus and others in northern Israel bloom once more. These cacti are an attractive part of our landscape and they bear wonderful fruit. Israelis are called after them [the word “sabra” comes from the Hebrew tzabar, which means “prickly pear”], and we need them to survive.”

His son Yotam Shenhar, who is now thirty-one years old, has lived on Klil since he was six. “Nature and the outdoors are a central part of my life,” he said. “I remember how we brought some prickly-pear pads here a great many years ago, and I planted them, took care of them and enjoyed watching them grow. We ate the fruit of that prickly pear all those years, and I am very sad to see what has happened to it. We have tried all kinds of treatments, but nothing has helped. Perhaps the Mexican fly will bring us fresh hope. In any case, I believe that this is the right direction – we are right to use biological control, not poisonous pesticides.”

Dr. Protasov produced a small jar of tiny flies. Who could believe that so much hope has been invested in such a minute creature? He laid the jar on the cactus pads, tapped it lightly to encourage the flies to emerge, and they flew out into the open air to investigate their new home. Much nicer here than locked up in the laboratory, that’s for sure – and there’s plenty of tasty food around!

The next stop was Rakefet, a community in the Misgav area. “We’ve been living in Rakefet for twenty-five years now, and this prickly pear was here for decades before we arrived,” local resident Eldad Garfunkel told us when we visited his garden. The large cactus he indicated was covered in the deadly white powder that reveals the presence of the cochineal scale insect.

“I’d heard about this pest that attacks prickly pear in northern Israel, and I was very sorry to see that we’d been affected by it, too,” Garfunkel continued. “We don’t use insecticides at all, and we very much hope that these flies will get the job done.”

In the months to come the researchers will continue to follow the development of the cochineal scale insect’s natural enemies and the condition of prickly pear cacti in the north. Professor Mendel believes there are plenty of reasons for optimism: “With the help of the Mexican flies and beetles we hope to curb the cochineal population quickly and drastically and prevent it from causing further damage to the cacti,” he said.