Since 2006, KKL‑JNF foresters have been combating a fatal aphid that has been wreaking havoc on Israel's pine trees. The woolly pine aphid kills from 10 to 25 percent of the trees it attacks, and the tree most sensitive and vulnerable to this aphid is the Umbrella pine, also known as Pinus pinea. This aphid was identified first in Northern Israel, in Baram Forest in the Upper Galilee, and in several other forests, but it spread and reached forests in the Jerusalem region.
The pest control solution for the woolly pine aphid was found in a fly which preys on this aphid, a fly that was used as a biological pesticide in Hawaii about thirty years ago to solve a similar problem. Research done by KKL‑JNF foresters found that the US Forest Service had imported the fly from Pakistan and acclimatized it in Hawaii. The usefulness of the fly as a pesticide to control the aphid proved to be very effective, and, consequently, it is hard to find this aphid in Hawaii at present (or the predatory fly).
Pursuant to information about the successful pest control of the woolly pine aphid in Hawaii, David Brand, KKL-JNF Chief Forester, and Prof. Zvi Mandel of the Volcani Institute, went to the islands of Hawaii. Assisted by the US Forestry Service and the US Department of Agriculture (USDA), they succeeded in locating the predatory fly and gathered a number of flies in containers. The flies were brought to Israel, and, after thorough testing done by the Plant Protection Service of the Israel Ministry of Agriculture, they will be set free for their first “job” in Baram Forest in the Upper Galilee.
What is the Woolly Pine Aphid?The woolly pine aphid (Pineus Pini) is an aphid from the Adelgidae family, a family of harmful insects that live in conifers of the Pinea family. When the insect reaches the tree, it settles under the bark and is therefore hard to discover. It then spreads to the branches, and the females lay their eggs in whitish woolly wax covered sacs. By then, one can observe from afar that “something is wrong” with the tree. A mass of white webs on the trunk, on the branches and on the growing edges, will attest to the woolly pine aphid. When they are hatched, the larvae will proceed to the young foliage and suck the content of the cells. On a diseased tree one sees phenomena such as yellowing leaves, desiccated branches, and distortions in the new growth. The aphids also cause the development of black soot, as they excrete a sticky sweet liquid called “honeydew” on which a parasite mold develops and creates a black coating of spores. Ten to twenty-five percent of the trees afflicted by the woolly pine aphid wither and die.
The origin of the woolly pine aphid is in Europe and Western Asia. In our region it was already observed in 1964 in the Jericho area. In early 2006, it appeared in a pine grove in Jerusalem. In order to prevent diffusion of the aphid, the Plant Protection Department of the Israel Ministry of Agriculture made sure to fell and burn the infected trees. Nevertheless, the aphids reappeared in November 2006, this time in the Baram Forest in the Upper Galilee, and in 2007, massive withering of pine trees was observed in the Upper Galilee.
“As of today,” said Prof. Zvi Mandel of the Agricultural Research Authority (ARA), “one can see the woolly pine aphid all over Northern and Central Israel. The aphid is flourishing especially in the cool and damp areas—in the hills, in the Galilee, in the Golan and in Samaria. The aphid is dispersed mainly by the wind, which blows the larvae from one tree to another. Apparently, the aphid reached Israel from Lebanon.” The aphid’s diffusion and proliferation pose a grave threat to the pine forests of Israel.
A Biological PesticideAphids, like other harmful insects, have been attacking natural vegetation and agricultural crops from time immemorial. Already in the early 19th century, farmers were systematically using chemical poisons as pesticides. Over the years, new pesticides were developed such as the famous DDT and organic phosphates, which were highly effective in controlling pests but were also very dangerous for human health and for the environment. Only in the middle of the 20th century did the world begin to understand the high ecological and health price of chemical pesticides, many of which are toxic for people, animals and plants. Their decomposed elements remain in the earth, reach the groundwater, create environmental pollution and are an ecological hazard. Moreover, by using chemicals for pest control, new species of pests develop, which are impervious to the sprays.
An alternative to the chemical pesticides of last century is the use of biological pesticides—having the pests decimated by their natural enemies. All the creatures in nature are part of a food system in which each creature serves as a source of energy for another creature. The principle underlying biological pesticide is to allow the natural enemy to decrease the population of the pest and to stabilize it.
But what was the natural enemy of the woolly pine aphid? As we said, the woolly pine aphid is not an indigenous aphid, and it arrived in Israel without its natural enemy—a predatory fly originating in Pakistan, so in Israel it became a pest without any biological controls.
A Delegation Tracks the FlyYears ago, as it turns out, the pine forests in Hawaii also suffered from the woolly pine aphid. In the 1980s, the US Forest Service located the natural enemy of the woolly pine aphid, a predatory fly originating in Pakistan (Neolucopis tapiae), and acclimatized it in Hawaii. The fly, which subsists solely on woolly pine aphids, devoured the aphids on the islands so effectively that it is hard to find any of the aphids there any longer or any of the predatory flies.
In order to eliminate the woolly pine aphid in Israel in a similar way, a joint project was undertaken by KKL‑JNF and the ARA, for which David Brand, Director of the KKL‑JNF Afforestation Department, and Prof. Zvi Mandel of the ARA, traveled to the forests of Hawaii in order to locate, gather and import this predatory fly to Israel.
With the assistance of Dr. Tom Coolney from the US Forest Service, the delegation visited three islands—Maui, Oahu and Hilo. Local entomologists and ecologists joined the expedition, and the delegation succeeded in finding colonies of the woolly pine aphid on pine trees populated by larvae of the predatory fly.
The plant material was gathered, sorted and packed in the labs of the Hawaii Department of Agriculture in Honolulu and sent to Israel. When the plant material and the insects on it arrived in Israel, they were quarantined in the Plant Protection and Control Service station. Isolation is a very important stage of the process. “During the quarantine,” explained Prof. Mandel, “the scientists examine how the flies develop on local pine saplings, and the specificity of the fly to the aphid is also checked. Freeing the fly is approved only after it is proven without a doubt that it will not harm other local insects or interfere with the ecological balance in Israel’s forests, and only then is it permitted to disperse it in the areas afflicted by the aphid.”
In mid 2011, the isolated testing of the predatory fly was completed successfully, and its dispersion in afflicted areas began. There was some concern about the fly's ability to survive the winter, but today, a half a year later, it can be definitively stated that the predatory fly has successfully acclimated in Israel. Final conclusions will be reached only after seeing if the fall and spring growth of the pines is not damaged by the aphids. Based on the example of other countries in the world, it is hoped that the predatory fly will be able to decimate the woolly pine aphid, limit its diffusion and save the pine forests of Israel.
* Scientific information: David Brand, KKL-JNF Afforestation Division and Prof. Zvi Mandel, Agricultural Research Authority (Volcani Institute)