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A shipment of predator wasps arrived in Israel two months ago to take on the gall wasp pests that have been ravaging Israel's eucalyptus trees. The predator wasps have already successfully routed one pest species, Ophelimus maskellis.
"We had real concerns about the threat of extinction for Israel's eucalyptus groves," said David Brand, manager of the Jewish National Fund's Department of Forestry and Development. "Fifty percent of the problem has been taken care of now," said Brand, referring to the success with fighting Ophelimus maskellis.
JNF researchers plan to have the predators ready for the other pest, Leptocybe invasa, within a year. The recent shipment of predator wasps from Australia is part of this effort, and is currently undergoing testing in Israel.
The two species of gall wasps have been attacking Israel's eucalyptus trees, primarily the red-gum eucalyptus trees, for five years. Both pests are thought to have come to Israel from Australia, and have since spread to the Middle East, China, and Africa.
Both the gall wasps and their predators are all quite small, with lengths of less than one millimeter.
The two gall wasp species leave their eggs in the leaves of eucalyptus trees. The leaves then try to protect themselves by producing a gall, or cancer-like scar tissue, to cover over the eggs. The galls, however, provide nutrition for the larvae as they eat their way through the galls. The pests dehydrate and can kill eucalyptus trees.
Ophelimus maskelli causes acne-like scar galls that spread by the hundreds over eucalyptus leaves, while Leptocybe invasa causes large tumor galls over the main veins of the leaves.
Eucalyptus trees are native to Australia, and exotic to Israel. Therefore the two types of gall wasps lack the predators in Israel they would otherwise have. In Australia, predators kept the gall wasp levels in check, but the gall wasps spread like fire in Israel.
JNF researchers, including Dr. Zvi Mendel of the Volcani Agricultural Research Institute in Beit Dagan and Brand, went to Australia twice in the past four years to find enemies for the two pests.
"It was a lot of work," said Brand, "like finding a needle in a haystack." The group had to find similar galls in Australia to those found in Israel. They isolated those galls to see what would emerge, and identified those wasps as the same as those in Israel. They then had to find the wasps' natural enemies.
After discovering the enemy for Ophelimus maskelli, they unleashed it in Israel. Since this effort's success, countries like Greece and Portugal have sought Brand's and Mendel's help.
Researchers for the study included Dr. Zion Madar and Mrs. Sapir from the Jewish National Fund, and Dr. Alex Protasov and the late Mrs. Fabienne Assael from the Volcani Institute. The JNF contact person in Australia, Joe Krycer, also helped in the research.
Eucalyptus trees have long served as a symbol of Israel's pioneering history. All eucalyptus trees found today in Israel were planted by foresters. They were first imported at the end of the 19th century to dry swamps covering large parts of the coastal plains and other areas.
Thousands of eucalyptuses were planted in the 1950s along intercity highways to make green the brown, desolate roadways and to provide employment for the country's newcomers. Due to the toughness of its wood and thick trunk, eucalyptus became a major source of lumber.