Dr. Murad Ghanim: The [whiteflies] feed on the plants, weaken them so that other pests and diseases can attack, and transmit viruses such as the dreaded tomato yellow leaf curl virus.With gossamer white wings and a body less than 1.2mm, the whitefly does not look menacing. But beware, looks are deceiving. The pest inflicts enormous damage when it attacks the leaves of decorative flowers, cucumbers, tomatoes, watermelon, and cotton.
“The whitefly attacks 500 different types of plants – vegetables, and ornamental flowers,” said Dr. Murad Ghanim, an entomologist at Israel’s Volcani Institute of Agriculture in Bet Dagan. The Volcani is the main center for agricultural research in Israel, and its sprawling center has a reputation for excellent basic and applied research.
“The [whiteflies] feed on the plants, weaken them so that other pests and diseases can attack, and transmit viruses such as the dreaded tomato yellow leaf curl virus,” Ghanim told ISRAEL21c during a visit to his lab at the institute. “Wilting and wimpy plants are tell-tale signs of invasion. In a worse case scenario, when the whitefly sucks food from plants (such as cotton), it excretes sugars which stick to the cotton and ruin the quality; worse, the black spots it creates attract a fungus which inhibits photosynthesis, threatening an entire crop.”
Ghanim, who began collecting insects in high school at the Yamma Agricultural School near Netanya, explained that the battle against plant pests is a serious problem.
In the 1990s, swarms of the B-biotype whitefly swept through North American crops, inflicting more than a billion dollars worth of damages on farmers in the US and Mexico, according to a report in the journal Nature. Beautiful imported red poinsettia plants were dangerous carriers of the insect that managed to sneak across the border. In 2005, the superfly was detected in 22 states.
Experts in pest control say that the whitefly is the gravest threat to crops worldwide. But according to Ghanim, who earned his PhD from the Hebrew University Faculty of Agriculture in Rehovot, and went on for a post-doc in insect genetics at Yale University,
chemical pesticides seem to be a no-win solution.
“In addition to being poisonous to humans, you have to spray every few days,” Ghanim said. And the high doses used to control them do peripheral damage, killing other good bugs and birds.
“The whitefly has two clever innate ways to deal with pesticides,” Ghanim explained. It mutates, or modifies its genes to survive, so that a molecule from the pesticide cannot bind with the protein being targeted; and additionally, it alerts a gene to detoxify a pesticide by overexpression of a detoxification enzyme.
The Israeli team is doing basic research on how pesticides work, how the whitefly develops resistance, and optimum concentrations to use to prevent resistance. Ghanim is keen on developing a genetic understanding and solution to the problem.
The most promising innovative pest control method is Symbiont-Based Protection (SyBaP), which uses genetic engineering. The target is the hidden symbiont, bacteria that lives in specialized organs of the insect providing it with amino acids, and is in turn being protected from the environment by the insect.
“If you kill the bacteria, you kill the bug,” said Ghanim.
The first major symbiont breakthrough was the successful discovery in the control of Chagas disease, a disease caused by a parasitic protozoan, and transmitted to humans by ‘kissing bugs’. By genetically modifying the symbiotic bacteria residing in the bug’s gut, inserting genetic material – an antibody – that inhibits the activity of the parasite so that it is unable to bind with the insect, the insects cannot transmit Chagas disease. Scientists working in plant protection are hoping for similar results.
“Our first collaborative initiative to battle the whitefly and other pests began with cooperation with scientists in France,” said Ghanim. Israel hosted a seminar “On Innovations in Pest Control,” in Safed in January, and SyBaP was a key topic.
“The trip to Israel gave us the opportunity to meet experienced Israeli scientists who have been working for years on whitefly, considered a newly invasive pest in France,” said Frederic Fleury of the University of Lyon, who shares Ghanim’s goal of developing new methods of pest control by manipulating symbiotic bacteria in pests.
The successful meeting was the trigger for a broader meeting in Italy, attended by scientists from France, Holland, Italy, Israel, Greece, England, and the US.
Given the fact of today’s one world agriculture, hitchhiking pests defy control. Exacerbating the problem, the ornamental flower trade is usually opposed to quarantines at borders, because the flowers cannot take delays to market. Vegetables and cotton are put at risk without thorough border investigations.
“Pests are without borders,” said Ghanim, who together with his colleagues, is spearheading an initiative to form a united European front to find innovative ‘friendly’ approaches to pest management not based on costly and dangerous pesticides.
“The idea is to establish sustainable agriculture research networks connecting with 15 European Union research centers,” he said. Two companies – Bio-Bee in Israel and Bio Insecta in Greece – that use ‘natural enemies’ to battle pests are also part of the partnership. Bio-Bee in Kibbutz Sde Eliayhu uses wasps to kill the whitefly. The larvae of the wasp eats the larvae of the white fly.
The European/Israel front is focusing on five pests – the whitefly (Israel and France independently); the olivefly (Greece); thrips – insects that attack strawberries, flowers, trees (Holland); leafhoppers that attack grapes (Italy); aphids that suck the sap from plants (England). The groups will share the results of their research.
Volcani plant protection scientists including Ghanim are mobilizing against the whitefly, and are already making progress.
“Whiteflies taste the sap in a plant. If they do not like it, they move on. We have found that whiteflies avoid plants, like kohlrabi, that has a high glucosinolate (secondary metabolites used by plants to defend themselves against herbivore attacks) content. They will choose a plant with less toxicity for them,” said Ghanim. “If we find important genes that are involved in the metabolism of glucosinolate and we are able to modify these genes, we can inhibit the whitefly.”
According to Ghanim, all damage is related to the bacteria. Eliminate the bacteria, and you eliminate the damage it causes.
“Now our hope is to be able to identify genomes of the bacteria that live symbiotically inside the bug,” he said.
“We have to sequence the genome. Compared to humans with 30,000 genes, bacteria only have a few hundred to few thousand genes,” said the scientist optimistically. One possibility is to use the genes from scorpions, which could be cloned in the bacterial genomes to kill the pest.
Using such innovative technology and shared research, the EU/Israeli ‘swat’ teams are bolstering their united front in the battle for pest control without toxic pesticides.