The End of Orange Juice Abstract
Kuchment, A. The End of Orange Juice. Scientific American, 52-59.
One day in 2005, Susan Halbert was looking at a pomelo tree on a farm outside Miami. She thought the tree didn’t look right, and that there was a lack of leaves on the tree, as well as the fact that the citrus fruit was growing lopsided. She determined that the root of her problem was a disease known as Huanglongbing.
Huanglongbing (HLB), also known as “yellow drag-on disease” is a disease that primarily impacted citrus trees growing in India, China, Indonesia, and South Africa. It works by clogging up the circulatory systems of trees, making it hard for the tree to transfer nutrients, causing the fruits to be disproportionate and bitter. Currently, there is no known cure for HLB.
Once HLB was found in the citrus trees, immediate action was taken. They dug up infected citrus plants, and started trying to breed trees that were resistant to HLB. Scientists starting spraying a lot of pesticides and injecting trees with antibiotics to try to stop the spread of HLB. The disease managed to spread from Florida to California, Georgia, South Carolina, Louisiana, and Texas.
Halbert is one of the few people who are experts of aphids, one of two in the state of Florida. Aphids, such as psyllids, are insects that suck juice from plants. In June of 1998, Halbert noticed the first psyllid in the United States. Halbert started testing psyllids consistently, and in 2005, expanded her search range and increased the amount of different species of trees she tested, which is when they first discovered HLB in the United States.
Tamarixia radiata was the key to fixing this problem. Tamarixia radiata are wasps that prey on the psyllids. These wasps are found in Punjab, Pakistan, which has very hot, dry summers, and humid, cool winters, a very similar climate to that of central California, the place where they would be released (due to the fact that Central California is where most of California’s citrus is grown.)
The California Department of Food and Agriculture got a permit from the USDA, and it was time to start getting wasps from Pakistan. They set up a wasp-rearing operation so that they could guarantee that the wasps would be disease free, and they spent months testing that introducing a new species of wasp would not disrupt the current environment in Central California. Starting in December of 2011, they started releasing the wasps into Central California. They also started deploying pesticides in LA, to no avail, due to the fact that there are so many citrus trees, 1.2 million, inside of LA, and they could only reach around 4% of them.
The reason that the wasps are so efficient in killing psyllids is because they kill them in two ways. The first was is when a wasp kills a psyllid, then lays eggs under its stomach. Then this wasp larva eats the inside of the psyllid. The second was is what Mark, a researcher studying the psyllids and wasps, calls a “bonus kill.” Basically, the wasp gets onto the back of the psyllid, stabs it multiple time with its egg-laying tube, and then drinks its blood. This kills the psyllids at a rather quick and effective rate.
The scientists in Florida are trying a different strategy to help the citrus trees. They are supplying the trees with nutrients, since the disease attacks the roots and prevents nutrient absorption. This strategy has had no success so far, and Erik Mirkov, the plant pathologist at Texas A&M believes the best way to stop HLB is gene modification, however, at the time of this articles release, has not been tested enough and is too expensive.
The End of Orange Juice Abstract