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Altering the DNA of oranges to save them from psyllid-infested Huanglongbing (HLB) disease

Posted on July 30th, 2013 in ecology,Food & Wine,Technology by Robert Miller

Burning Florida orange trees infested with Asian Citrus Psyllid (From New York Times)

Few of us are aware of the destructive forces that have plagued the Florida citrus industry over the last few years. But a few days ago, Amy Harmon, writing in the New York Times published a major article on the problems facing orange growers in Florida, with similar threats beginning to appear in the citrus trees of California and other southern states. This new threat has been created by  the Asian Citrus Psyllid (Diaphorina citri), a new invasive species which lays its eggs in citrus tree leaves and sometimes carries a tree-fatal bacterium: Candidatus Liberibacter asiaticus, that ultimately causes the citrus disease “Huanglongbing” (HLB), characterized by half green oranges hanging on trees that are obviously diseased and doomed. Trees infected must be destroyed and the accompanying  image illustrates this on-going strategy to combat the infestation. Estimates are that Huanglongbing (HLB) disease has already cost the citrus industry in Florida and is beginning to mount such a threat that many growers can visualize the end of Florida orange juice if something isn’t done quickly to stop this raging contagion.

This new threat began in Asia and India and was first discovered in Florida in 1998. By 2001 the psyllid invasion had spread to 31 counties in Florida, primarily due to the movement of infested nursery plants. In 2001, the psyllid infestation spread to the Rio Grande Valley in Texas on nursery stock (orange jessamine); it also was detected in Louisiana. The insect subsequently spread to other states and now is found in Alabama, Georgia, Mississippi, South Carolina, Arizona, California, and Hawaii as well as Mexico. California has been aggressive in trying to identify and destroy trees infested with psyllids, which by themselves inhibit tree growth when the eggs hatch and nymphs feed from tree sap, damaging the tree without killing it. But if the bacterium Candidatus is also injected when the adult feeds and exchanges the bacterium for sap, then the tree will develop HLB disease and eventually die, though it takes several years for this disease to run its full course. HLB is the most serious threat to the citrus industry in history and projections are that if something isn’t done to halt this disease, the Florida citrus industry could be destroyed within a decade.

Closeup of the small psyllid insects on the leaves of an orange tree

Once the devastating nature of this disease became apparent, the citrus industry, aided by the National Academy of Sciences and the Federal government scoured the earth to find trees that had developed a natural immunity to the disease. If a disease has been around for some time, one can usually find trees that have developed a natural resistance, but in the case of HLB, no naturally resistant strain could be found anywhere in the world. Orange trees are not the only target of psyllid attack; they also infest other Citrus trees, including limes, lemons, grapefruit and mandarins as well as kumquats, cherry orange, orange jasmine, Indian curry leaf, Chinese box orange, limeberry and desert-lime. In recent years Florida orange growers have attempted to apply heavy doses of pesticides, but that strategy has also been unsuccessful and growers are increasingly wary of the public reaction to the heavy use of pesticides. Nurseries that supply citrus trees to growers however are warned to use both a systemic and foliar spray before shipping any trees that have signs of infestation. The insecticide carbaryl (Sevin), applied as a foliar spray, has been effective against adult psyllids. The nymphs however are harder to kill with an insecticide spray, because they are tucked inside the small leaves of new growth, which protects them. That is why nurseries use a systemic insecticide to ward off psyllid nymphs. Carbaryl is very toxic to honey bees and to natural enemies of other citrus pests, so growers are warned to only apply it if they are certain of a psyllid infestation.

Psyllid infestation of orange trees illustrating the small nymphs that feed on orange tree sap and the green oranges that have been ruined by the bacteria that causes HLB disease

Florida oranges provide the major source of the nation’s orange juice supply and globally, Florida is second only to Brazil in orange juice production. It is a $ 9 billion industry which provides 76,000 jobs in the state which hosts the Orange Bowl in NCAA football as a fitting recognition to acknowledge the importance of the industry. Last year alone, orange production fell by nine percent, attributed to HLB disease, but there are still 60 million orange trees planted in Florida and all of them are at risk of HLB.  This threat to the Florida orange growers is so alarming that it forced them into something they never imagined they would agree to: search for a genetically modified organism (G.M.O.) to achieve a possible cure against HLB. Given the controversies surrounding genetically modified organisms, it is not in the grower’s personal DNA to consider this strategy unless it is one of last resort, which apparently is the case. Although orange trees are not native to Florida, it is said that they were brought to the state by Ponce de Leon and have thrived there ever since. Already hundreds of thousands of trees have been destroyed and the failure of traditional methods to modify the advance of this scourge, have stimulated the development of genetic modification of the orange tree DNA to find one or more genes that will combat the disease and remove the threat to an agricultural way of life that has existed in Florida for several hundred years.

Whether Florida orange tree farmers are guilty of over investing in monoculture orange trees remains an issue; perhaps more diversity in the orange tree DNA would have provided a resistant hybrid within the farmer’s orchards. In a way, what the farmers are seeking now is more diversity in the orange tree DNA which they might have provided on their own with more diversity and interbreeding among the trees suitable for producing and harvesting oranges.

Several gene candidates for orange DNA modification have been proposed, but the one furthest along was developed by Erik Mirkov of Texas A&M University. The new orange DNA from Mirkov’s laboratory contains a gene from spinach that generates proteins that help ward off bacterial infections. To speed the evaluation of the transgene, shoots from Dr. Mirkov’s plants were grafted onto normal, uninfected trees and so far the result has been successful in eliminating  psyllid infestation. It will take several more years and testing through the Department of Agriculture before this new orange tree DNA can be evaluated and approved for production, but there is hope that this step in bioengineering might lead to a cure for a disease that has threatened a vibrant form of agrarian economy.

Approval for using trees modified by the spinach gene however is only the beginning of an acceptable solution for Florida orange growers. If the spinach gene insertion passes muster with the Department of Agriculture, will it past muster with the public that has expressed increasing concerns about genetically modified organisms? In the past few months Whole Foods yielded to customer demand and announced that it would avoid stocking most G.M.O. food and require labels by 2018. Europeans are generally opposed to genetically modified foods and the public will certainly want to know whether the spinach gene makes orange juice taste like spinach. One cannot help but feel compassion for the orange growers of Florida. Whether they created their own dilemma by not insisting on more genetic diversity in their orange trees, they have adopted a strategy that will hopefully avoid the heavy use of pesticides even though the addition of the spinach gene to orange tree DNA seems more like satisfaction out of desperation rather than a gift from insightful planning.The National Academy of Sciences and the World Health Organization have both argued that G.M.O. crops are generally safe for consumption, but one worries about secondary actions. For example Monsanto’s genetically modified corn and soy seed produces plants that are immune from their herbicide “Roundup.” In that way farmers can administer the herbicide without fear of damaging their primary crop, but some have argued that this strategy has reduced the milkweed population, the plant source in which the Monarch butterfly lays its eggs and young caterpillars must feed. We are currently experiencing a dramatic reduction in the Monarch butterfly population and while the cause of this decline has yet to be established, many suspect increased use of “Roundup” as the most likely explanation. Are we willing to lose species in order to spread the use of monoculture farming techniques created by a single giant of agribusiness? I have not seen a single Monarch butterfly this summer, though my wife claims to have seen two. We use to see dozens during a summer and our own yard has plenty of milkweed plants, many of which I have searched for evidence of Monarch eggs, but I haven’t seen any such evidence as yet and I have searched beyond my own yard into many regions of the Twin Cities looking for them. No one yet seems to understand the cause of Monarch butterfly depletion.




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Erratum: 2005 remains the most costly year for $ billion climate events

Posted on July 27th, 2013 in Climage Change by Robert Miller

Storm Damage over 1$ Billion/event 1980-2012 Data from NOAA

An error in my own addition cries out for correction: because of Katrina, at a cost of $ 125 billion, the year of Katrina (2005) remains the most costly in terms of $ billion dollar climate events, reaching a total for that year of $ 160 billion. That puts 2012 in second place (I had errantly put it in 1st place), largely because of Hurricane Sandy. As an act of compensation for my senior moment, I calculated the total climate event cost for each year, from 1980 to 2012, for those climate events that meet or exceed 1 $ billion, with data taken from the NOAA website. To compensate for inflation, some events that were originally below the 1 $ billion threshold, managed to reach that threshold and they are included in the calculation. However, I did not include inflation-adjusted totals for all weather events, just those that reached the $1 billion threshold. Remember too that NOAA includes droughts, floods, hurricanes, winter storms, freezes, tropical cyclones, wildfires and winter storms in the calculations: I chose “all disasters” which retrieves all of them.

Since 1980, the only year we didn’t have storms reaching the 1 $ billion threshold was 1987; yet the 1980s overall were relatively calm. The two standout years of 2005 and 2012 achieved their lofty status because of major hurricanes, Katrina in 2005 and Sandy in 2012. Although tornadoes can create large swaths of complete destruction, they are more localized in area than a large hurricane, which can carry Biblical floods as part of its devastation. Katrina and Sandy qualified for Biblical classification. While this graph illustrates an upward trend in total climate event damage along the timeline, we cannot eliminate the possibility that the Federal government has become more generous in meeting climate damage costs. Nevertheless, a quick glance at the graph indicates that since 2005 there are years in which climate event damage costs are more likely to be large rather than small. The decade of 2002 to 2012 resulted in $ 517.2 billion in climate disasters, while the decade of 1980-1990 generated $ 98.0 billion in climate damage.

There is clearly motivation for reducing the cost of climate change disasters, but some are easier than others. Protection against flooding in major coastal cities is one example, but it is not clear if cities such as New Orleans are better protected against major hurricane events than they were before Katrina and the reaction to Hurricane Sandy is just beginning to take shape. Cost is always a major factor in these considerations. In contrast, we don’t have good ways of protecting ourselves against drought, wildfires or tornadoes. Nature still rules. Drought and wildfires are often related to one another and assume their most destructive form in the Southwest United States, where water shortages and drought are looming as threats to human expansion in those regions. Phoenix is generally regarded as the most vulnerable city in the world for it’s future viability. If you want to read about the perilous state of Phoenix and its future, read “Bird on Fire: lessons from the world’s least sustainable city” by Andrew Ross.


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A new record year for climate change disasters

Posted on July 24th, 2013 in Climage Change by Robert Miller

Hurricane Katrina

The National Oceanic and Atmospheric Administration (NOAA) keeps track of climate disasters in the U.S. that cost more than $ 1 billion. At their site, you can choose any year or span of years going back to 1980 and select the type of disaster you want to follow such as flood, drought, wildfire, winter storm and then too you can rank them by cost or date. You can already guess the most expensive disaster on record in the United States: hurricane Katrina at $ 125 billion and still counting, but in second place and still growing in cost is hurricane Sandy at $ 65 billion. If you look at the disasters in terms of lives lost, you get a different rank order with Katrina in third place with 1833 lives lost, while the number one killer was an East coast heat wave in 1980 that lasted almost four months and was credited with taking 10,000 lives. There is no tabulation for the rate of human loss, which would probably give Katrina a commanding lead, since the storm is listed as lasting five days.

The total cost for climate disasters in 2012 adds up to $ 114 billion. By a wide margin that total sets a new record, because the old record of ~ $ 60 billion was set in 2011. While climate change deniers keep the issue of the cause of climate change disasters off the front pages, insurance companies keep such information front and center. Insurance costs will continue rise in the face of such severe storms and perhaps force some who live in flood-prone areas to move out. Already claims adjusters are pointing out that North America seems to have more weather-related disasters than any other region of the planet,  as if rampant climate change denial has put a target on our backs. The truth is that we are the home of so many climate change events because we have such a varied geology and mixing of so many different weather patterns,  with a very dry weather in the southwest and hot moist air available from the Gulf, such that periodic mixing of these weather systems, together with the changing patterns of the jet stream and the fact that we have more energy in the atmosphere due to warmer air which holds more moisture and voila! I doubt that we will be giving up our well-deserved title of climate change disasterville anytime soon. We seem to be the new laboratory for climate disaster. Yet, it is almost anti-human that we should be in the midst of such an escalation in the frequency and cleanup costs to our climate disasters that we also seem to be in denial of belonging to Homo sapiens, from whom some expression about the cause of these escalating disasters would have at least been raised around the campfire. In the absence of such an open discussion, we have surely placed our denial aim, right where it can be the most effective: denial towards the use of our frontal lobes that are supposed to evoke human curiosity about cause and effect.

For many years, it was generally regarded that in the United States, we might have a few storms or weather-events that totaled $ 1 billion. So reaching more than $100 billion in a single year is utterly astounding and yet we hear no mention of this dubious achievement from congress and no discussion of the problem within our daily newspapers. To my knowledge no Senator or Congressman/woman has taken to the floor and brought this issue up—that for the first time in our history we have achieved a landmark event of huge and shocking significance, made all the more so because it has completely escaped our national psyche. The only action I have seen lately from Congress came from the Tea Party who want to reduce the Federal budget by the same amount that FEMA has to dish out to cover disasters. Given the climate change disaster bill of 2012 that would be like a second sequester deja vu all over again, at a time when the government is already spending too little to boost our economy and create more jobs. Perhaps there is something in the water.


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