What is in this article?:
- Can spinach proteins save the U.S. citrus industry?
- Field test findings
- Better understanding HLB
- Suggestions for western citrus growers
- Texas A&M plant pathologist Erik Mirkov is fine-tuning a transgenic process which could help the citrus industry survive its worst scourge, the disease Huanglongbing.
- Mirkov is inserting multiple protein genes – called definsins – from spinach into young citrus plants to create transgenic trees which act as a protective shield against HLB.
- Field tests reveal either complete immunity to HLB or extremely high resistance.
Erik Mirkov, Texas A&M plant pathologist, Weslaco, Texas, creates transgenic citrus plants using spinach genes which make the tree either highly resistant or immune to the citrus disease Huanglongbing.
Better understanding HLB
All eyes of the U.S. citrus industry are focused on research by Mirkov and others at the university, government, and private sector levels in the U.S. and abroad. Citrus researchers have traveled to HLB-infested citrus regions to learn about this devastating disease.
The western U.S. is the last major citrus-producing region in the world to get HLB.
Florida is the nation’s largest citrus-growing area, mostly oranges for processing into juice. California ranks second where about two-thirds of the citrus is grown for the fresh market. Texas and Arizona rank third and fourth, respectively where most fruit is sold fresh.
The California, Arizona, and Texas commercial citrus industries have their eyes focused on the Florida experience to learn from its mistakes with the psyllid and disease. The first psyllid was found in Florida in 1997 and quickly spread like wildfire across the state.
Ron Brlansky, University of Florida plant pathologist, discussed the worsening ACP-HLB situation in Florida. Brlansky has 34 years with the Citrus Research and Education Center in Lake Alfred, working extensively on a wide array of citrus pests and diseases.
The first major mistake in Florida, Brlansky says, was failing to gain good psyllid control early on.
“We did not do a good job of keeping the psyllid contained in Florida, mainly due to the movement of plant materials,” Brlansky told the group.
He says the most important grower effort against the psyllid is insecticide sprays. Some growers spray once a month – 12 times a year – which is expensive and not financially sustainable over the long haul.
A major concern, Brlansky says, is the fear of insecticide resistance to the psyllid.
On young non-bearing citrus trees, growers can apply three soil-applied systemic insecticides including imidacloprid, thiamethoxam, and clothianidin. Aldicarb (Temik) is no longer allowed for use on bearing trees since the registration in citrus was cancelled.
“We’re trying to get growers to alternate insecticides to prevent resistance from occurring,” Brlansky said.
HLB shuts down the phloem in the tree, living tissue which carries photosynthetic products to roots and developing shoots and fruit. As a result, the tree basically starves to death.
Brlansky discussed a new procedure – a nutrient treatment - tried by one Florida citrus grower over the last several years in a 90-percent to 100-percent HLB-infected grove. The grower gives the trees a nutrient cocktail of sorts, including about 20 ingredients.
The nutrient kick start allegedly has helped build new phloem in diseased trees; ahead of the plugging and collapse of the tree’s original phloem tied to HLB. The grower also practices good psyllid control in the grove.
Remarkably, the HLB-infected trees are producing good fruit despite the HLB infection. The fruit is marketable.
A doubtful Brlansky inspected the grove and after close examination confirmed the trees were generating new phloem.