- Knowledge about micronutrient deficiency symptoms in citrus trees is extremely important to growers and pest control advisers in determining if a malady found in the field could be the lack of an important element or the dreaded Huanglongbing disease.
- “Some deficiencies have fairly similar symptoms,” says University of California Extension citrus farm advisor Neil O’Connell, Tulare County. “If you are very familiar with the deficiency patterns in these elements then it is much easier to separate this out. You can recognize whether the problem is zinc, iron, manganese, or another element while possibly ruling out HLB.”
- Zinc deficiency symptoms in the leaf most closely resemble symptoms from a HLB-infected citrus tree.
Neil O'Connell, UC Cooperative Extension citrus farm advisor, Tulare County, examines a citrus tree for maladies.
O’Connell says many excellent resources are available to growers, PCAs, and others on HLB. The University of California, Davis ANR Publication 8218, “Citrus Bacterial Canker Disease and Huanglongbing (Citrus Greening),” reviews macronutrient and micronutrient deficiencies compared to HLB-related symptoms.
The publication is available online by clicking on this link - .
The publication also includes photo comparisons; for example photos of a normal citrus leaf side-by-side with an iron-deficient leaf and a HLB-infected leaf. It also includes photos of misshapen and off-colored fruit from a HLB-infected tree.
Publication 8218 is authored by MaryLou Polek of the California Citrus Research Board, Georgios Vidalakis of UC Riverside, and Kris Godfrey of the California Department of Food and Agriculture (CDFA).
Another good UCD-ANR resource is Publication 8205 available online by clicking on this link - http://anrcatalog.ucdavis.edu/pdf/8205.pdf. The publication explains the Asian citrus psyllid (ACP) insect; the bug which carries the bacteria Bacterium liberibacter to citrus trees to cause an HLB infection.
The authors - Beth Grafton-Cardwell of UC Riverside, Kris Godfrey, and others – cover the insect’s life cycle and the damage from the ACP feeding on citrus trees.
In the spring and early summer, growers and PCAs often find atypical leaf patterns during orchard walkthroughs. O’Connell says this is the perfect opportunity to utilize these and other pest and disease resources.
He encourages those involved in citrus at the field level to carry printed or electronic copies of publications in vehicles as hands-on reference materials.
“I hope growers and PCAs will become very familiar with detailed nutritional deficiency patterns so they can more easily distinguish and identify symptoms in the orchard,” O’Connell said. “Patterns can change over time so a good understanding is critical to discern between an element deficiency and HLB.”
O’Connell recommends that citrus packinghouse field staff also be well versed on these issues since they are in the field daily during the citrus harvest.
“The potential for devastation from HLB in the western citrus industry is very real,” the citrus veteran said.
The industry is conducting a major educational campaign to inform residential and commercial citrus tree owners about the pest, the bacterium, and the disease.