- Author: Ben Faber
Commercial Citrus – How will the citrus grower manage the pest and disease in commercial groves?
The deadly huanglongbing (HLB) is spreading in California and threatens commercial citrus production. This website provides a map of where the Asian citrus psyllid (ACP) and HLB disease are located. Since there is currently no cure for the disease, the best management strategy is reducing the psyllid vector with insecticides and removing HLB-infected trees. This website provides a list of the ACP-effective insecticides, information about the best timing of their use & strategies for treatment.
Residential Citrus – What should I do to protect the citrus in my yard?
There is currently no cure for the huanglongbing (HLB) disease that kills citrus trees and is spread by an insect, the Asian citrus psyllid. It is estimated that 60% of Californians have at least one citrus tree in their yard, meaning that HLB may have a devastating effect in residential areas of California. Currently the only way to control the disease is to reduce the psyllid that spreads it and to remove trees that are infected or located near known infections. This website provides information about how near the insect and disease are to your home, and what you can do to help protect your trees.
How can I help educate the public on this very important subject?
This site has important resources for you to use to teach others about Asian citrus psyllid and huanglongbing.
Watch the 4-minute video below to learn what you can do to help control Asian citrus psyllid & HLB
Authors of this website are Dr. Matt Daugherty and Dr. Beth Grafton-Cardwell (retired) Extension Specialists in the Department of Entomology, UC Riverside, and Robert Johnson with UC Agriculture & Natural Resources, Informatics & GIS Statewide Program
/h2>/span>- Author: Ben Faber
It turns out, specially trained dogs can find citrus trees infested with Asian Citrus Psyllid (ACP). Canine Detection Services in Fresno has a grant from USDA to provide dogs that will sniff out the insects. The grant runs until March 2022.
The dogs are trained to sniff out ACP using training aids which contain ACP scent which does not have the bacterium causing the disease. The dogs run a pattern within an orchard or along the perimeter of the orchard. Dogs will sniff all sides of the trees in a given pattern. Depending on the environmental conditions, the dogs can smell the psyllid within 22 feet of an infested tree.
Canine Detection Services is also working with CDFA inspectors in residential neighborhoods, according to Victoria Hornbaker, director of the Citrus Pest and Disease Prevention Division within the CDFA. In this instance, the dog handlers shadow CDFA inspectors as they survey residential citrus trees for the pest and disease.
Hornbaker says the dogs can be a valuable tool for state inspectors to survey neighborhoods more quickly. If a dog alerts on a tree, inspectors can investigate for ACP adults or nymphs, and collect insect samples. This is also done in conjunction with surveys for the HLB disease.
The dog team services are free to commercial growers in California, Arizona, and Texas through next March, according to Finke. To schedule a visit or for answers to specific questions, contact Lisa Finke by email at lisa@canine-detection.com.
- Author: Ben Faber
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- Author: Ben Faber
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By Christopher Vincent, Anirban Guha, Joon Hyuk Suh and Yu Wang
It may surprise you to learn that citrus trees can get too much sunshine in the Sunshine State. Manipulating the light environment around a plant can have several surprising benefits. Shade can suppress the HLB cycle and enhance citrus health and yield. Overall, a mildly shaded citrus plant is likely to have fewer signs of stress, less HLB-spreading psyllids, less severe HLB symptoms and higher yield.
Our groups have joined with several others at the University of Florida to assess how shade impacts the various dynamics of pests, disease, plant health and horticulture. HLB is spread by Asian citrus psyllids landing on trees. Previous researchers observed that low light reduced psyllids landing on trees in a laboratory and that the shaded sides of trees in the field had fewer psyllids.
In our initial study at a natural forest site, we found it was difficult to find psyllids on feral citrus trees in shaded hammocks, and very few trees were infected with Candidatus Liberibacter asiatius (CLas), the bacterium that causes HLB. We think fewer psyllids land on shaded trees because psyllids use light reflecting off distant trees to locate them. If there is less reflection, the trees are less likely to be spotted. We also found very few symptomatic leaves in the forest site. Leaves showed few signs of stress to their photosynthetic machinery, regardless of whether the trees had HLB.
We followed our forest study by examining sweet orange in the field with 4-year-old Hamlin trees that were all infected and showed strong HLB symptoms. We installed shade netting with 30, 50 or 70% shade over the trees in late 2018 and followed their growth and health over two years.
IMPROVEMENTS
There is evidence that the trees' health has improved, though they are HLB infected. When we performed a whole leaf metabolomic analysis in spring and fall, we found many changes in the metabolic profile, including prominent changes in leaf hormonal balance and the metabolism of sugars and nitrogen. In association with the hormonal changes, the shaded trees have less intense flushes, though their canopies are not less dense. This indicates the leaves likely have longer lifespans in the shade, counteracting an important symptom of HLB: leaf drop.
The shaded leaves had less foliar starch, meaning shade mitigates the typical starch accumulation induced by HLB. Along with the reduction in starch, the shaded leaves also accumulated more of the sugars involved in carbohydrate export from the leaf, indicating that phloem may be functioning more effectively, though this point needs more research.
These results, combined with evidence that leaf water status has improved, suggest that CLas-infected trees in the shade are healthier than in full sun. Thus, it comes as no surprise that shade improved yields. Over the two years of the study, the trees under 30% shade produced twice the yields of those in full sun.
Of course, too much of a good thing is still too much. Increasing shade beyond 30% continued to mitigate stress in the leaves but did not improve yields. Based on work done by our predecessors at the Citrus Research and Education Center, increasing shade intensity too much leads to a reduction in the flowering needed to set a good crop. The shade needs to be sufficiently moderate to help avoid the worst of the sun- and heat-induced stress while still spurring the trees to make fruit.
SHADE OPTIONS
Despite these benefits, there are challenges to using shade in horticulture. Although shade netting is frequently used in some international citrus regions, such as South Africa and Australia, installing large shade structures may not be cost effective for many Florida growers.
A notable exception to this is the construction of many citrus under protective screen (CUPS) structures and individual protective covers that are installed on young trees. Although these are implemented as exclusion netting to prevent the arrival of psyllids on the trees, the nets also provide the environmental benefits of shade, including a warm humid environment that does not overload the leaves with too much light.
Particle films can also provide temporary, sprayable shade. These consist of particles that can be put in suspension and sprayed on leaves, leaving them to dry as a film.
Our ongoing experiments with kaolin particle films have demonstrated that these treatments also reduce disease pressure and leaf water deficit while enhancing tree growth and yield. We studied the application of red and white kaolin particle films over the first four years of a planting, where we saw the kaolin treatments more than quadrupled the yield compared with a treatment that used foliar insecticides to control psyllids.
We have also found that these treatments in young trees lead to larger, denser canopies and help avoid water stress when the soil water depletes. These treatments are cheaper than other approaches to shading trees and may be more effective in keeping Asian citrus psyllid populations low. Thus, particle films may be more accessible to many growers.
There is still much to learn about how different approaches to shade affect the health, ecology and horticulture of citrus. However, recent promising results indicate that manipulation of the light environment in the canopy is an approach worth considering. In the next few years, we hope to research and develop more effective and practical methods that can help growers find a balance of light for improving tree health and yields in the era of HLB.
Christopher Vincent and Yu Wang are assistant professors, Joon Hyuk Suh is a research assistant scientist, and Anirban Guha is a postdoctoral research associate — all at the University of Florida Institute of Food and Agricultural Sciences Citrus Research and Education Center in Lake Alfred.
https://citrusindustry.net/2021/04/05/tweaking-the-sunshine-for-better-citrus-health-and-yield/