Are you a homeowner in Florida? Do you have citrus on your property? Consider helping the University of Florida/IFAS Extension by taking a survey!
This survey is part of a research project carried out by the UF/IFAS to gather information on citrus pests in residential settings in Florida. This survey is designated for Florida residentswho have citrus on their property that are not intended for commercial use. The outcomes of this survey will serve to develop appropriate control methods against critical citrus pests for dooryard citrus. We kindly ask that you complete all questions on this survey which will take approximately 20 minutes.
The University of Florida is conducting a survey among Florida homeowners that have citrus on their property. This survey is supported by USDA-NIFA and is about pests that might be found on citrus and how to manage them. The survey should take only 10 min and will help the University of Florida to develop an Extension program adapted to residential areas.
Thank you for your help!
Citrus: Bearing Branches. Image Credit Matthew Orwat, UF/IFAS
Citrus canker has made its way to Escambia County and may be more widespread that we realize. This bacterial disease was first seen in Northwest Florida almost 10 years ago in Gulf Breeze. Given time and the ease of transmission of this disease, we are now seeing affected citrus trees in both the east and west portions of Escambia County.
This disease is specific to citrus with grapefruit, lemon, and lime being the most susceptible to infection. The disease can infect all above ground tissues and often enters through natural openings and wounds of leaves, stems, and fruit. If you find an infection early in an isolated area of the tree, you can prune out and double bag the affected tissue for disposal. Often times, the disease is noticed only after a considerable amount of tissue and fruit are affected making it difficult to keep the disease in check.
Since the bacteria is so easily transmitted through rain and wind, it is difficult to prevent movement during our frequent storm events. People can also spread the disease by movement of unregulated citrus trees, on equipment, and even on clothing.
Citrus canker lesions appear on both the upper and lower surfaces of the leaves. Photo by Beth Bolles, UF IFAS Extension Escambia County
Lower surface with citrus canker. Photo by Beth Bolles, UF IFAS Extension Escambia County
If you suspect a citrus in your landscape has canker, do not bring a sample to your Extension office for identification. Take a photo of plant symptoms of upper and lower leaves, fruits, and stems so that your local Extension educators can assist with identification. The University of Florida publication https://edis.ifas.ufl.edu/publication/PP323 has quality photos and descriptions of the different stages of citrus canker, along with photos of other citrus issues.
Stem lesions on grapefruit. Photo by Beth Bolles, UF IFAS Extension Escambia County.
The bad new for homeowners is that there is not a treatment to cure citrus canker. If the infection is small (a few leaves or a branch), it may be possible to remove and dispose of the material, following proper sanitation guidelines. Homeowners may also suppress a small infection on fruit by using copper-based fungicides, applied at appropriate intervals. These fungicides only protect plant tissue for a short time by acting as a barrier to infection. See this UF publication for timing of copper sprays for fruit.
Once susceptible citrus are heavily infected, trees will have fruit and leaf drop, along with general decline and dieback. At this stage of the disease, homeowners should strongly consider removing the tree. If it can be burned on site in accordance with local burn laws, that keeps the material contained and may reduce disease transmission. Otherwise, all material should be double bagged and sent to a landfill. Do not compost any material onsite or at local composting facilities. Be sure to follow disinfecting techniques outlined in the University of Florida publication https://edis.ifas.ufl.edu/publication/PP323 for tools, hands, and clothing.
Since management of citrus canker is so difficult, prevention is the best method to protect your tree. If you are considering a citrus, choose a more resistant selection outlined in the UF publication, Table 2. Always purchase a citrus from a certified nursery and follow state guidelines which prohibits all propagation of citrus, unless registered to do so.
Asian citrus psyllid, Diaphorina citri. UF/IFAS/Entomology Photo: Michael Rogers.
In late 2016, as many of us were enjoying the harvests from our backyard citrus, a bacterial plant disease that can affect all citrus, citrus greening, was widespread in central and south Florida but had not made it this far north. That year, the vector, the insect that spreads the disease from tree to tree, had been found in Leon County and a few other surrounding Panhandle counties, but the disease had not. By mid-2017, the disease had been confirmed in Franklin County and we hoped that our cooler temperatures could keep the insect and disease at bay. Well, I regret to inform you that the disease has also now been confirmed in Leon County, growing in a residential yard in Tallahassee. Now that it is confirmed in non-coastal (and cooler) north Florida locations, I thought a review of the signs and symptoms – as well as what to do with your tree if you suspect or confirm greening – would be helpful.
The tricky part about diagnosing citrus greening is that it has symptoms that look very similar to soil nutrient deficiency symptoms, especially when first infected. This is a good time to mention that citrus require certain micro-nutrients for optimal growth and a citrus-specific fertilizer product should be used when applying fertilizer. Both the disease and certain nutrient deficiencies cause yellowing of the leaves. With greening, the yellowing is typically blotchy and/or not in any particular pattern. Nutrient deficiencies typically cause unique patterns of yellowing, such as a V-shape or artistic-like symmetrical patterns on each side of the leaf’s midvein. The soil’s acidity, or pH, can also cause some nutrients to not be taken up by the plant even if they are present. Soil testing, available from your local UF/IFAS Extension office, and scheduled fertilizations with a citrus-specific fertilizer can ensure that nutrients are not to blame for the discoloring of leaves. More advanced stages of the disease cause such symptoms as leaf drop, fruit drop, lop-sided fruit, uneven inner fruit cores, and reduced fruit quality.
Citrus greening symptoms of the fruit. Photo by Brooke Moffis.
A more obvious sign of potential problems for your citrus are the presence of the insect vector, the Asian citrus psyllid. This is a tiny little insect that goes from one leaf to the other sucking up plant saps for food and unknowingly spreading the bacterium responsible for citrus greening. You can monitor for them by looking closely at the new flushes of growth. If the psyllids are present, you will likely notice most their small, peach-colored eggs and/or white, waxy secretions. If found, it doesn’t necessarily mean that your tree has greening, but you will want to minimize the chance that they could carry it to your tree. The psyllids can be treated with pesticides, ranging from the less harsh options (horticulture oils, neem oil, kaolin clay) to the more hardcore stuff (malathion, carbaryl, imidacloprid). Of course, always read the label of any pesticide before use and/or consult a qualified landscape professional for assistance.
Blotchy leaf symptom of citrus greening. Photo by Jamie D. Burrow.
If you suspect your tree is infected, a diagnostic test can be performed by UF/IFAS plant pathologists at the North Florida Research and Education Center (NFREC) in Quincy to confirm. The test does cost $50, which may seem a little steep, but it’s an expensive lab analysis to run and may be worth piece of mind.
If citrus greening is confirmed in your tree, the right thing to do, unfortunately, is to remove and burn the plant material as there is no known cure. While the Florida Department of Agriculture and Consumer Services (FDACS) doesn’t have any removal requirements for infected dooryard citrus, tree removal is best to prevent additional spread of the disease to other trees, especially those grown by commercial producers in our area. This may seem drastic but eventually the health of the tree and quality of the fruit will decline to a point where you will want to remove it anyway. Don’t forget that movement of any citrus plant outside of the state is prohibited for the very reason of preventing spread of citrus diseases.
You may be asking, “Is it okay to replace it with another citrus tree?” The answer is yes you can, but you do risk re-infection and will want to be monitoring the new planting.
You may also be thinking, “What is going to happen to Florida citrus?” That’s a question that many researchers at UF/IFAS are trying to answer. There is some hope that intense irrigation and nutrient management, as well as specific pruning practices, can help infected trees continue to be profitable for commercial growers. Recently, UF/IFAS researchers were awarded several grants to try and figure a way out of this problem. Some of the lines of research focus on exploring the resistance found in different citrus varieties, including an Australian lime that appears to be greening resistant. This could potentially be used as a future rootstock. Another approach is to try and treat the plants with a particular peptide that would prevent the disease from binding in the insect’s gut. Isn’t that amazing?
Until a fix is found, we should be monitoring for this disease in our area and taking steps to reduce its presence through controlling the psyllids and removing infected trees. If you suspect a tree has greening, please contact your local county Extension office to review the symptoms and discuss your options.
Satsuma fruit ready to harvest. Photo credit: Larry Williams
A. Florida uses five indexes to determine maturity of citrus, including soluble solids, juice content, acid level, soluble solids/acid ratio and skin color. But, the home gardener can easily decide when most citrus types are ready to be harvested. As the fruit reaches full size and the skin color changes from green to greenish yellow to orange, simply pick some fruit and taste it to see if it is sweet. If not, wait a little longer (a week or two) and taste test another fruit. Meyer lemons are ready when the skin color changes from green to greenish yellow. Satsuma fruit may be ready to eat before the skin becomes completely orange, especially if the early fall is warm. Kumquats are usually at their peak in taste when they become fully orange.
Citrus fruit does not ripen additionally after it is harvested. So, let it mature sufficiently on the tree.
Harvest season for satsuma is October to December. Harvest season for Meyer lemon is November to March. Harvest season for kumquat is November to April. Most grapefruit have a harvest season from November to May. Harvest season for sweet oranges varies. Early season oranges are harvested October to January, mid-season oranges are harvested December to February and late-season cultivars are harvested March to June. Citrus fruit may mature a little earlier in the harvest season on mature trees and more toward the end of the harvest season on young, vigorous trees.
Q. What cold-hardy citrus is best for North Florida?
A. Citrus species are tropical and subtropical in origin. As a result, citrus is not well suited for extreme North Florida. Commercial citrus production has progressively moved further south in Florida due to historic freezes. So, you’d be wise to choose the more cold-hardy citrus types for our area. But, even cold-hardy citrus can be severely injured or killed by a hard freeze in North Florida.
Some of the better choices for cold-hardy citrus in North Florida include kumquat, satsuma, calamondin and Meyer lemon. There has been some success with grapefruit and sweet oranges in our area. Lemon and lime are much less likely to survive in North Florida. There has been some discussion concerning future success with growing citrus a little more north in its current range related to climate change. There already has been some success with growing the more cold-hardy citrus types such as satsuma and kumquat in middle Georgia. We’ll see how this works out.
Citrus: Bearing Branches. Image Credit Matthew Orwat, UF/IFAS
Many dooryard fruit growers have asked me this Fall: When is the correct time to prune citrus? How do I prune Citrus right now? The answer may seem obvious, but when we delve into the question further, we find out that it is not.
Two different pruning strategies exist depending upon the citrus plants age. When training young citrus plants, it is essential to develop three to four main scaffold branches with wide crotch angles. This is done by selecting branches growing different directions that intersect with the trunk or each other at the widest angle possible. Other branches need to be pruned off and these need to be left alone to develop into the main scaffold. Once the branching system has been developed, traditional heading back, as seen in peaches and apples, is unnecessary.
Young Citrus Tree with good vase shape
There are several instances in which pruning mature citrus trees is beneficial. First, branches should be pruned approximately one foot off the ground so developing fruit is not sitting on the ground. This also helps with weed control and fertilization. Next, it is important to remove growth that is positioned extremely upward or inward to promote an open, vase-shaped habit. Finally, it is necessary to remove any dead wood resulting from winter dieback.
Many growers are eager to remove branches that have been bent downward by heavy citrus crops. This is not necessary; they will bear well in subsequent years.
The last pruning item to consider is removal of suckers from below the rootstock. If the tree is grafted, this is necessary so that the rootstock does not overtake the scion cultivar. Trees propagated from seedage or cuttings will not need this type of pruning since root suckers will be true to type.
It has been noticed that when trees are not over pruned, they exhibit greater cold hardiness. Keeping that in mind, any pruning of citrus should be done at the beginning of March or later, not in the fall or early winter. With proper pruning practices, gardeners should expect healthy trees with bountiful harvests. For further information please consult the publications listed below or contact your local Extension office.