Temperatures in December 2022 were very damaging to many citrus in North Florida. It is necessary to give plants plenty of time into spring and summer to see if they will regrow and where that growth will occur. Learn how to care for your citrus that is suffering from cold temperature damage with Beth Bolles, UF IFAS Extension Escambia County.
By Dr. Muhammid Shahid
What is puffiness?
Taste and size of citrus fruits are important attributes that determine profit. Since, consumers prefer firm citrus fruit, packing houses only accept fruits of specific size without softness. Therefore, fruit that grow too large and don’t fill out properly are unmarketable and growers discard all these types of fruits. This condition is called puffiness. As fruit diameter becomes ever larger, fruit pith (the area between flesh and the peel of fruits) becomes thick and causes the fruit to shrink inward and lose its normal spherical shape. So far, this problem has been observed in both backyard and commercial Satsuma groves in North Florida, South Georgia, and Southeast Alabama. Citrus puffiness is a threat for all growers from an economic and overall yield point of view, because puffed fruits are unmarketable resulting reduced profit margins.
A few scientific reports suggest that low fruit loads on citrus trees can cause puffiness, but the actual mechanism of puffiness still need to be explored. Based on observations, the team from our lab (Fruit Physiology lab, NFREC, Quincy) and collaborators lead by Dr. Muhammad Shahid has concluded that there are three possible causes of puffiness in citrus i.e., genetic, environmental, or nutritional. In our next phase of research, we will dig deep into this issue and try to determine what is the actual cause of puffiness. Fruit puffiness is observed more in young (4-6 years) satsuma groves than in mature groves. Puffiness on old trees could be due to fruit setting on late blooms during hot conditions. Overall, fruit puffiness is less of a concern in sweet oranges, limes and lemons as compared to satsumas.
Puffiness study by Fruit Physiology Lab, NFREC, Quincy
In our preliminary study, we divided puffiness into five different grades based on fruit size. Grade one is marketable fruits (firm without puffiness). Fruit diameter and puffiness increase gradually in grades 2, 3, 4, and 5, respectively. We have collected fruits from different groves in north Florida and the common denominator among these fruit was decreased Brix value (a common measure of sweetness) with increased puffiness. Average fruit diameter with maximum puffiness was around 40cm and these puffy fruit weighed around 475g. With increasing puffiness, peel weight was increased while juice contents were reduced – not great!
Most satsuma groves in North Florida have some degree of puffiness. However, amount and grade of puffiness varies by grove. In our observations, citrus groves in South Georgia also have puffy fruit, which clearly indicates that puffiness is not geographically specific and can develop in any citrus growing region. After visiting a number of farms in North Florida, we concluded that puffiness is mostly an issue with the Satsuma cultivar ‘Owari’ regardless of different rootstocks. Having said this, we can’t say with confidence that puffiness couldn’t appear on other varieties of citrus without further study. We are carefully monitoring all our variety evaluation trials at the UF/IFAS North Florida Research and Education Center (NFREC), Quincy, in collaboration with citrus breeding and postharvest experts from Citrus Research and Education Center (CREC) and Indian River Research and Education Center (IRREC). We are working on different aspects of citrus production including nutrition, crop load, and pruning to identify the actual cause of puffiness and how to effectively mitigate it in Satsuma groves in north Florida.
By Danielle Sprague & Dr. Xavier Martini
Citrus is one of the most cherished fruit trees in the Panhandle. Citrus owners are well aware that every year the main damage to their trees come from citrus leafminer (CLM). CLM is a small moth and its larvae feeds between the tissue layers of new leaf growth, causing serpentine mines to form under the leaf cuticle (Fig. 1). The feeding damage results in leaf curling and distortion, and severe infestations of CLM on young trees can retard the growth of trees. Another threat concerning CLM in Florida is that the mines provide an open wound for citrus canker to enter, a bacterial disease that has been found recently in the Florida Panhandle, Georgia, and Alabama.
Most commercial growers deal with CLM in young trees by a soil application of systemic insecticide before the flush season, followed by a foliar insecticide when the systemic drench’s toxicity is declining. Homeowners, however, have limited access to these chemistries. Garden systemic insecticides that include imidacloprid (Bayer’s Tree & Shrub Insect Control™, Merit®, etc.) and dinotefuran (Greenlight Tree and Shrub Insect Control™, Safari®, etc.) are among the few options for CLM control. For the best efficacy, those insecticides should be applied two weeks before the start of the flushing season to allow time for the insecticide to move from the roots into the canopy. To avoid leaching of insecticide away from the root zone, soil applications should be made within a 24-hour period without rain. Citrus trees usually have several flushes per year, depending upon cultivar, climate, and crop load. However, in the Florida Panhandle, most citrus cultivars have two major flushes in May and September.
Importantly, systemic insecticides are only efficient against CLM for small immature trees; therefore, the only products labeled for use against CLM on mature trees are foliar sprays. Horticultural oils or insecticides with spinosad (such as Monterey® Garden Insect Spray) are some options available for homeowners. However, achieving leafminer control with foliar applications on mature trees is challenging due to unsynchronized flushing of trees. Foliar applications should be timed with the appearance of the first visible leaf mines. In any case, be sure to READ THE LABEL and follow all the label directions.
Cultural practices, and non-insecticidal methods.
For isolated trees in a backyard, cultural practices and control through mass trapping are usually sufficient to control CLM and insecticide use is not recommended, especially for mature trees. One of the basic cultural practices is to remove any stems that grow below the bud union or from the rootstock, also called ‘suckers’ (Fig. 2). Those rootstock shoots compete with the scion shoots and are great reservoirs for CLM; removing them will help reducing CLM population. On isolated trees, mass trapping using CLM pheromone provide good results (Fig. 3). The mass trapping method is constituted of a delta trap baited with a lure that emits a large quantity of CLM sex pheromone. CLM males are attracted by the odor and are captured in the delta trap’s sticky liner. Those traps are commonly used by growers to monitor CLM populations, but for homeowners they are sufficient to control CLM on a single tree. This trap and a lure method should protect a single tree for approximately 3 months. Finally, the last option is the use of biological control. Several natural enemies are predators or parasitize CLM. In some case, biological control can reduce CLM populations by 90%. Primary predators of CLM include ants, lacewings, and spiders, as well as a parasitic wasp, Ageniaspis citricola that was introduced into Florida and has become established (Fig. 4).
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 residents who 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.
For more information, please contact Dr. Xavier Martini- Principal Investigator, phone: (850) 875-7160 or e-mail at firstname.lastname@example.org
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!
Alternatively copy and past the following link on your browser: https://ufl.qualtrics.com/jfe/form/SV_ey3sRMQXyF7q8yW
To obtain more information on this survey, please contact:
Dr. Xavier Martini
University of Florida
If you have questions about your rights as a research participant, please contact the UF IRB Office: call 352-392-0433.
IRB Study No.: IRB202200230
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.
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.
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.