by Matthew Orwat | Feb 17, 2022
Citrus red mite leaf damage, red mites may overwinter, but are susceptible to control by dormant oil. Image UF / IFAS HS-806
During cold winter weather, one doesn’t often think about spraying fruit trees and ornamental shrubs for spring insects and diseases. It’s just not on the radar, but it turns out that January and February are the best time to apply dormant sprays to combat insect and disease issues. Many ask, “What are dormant sprays”?
Dormant sprays act on insects or disease pathogens differently. Many insects overwinter on trees and shrubs, either as eggs or immobilized in a protective shell (scale insects). Horticultural oils applied during cool dormant conditions work by smothering the eggs of some insect species or encapsulated scale insects. Since they cannot breathe, they die.
On the other hand, dormant sprays containing copper or sulfur actually kill latent fungal spores that are ready to infect the moment weather warms. They also burn tender young plant tissue, so can only be used when the plant is not actively growing. These preventative sprays can delay disease incidence in early spring and allow for reduction or elimination of regular fungicide applications. The old adage “an ounce of prevention is worth a pound of cure” surely applies to these situations.
Phomopsis leaf and stem symptoms. Dormant fungicide sprays may lessen the severity of this disease.
Credit: N. Flor, UF/IFAS
There are several products on the market for dormant applications.
Dormant oil is a type of horticultural oil, made of refined petroleum products, for application on trees or shrubs when the trees are not actively growing. It has been in use for over 100 years. They are effective in the suppression of scale insects and mites. Care must be used to not apply them when daytime temperatures are above 75 degrees or night temperatures below 28 degrees. Other horticultural oils exist that may be applied during the growing season to control soft-bodied insects, but not during extremely hot weather. Many different brands exist, some are certified organic. They can be purchased at most garden centers, but the best selection is usually found at your independent nursery or farm store.
Cottony Cushion Scale, often controlled by Dormant Horticultural Oil. Image Credit, Matthew Orwat, UF / IFAS Extension
Dormant fungicides can be classified into two groups. Those that contain copper and those that contain sulfur. The most common preventative remedy for fungal disease had been lime-sulfur. It is no longer available in small home garden quantities due to shipping container restrictions, it can be purchased online in larger quantities for use in Florida. When applied to dormant plants, lime sulfur actually works by sanitizing the stem, killing all fungal spores. It cannot be used during the growing season since it burns leafy tissue. Caution must be taken when mixing and loading since, being an acidic product, can burn the skin. Wear chemical resistant gloves when applying (bought at your local hardware store for $4.00-$10.00), safety goggles and follow all label directions carefully since it is caustic and labeled DANGER. Also, never apply lime-sulfur within one month of horticultural oil applications. It should be applied in early to mid February, avoiding hard freezes for the 24 hours around application time. Sulfur based fungicide sprays may also be used instead of Lime-Sulfur as a dormant application.
Dormant copper sprays are effective on both bacterial and fungal pathogens and used primarily on fruit crops for the suppression of many fruit diseases including fire blight, bacterial leaf spot, powdery mildew, downey mildew and anthracnose. There are several different brands of copper fungicide preparations on the market, most nurseries and garden supply centers will have some in stock. Always read the label for proper personal protective equipment and dosage rates, to avoid copper buildup in the soil over time.
For more information, contact your local extension agent or consult these extension publications from: Disease Management Strategies, Florida Blueberry Disease Guide and Pest Control Using Horticultural Oils .
This article was originally published on January 2016, and has been modified to reflect current information.
by Matthew Orwat | Nov 22, 2021
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.
Citrus Culture in the Home Landscape
Cold Hardy Citrus for North Florida
Louisiana Home Citrus Production Manual
by Matthew Orwat | Oct 1, 2021
A spotted Japanese Persimmon leaf, Image Credit: Matthew Orwat
In gardening, brown or black spotted leaves are most often an indicator of disease problems or growth issues. This causes us to worry and seek answers as to why this is occurring. This is good since the first step in solving a plant growth or disease issue is diagnosis.
During Fall, the presence of brown or black spots on leaves of shade and fruit trees is usually not cause for alarm, as it might be in the spring or summer. Certain shade trees such as Southern Magnolia, Japanese Magnolia, various maple, persimmon and oak in the Red Oak group show substantial brown and black leaf spotting as Fall arrives. This is due to the fact that these leaves have been attacked by fungal pathogens and insects since Spring and resistance to damage has broken down over time. As Fall progresses, these leaves will senesce (purposeful deterioration due to age, such as at end of season) and fall to the ground. Therefore, this ugly spotting is part of natural seasonal leaf decomposition in deciduous trees.
Although Fall leaf spotting may not be something to worry about, oftentimes we run into plant problems that need quick diagnosis. Fortunately, your local Extension Office and the Plant Disease Diagnostic Clinic at NFREC exists for these situations. If you need help with plant problems, feel free to contact your local Extension Agent or Master Gardener Volunteer group and they will figure it out or send it along to the Diagnostic Clinic (small diagnostic fee if using NFREC clinic services).
If you happen to live in or near Washington County, we are launching our Second Mondays Free Plant Clinic. Staffed by knowledgeable and friendly UF / IFAS Master Gardener volunteers and your County Extension Agent, we will be available every second Monday of the month from 10am to 2pm at the Washington County Ag Center, which houses the UF / IFAS Extension Office. We will be located in the Master Gardener Volunteer Library which is just left of the central auditorium double doors. The launch date of this plant clinic is Monday, October 11th. See you then!
by Matthew Orwat | Sep 30, 2021
By Matthew Orwat and Judy Corbus
Cayenne Peppers growing this summer. Image Credit Matthew Orwat UF / IFAS Extension Washington County
As fall begins we often begin to think about the successes and failures of our vegetable gardens. Two of my successes this past summer have been pepper and basil.
A variety of peppers work great as transplants in mid to late spring. This spring a large variety of peppers were planted including Cayenne, Bell, Cubanelle, Habanero, Poblano, Anaheim, Cajun Belle, Havasau, Serrano, Jalapeno, and Banana. A loose, rich media was used containing coconut coir and composted organic humus to provide an excellent well-drained location which also retained moisture. Finding this delicate balance is difficult but can be achieved by using coconut coir and organic matter based garden soil mixtures. After the peppers were planted, they were side-dressed twice with a standard bagged 8-8-8 fertilizer blend containing micronutrients and once with an organic fertilizer. During the heat of the summer it was important to water the peppers at least every other day. Need for watering decreased as the fall weather approached, but was still necessary.
Bountiful Pepper Harvest. Image Credit Matthew Orwat UF / IFAS Extension Washington County
Sage and Basil Image Credit Matthew Orwat UF / IFAS Extension Washington County
In fall, many gardeners think it might be a good time to remove their peppers plants, but they can be encouraged to produce peppers until frost and maybe a little later with protection. Oftentimes it is more practical to start or transplant new pepper plants the following spring, but it is possible to pot up and overwinter peppers in a sheltered area or greenhouse.
In addition to peppers, basil was especially bountiful this year. To save my basil bounty for the winter I have options to dry, blanch or make pesto. This should be done before the first frost, since basil is very sensitive to freezing temperatures. Other herbs that will usually overwinter well in the garden include thyme, chives and rosemary. They will need little to no protection. Additionally, sage might come back the following year if it is in a protected area. Herbs such as cilantro and parsley will thrive in our North Florida winters and should be planted now.
To preserve the bounty of your harvest for later use, you may can, pickle, or freeze peppers. Follow these USDA-approved guidelines from the National Center for Home Food Preservation:
Credit : National Center for Home Food Preservation
Canning: https://nchfp.uga.edu/how/can_04/peppers.html
Pickling:
Freezing:
by Matthew Orwat | Jul 29, 2021
Strawberries growing on “plastic” to protect them from water splashed fungal spores found in soil. Image Credit: Matthew Orwat UF/IFAS Extension Washington County
As the alternating cycles of sun, heat and rain shape our summer days, I start thinking about cooler times of the year, the fall planting season. One plant to consider planting in the fall are strawberries. Planting strawberries in the fall is really an exercise in preparation for bountiful production of fruit beginning in January and continuing into May and June. The following procedure will lead to a successful strawberry production if followed!
The best location for strawberry production provides well-drained, moist, sandy soil with substantial organic matter. It must not be too wet. pH should be between 5.5 and 6.5, which is considered slightly acidic. A fertilizer scheme of 2 lbs. of a 10-5-10 fertilizer per 100 sqft of raised bed or 10 feet of row should be applied at pre-plant, with ¼ of the fertilizer over the top and the rest in a one-inch-deep band near the location of drip irrigation.
*DO NOT apply fertilizer directly below the plants, as the fertilizer may burn the young transplants.
This is a raised bed of strawberries, which has been filled with rich composted growing media. Image Credit: Matthew Orwat UF/IFAS Extension Washington County
Commonly, a preferred system is the development of a hill system, which is 6-8 inches high and 24 inches wide. Drip irrigation should be installed for best results, thus keeping the leaves free of irrigation water. This hill should be covered with weed barrier, such as grower’s polyurethane plastic to reduce weed growth and soil splashing onto leaves. Additionally, strawberries do well when planted in a raised bed. This system can still utilize weed barriers and drip irrigation but gives the gardener the added benefit of manipulation of the growing media. Growing media made up of compost and coconut coir works especially well for this and may be found at local large garden centers.
Short day cultivars that have been proven to do well for home gardeners in Northwest Florida production are Sweet Charlie and Camarosa and should be purchased certified disease free from a reputable nursery. Both dormant bare root and actively growing plug plants are available for purchase, but I have had best luck with actively growing plug transplants.
While strawberry plants can easily withstand our winter temperatures, fruit can suffer damage from frosts below 32 degrees Fahrenheit. The good news is that small row covers or “low tunnels” can be constructed to prevent fruit loss and encourage early fruiting.
When setting out the transplants:
- Keep plants moist before planting
- Spread roots out in fan-shape
- Set plants in moist soil at the correct depth. Do not cover the plants crown with dirt or leave its roots exposed above the soil.
- Space plants 12 to 18 inches apart.
- Pack the soil firmly around the roots, then sprinkle with water. Overhead sprinkling may keep the tops from drying out until the roots can get established.
Homemade row cover for strawberries made of cow panels and sheets. Commercial row covers can be purchased using hoops and frost cloth. You can also make your own with pipes and bulk rolled frost cloth. Image Credit: Matthew Orwat UF/IFAS Extension Washington County
As stated above, strawberries should be mulched. Black polyethylene plastic mulch at 1 to 1½ mil thick is best (completely cover the top and sides of bed before planting). Be sure the bed is firm, formed correctly, moist, and fertilized adequately. Place soil on the edges of the plastic to hold it in place. Cut slits in the plastic for the transplants.
When using alternatives like straw, bark or other natural organic materials mulch to a depth of 1 to 2 inches, but do not completely cover the plant.
For more information, Please consult these references or contact your local extension agent:
