by Danielle S. Williams | May 7, 2020
‘Early Pride’ Tangerine. Photo courtesy of Danielle Sprague.
Citrus is not only a vital part of our economy in Florida but it’s also a major component in our landscapes. Having grown up in the major grapefruit producing region of Florida, the citrus industry is near to my heart. So for me, it is very exciting to see all of the interest in the citrus industry in North Florida despite the devastation the industry is facing in South Florida. With many folks spending more time outdoors and working in the landscape, I wanted to share some ways homeowners can enjoy citrus in their landscape all while protecting the future of the citrus industry in North Florida!
First thing’s first…identification!
It’s important to be aware of some of the major pests and diseases affecting citrus. Fortunately for us in the Panhandle, many of the major pests and diseases troubling citrus to the south haven’t become quite as widespread in our area, and with your help we can keep it that way! Regularly scouting the citrus in your landscape and detecting any major pests or diseases early will be very important to prevent it from spreading.
The first major disease all Floridians should be aware of is citrus greening. Citrus greening or huanglongbing (HLB) is the major disease affecting the citrus industry worldwide. It is a bacterial disease caused by the bacteria Candidatus Liberibacter. The bacterium is spread from tree to tree by a tiny insect known as the Asian citrus psyllid. Psyllids spread the disease by feeding on infected trees and moving on to non-infected trees. Once the tree is infected, there’s little hope for survival as there is no cure for citrus greening.
Citrus greening can be difficult to diagnose as it can be easily confused with nutrient deficiency. Symptoms of citrus greening include yellowing of the veins and a blotchy mottle pattern. Nutrient deficiencies tend to have a symmetrical pattern on each side of the leaf vein whereas citrus greening is asymmetrical. Overall, a tree infected with citrus greening will appear unhealthy with discolored leaves, a thin canopy, and reduced fruit production.
Citrus Canker presenting on a leaf. Photo courtesy of Danielle Sprague.
Another disease to be on the lookout for is citrus canker. Citrus is also caused by a bacterial pathogen but is spread primarily though wind, rain and human movement. Citrus canker is highly contagious and can spread very rapidly. Transporting infected plant material from an area where canker is present is the primary means of spreading the pathogen.
Purchase from a certified nursery!
One of the absolute most important things you can do if you are planting citrus is to purchase your trees from a certified citrus nursery! A certified nursery has been inspected by the state to confirm that the nursery is producing clean, disease free trees. Citrus trees grown in a certified nursery will have a tag with the name of the nursery, registration number, the tree variety, and rootstock.
When buying a tree from a secondary retailer, you will want to be sure to examine the tree for any signs and symptoms of pests and diseases. A healthy tree will have dark green leaves, a smooth trunk and show no signs of wilt.
Certified nursery label. Photo courtesy of Danielle Sprague.
Other ways to protect citrus:
- Learn how to properly care for citrus trees. Proper watering an fertilization will make them less susceptible to pest and disease.
- Report any suspected pest and diseases to the Florida Department of Agriculture and Consumer Services (FDACS) Division of Plant Industry by calling 1-888-397-1517
- Don’t bring back plants or fruit into Florida! They could introduce new pests and diseases.
Keeping the Panhandle free of citrus greening and citrus canker will play a major role in the success of the citrus industry in North Florida. For assistance with pest and disease identification or for more information, contact your local Extension agent.
by Danielle S. Williams | Apr 1, 2020
Fertilizer Spreader – Image Credit Les Harrison ,UF / IFAS Extension
Plants require nutrients to grow and they typically get them from the soil. Oftentimes, we apply fertilizer to help them along. Fertilizers provide specific nutrients for your plants and are available in a variety of different forms. When used correctly, fertilizers are a great tool that can help plants thrive. If used incorrectly, fertilizers can harm plants and also the environment.
Different plants have different nutrient requirements and in many cases, fertilizer may not be necessary so do your research before purchasing fertilizers. Sometimes, certain plants, like azaleas or blueberries, need a special formulation of fertilizer.
Think about having your soil tested to see what nutrients are already present in your soil. Contact your local Extension Office for sampling procedures.
Fertilizer Components
Most fertilizers used in the home landscape and garden are blends of several elements mixed together to create a specific formulation of plant nutrients.
Macronutrients
Macronutrients are nutrients required by plants in relatively large amounts for optimum growth. The three main nutrients contained in fertilizers are nitrogen (N), phosphorus (P), and potassium (K). Most folks are familiar with these because they are represented by three numbers that appear on the fertilizer bag. You may be familiar with the term ‘complete fertilizer’. This means the fertilizer with contain all three of the major plant nutrients – N, P and K. Other macronutrients include calcium (Ca), magnesium (Mg), and sulfur (S).
Micronutrients
Micronutrients are nutrients most plants need in small quantities. They are sometimes referred to as trace elements or minor elements. These nutrients include boron (B), chlorine (Cl), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), and zinc (Zn). They are often available in sufficient quantities in the soil, but are also present in many fertilizers. Micronutrients are also sold as individual nutrients.
Types of Fertilizer
Inorganic Fertilizers
Inorganic fertilizers are materials that are mined or synthesized from non-living materials. Many inorganic fertilizers contain nutrients that are immediately available to plants. Others are formulated to be released over a period of time.
Organic Fertilizers
Organic fertilizers are materials that are derived from plants and animals. One of the most common forms of organic fertilizers is manure. Organic matter incorporated into the soil before planting will help fertilize your vegetable plants, but you’ll need to add additional fertilizer after planting.
The quick availability of nutrients, especially nitrogen, is very important in vegetable growing. Therefore, you may want to supplement any organic fertilizer you apply with some inorganic fertilizer for quick feeding. It is a common practice for gardeners to use a combination of fertilizers and techniques in the garden.
Slow- or Controlled-Release Fertilizers
Slow- and Controlled-Release fertilizers provide nutrients to plant roots over an extended period of time. This allows you to fertilize less frequently and prevent nutrients from leaving your landscape and entering groundwater or waterways.
Understanding a Fertilizer Label
The fertilizer label includes a series of numbers that indicate the percentage of nitrogen, phosphorous, and potassium, by weight. The numbers will read something like 15-0-15 or 16-2-8. The first number represents the percentage of nitrogen in the bag, the second refers to phosphorus, and the third number is the amount of potassium. For example, a 50-pound bag of 16-2-8 is 16% nitrogen (8 pounds total); 2% phosphorus (1 pound total); and 8% potassium (4 pounds total). The remaining weight is usually comprised of inert ingredients.
Preventing Pollution
- Follow UF/IFAS Recommendations. Rates, application timings and formulas vary depending on the plant.
- Do not fertilize before a heavy rain. If rain is in the forecast for the next 24 hours, wait to apply fertilizer. Heavy rains can cause fertilizer to leach into groundwater.
- Keep fertilizer off hard surfaces. If fertilizer is spilled on a driveway or sidewalk, sweep it up and dispose of it. Fertilizers can wash into storm drains and nearby bodies of water.
For more information on fertilizers visit:
The Fertilizer Label
by Danielle S. Williams | Jan 23, 2020
Resurrection Fern on Pecan Tree. Image Credit Danielle Sprague, UF/ IFAS Extension
This week, I received a call about identifying a plant growing on a pecan tree in someone’s yard. With the recent rain we’ve experienced after a rather dry period, I had a pretty good feeling it was a resurrection fern. A quick picture sent in to me by the homeowner confirmed this.
Resurrection fern, Pleopeltis polypodioides is a native fern found in many hardwood trees throughout the southeast. In our area, it is found most often on the branches and trunks of live oak and pecan trees. The resurrection fern gets its name from its ability to withstand extensive periods of drought by shriveling up and appearing dead. When it is exposed to water again, it will ‘come back to life’, uncurling its fronds and appearing bright green.
This creeping fern has a long, skinny stem to which the fronds or leaves are attached. The stem is less than 1/12″ in diameter and fronds are anywhere from 4 to 12 inches long. Unlike other plants, resurrection fern reproduces by spores, not seeds. These spores can be found on the underside of the fronds in clusters known as sori. The sori look like brown to black scales.
Resurrection Fern before and after, Image courtesy IFAS Gardening Solutions
Resurrection fern is a perennial epiphyte or ‘air plant’, meaning that it attaches itself to other plants, but it does not steal water or nutrients from its host plant. Instead, it absorbs water and nutrients that collect on the outer surface of the bark. One of the questions posed by the homeowner was the need to control the resurrection fern, however, since it is an air plant and does not harm the tree, there are no chemicals recommended to control it.
In 1997, the resurrection fern made its first debut in outer space! Because of its unique attributes, the National Aeronautics and Space Administration (NASA) launched into space for an experiment to study the ‘resurrection’ in zero gravity. Amazingly enough, they found that the resurrection fern was able to rehydrate and recover in zero gravity!
For more information on resurrection ferns:
UF/IFAS Gardening Solutions: Resurrection Ferns
Island Ecology: Resurrection Ferns
by Danielle S. Williams | Aug 22, 2019
Recently, I received a call about a garden not producing the way it used to. After speaking with the homeowner, I decided to take a visit to see what was going on. On my visit, I could see that the tomatoes were stunted, yellow and wilting, the squash plants were flowering but not setting fruit, and the okra was stunted. After digging up some of the sick plants and examining the roots, the problem was as clear as day…root-knot nematodes.
Galls on roots from root-knot nematodes
Root-knot nematodes are microscopic, unsegmented roundworms that live in the soil and feed on the roots of many common garden plants. Some of the most commonly damaged crops are tomatoes, potatoes, okra, beans, peppers, eggplants, peas, cucumbers, carrots, field peas, squash, and melons. Root-knot nematodes enter the root and feed, causing knots or galls to form. These galls are easily recognizable on the roots. If you’re inspecting the roots of beans or peas, be careful not to confuse nematode galls with the nitrogen-fixing nodules that are a normal part of the root system. As the nematodes feed, the root system of the plant becomes damaged and the plant is unable to take up water and nutrients from the soil. As a result, the plant may show symptoms of stunting, yellowing, and wilting.
What can I do about nematodes?
There are currently no nematicides labeled for use in the home garden but the best means of root-knot nematode management involves using a combination of strategies that make your garden less susceptible to attack.
Grow Resistant Varieties
Some varieties of crops are resistant to root-knot nematodes. This means is that a particular nematode can’t reproduce on the plant roots. When buying seed, read the variety label. The label may have ‘VFN’ written in capital letters. These letters indicate that the variety has resistance to certain diseases: V = Verticillium wilt; F = Fusarium wilt; and N = root-knot nematode. It’s best to use resistant varieties when root-knot nematodes are present.
Tomato plant showing signs of nematode damage – yellowing and wilting.
Sanitation
If you suspect you may have a nematode problem, be sure not to move soil or infected plant roots from an infected area to a clean area. Nematodes can easily be spread by garden tillers, hand tools, etc. so be sure to disinfect all equipment after use in problem areas.
Infected roots left in the soil can continue to harbor nematodes. After the crop is harvested, pull up the roots and get rid of them. Tilling the soil can kill nematodes by exposing them to sunlight.
Cover crops and Crop Rotation
Cover crops and crop rotation isn’t just a concept for farmers…gardeners need to implement the same practices! While this may take some planning, it is the most effective way to reduce pests and diseases.
Cover crops are crops that are not harvested and are typically planted between harvestable crops. They help improve soil quality, prevent soil erosion, and help control pests and diseases. Selecting cover crops that aren’t susceptible to root-knot nematode attack is key. When growing a cover crop that nematodes can’t reproduce on, populations should decline or not build up to begin with. Grain sorghum and millet can be planted as a summer cover crop and rye in the winter. French marigolds have been shown to reduce nematode populations as well.
Another simple way to manage root-knot nematodes is by crop rotation. Crop rotation is the practice of not growing crops that are susceptible to nematode attack, in the same spot for more than one year. Crops that aren’t susceptible to attack are cool season crops in the cabbage family such as broccoli, cauliflower, Brussels sprouts, collards and kale.
Root-knot nematodes can wreck havoc on a garden so it’s important to take the necessary precautions to avoid them. It may require planning and patience but it will be worth it in the long run!
For more information on this topic, use the links to the following publications:
Nematode Management in the Vegetable Garden
Featured Creature: Nematodes
by Danielle S. Williams | May 20, 2019
Citrus leafminer injury. Photo: James Castner
Spring is in full swing and citrus trees have begun actively flushing. With the new flush comes an array of insect pests. One of the most common being the citrus leafminer. The citrus leafminer is a small white moth, about 2.4 mm in length. It is more easily detected during its larval stage by the serpentine larval mines it produces on the underside of citrus leaves.
Citrus leafminer adult. Photo: James Castner
The larvae of the citrus leafminer feed on the new growth or flush of citrus causing serpentine mines to form under the leaf cuticle. This can result in leaf curling and distortion. Citrus leafminer injury to foliage can stunt the growth of young trees and in areas where the citrus canker pathogen is present, provide an opening for infection.
Distortion and leaf curling caused by citrus leafminer. Photo: Danielle Sprague
The term ‘flush’ is commonly used to describe the new foliar growth between bud break and shoot expansion. Citrus trees usually have several flushes per year, depending upon cultivar, climate and crop load. Generally, most citrus cultivars in our area have around three flushes. The main flush is the spring flush in late winter/early spring. Following that, two additional flushes occur around the end of June and late September.
Citrus leafminer on young flush. Photo: Danielle Sprague
Adult leafminers require the new citrus flush for development. Eggs are laid within the flush. After two to ten days, the larvae emerge and feed causing the mines to occur. Larvae are protected within the leaf and therefore difficult to control. Pupation occurs within the leaf mine and takes anywhere from six to 22 days, depending upon temperature. Adults emerge around dawn and are most active in the morning and evening. In Florida, one generation of citrus leafminer is produced about every three weeks but populations increase when citrus trees are flushing.
In Florida, several natural enemies assist with reducing citrus leafminer populations. Studies have shown that predation from natural enemies can reduce leafminer populations by 90%. Primary predators of citrus leafminers include ants, lacewings and spiders. A parasitic wasp, Ageniaspis citricola was introduced into Florida and has become established. The parasitic wasp attacks the immature stages of citrus leafminer. Ageniaspis citricola can be requested and obtained for free from the Florida Department of Agriculture and Consumer Services (FDACS). Because it is a specialized parasitoid of the citrus leafminer larval stage, it should be released only when mines start to become visible on flush.
Citrus leafminer can be difficult to control with insecticides due to the fact that they are within the leaf and protected. Applications of insecticides require proper timing and may require repeat applications. For a full list of insecticides, contact your local Extension Office.
For more information on citrus leafminer, use the links to the following publications:
Citrus Leafminer, Phyllocnistis citrella Stainton (Insecta: Lepidoptera: Phyllocnistinae)
Citrus Leafminer Control – UGA
