With the traditional planting date of Good Friday behind us, the home tomato gardening season in the Panhandle is in full swing. While tomatoes are the most persnickety veggie we grow, there are several practices you can adopt to help you succeed: selecting an adapted variety; regularly scouting for insects and disease; and watering and fertilizing appropriately. However, the most overlooked practice for success gardeners can adopt is proper pruning.
‘Big Beef’ Tomato with lower leaves removed. This is an excellent disease reduction practice. Photo courtesy of Daniel Leonard.
Correct pruning does a couple of positive things for tomatoes. First, it reduces the incidence of disease by preventing leaf contact with the soil, opening the interior of the plant, and allowing better airflow. This is important as many plant pathogens reside in the soil and only need a splash of water to travel onto plant leaves. Also, densely foliaged plants trap warm, moist air in their canopies, creating a perfect environment for disease to flourish. Letting the plant canopy “breathe” through pruning prevents that negative environment from forming! Second, correct pruning of “suckers” (extra growth points that can develop into shoots) helps tomato plants develop optimum yield and fruit quality. By removing suckers, more water, nutrients, airflow, and light are directed to the main stems, where the majority of tomato fruit production occurs. Failing to remove suckers (especially on indeterminate varieties) can result in reduced yields, increased disease, and generally messy plants!
With the reasons for pruning tomatoes established, the next step is learning exactly what to prune and how to do it in a sanitary matter.
Get rid of any foliage that could encounter the soil, generally all leaves occurring on the lower 12-16″ of the plant. All kinds of nasty tomato destroying diseases, like Early Blight and Bacterial Leaf Spot, reside in the soil and are just waiting to be splashed onto your plants – don’t let that happen.
Determine how many primary shoots you want your plant to have. Leave enough lower suckers to achieve that number (generally just one, two, or three as more than 3 primary stems gets hard to manage), and prune or pinch out all the rest. To prevent stress from pruning, be diligent in removing suckers when they are still small, 2” or less.
Always clean and disinfect your pruners before making a cut on a tomato plant. This is best accomplished by rinsing the blades with warm soapy water, drying, and following with by a quick alcohol spray. A 10% bleach solution will also work, but if not thoroughly rinsed after, bleach can corrode pruner blades and other working parts. If you make cuts on a plant that appears diseased, repeat the sanitizing process before you begin pruning another plant as “dirty” pruners are an easy way to spread pathogens in the garden.
Developing vegetative “sucker” that will need to be removed. Photo courtesy of Daniel Leonard.
While tomatoes are indeed a difficult vegetable to grow, learning to prune them correctly will greatly help to make this a successful season. If you just keep leaves off the ground, suckers pinched, and pruners cleaned, you’ll be well on your way to less disease, prettier plants, and more tomatoes to pick. For more information on growing tomatoes and any other horticultural topic, please contact your local UF/IFAS County Extension office. Happy Gardening!
Tomatoes ripening on the vine – Image Credit Matthew Orwat UF/IFAS Extension
It is late-February, so the spring growing season is just around the corner. Now is the time to be thinking about which tasty tomatoes you want to plant in your home garden! Although tomatoes are a favorite kitchen staple, they prove challenging to grow in the Florida Panhandle climate.
While many tomato diseases can kill plants, damage fruit, and reduce yields, genetic resistance or tolerance to select diseases exist. The following are three of the most common diseases and viruses home gardeners face, for which resistant and tolerant varieties exist.
Tomato spotted wilt affects tomatoes, and numerous other vegetables, ornamentals, field crops and weeds. The disease can cause significant yield losses of tomato. Image Credit UF/IFAS Plant Pathology UScout Site
Tomato Spotted Wilt (TSW) is a viral disease which is transmitted by thrips, a species of insect that is very small and not always visible when checking the garden for insect pests. They love to feed on the sugary juices of the tomato flowers, and while feeding, they have the opportunity to transmit the virus through their piercing and sucking mouth parts. Lots of different symptoms may occur with TSW. Initially growers will notice light or dark brown spots on leaves of affected tomatoes, next wilting or stunting will occur, along with brown or purple streaks on the stems. Finally, fruit will exhibit unsightly brown rings throughout. The good news is that home gardeners can get a head start on this disease by planting resistant cultivars. When shopping for seed or transplants, growers should look for plants listed with the codes TSW or TSWV, because these have demonstrated resistance to Tomato Spotted Wilt Virus.
Another viral disease often found in the tomato garden is Tomato Yellow Leaf Curl (TYLC) Virus. TYLC first appeared in Miami in 1997 and was brought to Florida by infected whiteflies. Much like TSW, TYLC is spread from plant to plant by feeding whiteflies. As the name indicates, TYLC symptoms include curled leaves and stunted growth. Infected plants produce little to no fruit. Strategies to reduce the possibility of virus transmission to the garden include reducing the population of weedy plants, which may harbor whiteflies. Fortunately, resistant cultivars are available in plant catalogs, and are denoted by TYLC to indicate resistance.
Spread of TYLC is by the feeding of TYLCV infected adult whiteflies. Mechanical or seed transmission is not known to occur. Upward curling and yellowing of the leaves is an early symptom. Credit: UF/IFAS Plant Pathology UScout Site
Blighting of leaves and wilting of part or entire plant can expose fruits to sunscalding thereby further affecting yield of affected plants in production. Credit: UF/IFAS Plant Pathology UScout Site
Fusarium Wilt is one of the oldest diseases to affect tomatoes in the state of Florida and is caused by the fungal pathogen Fusarium oxysporum f.sp. lycopersici races 1, 2, or 3. This pathogen is often present in regional soils and moved by wind. Once it enters the roots of tomato plants, fusarium wilt proliferates and clogs the vascular system, much like a clog in the plumbing of a building. Thus, the primary symptom is the wilting of the plant, which will first be noticeable on hot days, despite adequate irritation. Once infected, there is no cure, and infected plants should be removed and destroyed to stop the spread. The good news is that resistant cultivars are available to the various fusarium races. They are usually denoted as F-R 1, 2, or 3 in seed catalogs. Additionally, look for plants labeled VFN. These cultivars are resistant to a different kind of wilt, called verticillium, as well as fusarium and nematodes.
Fortunately, the UF / IFAS publication “Tomato Varieties for Florida—Florida “Red Rounds,” Plums, Cherries, Grapes, and Heirlooms” by Monica Ozores-Hampton and Gene McAvoy has provided us with a handy chart of tomato varieties with disease resistance. Codes in the columns indicate disease resistance to specific pathogens. While there is no single tomato variety resistant to all possible disease pathogens, planting different varieties with several different types of resistance will allow growers to hedge against attack by a number of potential disease problems. Some of the more common disease resistant tomato varieties planted in this area are ‘Quincy’, ‘Bella Rosa’, ‘Amelia’, ‘Tasti-Lee’, ‘BHN 602’, and ‘Volante’.
For a further look at the various diseases of tomato, the EDIS publication“A Series on Diseases in the Florida Vegetable Garden: TOMATO”offers more detail. Another resource UF/IFAS offers for disease diagnosis is the NFREC U-Scout website. U-Scoutprovides information on more than 40 potential disease issues in tomato. Additionally, any plant disease can be diagnosed through yourCounty Extension Officeor by submitting samples to the Plant Pathology Clinic, at the North Florida Research and Education Center, for only $30/sample for basic services.
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Fig. 1 An adult redbay ambrosia beetle compared to the size of a single penny. Credit: UF/IFAS File Photo.
While most bark beetles are important in forest ecology by recycling fallen dead trees and eliminating sick and damaged trees, some of them may impact healthy trees. A group of bark beetles that has become a major concern to forest managers, nurseries, and homeowners is the ambrosia beetle. Ambrosia beetles are extremely small, 1-2 mm in length, and live and reproduce inside the wood of various species of trees (Fig. 1). Ambrosia beetles differ from other bark beetles in that they do not feed directly on wood, but on a symbiotic fungus that digests wood tissue for them. Every year, non-native species of ambrosia beetles enter the United States through international cargo and we have now nearly forty non-native species of ambrosia beetles confirmed in the United States. Among them, the redbay ambrosia beetle (Xyleborus glabratus), originally from Southeast Asia, is the vector of the fungal pathogen causing laurel wilt, a disease that devastated the Lauracaea population in the southeastern USA, killing millions of redbay, swamp bay, sassafaras and silk bay.
Fig. 2: A mature dooryard avocado tree with large sections of dead and missing leaves, caused by laurel wilt disease. Summer 2009 Impact Magazine image. Credit: UF/IFAS File Photo.
When these beetles attack a laurel tree, the symbiotic fungus is vectored to the tree’s sapwood after the beetle has tunneled deep into the tree’s xylem, actively colonizing the tree’s vascular system. This colonization leads to an occlusion of the xylem, causing wilting of individual branches and in a matter of weeks progresses throughout the entire canopy, eventually leading to tree death (Fig. 2). The laurel wilt disease has spread rapidly after the vector was first detected in Georgia in 2002. The redbay ambrosia beetle was first detected in Florida in 2004, in Duval County, attacking redbay and swamp bay trees. At this point, it is estimated that more than one-third of redbay in the U.S.A., 300 million trees, have succumbed to the disease.
Starting in 2017, we examined the efficacy of verbenone against redbay ambrosia beetle in live laurel trees in a natural forest setting. Verbenone is an anti-aggregation pheromone that has been used since the 1980’s to protect lodgepole pine. Verbenone also has the potential to be used over large areas and is currently being used to protect ponderosa pine plantations from the Mountain Pine Beetle in the western US.
We have found verbenone to be an environmentally friendly and safe tool to prophylactically protect laurel trees against redbay ambrosia beetle. Our protocol consists of the application of four 17 g dollops of a slow-release wax based repellent (SPLAT Verb®, ISCA technology of Riverside, CA) to the trunk of redbay trees at 1 – 1.5 m above ground level (Fig. 3). The wax needs to be reapplied every 4 months during fall and winter and every 3 months during spring and fall when temperature is higher. When compared to the control trees without repellents, we found that trunk applications of verbenone reduced landing of the redbay ambrosia beetle on live redbay trees and increased survivorship of laurel trees compared to untreated trees (Fig. 4). Verbenone should be considered as part of a holistic management system against redbay ambrosia beetle that also includes removal and chipping of contaminated trees.
If you have Redbay or other bay species on your property and are concerned about Laurel Wilt Disease or Redbay Ambrosia Beetle damage, contact your local UF/IFAS Extension Agents for help!
This article is courtesy of Dr. Xavier Martini and Mr. Derek Conover of the UF/IFAS North Florida Research and Education Center (NFREC) in Quincy.
Fig. 3: Application of SPLAT Verb on a redbay tree during a field trial
Figure 4: (A): Cumulative capture of redbay ambrosia beetles Xyleborus glabratus following a single application of verbenone vs untreated control (UC). (B) Survivorship of redbay and swamp bay trees treated with verbenone on four different studies conducted in 2017 and 2018.
Early BLS symptoms appear on lower leaves. Photo courtesy of the author.
Tomatoes are among the most notoriously difficult vegetable species to grow in Florida. Even when you do everything right (choose disease resistant varieties, buy clean seed/healthy transplants, plant early, rotate crops, scout for insects, prune and support vines, etc), things can go wrong in a hurry. Bacterial Leaf Spot (BLS) caused by the pathogen Xanthomomas perforans, is one of those things. BLS often hitches a ride into gardens undetected on seed and transplants and presents itself as warm and humid weather arrives in late April/early May. Outbreaks typically happen in concurrence with the frequent heavy rainstorms that accompany these months and quickly wreak havoc on tomato plants.
BLS occurrence, much worse in some springs than others, has exploded this year in home gardens. First noticed on the plant’s lower leaves, BLS pathogens enter through natural openings in leaves called stomata, manifest as small, “water-soaked” leaf lesions and then develop within days into dark circular spots, sometimes surrounded by a yellow halo. As conditions worsen, all these individual infections cause a general yellowing or “blighting” of entire leaves. Though the issue begins on tomato leaves, BLS can affect all parts of the plant, including stems, flowers and fruit too! It’s at this point, when blighted leaves become obvious and lesion developing on flower stalks cause both flowers and small fruit to drop, that most home gardeners notice that something is up.
Advancing progression of BLS with “blighted” leaves. Photo courtesy of the author.
Unlike with many other pathogens, gardeners don’t have an abundance of options to control BLS. However, taking the following preventative measures can reduce the pathogen’s impact and stave off disease progression until ripe fruit can be harvested.
Don’t irrigate overhead. Utilize drip/microirrigation or hand water beds and containers at soil level. This prevents the leaves from becoming wet; wet leaves become a perfect host for BLS.
Never work tomato plants when leaves are wet. No staking, pruning, tying, or anything else until plant tissue is dry. Working wet tomato plants is an excellent way to spread bacteria!
Sanitize pruning tools often and wash hands after working infected plants.
Maintain airflow in plants by planting at correct spacing and thinning interior leaves as necessary to facilitate quicker drying of the plant.
Prune lower leaves to at least 12” from the soil’s surface to prevent disease transmission from soil to leaves through splashing water.
Remove infected leaves (when plants are dry!) to slow disease progression.
Rotate crops and destroy infected plants to prevent buildup of BLS organisms in soil.
BLS lesions on tomato flowers. Photo courtesy of the author.
Preventative measures are best, but if your garden has a history of BLS and local weather forecasts call for warm/wet/humid weather, it is best to spray fungicides proactively to protect your crop. A weekly spray with a tank mixture of copper and mancozeb is effective at keeping BLS at bay. This is the only chemical spray combination proven to be effective in controlling BLS.
Unlike many common tomato pathogens that can be reliably avoided through planting resistant cultivars like ‘Big Beef’, ‘Celebrity’ and others, no varieties are resistant to BLS.
While BLS is an extremely destructive pathogen of both home and commercially grown tomatoes, growers can lessen the disease’s effects by following the preventative measures outlined above and spraying with a copper/mancozeb mix if necessary. Growing tomatoes this year hasn’t been easy, but it’s worth it to fight back and realize a harvest despite difficulties like BLS!
If bacteria have given you the blues or other garden issues are bringing you down, give your local UF/IFAS County Extension Agent a call! We’re here to help you be successful in all your horticultural endeavors. Happy gardening!
