by Daniel J. Leonard | May 7, 2020
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!
by Mark Tancig | Apr 30, 2020
Symptoms of oak leaf blister on swamp chestnut oak. Credit: Gordon Magill.
Even during global pandemics, it’s a joy to be outside during the great north Florida spring we’ve been experiencing lately. As cold fronts come through with their rain bands, some packing a punch, they leave behind the most pleasant mornings, clear blue daytime skies, and crisp evenings. Unfortunately, we’re not the only organism that also enjoys those cool days. Many species of fungi are quite active this type of year as the rains, followed by warmer, yet not too hot temperatures, create the perfect conditions for fungal growth. Some of these fungi grow right on or in the plants we’d like to be enjoying for ourselves, stealing nutrients and causing plant decline or merely causing aesthetic damage. As this is an active time for certain species of fungi, local extension offices are getting more calls and questions regarding lawn and landscape damage due to fungal pathogens. A recent call was a new one for me and an example of a native fungi-plant interaction that looks bad but requires no intervention from us. It also highlights how correctly identifying a disease leads to the best action and can often save time and money and prevent unnecessary pesticides (in this case a fungicide) from entering the environment.
Close up of oak leaf blister on swamp chestnut oak. Credit: Gordon Magill.
The fungi and plant involved here was the oak leaf blister (Taphrina caerulescens) on a swamp chestnut oak (Quercus michauxii). It forms, you guessed it, blisters on the leaves of any of the oaks, though live oak (Quercus virginiana), laurel oak (Quercus laurifolia), and water oak (Quercus nigra) seem to be preferred hosts. The spores of the fungi, dormant since the previous summer/fall and which happen to get lodged in bud scales through wind and rain, germinate in cool, wet weather. The fungus then infects young leaves as they flush and its growth causes a disruption in the leaves’ development. This leads to the blistered look of the leaf tissue and, during extended periods of cool, wet weather, the entire leaf sort of shrivels, browns, and eventually falls off. Spores are eventually released from the fallen leaves to start the process over the next spring.
Severe oak leaf blister on swamp chestnut oak. Credit: Gordon Magill.
Though the leaves look pretty terrible, this fungal disease rarely causes plant health issues and the tree recovers just fine. Specimen trees that experience it year to year may be treated with a fungicide, but most homeowners can just let it go. Raking up and disposing of the leaves may help prevent further infections by reducing the number of spores released in the area.
As you enjoy another cool morning after an evening rainstorm, remember that the fungi all around you are also having a great day. You may want to look at your landscape plants and see if there’s anything abnormal going on. If so, take a photo and send it to your local extension office for help with identification and best methods of control, or, like in this case, just leaving it alone.
p.s. As I said this was a new one for me and I want to thank Stan Rosenthal, Extension Agent emeritus, for assisting with identification.
by Daniel J. Leonard | Apr 29, 2020
‘Multipik’ fruit. Photo courtesy the author.
Never one to be satisfied growing “standard” vegetable varieties, last year I decided to peruse various seed sources in search of a superior yellow summer squash selection. Plain ‘Yellow Crookneck’ just wasn’t doing it for me anymore. After doing a little research and consulting a friend who works for Johnny’s Selected Seeds, I settled on a straightneck variety called ‘Multipik’.
Developed in the 1980’s by Harris Seed and now sold by many seed purveyors, ‘Multipik’ enjoyed immediate popularity with commercial squash growers due to its many outstanding qualities but curiously, is just making inroads with the home garden market. Even as it is set to celebrate its 30th anniversary next year, two years of personal experience with ‘Multipik’ verify several important characteristics making it a superior choice to many other traditional summer squash varieties: earliness/heavy yields and a precocious gene.
Newly developing ‘Multipik’ fruit. 4 weeks after planting. Photo courtesy the author.
The longer I garden, the more I’m convinced that earliness to maturity is directly related to yield potential in home gardens, especially in the Panhandle. Lots of varieties have high yield potential but that potential is often at least partially wasted here due to the length of time from seed to harvest. Ideally, you could plant, grow a crop and be done by mid-late June, before intense heat, humidity and all the wonderful garden pests and diseases arrive to destroy spring gardens. Maturing just 50 days from planting, ‘Multipik’ beats that deadline (when planted on time in late March) and yields heavily for at least a month before succumbing to the harsh Panhandle summer. Many traditional summer squash varieties, including ‘Yellow Crookneck’ mature 8-14 days later. While 8-14 days doesn’t sound like much, it can mean a major yield difference when factoring in the almost certain late season pests, diseases, and adverse weather conditions.
The next major advantage ‘Multipik’ offers is a precocious gene, meaning that it will mask symptoms and maintain its yellow color if infected with either Watermelon Mosaic Virus (WMV) or Cucumber Mosaic Virus (CMV), two destructive pathogens commonly affecting squash by discoloring fruit and reducing yield. This trait is critical to commercial growers because yellow squash that isn’t yellow isn’t marketable and is important to home gardeners too as a means to eke out higher yields under virus pressure. While the precocious gene isn’t a cure for either virus, it can help hold them at bay while you harvest! Another quirk caused by the precocious gene is the all-yellow appearance of the fruit, from the peduncle (the stalk holding the fruit to the plant) to the apex! From one end of the fruit to the other, Multipik ensures that when you plant yellow squash, you harvest yellow squash.
‘Multipik’ just days from harvest. Photo courtesy the author.
Whether you are trying to avoid yield loss from late season insect and disease pressure plaguing your traditional squash plantings or just want to try something a little different, I highly recommend planting ‘Multipik’ Squash. This early, disease-resistant cultivar with delicious medium sized, light yellow fruit is sure to be a hit in both in the garden and on the table. As always, if you have any questions about vegetable gardening or any other horticultural topic, give your local UF/IFAS County Extension Office a call! Happy gardening!
by Mary Salinas | Apr 29, 2020
Swarm of eastern subterranean termites. Photo by Susan Ellis, Bugwood.org.
Spring is in the air and that means termite swarming season is near!
Northwest Florida is home to fifteen native species of termites and six species that have invaded from other parts of the world. One invasive species of termite, the Formosan termite, arrived in the southeastern United States in the 1950’s and has been expanding its range and numbers ever since. While our native termites have colonies in the thousands of individuals, Formosan termite colonies can contain millions of individuals and that makes them a greater threat if they invade your home.
Here are some steps you can take to protect your home:
- Turn off outside lights during termite swarming season – late April through June – the swarms are attracted to the light and may then find entry into your home.
- Reduce moisture around your home by keeping gutters clean and having them drain at least a foot away from the foundation.
- Avoid irrigation hitting the house.
- Plants and mulch should be a foot away from the foundation.
- Repair leaks and cracks – termites can get into the smallest of spaces.
- Avoid wood, stucco and siding in contact with the ground.
- Have an annual inspection by a licensed pest control company. Read the fine print of what is covered and what species/type of termites are included. Some policies exclude coverage for Formosan termites.
For more information:
Subterranean Termites
The Facts About Termites and Mulch
UF/IFAS Featured Creature: Formosan Termites
Florida Department of Agriculture and Consumer Services Termite Control Information
Florida Department of Agriculture and Consumer Services Formosan Termite Program
by Larry Williams | Apr 23, 2020
One of the things to do while stuck at home due to COVID-19 restrictions, is to look for caterpillars and butterflies in your landscape. I’ve noticed giant swallowtail butterflies (Papilio cresphontes) a little early this year. The giant swallowtail is one of the largest and most beautiful butterflies in our area. Its larval stage is known as the orangedog caterpillar. This unusual name comes from the fact that it feeds on young foliage of citrus trees.
Orangedog caterpillar. Photo credit: Donald Hall, University of Florida
The orangedog caterpillar is mostly brown with some white blotches, resembling bird droppings more than a caterpillar. When disturbed, it may try to scare you off by extruding two orange horns that produce a pungent odor hard to wash off.
I’ve had some minor feeding on citrus trees in my landscape from orangedog caterpillars. But I tolerate them. I’m not growing the citrus to sell. Sure the caterpillars eat a few leaves but my citrus trees have thousands of leaves. New leaves eventually replace the eaten ones. I leave the caterpillars alone. They eat a few leaves, develop into chrysalises and then emerge as beautiful giant swallowtail butterflies. The whole experience is a great life lesson for my two teenagers. And, we get to enjoy beautiful giant swallowtail butterflies flying around in our landscape and still get plenty of fruit from the citrus trees. It is a win, win, win.
In some cases, the caterpillars can cause widespread defoliation of citrus. A few orangedog caterpillars can defoliate small, potted citrus trees. Where you cannot tolerate their feeding habits, remove them from the plant. But consider relocating the caterpillars to another area. In addition to citrus, the orangedog caterpillars will use the herb fennel (Foeniculum vulgare) and rue (Ruta graveolens) as a food source. Some butterfly gardens plant citrus trees to provide food for orangedog caterpillars so that they will have giant swallowtail butterflies. So you could plan ahead and grow some fennel, rue or find a butterfly garden in your area for the purpose of relocating the larvae.
Yellow giant swallowtail butterfly on pink garden phlox flowers. Photo credit: Larry Williams
The adult butterflies feed on nectar from many flowers, including azalea, bougainvillea, Japanese honeysuckle, goldenrod, dame’s rocket, bouncing Bet and swamp milkweed. Some plants in this list might be invasive.
Keep in mind that mature citrus trees can easily withstand the loss of a few leaves. If you find and allow a few orangedog caterpillars to feed on a few leaves of a mature citrus tree in your landscape, you and your neighbors might get to enjoy the spectacular giant swallowtail butterfly.
More information on the giant swallowtail butterfly is available online at http://edis.ifas.ufl.edu/in134.
by Matt Lollar | Apr 23, 2020
I was recently sent some pictures of some unusual growths on pecan tree leaves. At first glance, the growths reminded me of the galls caused by small wasps that lay their eggs on oak leaves. However, after a little searching it became apparent this wasn’t the case. These galls were caused by the feeding of an aphid-like insect known as phylloxera.
Leaf galls caused by pecan phylloxera. Photo Credit: Matt Lollar, University of Florida/IFAS Extension – Santa Rosa County
The feeding from the phylloxera causes the young leaf tissue to become distorted and form a gall that encloses this female insect called a “stem mother”. These insects are rarely seen, but the hatch from over-wintering eggs in March/April just after budbreak. Once hatched, these “stem mothers” crawl to the new leaves and begin feeding. Once the gall forms, they start to lay eggs inside the gall. The eggs hatch inside the gall and the young phylloxera begin to feed inside the gall and the gall enlarges. The matured insects break out of the gall in May and some will crawl to new spots on the leaves to feed and produce more galls.
Pecan stem damage from phylloxera. Photo Credit: University of Georgia
There are two common species of phylloxera that infect the leaves. The Pecan Leaf Phylloxera seems to prefer young trees and the Southern Pecan Leaf Phylloxera prefers older trees. The damage from each of these insects is nearly indistinguishable. Damage from these insects is usually not severe and merely an aesthetic issue.
Once the damage is discovered on a tree, it is too late to control the current year’s infestation. There are currently no effective methods for control of phylloxera in home gardens. Soil drench applications witha product containing imidacloprid have been limited in their effectiveness.
