A common question for gardeners at the end of the season is if one should till the soil or use no till practices. Opinions vary regarding this question, even among Extension Agents. However old crops harbor insects, both good and bad. This phenomenon was noticed on some recently cut back tomato plants. The intention was to cut the leftover spring garden tomatoes back to encourage fall production. Instead, a host plant for mealybugs was provided.
Mealybugs on a tomato plant. Photo Credit: Matt Lollar, University of Florida/IFAS Extension – Santa Rosa County
Mealybugs are soft-bodied insects that possess a covering of flocculent, white, waxy filaments. They are about 1/8 inch in length and usually pinkish or yellowish in color. Mealybugs have piercing-sucking mouthparts which they use to siphon fluids from the leaves, stems, and sometimes roots of many ornamental and vegetable plants. Mealybug damage produces discolored, wilted, and deformed leaves.
One very common example of an insect pest likely to claim residence in your garden’s crop residue, are squash bugs. They like to overwinter on squash, cucumber, and other cucurbit crop residue. If you choose to not till your garden and leave a portion of last seasons crop in your garden, then you should consider applying an insecticide to your spent crop at the end of the season. A product containing a pyrethrin or pyrethroid as an active ingredient would be a good broad spectrum insecticide to control any pest that may reside on plant residue. More information on pyrethrins and pyrehtroids can be found at the EPA webpage: Pyrethrins and Pyrethroids. If you choose to apply an insecticide, it is important that you follow the information on the label regarding pollinator protection. Another option is to plant a trap crop on the edge of your garden to help attract pest insects away from your desired crops. More information on trap crops can be found in the EDIS Publication: Intercropping, Pest Management and Crop Diversity.
An adult squash bug on a zucchini leaf. Photo Credit: Matt Lollar, University of Florida/IFAS Extension – Santa Rosa County
So the answer to the till or no till question is…it depends. It is really up to the gardener. Yes, the residue from crops will add nutrients and organic matter to your soil, but it could also increase pest pressure in your garden. If you don’t plan to remove crop residue and don’t plan to till, then keep an eye out for what could be hiding in your garden.
I live in the woods, so I mainly have a “natural” landscape. I remove trees, shrubs, and weeds as I see fit, but for the most part things just grow wild. However, there are a few spots in the yard where the previous owners did a little landscaping. Unfortunately, these spots have become a bit overgrown. One spot in particular features some gardenia plants around the HVAC units. At first, I was a little hesitant to prune these shrubs because they provide some shade to the units. However, they have become overgrown and I know they will grow back. I was patient to wait for them to finish flowering.
A gardenia shrub that has become a bit overgrown. Photo Credit: Matt Lollar, University of Florida/IFAS Extension – Santa Rosa County
As you can see in the photo above, this gardenia has become a bit leggy. It is important to also note the good amount of branching and new growth at the base of the plant. There are a few pruning options available for shaping shrubs such as hedging/terminal pruning, selective pruning, and renewal pruning. While a tree form gardenia can be attractive, it wasn’t desired in this situation. This particular case called for renewal pruning to improve the form of the plant. Renewal pruning is probably the easiest type of pruning, because it requires the least amount of thinking. It basically involves removing the majority of old growth.
A gardenia shrub that has been renewal pruned. Photo Credit: Matt Lollar, University of Florida/IFAS Extension – Santa Rosa County
The picture above is of the same shrub that has been pruned heavily. Not only have the older, leggy branches been removed, but some of the newer growth has been removed to allow for better air circulation within the shrub. This will help reduce the incidence of disease.
A gardenia shrub six weeks after renewal pruning. Photo Credit: Matt Lollar, University of Florida/IFAS Extension – Santa Rosa County
Six weeks after being pruned, this shrub is flowering for a second time. In a matter of short time it will be providing much needed shade for the HVAC units again. (That is..if I remember to selectively prune throughout the year.) For more information on how to prune and what to prune, please visit the UF/IFAS Gardening Solutions page on pruning.
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!
‘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.
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.