Being a gardener in Florida is exciting. We have many plants to choose from and the weather is mostly pleasant but always seeming to surprise us. One disadvantage of living in such a place, in addition to having so many growing zones, landscape nurseries, and major shipping ports, is that invasive species that land in Florida don’t like to leave. One newcomer in the lineup of invasive pests is the crape myrtle bark scale (Acanthococcuslagerstroemiae). This invasive insect pest made its way from Texas and, as of a few weeks ago, the only Florida sighting had been in Santa Rosa County. Unfortunately, this pest has now been confirmed in Leon County. Landscapers and gardeners in north Florida should learn how to identify this pest and what options are available for control.
The crape myrtle bark scale, as the name suggests, has a pretty specific host – the crape myrtle (Lagerstroemia spp.). However, in the United States, this scale has also been found feeding on our native beautyberry (Callicarpa americana). Due to the widespread planting of crape myrtles, these should be the gardeners primary focus when looking for this new pest. If present on the tree, it is hard to miss. These scales feed on the bark and are a snow-white color. Being a scale, they produce honeydew that is then covered in black sooty mold. So, if you see a crape myrtle with black branches, look closely and you may see the white scales. If you crush these scales and they leave a pink goo on your fingers, then you very likely have crape myrtle bark scale. Of course, you can send a picture or sample to your local county extension office for confirmation.
Black sooty mold and white scales along the trunk and branches are a tell-tale sign of crape myrtle bark scale. Credit: Mark Tancig, UF/IFAS.
If you do happen to find crape myrtle bark scale in your own landscape, or one that you manage, proper control is important to prevent it from moving along any further. Since scales suck on sap and are protected by an outer shell, systemic insecticides are the preferred product for effective control. These include the neonicotinoids, such as imidacloprid (Merit) and dinotefuran (Safari). The larval stage can be controlled with a horticultural oil, sometimes mixed with another insecticide like bifenthrin (Talstar), however, this will not control the adults. Another option is to completely remove the tree and burn all of the plant material.
Excessive sooty mold has turned these branches black. Be on the lookout for crape myrtles looking like this to help identify crape myrtle bark scale. Credit: Jim Robbins, Univ. of Ark. CES. Retrieved from bugwood.
The crape myrtle bark scale can significantly reduce the aesthetic value of crape myrtles due to the black sooty mold that covers the bark. It is also known to reduce flowering and can lead to thinning of leaves. Since crape myrtles make up a big part of our managed landscapes, let’s all work together to scout for this pest and control it when found. If you have questions, please contact your local county extension office.
Difference in flowering due to crape myrtle bark scale damage. Credit: Jim Robbins, Univ. of Ark. CES. Retrieved from bugwood.
Citrus is one of the most cherished fruit trees in the Panhandle. Citrus owners are well aware that every year the main damage to their trees come from citrus leafminer (CLM). CLM is a small moth and its larvae feeds between the tissue layers of new leaf growth, causing serpentine mines to form under the leaf cuticle (Fig. 1). The feeding damage results in leaf curling and distortion, and severe infestations of CLM on young trees can retard the growth of trees. Another threat concerning CLM in Florida is that the mines provide an open wound for citrus canker to enter, a bacterial disease that has been found recently in the Florida Panhandle, Georgia, and Alabama.
Most commercial growers deal with CLM in young trees by a soil application of systemic insecticide before the flush season, followed by a foliar insecticide when the systemic drench’s toxicity is declining. Homeowners, however, have limited access to these chemistries. Garden systemic insecticides that include imidacloprid (Bayer’s Tree & Shrub Insect Control™, Merit®, etc.) and dinotefuran (Greenlight Tree and Shrub Insect Control™, Safari®, etc.) are among the few options for CLM control. For the best efficacy, those insecticides should be applied two weeks before the start of the flushing season to allow time for the insecticide to move from the roots into the canopy. To avoid leaching of insecticide away from the root zone, soil applications should be made within a 24-hour period without rain. Citrus trees usually have several flushes per year, depending upon cultivar, climate, and crop load. However, in the Florida Panhandle, most citrus cultivars have two major flushes in May and September.
Importantly, systemic insecticides are only efficient against CLM for small immature trees; therefore, the only products labeled for use against CLM on mature trees are foliar sprays. Horticultural oils or insecticides with spinosad (such as Monterey® Garden Insect Spray) are some options available for homeowners. However, achieving leafminer control with foliar applications on mature trees is challenging due to unsynchronized flushing of trees. Foliar applications should be timed with the appearance of the first visible leaf mines. In any case, be sure to READ THE LABEL and follow all the label directions.
Cultural practices, and non-insecticidal methods.
For isolated trees in a backyard, cultural practices and control through mass trapping are usually sufficient to control CLM and insecticide use is not recommended, especially for mature trees. One of the basic cultural practices is to remove any stems that grow below the bud union or from the rootstock, also called ‘suckers’ (Fig. 2). Those rootstock shoots compete with the scion shoots and are great reservoirs for CLM; removing them will help reducing CLM population. On isolated trees, mass trapping using CLM pheromone provide good results (Fig. 3). The mass trapping method is constituted of a delta trap baited with a lure that emits a large quantity of CLM sex pheromone. CLM males are attracted by the odor and are captured in the delta trap’s sticky liner. Those traps are commonly used by growers to monitor CLM populations, but for homeowners they are sufficient to control CLM on a single tree. This trap and a lure method should protect a single tree for approximately 3 months. Finally, the last option is the use of biological control. Several natural enemies are predators or parasitize CLM. In some case, biological control can reduce CLM populations by 90%. Primary predators of CLM include ants, lacewings, and spiders, as well as a parasitic wasp, Ageniaspis citricola that was introduced into Florida and has become established (Fig. 4).
New growth from the rootstock (called ‘suckers’, red arrow) are a source for CLM infestation and should be removed.
Baited pheromone trap for citrus leafminer (picture Danielle Sprague).
Homeowner accounts of white fluffy woolly masses on woody ornamentals, oak trees and Muhly grass have been on the rise. The good news is they are native insects that need a nursery for their young and will cause little harm to the host plant. The bad news is scientists know very little about the complete live cycle and role in the environment of these insects.
Within the cottony mass there are citrus flatid planthoppers, woolly oak aphids, or Muhly mealybugs. The adults have laid eggs or birthed their young on the leaves. The young nymphs have excreted large amounts of the woolly wax to protect them from predators and weather while they grow larger. Food from the plants is needed to grow, so these piercing-sucking insects are removing sugars from the host plant. But, typically it is not enough to significantly change the plant’s appearance, so most people are not alarmed until they notice “all the white stuff”.
Adult citrus flatid planthopper, Metcalfa pruinosa
(Say). Credits: Photograph by: Lyle J. Buss, University of Florida
The only one that moves quickly are the citrus flatid planthoppers. When a person reaches for the flocked branch, something small moves and seems to jump at you. Most likely the jumping direction is away from you, but it still may be startling. They are planthoppers (Metcalfa pruinosa), an insect in the order Hemiptera. As the name implies, they occur on citrus but can also be found on many woody ornamentals and other fruit trees. The adult planthopper wing arrangement is tent-like, meaning that the forewings are held over the insect abdomen in a tent configuration.
Stegophylla brevirostris Quednau colony on oak. Photograph by Susan E. Halbert
Woolly oak aphids are conspicuous pests on oak (Quercus spp.), because they are covered with large amounts of flocculent wax. Two genera of woolly oak aphids occur in Florida. One species, Stegophylla brevirostris Quednau, is common, and the other, Diphyllaphis microtrema Quednau, is rare. Florida woolly oak aphids are recognized easily by the large quantities of woolly wax that they secrete. Beneath the wax, aphid bodies are pale. Young nymphs are typically pale green, and they tend to be more mobile than adults. The majority of reports of woolly oak aphids indicate a preference for live oak (Quercus virginiana Mill.) as the host. These aphids are live-bearing females. It is not known how these aphids disperse, but possibly they are picked up and carried by birds and larger flying insects because of the sticky wax that surrounds the bodies of the aphids.
Muhly grass infested with mealybug. Photo: Beth Bolles
Muhly grass (Muhlenbergia capillaris) is a generally pest free plant in its native habitat, however, the native mealybug, Stemmatomerinx acircula, has made an appearance on plants in various landscapes. Insects feed on the leaves and are grey with white wax that may have some filaments. You may also see long ovisacs on the leaves which contain eggs and crawlers. With close inspection, you will notice they have legs and can move about.
So “what do you do?’ If the plant doesn’t appear to be suffering, let nature take its course. “This to will pass.” If someone demands perfection, use insecticidal soap to reduce the population. The soft-bodied creatures will dry up before they can become adults. To read more about these odd creatures of nature go to: https://entnemdept.ufl.edu/creatures/
It is late summer and many of us enjoy being outdoors in the landscape and taking early morning walks before the temperature rises for the day. There are precautions to take while being outdoors and the activities as many insects are very active, including the yellow jacket. Late summer and many of us being outdoor brings us increases the change of being stung by this insect. The Yellow Jacket sting can be painful and potential dangerous to certain individuals with strong reactions to stings.
Yellowjackets are pollinators and eat caterpillar pests! Credit: Whitney Crenshaw, Colorado State University, Bugwood.org
In the State of Florida there are two species of this Yellow Jacket Wasp, the Eastern Yellow Jacket and the Southern Yellow Jacket. It is difficult to distinguish between them and for this article I will refer to them as Yellow Jackets. Yellow Jackets most often colonize in the ground and are often found in lawns that tend to stay dry, landscape beds and edge of woodlands. Colonies of this flying insect can grow into hundreds or even larger numbers. Often by observation in morning or evening light the entry and exit point of the nest can be see with some luck. It looks like an extremely busy airport with lots of landings and departures. The unfortunate way to find the nest can occur by mowing the lawn disturbing the nest with many yellow jackets emerging from the nest to protect it. The colony quickly goes into defense mode with vibrations occurring nearby. This has occurred with me on more than one occasion. All modesty can be lost while run away from the nesting area with several yellow jackets stinging you move quickly move away. Clothing has been known to be shed to hopefully remove the yellow jackets busily stinging either under or on the outside of clothing.
Southern yellowjacket, Vespula squamosa (Drury), nest dug from ground.
Credit: Gerald J. Lenhard; http://www.insectimages.org/
During the early part of the spring and summer season yellow jackets are busy foraging for protein sources to feed to queen and young larvae. During the consuming of the insects, with many of those harvested being harmful insects to plants. The yellow jackets derive their sugar sources from the larvae secretions as they consume the proteins provided. This is part of the reason we do not often see Yellow Jackets in late spring and early summer. As the queen begins to reduce the amount of egg laying, hence the less numbers of larvae to feed and harvest the sugar for a wasp population at its peak creates a more aggressive need to find alternate sources of sugar. This is part of the reason why yellow jackets show up in greater numbers at outdoor sporting events and other places to look for additional sugar sources. Sugar water for hummingbirds is another backyard site for yellow jackets to work hard for the sugar. Even the birds are careful about approaching the feeders.
I do not advocate the destruction of yellow jacket nesting sites unless they are in proximity to human activity as this can set the situation of stings and potential health challenges for people. If you identify a nest location do not approach and call a company that specializes in addressing these types of stinging insects. Keep in mind that this insect provides a benefit in harvest of many harmful pests to plants yet do pose a potential threat. Be observant as you garden situations that seemed fine last month may have changed quickly.
Summer should be the time to relax and enjoy the fruit of all the hard work performed in the landscape over the previous winter and spring. However, there are still some essential tasks that need to be completed during the summer. Perform them in short energy bursts early in the morning or late in the evening.
1. Aerate Your Lawn
If your yard is starting to look weak and thin, even with fertilizing and proper moisture, it may need aeration. Aeration, which is creating channels into your lawn, allows water and nutrients to reach the deep roots of your grass more efficiently.
To test if you need to aerate your lawn, shovel up a patch of grass to a depth of at least four inches. If the layer of thatch is a half-inch thick or higher, your yard would benefit from aeration. There are self-drive aeration machines and tractor-pulled devices you can rent to make quick work of large areas. For smaller areas, simply punching multiple holes with a pitchfork will do the job.
2. Fertilize
Commercial landscape fertilizer applicators must obtain state certification.
Turf grass often displays a yellow color during the mid-summer rainy seasons due to the heavy rains flushing nitrogen away from plant roots. If your lawn is looking sad and yellow, chelated iron can often give a temporary green-up. Iron is not a replacement for nitrogen, but it can work well during our summer rainy season.
If you soil test revealed a potassium or magnesium deficiency, summer is a good time to make the last corrective application. Potassium (K) is an essential macronutrient. Fertilizer bags typically show the percentage of potassium in a product as the third number displayed on the front of the bag (e.g., the “8” in 16-2-8). Potassium acts as a “vitamin” for turf grass, increasing root strength, disease resistance and cold hardiness.
Magnesium (Mg), also a macronutrient, is essential for the production of chlorophyll, necessary for photosynthesis, and also plays a part in the movement of carbohydrates from leaves to other parts of the plant.
3. Don’t Mow Too Short
It’s a natural inclination to want to mow your grass as short as you can, so you have the longest time until you have to mow it again. However, giving your grass a buzz cut every time you mow can hurt your lawn over time.
While some turf grasses can be mowed relatively short, like Bermudas and some Zoysias, most grass types shouldn’t be cut shorter than two-and-one-half to four inches high. Mowing shorter than that can damage the growth point and leave it susceptible to disease and pest infestation. It can also dehydrate the grass and lead to long term damage.
5. Water Infrequently but Deeply
One common mistake made by many is watering too often and too shallow. When only given frequent shallow waterings, grass will begin to grow their roots upwards to take advantage of the small amounts of water, which makes weak and unhealthy. The grass becomes even more dependent on water and very susceptible to disease and insect attack.
Try watering only once or twice a week, but for a considerably longer time so that the water can penetrate deeper into the soil and encourage downward roots. Ideally, each irrigation zone is calibrated to determine the length of time it take to deliver ½ – ¾ inch. Then set the system to run every 3-4 days for that number of minutes. While checking the irrigation delivery system, make sure the rain shut-off device is working and set to the same ½ – ¾ inch.
6. Prevent Mosquitoes
Summer rains on a nearly daily basis lead to lots of standing water. In less than one inch of water, hundreds of mosquitoes can hatch 3 -5 days later. Not only are these blood-sucking pests annoying, but they can also transmit dangerous diseases like West Nile and Zika Virus. Even without disease, their bites are painful and irritating.
To prevent mosquitoes, make sure no standing water is allowed to remain in your yard, either in low points or in empty containers like flower pots or wheelbarrows. Any amount of stagnant water is the perfect breeding ground for mosquitoes. Take a walk around the yard, dumping out water and disturbing the oak and magnolia leaves that are acting a collection cup. Treat birdbaths and water features with floating “donuts” specifically designed to kill mosquito eggs.
While getting tasks done in quick morning trips to the yard, make sure to keep hydrated. Heat exhaustion can happen fast.
Biological control is a pillar of integrated pest management. It may seem a bit daunting the principle is simple. All things in nature have predators including insects. Biological control is simply building a conducive environment for the predators of undesired pests. One animal not often thought of in this capacity is bats. Insectivores by nature, these underutilized creatures have a big impact to your open spaces. Their steady diet of moths (Lepidoptera), beetles (Coleoptera) and flies (Diptera, which includes mosquitoes) reduce insect pressure to your gardens and landscaping.
I know what you are thinking. How effective can they possibly be? Pregnant females consume up to two thirds of their body weight through the summer months while rearing pups. Bats are small but keep in mind that these are not solitary animals. In south Texas, a single large colony consumes enough insects to save cotton farmers an estimated $741,000 per year in insecticides. That is just to illustrate the point as you won’t be able to attract huge colony. There is no reason to believe a smaller colony will not provide similar services in your gardens.
Habitat
Now that your interest is piqued, how can you attract bats to your property? Installing a bat house is the easiest way. They are typically a two foot by one foot structure holding single or multiple chambers in which bats roost. It provides shelter from predation and weather while providing a place to rear pups. Though commercially available they may be built at home with minimal cost. Place the bat house in a location with morning sun at least 12 feet off the ground. Ensure there is enough airflow around the house to keep them cool, but that the structure is watertight. Mount houses on poles next to buildings and you’ll have better success attracting residents. With everything in place, it is time to discover who will most likely be your new neighbor.
photo: Joshua Criss
The Bats of North Florida
Florida is home to 13 species of bats statewide. Of these, 11 may be found in the Panhandle but only 3 are common enough to be routinely seen. The Brazilian free-tailed bat (Tadarida brasiliensis) is the most common. Medium sized with brown fur, they have a long tail, wrinkled cheeks, and roost in man-made structures.
Photo: IFAS
Second most common are Evening bats (Nycticeius humeralis). These dark brown to yellow bats have short ears with a broad hairless muzzle. They are tolerant of other bat species often roosting in tandem with them.
Photo: IFAS
Finally, the panhandle is home to Southeastern Myotis (Myotis austroriparius). Easily the smallest of these bats, they are dull gray to brown with a lighter belly and long hairs between their toes. This species is the bat most likely to eat mosquitoes.
Photo: Jeff Gore, FWC
Finally, the panhandle is home to Southeastern Myotis (Myotis austroriparius). Easily the smallest of these bats, they are dull gray to brown with a lighter belly and long hairs between their toes. This species is the bat most likely to eat mosquitoes.
A Word of Caution
No article on wildlife would be complete without a word of caution. Bats are wild animals and should be treated as such. Never touch a bat on the ground as it most likely is not healthy. Bats do not generally cause issues but have been known to be disease vectors. Call a professional to collect the animal and never bring it into your home.
Bats can be a wonderful tool in controlling pests on your property. Creating habitat can help reduce pesticide need and cost to the homeowner. For more information on bats, see this Ask IFAS document, or contact your local extension agent for additional information on this and any topic regarding your gardens and more.
