Insects use pheromones to attract their mates and communicate with each other. Ants use pheromones to tell fellow ants where to find food. Aphids use pheromones to warn each other about potential predators. And all insects use pheromones to call for a mate.
So what exactly are pheromones? Pheromones are substances that are secreted by an individual and received by another individual of the same species. In humans, pheromones are most commonly found in sweat and detected by the olfactory system. Most animals have a functioning vomeronasal organ inside their noses to detect and process pheromones. However, it is debatable whether adult humans possess a functional vomeronasal organ.
Although most of us may not be able to detect insect pheromones, scientists have been able to identify and synthesize the pheromones of many economically important insects. These pheromones are impregnated on rubber and plastic dispensers and placed in different types of traps depending on the pest. The pheromone traps attract males of the target species. These traps are commonly used for monitoring, but in some cases can be utilized to disrupt mating habits which can help control some pests.
The most common pheromone trap in this part of the country is probably a boll weevil trap. Growing up, I thought they looked like little green lighthouses. These traps consist of a yellow-green cannister with an inverted funnel on top that contains the pheromone. While you may not be growing cotton in your home garden, there are some other common insect pests you may want to monitor and possibly disrupt.
Pecan nut casebearer trap with pheromone bait. Photo Credit: UGA Cooperative Extension
Pecan Nut Casebearer (PNC) – These moths are gray with a dark line of scales on their forewings. PNC moths are about 1/3 inches long. They lay their eggs on the outside of pecan husks in April/early May. Their larvae bore into the base of developing nuts and remain inside the nuts for four to five weeks to feed then pupate. A tent-type trap with pheromone can be hung in a pecan tree in April or May to help monitor for this insect. Depending on how many trees you have, multiple traps can be installed to possibly disrupt the mating cycle of this pest.
A yellow sticky trap with Asian citrus psyllids circled. Photo Credit: Matt Lollar, University of Florida/IFAS Extension – Santa Rosa County
Asian Citrus Psyllid (ACP) – These tiny insects are about the size of the tip of a pencil (about 1/8 inches long). They vector the Huanglongbing (HLB) disease also known as citrus greening. This disease blocks the nutrient uptake tissue of citrus trees and eventually kills infected trees. Traps consist of a yellow sticky card with a pheromone bait sometimes impregnated on the twist tie hanger. The citrus industry has been heavily impacted by citrus greening, so monitoring for this pest is very important.
An abundance of clearwing moths on a pheromone trap that has been pulled apart. Photo Credit: Matt Lollar, University of Florida/IFAS Extension – Santa Rosa County
Clearwing Moth – There are numerous species of clearwing moths that bore into the trunks of fruit and ornamental trees and shrubs. One of the most common is the peachtree borer. These insects don’t look like a typical moth. Instead, they resemble wasps. Tent-type pheromone traps can be used to monitor for clearwing moths and potentially disrupt their mating habits. Another common clearwing moth is the ash borer (lilac borer). As their name would suggest, these moths bore into the wood of ash trees, but they also like various Ligustrum species and olive trees.
These are just a few of the species of insects that can be monitored by pheromone traps. To help with the timing of trap dispersal and placement, you should get a grasp of concept of “Degree Days”. Degree day accumulation is used to predict important life events for particular insects such as the average egg laying date, egg hatch date, and larval development. More information on calculating degree days can be found in the article “Predicting Insect Development Using Degree Days” from the University of Kentucky. Fortunately for us, we can skip some of the math by utilizing the AgroClimate Growing Degree Days Calculator. Simply select the weather station closest to you on the provided map and a graph will appear.
Welcome to the world of symbiotic serenity, where ants and aphids work in harmony to create a thriving ecosystem. Ants farming aphids is a fascinating phenomenon in nature, where ants tend to aphids, protecting and nurturing them like precious livestock, while aphids provide the ants with a sweet and nutritious honeydew secretion.
The relationship between ants and aphids is complex and benefits both parties. Aphids, which are soft-bodied sucking insects that feed on plant sap, secreting honeydew – a sugary secretion that aphids produce as waste from their sap consumption. This sweet substance is highly attractive to ants, who actively tend to aphids in order to obtain honeydew as a food source.
One of the most fascinating aspects of ant farming aphids is the behavior exhibited by ants when caring and protecting aphids. Ants are known to carefully tend to aphids, often referred to as “herding”. In doing so, they stroke the aphids with their antennae, stimulating them to release honeydew. Ants then collect and consume this honeydew, which serves as a valuable source of nutrition for them.
Aphids also benefit from this mutualistic partnership by relying on ants for protection from predators such as ladybugs, lacewings, and other aphid predators. In the presence of ants, aphids are less likely to be attacked by natural enemies, which allows them to feed and reproduce more freely. In addition, ants can transport aphids to new feeding sites, which helps aphids access fresh sources of sap.
However, this mutualistic relationship between ants and aphids can also pose problems for gardeners and homeowners. When ants protect aphids from natural enemies, this can result in increased aphid populations and plant damage. Therefore, it is important to control ant farming of aphids in order to manage aphid infestations effectively.
There are several methods gardeners/homeowners can use to manage ant farming of aphids:
Early detection is key. Regularly check for aphids at least twice a week while plants are growing rapidly.
Utilize natural enemies of aphids such as parasitic wasps, lady beetles, lacewing larvae, soldier beetles, and syrphid fly larvae. These insects can help keep aphid populations at an acceptable threshold.
Ant management is crucial. A band of sticky material can be wrapped around the trunk to prevent ants from reaching the aphids.
Prune and dispose of infested branches.
Insecticidal soaps and oils can be used to suffocate aphids. However, these products only kill aphids on contact. Other synthetic insecticides like malathion, permethrin, etc. are alternatives that can control aphids, but they may harm natural enemies and pollinators such as bees.
*Important to note, follow all manufacturers instruction when using chemical products.
In conclusion, ants farming aphids is a captivating example of mutualistic interactions in nature and serve as a compelling reminder of the wonders and intricacies of the natural world.
While the azalea blooms are beautiful, it’s hard to remember what the leaves looked like last summer. But, if you look carefully, you may see some off-colored, bleached out leaves. Those are from a piercing-sucking insect. Its azalea lace bug, Stephanitis pyrioides. They overwinter as eggs on the underside of infested leaves or in the leaf litter or mulch under the shrub. Eggs hatch in late March and early April. The insect then passes through five nymphal instars before becoming an adult. It takes approximately one month for the insect to complete development from egg to adult and there are at least four generations per year. Valuable plants that are susceptible to lace bug damage should be inspected in the early spring for the presence of overwintering lace bug adults, eggs and newly hatched nymphs. Inspect these plants every two weeks during the growing season for developing lace bug infestations.
Damage caused by azalea lace bug, Stephanitis pyrioides (Scott), feeding. Photograph by James. L. Castner, University of Florida.
Both adults and nymphs have piercing-sucking mouthparts and remove sap as they feed from the underside of the leaf. Lace bug damage to the foliage detracts greatly from the plants’ beauty, reduces the plants’ ability to produce food, decreases plant vigor and causes the plant to be more susceptible to damage by other insects, diseases or unfavorable weather conditions. The azalea can become almost silver or bleached in appearance from the feeding lace bug damage.
Adult azalea lace bug, Stephanitis pyrioides (Scott). Photograph by Jamba Gyeltshen, University of Florida.
However, lace bugs often go undetected until the infested plants show severe damage sometime into the summer. By then several generations of lace bugs have been weakening the plant. Inspecting early in the spring and simply washing them off the underside of the leaves can help to avoid damage later and the need for pesticides.
Adult lace bugs are flattened and rectangular in shape measuring 1/8 to 1/4 inch long. The area behind the head and the wing covers form a broadened, lace-like body covering. The wings are light amber to transparent in color. Lace bugs leave behind spiny black spots of frass (excrement).
Lace bug nymphs are flat and oval in shape with spines projecting from their bodies in all directions. A lace bug nymph goes through five growth stages (instars) before becoming an adult. At each stage the nymph sheds its skin (molts) and these old skins often remain attached to the lower surface of infested leaves.
Azalea leaf with azalea lace bugs, Stephanitis pyrioides (Scott), and excrement spots. Photograph by James. L. Castner, University of Florida.
Azalea lace bug eggs are football-shaped and are transparent to cream colored. Lace bug eggs are found on the lower leaf surface, usually alongside or inserted into a leaf vein. Adult females secrete a varnish-like substance over the eggs that hardens into a scab-like protective covering. Other plant species, such as lantana and sycamore, may have similar symptoms. But, realize that lace bugs are host specific. They feed on their favorite plant and won’t go to another plant species. However, the life cycle is similar. Be sure to clean up all the damaged leaves. That’s where the eggs will remain for the winter. Start next spring egg-free.
Written by: Muhammad Adnan Shahid and Mujahid Hussain
What made this freeze event damaging?
The duration of temperatures below freezing determine the amount of damage to citrus plants. In January 2023 the temperature dropped down to 17 F and stayed at that temperature for a longer time than in recent years. Unlike 2022-23, during the winters of 2013-14, the recorded low temperature was 18 F for half an hour. Similarly, during 2014-15, the temperature touched 19 F and stayed only for 15 minutes. Except for these two winters, in the past 12 years, temperatures never dropped below 20 F. What made this freezing event of December 2022 devastating is the long freezing hours between 17-20 F for 11 hours and even more the temperature stayed for about an hour at 17 F (Fig. No.1).
Fig. No.1. Shows the temperatures (17-20 F) duration during the past winters of 2011-2023. The temperature data is retrieved from Florida Automated Weather Network, UF/IFAS Extension Service (https://fawn.ifas.ufl.edu/). During these years, according to this data, only in December 2022, the temperature fell to 17 F which caused severe damage to the citrus in North Florida.
Symptoms After Freeze
Early Symptoms
The duration of appearance of symptoms after freezing was different for different citrus varieties. Even within the same varieties, the age of the plant and the rootstock are also factors that determined the duration of the appearance of symptoms. For example, in the UF 950 rootstock evaluation block at North Florida Research and Education Center in Quincy, the symptoms appeared on young UF 950 plants on Sour orange rootstock after 24 hours and after three days the plant completely turned brown.
Fig. No. 2. Shows the effects of freezing on UF 950 on Sour orange rootstock after day 1 (a) and day 3 of freezing (b). The young plants completely turned brown after three days of freezing.
However, a few symptoms that appeared after about 24 hours of freezing were similar on all plants regardless of age, variety, and rootstock. These include the blackening of new leaves and branches, hardening and yellowing of leaves, and formation of greenish and brownish patches (Fig. No. 3). The leaves of old citrus trees also became curly, stunted, and yellow. During the freezing event, the fruits on the trees became hard due to the nucleation of water.
Fig No. 3. Symptoms after 24 hours of freezing.
Low temperatures below freezing point cause the formation of ice crystals inside the plant, particularly in leaf tissue, causing a damaging effect of cell walls, and leaves appeared water-soaked upon thawing when temperature rose above the freezing point (Fig. 4).
Fig 4: Water-soaked leaves due to the ice crystals formation and their thawing inside the tissues.
Late Symptoms
One week after freezing, leaves started curling – turning brown and dry. At this stage, both leaves and fruits dropped very quickly, within a week giving plants a bush like appearance (Fig. No. 5 and 6). The fruits that remained on the tree developed multiple symptoms depending on the varieties. Fruits of some varieties formed micro-pits on the peel, however, the fruits of other varieties showed patterns of bright orange and yellow colors (Fig. No. 6a). The rotting leaves and fruits also attracted ladybug beetles, consequently this increased populations of other insects in freeze damaged citrus groves. You should keep in mind that the fruits that have been harvested after freezing need extra care as these fruits are more prone attacked by rotting fungi.
Fig. No. 5. Late symptoms of freeze damage on citrus trees.
Fig. No. 6. Fruits turn black and fall from the tree after freezing.
Fig. No. 7. The freezing caused the fruit’s peel to form patterns of bright orange and light-yellow color on the fruits (a). The rotting of leaves and fruits produces an odor after freezing that attracts ladybug beetles (b).
Bark splitting or cracking is a late symptom of freeze damage. Bark splitting or cracking will mostly be seen on stem and branches directly exposed to the sun. Bark splitting starts when sun light increases the temperature on the surface of the bark during daytime, but temperature drops after sun set resulting in unequal shrinkage and contraction of bark and inner plant tissues (Fig 8). Dropping of leaves and fruits is a good indication of plant survival, but if leaves dry while attached and don’t drop then it’s the sign of severe damage to internal tissue with a low chance of plant recovery (Fig 9)
Figure 8. Bark splitting and cracking as a consequence of freeze damage.
Fig 9. Tree with dried leaves still on the branches – it is indication of sever freeze damage to internal tissues
Recovering Plant After Freeze Damage
The recovery of plants is entirely linked to the level of damage to the plant internal tissues during the freeze event. Freezing damage can exacerbate the plant’s health, thereby minimizing the recovery of the plant. However, plants can recover if the internal cells (cambium and xylem and phloem) are alive enough to regenerate the branches. After an extreme freeze event, like what happened in December 2022, some citrus plants will recover in spring due to the presence of living cells in the branches and stems, but if the internal transportation system is damaged, the plant again starts to die back for the next several months. You should not apply any recovery techniques immediately after the freeze event. The best strategy is to wait for the spring to see if plants are giving any indication of recovery and observe their growth at least till May-June.
Fertilization
It is true that after damage, plants require nutrients to regenerate and grow but the application of nutrients is critical as excessive fertilization can also increase the risk of damage. Do not apply any fertilizer until new growth starts in spring. Fertilizers should be applied frequently, but rates should be decided depending on the degree of damage. The plants that are severely damaged will not be able to produce fruits in the next season therefore, the rate of fertilizer should be lowered to promote a slow recovery, as the damaged plants will not be able to uptake all applied nutrients due to slow water flow caused by minimum transpiration rate in the absence of leaves. In this case, any excessive application of fertilizer can cause toxic effects that can further halt the recovery of plants. The application of micronutrients is also important for the recovery of plants.
Plant Protection
Care should be taken to protect the plants from pathogens, insects, and weeds to enhance recovery. Citrus plants regenerate in the spring and aphids and whiteflies like to attack the young leaves, branches, and shoots. Therefore, an effective plant protection plan should be devised that includes the application of insecticides and fungicides. In general, one to two applications of fungicide should be planned along with nutritional spray to prevent infection on new growth. Removal of all fruit from freeze damaged trees is also important for quick recovery (Fig 10)
Fig 10. Freeze damaged stems with living and non-living tissues. Stem with living tissues will recover easily as compared to those with dead tissues
Fig 11: Fruit are removed from freeze-damaged tree
Pruning
Pruning should be avoided because it is not clear how much damage has been done to the plant. Pruning should be delayed until spring or summer. Ideally, pruning should be done on living wood to make sure that all the damaged parts have been removed. If the citrus tree has been damaged below the rootstock/scion union, it is better to re-graft the new scion on the rootstock instead of pruning. Pruning of trees that have been damaged below the scion union will result in the generation of rootstock. Therefore, re-grafting the plant or replanting is the best option. The Fruit Physiology Lab at NFREC-Quincy is developing tissue imaging techniques for quick estimation of percentage of tissue damage in freeze affected citrus tree shoots and roots.
Irrigation
Irrigation after freeze damage should be reduced. Damaged plants do not uptake as much water as healthy plants, therefore, excessive water in roots can cause the nutrients to move away from the plants and even can cause suffocation for young emerging roots. It is not recommended to completely cut off the water supply, because this can further damage the plants.
Research
The Fruit Physiology Lab at NFREC-Quincy is developing tissue imaging techniques for quick estimation of percentage of tissue damage in freeze affected citrus tree shoots and roots. A series of preliminary studies on the use of growth hormones (brassinosteriods, abscisic acid and jasmonic acid) and nutrients (silicon, K and Zn) to improve the cold hardiness is in progress. Preliminary data indicates that the use of growth hormones and plant beneficial nutrients has the potential to reduce freeze damage (Fig 12), but more detailed research and validation in large scale field trials is required. Postdocs and graduate students in The Fruit Physiology Lab at NFREC-Quincy are fully engaged with different research projects to improve the cold hardiness in citrus by hormonal and nutritional therapies. Recently, the lab got a funding to study new scion and rootstock combinations with high cold tolerance.
Fig 12. Effect of Silicon on cold hardiness of citrus plants sprayed with 100ppm of silicon one week before exposed to freezing temperature (-6 C) in programed freezing chamber
Conclusion
Florida has faced record freezing this winter season with recent events that occurred in the last week of December 2022 causing severe damage to citrus trees in North Florida. Citrus growers in South Florida are already fighting with the HLB disease and freeze damage in the North has added to the damage to the citrus industry in Florida. Careful planning and proper care can help damaged citrus trees to recover and start fruiting again. Trees with little damage to their woody parts will recover soon and start fruiting in the next season. However, the trees with more damage to their woody parts will take two or more years to recover enough to start fruiting. Therefore, proper assessment of the damage is important and recovery strategies should be devised according to the degree of damage. Recent freeze events gave us a big message that microsprinklers are not enough freeze protection for established trees. There is also a need to identify growth hormones, nutrients, or combinations of which can improve the cold hardiness of upper plant parts. In addition, exact estimation of recent freeze damage won’t be accurate until April-June.
This article was written by: Joanna Jaramillo Silva1, Rachel Mallinger2, Xavier Martini3
1 Ph.D. Student, University of Florida, Department of Entomology and Nematology
2 Assistant Professor, University of Florida, Department of Entomology and Nematology
3 Assistant Professor, North Florida Research and Education Center, University of Florida, Department of Entomology and Nematology
Bees are the primary pollinators of plants, essential in natural and crop environments for guaranteeing global food security to the human population. Florida is home of more than 300 species of native wild bees, which rely on pollen and nectar from flowers to survive. However, a global pollinator decline reported for honeybees and wild species (including insects, birds, and bats), is decreasing the worldwide provision of pollination services. Food limitation (pollen and nectar), resulting from decreasing flower diversity and quantity, is one of the multiple causes of pollinator decline. Pollinator-friendly plants are receiving attention from people of various disciplines such as the scientific community, stakeholders, Master Gardeners, and citizen science groups willing to participate in pollinator conservation efforts.
Domestic gardens
Domestic gardens comprise a substantial proportion of land in the urban landscape and are often the most significant component of green space; they play essential roles in conserving plant genetic resources, insects, and other wildlife, and have social and economic value. Gardens behave as islands of usable habitat surrounded by urbanization, and they present varying benefits for pollinators. There is generally a positive relationship between high pollinator abundance, flower diversity, and bloom evenness. Gardens for pollinators propose to solve the pollinator crisis by enlarging greenspaces in urban areas by planting more flowers in urbanized environment and by improving the diversity of floral resources for pollinators.
Pollinator friendly plants
There are different categories of floral traits: qualities that attract pollinators such as floral size and color, and physical characteristics that reward the pollinator (nectar and pollen quantity and quality). Flowers with higher quality and quantity rewards are more attractive to pollinators. Nectar provides the main sugar source for insect pollinators; its energetic value is determined by its sugar concentration. The volume of nectar produced by flowers will directly affected visitation by honeybees and bumblebees, butterflies, and birds. Pollen on the other side, consists of the main source of protein for most pollinators.
RECOMMENDATIONS
1. Provide a Mix of floral shapes and sizes.
There is usually a positive correlation between flower size and nectar volume: long tube flowers usually provide more nectar, whereas open or flat flowers provide more pollen. In addition, flower shapes are also associated with different pollinator types (Fig. 1). Long-tongued insects (Butterflies, and some bees) visit deep corolla tube flowers, while short-tongued pollinators (wasps, flies and some bees) remain on short tube or open corolla flowers.
Figure 1. Examples of plants with long tube flowers, short-medium, and open corolla flowers (From left to right: Butterfly on a Pardon my pink (Monarda didyma) (Credits: Joanna J. Silva); Carpenterbee on Salvia Indigo spires (Salvia longispicata x farinaceae) (Credits: Kelly Thomas); Sweat bee on Gaillardia pulchella) (Credits: Joanna J. Silva).
2. Provide a mix of flower colors
Color patterns influence the flower’s attractiveness and increase the efficiency of pollination by helping insects orient on the flower and guide them to the reward (Fig. 2). Bees prefer white, yellow, or blue-purple flowers. Orange, pink, and red flowers attract other pollinators such as butterflies.
Figure 2. Examples of native plants to Florida that display different colors Native to Florida (From left to right: Butterfly on Spanish needles (Bidens alba), Tickseed coreopsis (Coreopsis leavenworthii), Sckullcap (Scutellaria arrenicola), Pitcher sage (Salvia azurea), Swamp Rose-mallow (Hibiscus grandiflorus), Carpenterbee on False-Rosemary (Conradina grandiflora), Spotted beebalm (Monarda puctata), Blanket flower or Firewheel* (Gaillardia pulchella) . Credits: Joanna J. Silva *A recent discovery suggests that Firewheel is not considered native to Florida, but it is widely cultivated. It is probably not native to the rest of the eastern USA as previously thought (ISB: Atlas of Florida Plants (usf.edu), Gaillardia – University of Florida, Institute of Food and Agricultural Sciences (ufl.edu)).
3. Include a pollinator hotel
Add a bee nest box for the native bees that build their nests above ground. Solitary bees and wasps will take up residence in a pollinator hotel after you place it outside.
4. Provide flowers throughout the year.
Pollen and nectar collection varies seasonally for honeybees, while many other solitary bee species collect pollen continuously during adult foraging to feed their larvae. Design the garden to have three or more different plants blooming at any given time during the growing season, which is March through November in northern areas of the state (Fig. 3).
Figure 3. Honeybee on Viburnum (Winter) (Credits: Joanna J. Silva), Honeybee on Salvia Indigo spires taking nectar (Spring-Summer) (Credits: Walker Bensch), False Rosemary and Muhlly grass (Muhlenbergia capillaris) (Fall) (Credits: Joanna J. Silva).
5. Include native plants.
A “Florida native plant” refers to a species occurring within the state boundaries prior to European contact, according to the best available scientific and historical documentation. Florida is home to over 4,867 species of plants; 3,314 species are considered native of which 230 species are endemic.
6. Chose the right plant for each location.
Success depends on using the right plant in the right place, especially by considering plant’s cold hardiness (Fig. 4). Plant selection for landscapers, nurseries, and gardens requires individual site criteria and an evaluation of individual plant performance under different environmental circumstances, such as water, soil, and temperature.
Figure 4. Hardiness zones in Florida (http://planthardiness.ars.usda.gov).
