by Sheila Dunning | Aug 19, 2014
Pine bark beetles are frequent pests of stressed pines in the southern United States. The five most common southern pine bark beetle species include three in the genus Ips. Ips beetles usually colonize only those trees that are already stressed, declining, or fallen due to environmental factors. Infestations may occur in response to drought, root injury, disease, lightning strikes or other stresses including flooding.
Ips calligraphus usually attacks the lower portions of stumps, trunks and large limbs greater than 4” in diameter. Early signs of attack include the accumulation of reddish-brown boring dust on the bark, nearby cobwebs or understory foliage. Ips calligraphus can complete their life cycles within 25 days during the summer and can produce eight generations per year in Florida. Newly-emerged adults can fly as far as four miles in their first dispersal to find a new host tree, whichever one is the most stressed.
Most trees are not well adapted to saturated soil conditions. With record rainfall this past April, the ground became inundated with water. When the root environment is dramatically changed by excess moisture, especially during the growing season, a tree’s entire physiology is altered, which may result in the death of the tree.
Water saturated soil reduces the supply of oxygen to tree roots, raises the pH of the soil, and changes the rate of decomposition of organic material; all of which weakens the tree, making it more susceptible to indirect damage from insects and diseases.When the ground becomes completely saturated, a tree’s metabolic processes begin to change very quickly. Photosynthesis is shut down within five hours; the tree is in starvation mode, living on stored starches and unable to make more food. Water moves into and occupies all available pore spaces that once held oxygen. Any remaining oxygen is utilized within three hours. The lack of oxygen prevents the normal decomposition of organic matter which leads to the production and accumulation of toxic gases such as carbon dioxide, methane, hydrogen sulfide and nitrogen oxide. Additionally, within seven days there is a noticeable root growth loss. Roots only develop when soil oxygen levels are at 5% -15%. Over time, the decaying roots are attacked by pathogens. The loss of root mass from decay and fungal attack leaves the tree prone to drought damage. After only two weeks of saturated soil conditions the root crown area can have so many problems that decline and even death are imminent.
When a tree experiences these anaerobic soil conditions it will exhibit symptoms of leaf loss with minimal to no new leaf formation. This usually appears two to eight weeks after the soil dries out again. Many trees will not survive, especially the more juvenile and mature trees. However, well established trees may still decline several years later, if they experience additional stresses such as drought or root disturbance from construction.
There is little that can be done to combat the damage caused by soil saturation. However, it is important to enable the tree to conserve its food supply by resisting pruning and to avoid fertilizing until the following growth season. Removal of mulch will aid in the availability of soil oxygen. Basically, it is a “wait and see” process. While water is essential to the survival of trees, it can also be a detriment when it is excessive, especially for drought tolerant pine species such as Sand Pine, which is prevalent throughout the coastal areas.
For urban and residential landscape trees, preventative strategies to avoid tree stress and therefore reduce the chances of infestation include the following:
1) avoiding compaction of, physical damage to, or pavement over the root zones of pines,
2) providing adequate spacing (15-20ft) between trees,
3) minimizing competing vegetation beneath pines,
4) maintaining proper soil nutrient and pH status and
5) limiting irrigation to established pine areas.
When infested trees are removed, care should be taken to avoid injury to surrounding pines, which could attract the more harmful pine bark beetle species Dendroctonus frontalis, the Southern Pine Bark beetle.
There is no effective way to save an individual tree once it has been successfully colonized by Ips beetles. In some cases, the application of an approved insecticide that coats the entire tree trunk may be warranted to protect high-value landscape trees prior to infestation. UF/IFAS Extension can assist with recommendations.
by Taylor Vandiver | Aug 4, 2014
Attracting Butterflies into Your Landscape
Have you been itching to add some life and color into your landscape? Why not plant a butterfly garden?! Butterfly gardens are a great way to add movement and life to an otherwise stagnant landscape. Most butterfly gardens are not only an attractant for our Florida butterflies, but are also a magnet for hummingbirds and beneficial insects. To start your garden all you need are a few key plants.
Gulf Fritillary. Photo Courtesy Scott Jackson.
Incorporate at least one host plant and one nectar plant into your garden. The host plant provides a suitable habitat for the female butterfly to lay her eggs. These eggs will hatch and the baby caterpillars will eat the leaves of the host plant. Host plants are often not as showy as nectar plants, nor are they even necessary to attract adult butterflies. However, while nectar plants invite butterflies into your garden to feed, host plants offer them a reason to stay and reproduce. And you can watch this entire cycle unfold in your own garden!
Most of your butterfly attractant plants will do best in full sun to partial shade. Try not to apply pesticides in areas where you want to maintain healthy caterpillar/butterfly populations. Providing water for butterflies is very important and easily done. One option is to fill a clay tray with sand and then place a rock in the center, where the butterfly can perch. Keep the sand wet, but avoid standing water. Feel free to contact your local extension office for more information on our winged friends!
Zebra Longwing, our state butterfly! Photo courtesy Scott Jackson.
Here are a few examples of butterflies and their preferred host plants:
o Host Plants – Fennel, Parsley, Bishopsweed
o Host Plants – Pawpaw
o Host Plants – Wild Lime, Hercules-club, Citrus spp.
o Host Plants – Ash, Black Cherry, Tulip tree, Sweetbay Magnolia
o Host Plants – Partridge Pea, Cassia
o Host Plants – Passion Vines
- Zebra Longwing (State Butterfly of Florida)
o Host Plants – Passion Vines
o Host Plants – Milkweed, Butterfly Weed
Here are nectar plants that will have the butterflies swarming to your garden:
- Firebush
- Milkweed
- Blanket Flower
- Sage (Salvia spp.)
- Butterfly Bush
- Blazing Star
- Yarrow
- Pentas
- Stoke’s Aster
by Larry Williams | Aug 4, 2014
Mud dauber, Photo Credit: UF/IFAS Extension
Paper wasp, Photo Credit: UF/IFAS Extension
I respect the fact that wasps can sting when threatened or disturbed. But I also respect the fact that they are beneficial.
Every time I’ve been stung by wasps, I either accidentally disturbed a nest that I didn’t know was there or I intentionally disturbed the nest and paid the price.
Paper wasps are common in Florida. They frequently construct and attach their paper-like nests to building eaves or the ceilings of porches. The adults seek out caterpillars, which they sting and paralyze. They then take the caterpillars back to their nest and place them in individual cells as food for the developing larvae.
I’ve witnessed the paper wasp as it stings and carries away a caterpillar from my vegetable garden. They are busy insects and are doing us gardeners a favor by reducing the population of caterpillars in our landscapes and gardens.
There are other beneficial wasps in Florida. Mud daubers, for example, build their mud-like nests on the sides of buildings close to human activity.
The mud dauber is not as aggressive as the paper wasp. It rarely stings people. It stings and paralyzes spiders. The mud dauber lays an egg on each paralyzed spider and seals it inside a chamber in its earthen nest. Upon hatching, the wasp larva feeds on the body of the spider. An emergence hole is made as the young wasp leaves the mud nest.
It may not be wise to tolerate all wasp species living in close proximity to your home. Even though yellow jackets, a type of wasp, could be considered beneficial, they are too aggressive and too likely to repeatedly sting to have as close neighbors. I also would be concerned with any type of wasp or bee nest existing in close proximity to individuals with a known allergy to insect stings.
Just because an insect has the ability to sting, it’s not all bad. Wasps can serve a beneficial purpose. But you’ll have to decide for yourself how close to you they can build their nests. The front porch may be too close.
by Julie McConnell | Jul 1, 2014
Panhandle residents have seen caterpillars in abundance this June. One common visitor to pecan trees is the Walnut Caterpillar Datana integerrima. The walnut caterpillar has a very narrow host range and feeds only on trees in the Juglandaceae family which includes walnut, pecan, and hickory trees. They are sometimes seen on other plant material, but feeding on non-host plants is unlikely.
Walnut caterpillar feed on the leaves of host trees through several growth stages and molts until they have reached the final larval instar and are ready to pupate into an adult moth. Their color changes from light green when newly hatched to reddish-brown to almost black with long white hairs as they mature. The caterpillars group together in large masses and may hang from each other and dangle from the tree branches when molting. Instead of creating a cocoon in the tree, the walnut caterpillar moves to the ground beneath the tree and burrows into the soil or leaf litter to pupate and emerges later as a moth.
What can you do if your pecan tree is hosting walnut caterpillars?
Although the numbers seen on trees may be alarming, a healthy tree can tolerate some feeding damage. Stripped branches may increases the chance of a lower yield of fruit because the removal of leaves does reduce the amount of energy the tree can produce, but overall health of the tree should not be significantly affected. However, many homeowners find falling caterpillars and their excrement unappealing and may decide to take steps to manage the population.
There are several natural enemies that feed on caterpillars, so avoid using a broad spectrum insecticide that might harm predatory insects and other animals. Consider using a biological control product such as Bt (Bacillus thuringiensis) that is only lethal to caterpillars. Other methods are “pick and squish” or drowning in a bucket of soapy water. Next year, in the spring, watch for masses of tiny green eggs on the underside of leaves and remove and destroy them before hatching.
For more information visit USDA Forest Service Forest Insect & Disease Leaflet 41 “Walnut Caterpillar”
by Alex Bolques | Jun 17, 2014
Homeowner accounts of white fluffy woolly masses on woody ornamentals have been on the rise. They can appear on the ends of a wide variety of woody ornamental branches in the landscape. A closer inspection of these white woolly masses can provide the curious observer with a startling surprise. “It’s Alive!” It moves and seems to jump at you, most likely jumping away from you. Once you have recovered from the mildly frightful encounter, you ask yourself, “What was that?”
Adult citrus flatid planthopper, Metcalfa pruinosa
(Say). Credits: Photograph by: Lyle J. Buss, University of Florida
They are planthoppers (Metcalfa pruinosa), an insect in the order Hemiptera. The common name for this woolly looking planthopper is the citrus flatid planthopper (CFP). As the name implies, they occur on citrus but can also be found on many woody ornamentals and fruit trees. The adult planthopper wing arrangement is tent-like, meaning that the forewings are held over the insect abdomen in a tent configuration.
Nymph of the citrus flatid planthopper, Metcalfa
pruinosa (Say). Credits: Photograph by: Lyle J. Buss,
University of Florida
The nymph, young immature insect, produces the white woolly material that is characteristic of CFP. At first sight, they can be mistaken for mealy bugs, which may look similar since they are covered with cottony white filaments. They can also be mistaken for cottony cushion scale.
Mealybugs. Credits: James Castner, University
of Florida
Cottony cushion scales, Icerya purchasi, on twig.
Credits: James Castner, University of Florida
In both of these cases of mistaken identities, the insect will not jump or hop around. No chemical control is necessary although sooty mold can occur on heavily populated plants. In that case, a soapy water treatment can be applied.
Follow these links to more information on the citrus flatid planthopper, mealy bugs, and cottony-cushion scale.
by Larry Williams | Jun 3, 2014
Glistening webbing formed by tree cattle (psocids) Photo credit: Doug Caldwell, University of Florida
Many people are noticing small insects on trunks and branches of their trees. When disturbed, these insects move in a group and are commonly called tree cattle because of this herding habit. They are ¼ inch brownish-black insects with white markings.
Some people assume that these insects will injure their trees but they are harmless. They could be considered beneficial.
These insects are called psocids (pronounced so-cids). They have numerous common names including tree cattle and bark lice. They feed on lichen, moss, algae, fungi, spores, pollen and the remains of other insects found on the tree’s bark. As a result, they are sometimes referred to as bark cleaners.
Tree cattle may form webbing. This webbing is tight against the tree’s trunk and/or limbs. It appears suddenly. The webbing is used as a protection from weather and predators. Underneath you may find psocids.
The glistening webbing may attract a person’s attention resulting in the tree being visually inspected from top to bottom. A dead branch or other imperfections in the tree may be noticed and then wrongly blamed on the tree cattle. I’ve talked to homeowners that sprayed their trees with insecticides or that hired pest control businesses to treat the trees as a result of finding the webbing/psocids. One person told me that he cut down a tree after finding tree cattle. He wrongly assumed that these insects were pests that might move through the area and kill trees. He thought he was doing a good thing.
Adult female psocids lay eggs in clusters on leaves, branches and tree trunks. After hatching, the immature insects (nymphs) remain together under their silk webbing. Adults have wings which are held roof-like over their body. Nymphs are wingless. Psocids usually have several generations per year in Florida.
After seeing the webbing and/or insects, many people insist on spraying insecticides because they believe these insec
Under the webbing live hundreds of psocids. Photo credit: UF/IFAS Jim Castner
ts are damaging their trees. But as mentioned, they are bark cleaners and do not damage trees. If the silk webbing is considered unsightly, a heavy stream of water from a garden hose can be used to wash insects and webbing off infested trees. If nothing is done, the webbing usually goes away in several weeks.
Psocids can be found on many rough-barked hardwood trees and palms. Occasionally, they may be found on wood siding, fence posts or similar areas.
