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.
by Beth Bolles | May 27, 2014
Frass (toothpick-like projections) extends from entry holes on a Jeruselum thorn damaged by cold temperatures. Photo by Beth Bolles, UF IFAS Escambia Extension
Winter injury and stress to many trees has attracted granulate ambrosia beetles to landscapes. These beetles mostly prefer weakened trees and cut stumps/logs but have been found to attack some healthy trees as well.
Adult beetles are very small, only about 1/16 inch long and bore into branches and trunks of many woody plants. They will push out small ‘strings’ of boring dust which look like toothpicks. These strings successfully protect the beetles as they establish galleries for laying eggs and rearing young within the tree. The adult females will introduce a fungus (ambrosia) into these galleries on which both the young beetles and adults feed.
Ambrosia Beetle Entry Point. Photo by Matthew Orwat
Many beetles will bore into a plant, mostly along the trunks. Plants may be ultimately killed, not by the beetles but by the fungi that interfere with the movement of fluids within the tree.
If you notice a tree infested with ambrosia beetles, it is best to remove the plant quickly. Remove all infested plant parts from your landscape. If you have a special plant that you want to save, you may be able to cut it back close to the ground, and allow it to resprout. It would be necessary to monitor the remaining portion carefully for reinfestation and treat with an approved insecticide to prevent beetle entry.
Interior of damaged stem.
by Gary Knox | May 20, 2014
Mexican Sycamore, Platanus mexicana.
Mexican sycamore (Platanus mexicana) is a fast growing, drought tolerant tree boasting smooth white-and-tan bark and large maple-like leaves with velvety, silver undersides. Native to northeastern and central Mexico, this tree’s cold hardiness is not well defined. However, Mexican sycamore grows well as far north as USDA Cold Hardiness Zone 8b in Texas and Florida.
Mexican sycamore is slightly smaller than our native American sycamore (Platanus occidentalis). While known to grow up to 80 feet or more in the wild, Mexican sycamore typically reaches a mature height of 50 feet in the landscape with a width of about 30 feet. The tree is deciduous with an upright rounded crown. Mexican sycamore grows best in full sun and is adapted to most soils, including alkaline soils. While considered drought tolerant, best success occurs when plants are irrigated until established.
The lobed, maple-like leaves are up to 8 inches wide and olive-green, sometimes turning yellow before falling in December. Leaf undersides of mature trees (at least 4 to 6 years old) develop short, dense, whitish hairs resulting in an attractive silvery appearance. The large leaves can be a nuisance if they fall where leaves must be raked. Like the American sycamore, the aggressive roots and relatively large mature size of this tree suggest it not be used near structures and pavement or under power lines.
Closeup of the silvery underside of a Mexican Sycamore leaf.
Male and female flowers are borne separately on the same plant from December through February and appear as greenish balls hanging from the branches. Aggregate-like fruit about 1 1/2 inches in diameter follow in April through August.
Mexican sycamore is resistant to bacterial leaf scorch, which can be a problem on American sycamore. This bacterium causes leaves to curl and turn brown and may eventually kill American sycamore. Two occasional fungal diseases affecting Mexican sycamore are anthracnose and powdery mildew. Anthracnose causes moderate to severe leaf drop during cool, wet springs. Initial symptoms are light brown areas forming along the veins of new leaves; if severe, anthracnose can cause cankers as well as leaf drop. Powdery mildew appears as a whitish dust on leaves.
Sycamore lace bugs may feed on leaf undersides in late summer and fall. The feeding results in a stippled appearance on the top of the leaf and black spots of feces on the underside. So far, observations of this tree in Florida suggest infestations of sycamore lace bugs are not as severe as on American sycamore. Aphids may also feed on leaves; they cause little damage to the tree but exude honeydew upon which sooty mold grows and turns leaf surfaces black.
Mexican sycamore is an attractive, smaller statured alternative to American sycamore. Unfortunately, it is not commonly grown by Florida nurseries and may be difficult to find.
Platanus mexicana (Mexican sycamore) has not yet been evaluated using the IFAS Assessment of Non-Native Plants in Florida’s Natural Areas (http://plants.ifas.ufl.edu/assessment/). Without this assessment, the temporary conclusion is that P. mexicana is not a problem species at this time and may be recommended.
by Taylor Vandiver | Apr 29, 2014
Now that spring has finally sprung and summer is well on its way, you may find yourself taking a stroll through your landscape and assessing damage done by late cold spells. However, it may not be a frost problem that has your plants looking worse for the wear. They could be experiencing nutritional imbalances which affect overall plant health. Most cases involving nutrition issues in plants can be linked back to the soil. Therefore, if you suspect a problem I suggest testing your soil to ascertain pH and nutrient levels. You can obtain a soil test kit at your local UF IFAS Extension office. Another way to diagnose your plant damage is to visually catalog its symptoms. Symptoms of mobile nutrients, such as nitrogen and phosphorus, tend to reveal themselves on older leaves first. Whereas, immobile nutrient symptoms (i.e. boron and calcium) will show up on newer leaves. These flow charts can help to narrow down which essential element may be lacking in your plant’s diet.
Mobile Nutrient Symptoms.
Immobile Nutrient Symptoms.
by Alex Bolques | Mar 25, 2014
Black Titi in bloom. Flower clusters upright at tips of branches. An excellent source of nectar and pollen for honey production. Image: Alex Bolques
Black Titi (also known as Spring Titi or Buckwheat Tree (Cliftonia monophylla (Lam.) Britton ex Sarg. is a native shrub or tree that can be found growing along streams and boggy areas of the Florida Panhandle. It can tolerate acidic wetland soils and once established can also tolerate dry soils in the landscape. Black Titi can reach 15 – 30 feet in height with 3 – 4 inches of trunk diameter. Its bloom period lasts February through March.
Bee visits a Black Titi flower. Image credit: Alex Bolques
Beekeepers love it because it is a wonderful source of nectar and pollen for honey production. Beginning beekeepers may confuse Black Titi with White Titi (also known as Summer Titi or Swamp Titi (Cyrilla racemiflora L.). It should not be grown as a honeybee pollinator plant. The nectar and/or pollen of White Titi can promote a condition known as “Purple brood”, which can be detrimental to honeybee immature stages.The flower of the spring flowering Black Titi is a raceme, a cluster of flowers along a central stem, that appears as an upright cluster on the tip of branches. The flower of the summer flowering White Titi is also a raceme, not as upright, more elongated. Visit the USDA Natural Resource Conservation Service plant database website and click on the image tab to see Black Titi (Buckwheat Tree) or White Titi (Swamp Titi) to view differences in flower morphology.
by Julie McConnell | Feb 18, 2014
Lichen on trunk of oak tree. Image: Julie McConnell, UF/IFAS
Spanish moss and lichen have earned an inaccurate reputation for damaging trees and shrubs in the Florida landscape. Although they may be found in plants that are in decline or showing stress symptoms, they are simply taking advantage of space available to survive. Both plants are epiphytes and are obtaining moisture and nutrients from the atmosphere rather than from the plants they rest upon.
Spanish moss. Image: Julie McConnell, UF/IFAS
Lichen are more commonly found on plants that are in poor health because they need a plant that is growing slowly and access to sunlight. These conditions can typically be found in thin canopies of trees and shrubs under stress. Although they are firmly attached to the surface of the plant, they are not taking nutrients from the tree or shrub, but rather from the air and other sources such as organic debris and bird excrement. If you find lichen on your landscape plants, look further into what stress factors might be causing the plant to grow slowly such as compacted soil, extreme weather conditions, drought stress, disease or insect pressure.
Spanish moss does not harm trees and many people find it an appealing asset to their landscapes. Common misconceptions about Spanish moss include that the weight causes branches to break and that it is a host site for chiggers. Spanish moss is very light and any additional weight is typically insignificant. Although it may harbor some insects and provide nesting material for birds and other wildlife, Spanish moss in trees is not a site conducive to chiggers because they favor low-lying moist environments.
To read more about Spanish moss, lichens, and other common epiphytes please read the EDIS publication “Spanish Moss, Ball Moss, and Lichens – Harmless Epiphytes.”
