Types of Locust Trees Listed and Explained With Pictures

Types of Locust Trees Listed and Explained With Pictures

Natives to North America, locust trees are well-known for their strong wood and fall foliage. This article provides a brief overview about the common types of locusts that are also popular as landscape trees.

Natives to North America, locust trees are well-known for their strong wood and fall foliage. This article provides a brief overview about the common types of locusts that are also popular as landscape trees.

Locust wood is so hard and durable that it is used for making rails and fence posts. As a young man, President Abraham Lincoln used to split rails from locust trees. Thus he earned the nickname Rail Splitter.

Locusts are fast-growing, hardy trees that belong to the pea family Fabaceae or Leguminosae. Most of the locust species are classified into two genera – Gleditsia and Robinia. While the genus Gleditsia has 12 species, there are around ten species in the genus Robinia. The most popular among them are Robinia pseudoacacia (black locust) and Gleditsia triacanthos (honey locust). Both are deciduous, and are grown as landscape trees. You may also come across different locust cultivars.

Even the carob tree (Ceratonia siliqua) and the African locust bean tree (Parkia biglobosa) are called locust trees. They too belong to the family Fabaceae. Though there are more than 20 species of locust trees, two species are very popular. They are black locust and honey locust trees. Here is a brief overview about some of the characteristic features of these trees.

Black Locust

The Tree

Otherwise known as false acacia, the black locust tree (Robinia pseudoacacia), is fast growing and hardy. It can grow to a height of around 25 meters and a diameter of around one meter. You may come across some of the very old black locust trees that have a height of around 50 meters and a diameter of 1.5 meters.

Flowers

The black locust tree produces white flowers that are intensely fragrant; and are arranged on axillary, pendulous racemes. You may also come across some black locusts with pink or purple flowers. The flowers are produced in hanging clusters that can be four to ten inches long. Each flower is around an inch in length. Black locust flowers are consumed in some regions.

Leaves and Seed Pods

The leaves are pinnately compound, with a length of around 25 centimeters. Each leaf has nine to nineteen leaflets, that are roughly oval. The leaflets resemble our thumbprints, in size and shape. Each leaf has a single leaflet at the tip. The leaves turn yellowish during autumn. The legume fruit contains seeds. As compared to some other locust species, the seed pods of the black locust are small and light.

Bark and Thorns

A mature black locust tree produces numerous branches, and has a dark and deeply furrowed bark. One of the characteristic features of this tree is the short, prickly thorns that are located at the base of the leaves. The thorns of black locust trees are short, when compared to that of honey locusts. They do not have the branched thorns that are seen on the trunk of honey locust trees.

Though they are mainly grown for ornamental purposes, black locusts are much valued for their hard and durable wood. In some regions, the black locust is cultivated as a honey plant. In other words, the blooms of black locust is a source of nectar for honey bees in that area. Apart from the flowers, the bark, seed pods and every other part of this tree are considered toxic; but it is also said that the toxicity can be nullified through cooking. It has also been contended that the tender seed pods as well as the seeds can be boiled and consumed.

Honey Locust

The Tree

The honey locust tree (Gleditsia triacanthos) is otherwise known as sweet bean, sweet locust, and honey shuck. It is a fast-growing tree that grows to a height of around 30 meters and a diameter of around one meter. The honey locust is grown for ornamental purposes, as it has an attractive fall foliage. Some varieties of honey locusts, like Gleditsia triacanthos inermis, do not have thorns and seed pods. The image below depicts a sunburst honey locust tree that has no thorns and seed pods. You may also come across honey locust cultivars that are very popular as landscape trees.

Leaves

The bright green leaves are pinnately compound, but you may also find compound pinnate leaves in honey locust trees. Unlike black locusts, most of the leaves of honey locusts have no leaflet at the tip. The bright green leaves turn yellow during early autumn. Both black and honey locust trees produce new leaves during late spring. However, honey locusts develop new leaves, slightly earlier than the black ones.

Thorns

Honey locusts carry thorns on their branches, and at the base of leaves. These thorns are longer (around 3 to 10 cm); and are seen in dense clusters. The young and tender thorns are green and soft. As they age, the thorns turn harder and reddish brown. Fully mature thorns are brittle, and are usually ash gray in color. The tree is also known as thorny locust.

Flowers

The strong-scented, creamy-green flowers are very small; and develop in clusters. Flowers of honey locusts are often found as inconspicuous spikes that develop from the base of leaf axils. While the male and female flowers are produced in different trees, some of them have both types in the same tree. The male flowers are found as dense clusters, whereas the female flowers are loosely arranged on the rachis.

Seed Pods

The female honey locust trees produce long, flat and twisted fruits (or seed pods). The pale green seed pods turn reddish-brown and black, when they mature. As they ripen, the seed pods produce a strong smell. The sticky pulp inside the pods are edible. These seed pods fall off the tree during winter.

Unlike black locusts, honey locust trees are not honey plants. The name may be derived from the sweetness of the pulp that is also used for making beer. Its timber is highly valued for making furniture, as it is hard and durable. The seeds pods are used as fodder for livestock. Like black locust, different parts of the honey locust tree are also used for medicinal purposes.

These are some of the interesting facts about locust trees. A basic understanding about their characteristic features may prove helpful for locust tree identification. In order to identify a locust tree; check the size of the tree, the color and texture of its bark, shape and arrangement of leaflets, flower color and structure, and nature of seed pods and thorns.

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How to Manage Pests

Pests in Gardens and Landscapes

Leaffooted Bug

In this Guideline:

Leptoglossus zonatus adult.

Leptoglossus clypealis adult showing sharply pointed clypeus.

Leptoglossus occidentalis adult.

Leaffooted bug eggs are laid end to end in strands.

Leaffooted bug nymph.

An adult parasitoid lays its eggs inside of the eggs of leaffooted bug.

Leaffooted bugs are medium to large sized insects that feed on fruits, fruiting vegetables, nuts, and ornamentals. They have piercing-sucking mouthparts that allow them to feed on plant parts, particularly seeds. Leaffooted bugs are in the family Coreidae and get their name from the small leaf-like enlargements found on the hind leg. They are closely related to other sucking insects, such as stink bugs (family Pentatomidae) that can also suck juices from plants.

IDENTIFICATION

There are three common species of leaffooted bugs that are native to California and the western United States. These include Leptoglossus zonatus, L. clypealis, and L. occidentalis. Adults of all three species are about 0.75 to 1 inch long and have a narrow brown body. Adults of all three species are similar in appearance, except that:

  • L. zonatus has two yellow spots just behind the head (on the pronotum).
  • L. clypealis has a thorn-like projection called a clypeus that extends forward from the tip of the head.
  • L. occidentalis has neither of these features.

All three species have a white zigzag pattern across the wings: this pattern is prominent in L. zonatus and L. clypealis and is relatively faint in L. occidentalis.

The brown, cylindrical eggs of all three species are laid end-to-end in a string-like strand on the host plant, often along a stem or leaf midrib. Most egg masses have 10-15 eggs, though more than 50 have been reported. Eggs hatch into small nymphs that have dark heads and dark legs on bodies that range in color from orange to reddish-brown. Small leaffooted bugs can be confused with nymphs of the assassin bug (Zelus renardii). Nymphs of this beneficial insect have light-colored legs and antennae and hatch from barrel-shaped eggs that are grouped together with a white cone top. As leaffooted bug nymphs become larger, they can easily be recognized by the development of the leaf-like projection on the hind legs.

LIFE CYCLE

Leaffooted bugs overwinter as adults, typically in aggregations located in protected areas, such as in woodpiles, barns or other buildings, palm fronds, citrus or juniper trees, under peeling bark, or in tree cracks. Cold winters kill many adults, and major outbreaks often occur after mild winters. Overwintered adults live from September/October until late spring. When weather gets warm, typically in March in the San Joaquin Valley and April in the Sacramento Valley, adults disperse to find food sources. Adults are strong flyers that may feed initially on the seeds of winter weeds and later move into gardens, landscapes, and farms in search of early-season fruit and a place to lay eggs.

Overwintering leaffooted bugs can lay over 200 eggs during a two-month period in the spring. Nymphs emerge from the eggs about 1 week after being deposited, after which they develop into adults in 5 to 8 weeks. Adults are long-lived and can lay eggs over an extended period, so the population can consist of all life stages by late June. At this time, overwintering adults are still alive as the first generation of their offspring develop into adults. During the spring and summer, there are typically two to three generations of leaffooted bugs. In the fall, all bugs develop until they become adults that overwinter in aggregations.

Population levels change from year to year depending on weather and parasitism of eggs. Populations are typically highest after mild winters that allow high survival of overwintering adults. Seasonal fluctuations in the number of bugs can also be related to rainfall, food availability, and the prevalence of natural enemies.

Host Plants

In the spring, leaffooted bugs often feed on thistles and other weeds. Adults migrate from weedy areas into gardens and landscapes, particularly when fruits have started to ripen. L. zonatus is the most destructive of the leaffooted bug species. It feeds on many types of plants and is most commonly reported by gardeners as a pest of tomatoes and pomegranates; farmers primarily report it as a pest of almonds, pistachios, and pomegranates. Other important hosts in California include young citrus fruit, cotton bolls, watermelons, and several ornamental trees and shrubs. L. clypealis also has a wide host range within gardens, landscapes, and farms and is the predominant species found on desert plants like palm trees, Joshua trees, and yucca. L. occidentalis, also known as the western conifer seed bug, is primarily found in association with conifer trees.

DAMAGE

Leaffooted bugs have piercing-sucking mouthparts that extend more than half of the length of the narrow body. They use this mouthpart to probe into leaves, shoots, and fruit to suck plant juices. The depth of the probing depends on the size of the bug: small nymphs feed shallowly on superficial plant juices, whereas adult bugs probe deep into fruit in search of seeds. If a hard seed is found, such as an almond kernel or juniper berry, the bug excretes digestive enzymes from its mouthparts to liquefy a small part of the seed so that it can be ingested. Leaffooted bug mouthparts are also known to carry a fungal yeast, Eremothecium coryli (formerly known as Nematospora). When leaffooted bugs feed, this yeast can be introduced into fruit causing a variety of symptoms usually related to discoloration. However, the yeast causes no damage that would limit the ability of the fruit to be harvested and consumed. This infection is most predominant when rains are abundant.

For most ornamental and many garden plants, feeding on the leaves and shoots causes no visual damage and is of little concern. The most destructive damage occurs when bugs feed on fruit. Early-season feeding on nuts like almonds and pistachios can cause the kernel to abort and die, and mid- to late-season feeding on nuts causes a black stain on the kernel. On pomegranates, late-season feeding as the fruit ripens generally causes no external damage but can cause aryls (seed-like structures) to darken and wither, especially if fungal spores gain entry into the fruit through the feeding wound. Large aggregations of leaffooted bugs can also leave excrement on the surface of the fruit that can reduce its aesthetic appeal. Feeding on small fruit (e.g., tomatoes) can cause the fruit to abort, while feeding on medium-sized fruit can result in depressions or discoloration at the feeding site as the fruit expands and ripens. Feeding on mature tomatoes can cause slight discoloration to the surface of the fruit that should be of no concern to backyard gardeners.

MANAGEMENT

During most years, leaffooted bug populations are low enough that damage to gardens is tolerable and damage to landscape plants is negligible. When outbreaks occur, a variety of methods will likely be needed to manage this pest, which may include removing overwintering sites or the use of weed host removal, row covers, physical removal, natural enemies, and insecticides. Achieving good control will likely require some combination of these methods.

Remove Overwintering Sites

Adult bugs overwinter in woodpiles, under the bark of eucalyptus, juniper, or cypress, and in outbuildings. Large numbers may pass the winter in culls of fruit such as pomegranates. Remove these overwintering sites where possible or inspect them for leaffooted bugs.

Weed Removal

Weedy areas serve as a food source for leaffooted bugs during winter and spring, when fruits are not available. Try to eliminate such areas near your garden or keep weedy areas closely mowed.

Row Covers

Covering plants with a row cover material can prevent feeding by leaffooted bugs. A row cover is a light, permeable material, usually made of polypropylene or polyester. Row covers are sometimes used to extend the harvest season past the first few frosts but are also valuable for preventing damage by a wide range of pests. Covers must be applied early, before bugs arrive and lay eggs on plants; otherwise, bugs will be trapped inside. Unfortunately, row covers will prevent pollinators and beneficial insects from reaching plants. Some garden plants like tomatoes are self-pollinating, but whiteflies or aphids may build up if beneficial insects are excluded.

Physical Removal

Thoroughly examine plants for all stages of the pest, daily to several times per week. The bugs may be hidden inside dense foliage layers or fruit clusters, and they may hide or fly when startled. Handpick and crush the bugs or brush them off plants into soapy water. Wear gloves because of the odor they will emit when handled. A handheld vacuum dedicated to catching the bugs can be effective at reducing numbers, if used regularly. It is especially important to remove the bugs as early in the season as possible, when the very young nymphs are tightly clustered together, and morning is best to reduce movement and flight. Be sure to also destroy the egg masses found on the underside of leaves.

For late-season infestations in pomegranate trees, prune trees so that there is a space between tree limbs and the ground. Leaffooted bug nymphs can easily be knocked out of the tree using a stick, by physically shaking the tree limbs, or using water from a pressure nozzle on a garden hose. Once bugs fall on the ground, they can be smashed. This method is effective against nymphs but will not dislodge eggs. It is less effective against adults, which are able to fly away. For this reason, this method should be repeated once every 1 to 2 weeks as necessary, until the majority of the bugs have disappeared. Laying a white ground cover beneath the plant can aid in seeing the insects when using this control method.

Natural Enemies

Native egg parasites, such as the tiny wasp, Gryon pennsylvanicum, if not disrupted, may reduce leaffooted bug populations by killing the eggs before they hatch. Adult leaffooted bugs may be parasitized by certain tachinid flies, such as Trichopoda pennipes, which lays its eggs on the sides of large nymphs or adults of several species of true bugs. Leaffooted bug predators include birds, spiders, and assassin bugs. Although they may control only a small number of the bugs, natural enemies are important to preserve because they control other pests as well. Avoiding use of persistent broad-spectrum insecticides and assuring pollen and nectar sources for adult beneficials are important ways to protect natural enemies.

Insecticides

Insecticides are rarely needed for leaffooted bug control because small blemishes on most fruit are tolerable in gardening situations and because landscape plants are rarely damaged. Also, because they are primarily seed feeders, leaffooted bugs are most common on garden plants near harvest, when the application of pesticides to fruits that are going to be consumed is undesirable. In addition, most insecticides available to homeowners only have temporary effects on the leaffooted bug.

However, in severe cases, insecticides can be considered as a last resort. If needed, insecticides will be most effective against small nymphs. Therefore, monitor infested plants for egg masses and try to make insecticide applications when small nymphs are present. The most effective insecticides against leaffooted bug are broad-spectrum, pyrethroid-based insecticides, such as permethrin. However, these products are quite toxic to bees and beneficial insects. Insecticidal soap or botanicals, such as neem oil or pyrethrin, may provide some control of young nymphs only. If insecticides are used close to harvest, make sure to observe the days-to-harvest period indicated on the insecticide label; and wash the fruit before eating.

REFERENCES

Chi, A.A. and R.F. Mizell III. Western leaffooted bug. University of Florida web site.

Bentley, W. J., R. H. Beede, K. M. Daane, and D. R. Haviland. 2012. Insects and Mites from UC IPM Integrated Pest Management Guidelines: Pistachio. UC ANR Publication 3461.

Grafton-Cardwell, E. E., D. Carroll, W. J. Bentley, D. R. Haviland and V. Walton. 2013. Insects and Mites from UC IPM Integrated Pest Management Guidelines: Pomegranate. UC ANR Publication 3474.

Zalom, F. G., C. Pickel, W. J. Bentley, D. R. Haviland, and R. A. Van Steenwyk. 2012. Insects and Mites from UC IPM Integrated Pest Management Guidelines: Almond. UC ANR Publication 3431.

PUBLICATION INFORMATION

Pest Notes: Leaffooted Bug

UC ANR Publication 74168

Authors: Chuck Ingels, UCCE Sacramento and David Haviland, UCCE Kern Co.

Produced by University of California Statewide IPM Program

PDF: To display a PDF document, you may need to use a PDF reader.

Statewide IPM Program, Agriculture and Natural Resources, University of California
All contents copyright © 2019 The Regents of the University of California. All rights reserved.

For noncommercial purposes only, any Web site may link directly to this page. FOR ALL OTHER USES or more information, read Legal Notices. Unfortunately, we cannot provide individual solutions to specific pest problems. See our Home page, or in the U.S., contact your local Cooperative Extension office for assistance.

Agriculture and Natural Resources, University of California

ipm.ucanr.edu

Mortal Combat — 5 Bad Bugs You’ll Battle This Summer

INCOMING! The following five awful pests will seek to utterly destroy both your garden and spirit this summer. How can you fight back against a voracious army that numbers in the tens of thousands? By reading this post and taking the advice tips from my friends at Orkin Termite Control Services.

Bad Bug #1 — Japanese beetle (above) Brief description: Unmistakable beetle with a green thorax, green head, and copper wings. Often dines (and mates) alongside hundreds of its fellow warriors. Good work if you can get it.

Favorite targets: It’s probably quicker to name what plants it doesn’t eat than the ones it does. Anything in the rose family (roses, apple, crabapple, plum, etc.) and mallow family (hibiscus, hollyhock, rose-of-Sharon, cotton, etc.) are toast, but it also consumes pines, crepe myrtle, annuals, perennials, and veggies.

Damage: Devoured flowers; skeletonized foliage (everything is consumed but leaf veins). Larvae (white grubs) in ground eat lawn roots, killing grass.

Fight back with: Spray target plants according to label directions with neem oil. Don’t spray flowers, though, as neem is toxic to bees. Sevin (carbaryl) is also very effective, if you don’t mind «chemicals.» Treat infested sod with a granular grub control applied with a spreader. Don’t bother with Japanese beetle traps. They only attract more beetles to your yard.

Bad Bug #2 — Aphid

Brief description: Aphids are small, blob like insects that suck plant juices. They can be yellow, green, orange, red, gray, or brown. Practically born pregnant, they multiply with amazing speed. The reason you see ants above is because ants «farm» aphids. They carry aphids to a host plant and drink the sweet honeydew aphids secrete. Yum.

Favorite targets: Almost any plant with juicy, green leaves and stems. They favor new, soft growth and flower buds. Often hide on leaf undersides. Don’t think I’ve ever seen a Chinese hibiscus without aphids.

Damage: Puckered, distorted, discolored leaves; dropping leaves and flower buds; stunted growth; black mold growing on leaves covered with aphid honeydew; plants contract diseases spread by aphids.

Fight back with: Fortunately, aphids are easy to kill. Spray according to label directions with neem oil, horticultural oil, or insecticidal soap. Or fill a spray bottle with 4-5 drops of liquid detergent to a quart of water and spray aphids wherever you see them.

Bad Bug #3 — Spider Mite

Brief description: OK, OK — spider mites aren’t true bugs that have six legs. They’re arachnids, like spiders, and have eight. They’re tiny — about the size of a sharp pencil point — and may be red, yellow, brown, or green. They suck plant juices and, like aphids, multiply amazingly fast. They usually hide on the undersides of the leaves. During severe infestations, they envelop leaves and stems with tiny webs.

Favorite targets: Almost any plant if the conditions are right. Spider mites like dry weather and low humidity. Indoor plants are spider mite candy.

Damage: The first thing you’ll notice on broadleaf plants is a speckling or bronzing of the leaves. Needleleaf evergreens often brown at the branch tips. Foliage yellows or browns and drops prematurely. Branches die back. Plants lose vigor and may die.

Fight back with: Water (surprise!) Spider mites hate getting wet. So the first thing to try is blasting them to kingdom come with a strong jet of water from the hose. Wet foliage also slows their reproduction. Or use the same controls Grumpy recommends for aphids.

Bad Bug #4 — Armored Scale

Brief description: Armored scales are weird bugs. Little scales have six legs and crawl onto the leaves and stems of target plants. There they insert feeding mouthparts into the plant to suck the juices, drop off their legs, build a protective shell over themselves to fend off predators, and remain in place until they die. Kinda like NASCAR fans. People often mistake them for harmless bumps or specks. Later, people regret this.

Favorite targets: Just about any kind of plant. Indoor plants are particularly susceptible because a scale’s natural predators aren’t around.

Damage: Foliage becomes spotted; growth is stunted; plant dies back; black mold grows on sweet honeydew secreted by the scales.

Fight back with: The first weapon I’d choose would be horticultural oil. Applied according to label directions, it smothers scales. Be sure to wet all upper and lower leaf surfaces, all stems, and the trunk too if it has scales. Or if you’re OK with «chemicals,» apply a systemic insecticide, such as Bayer Advanced 12 Month Tree & Shrub Insect Control.

Bad Bug #5 — Brown marmorated stink bug

Brief description: About a half-inch long, this shield-shaped insect is distinguished by its banded wings and antennae. It lays clusters of 20 to 30 elliptical yellow or yellow-red eggs on the underside of leaves of target plants. A recent arrival from Asia, it builds up incredible numbers in agricultural areas. When you smash one, it stinks.

Favorite targets: Fruits and fruiting vegetables, especially tomatoes, peppers, eggplants, apples, peaches, plums, beans, corn, strawberries, figs, and citrus.

Damage: Feeding causes spotted, distorted, and dropping produce unfit for consumption. In winter, hordes of these stink bugs invade houses to avoid the cold.

Fight back with: You’re not gonna like this. Most insecticides are totally ineffective against brown marmorated stink bugs. However, one natural insecticide that seems to work is spinosad. You can get this at garden centers. It’s only for outdoor use. Follow label directions carefully. You can also reduce stink bug numbers by inspecting leaves for egg clusters and destroying any you find; draping target plants with floating row covers to exclude stink bugs; and knocking stink bugs into buckets filled with soapy water. To keep them out of the house in winter, carefully seal around all doors and windows.

www.southernliving.com

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