1. Ornamental Pest Management (Category 3B)

    2. Biology and Management of Pests

    Chapter 6

  2. Seldom will a "stab-in-the-dark" approach to pest management adequately protect plants. Inappropriate pesticide applications are not likely to control pests, and may desstroy non-target organisms including the natural enemies of pests.
  3. Know ledge of the pest life cycle, reproductive behavior, feeding habits, and hosts is needed to create an economical and effective pest management program. The following slides review disease, insect, mite and animal pests of ornamental plants.
  4. Broadly defined, a disease is a disturbance of normal plant function. Noninfectious diseases are caused by nonliving agents such as drought and nutrient deficiency. Noninfectious diseases include cultural and environmental plant disorders. Pathogens such as fungi, bacteria, viruses, and other microorganisms cause infectious diseases. Only infectious disease can be spread between plants
  5. Th biology of pathogens is quite different from the biology of most other pests. Infectious diseases spread through direct plant contact or by seed-like spores carried by wind, water, animals, and humans. Apple scab has a life cycle typical of wind-dispersed diseases. Let’s track its life cycle.

    6. Disease inoculum (spores) must first contact a host plant ( Malus species). If moisture and temperature conditions are favorable, the scab spores infect or enter leaves. Infection is followed by a period of pathogen growth within the host; symptoms usually begin to appear during this time. Once the disease is established, spores are formed that can re-infect the host or infect other plants.

  6. Plant diseases are grouped according to the agents that cause them, or by the symptoms or signs they produce. Because symptoms are more easily detected and diagnosed than the microscopic pathogens causing them, most disease references are organized by symptoms. As you diagnose plant diseases, keep in mind that any one disease may produce a number of symptoms, and a symptom can result from a variety of pathogens or disorders.
  7. Know the symptoms and signs of the most common ornamental plant diseases.

    8. Leaf spots: caused by fungi, bacteria, nematodes, air pollutants. Discolored spot on leaf that eventually turns black/brown. May look like a target with different-colored rings.

    Scab: caused by fungi. Rough olive-green area on leaves and fruit. May cause premature defoliation and fruit disfigurement.

    Rusts: caused by fungi. Orange spots or lesions on leaves, twigs, or fruit. May cause galls or disfigurement.

    Powdery mildew: caused by fungi. This fungus grows on the surface of plants causing grayish, cottony layer on leaves, stems, buds, and flowers. Leaves may dry out and drop.

    Mosaics: caused viruses. Mosaic infection reduces plant vigor. Leaves show a light and dark green pattern. Leaf curling or other growth abnormalities may occur.

    Chlorosis: caused by viruses or poor soil drainage or fertility, and high pH. Yellowing of part or the entire leaf on one branch or the entire plant.

    Scorch: may be caused by several things including a lack of soil moisture, drying winds, limited root systems, and transplant shock. Yellowing and death of leaf margins and the areas between veins results. Early leaf drop may occur.

    Witches’ brooms: caused by a variety of organisms including viruses, fungi , mites and insects, or by environmental factor like deicing salt. Affected plant develop bush-like, dense, compacted cluster of shoots.

  8. Anthracnose: caused by fungi. Dead areas form on leaves along veins, fruit, and twigs causing deformation and cankers. Infections that kill buds result in witches’ brooms.

Cankers: caused by bacteria and fungi. Cankers are dead, often sunken areas on twigs, trunks, branches, or roots. Over time, cankers may girdle a branch or stem.

Blights: caused by fungi and bacteria. Blights kill young, growing tissues. Blighted areas are black and shriveled and remain clinging to drooping shoots. Tip dieback of young shoots results in brown, dead, or curled new growth.

Wilts: caused by water deficiency in stems and leaves due to a lack of soil moisture, root system injury, or pathogens. Vascular wilts are caused by fungi that plug up vessels and result in wilting, withering, and death of foliage, shoots, or the entire plant. Discolored sapwood is evidence of vascular wilts.

Decline: caused by a combination of environmental stresses and pathogens. Thin areas of foliage occur adjacent to apparently healthy branches. Dieback usually begins high in the canopy of deciduous trees and on the lower branches of evergreens.

Galls: caused by bacteria, fungi, mites, insects and nematodes. Galls are an overgrowth or swelling of plant tissue induced by the pest. Infected plants may suffer from reduced vigor and decline in appearance.

Rots: caused by fungi and bacteria. Disintegrates, discolors, and decomposes plant tissue. Hard rot is dry and firm; soft rot is watery and foul smelling. Crown and stem rots cause severe dieback or death. Root rots result in decline, wilting and death.

The next several slides provide graphic examples of the symptoms we just reviewed.
  1. Symptoms of the disease apple scab include the discolored rings and blackened spots characteristic of fungal leaf spots.
  2. This leaf spot is caused by a fungal rust disease. Rusts are aptly named for the color of the leaf spots.
  3. Here is the spore-producing gall, and signs, of cedar-hawthorne and cedar-apple rust.
  4. The white, fuzzy growth on these leaves are the actual fungal body of powdery mildrew. Mildew continues to grow and feed on leaves until the leaves dry up and die.
  5. Mosaic viruses leave the plant weakened, as well as an interesting leaf pattern.
  6. The leaves of this oak are chlorotic. In this case, chlorosis is caused by a lick of the micronutrient iron. This tree may be growing in an iron-rich soil, but a high soil pH makes the iron unavailable for absorption by the oak tree’s roots. The maple leaf is showing symptoms of manganese (Mn) deficiency.
  7. The branches of this sycamore tree are deformed into a witch’s broom. The dense cluster of twigs forming at the ends of branches is a result of bud kill by sycamore anthracnose fungi.
  8. Leaf blight is another symptom of the disease sycamore anthracnose. Large dead areas develop in newly forming leaves as the fungus infects and consumes leaf contents.

    9. Cankers form as sycamore anthracnose fungi infect and kill twig cambium.

  9. The dieback seen on this tree are caused by a serious bacterial disease, fireblight. Fireblight is carried from tender leaves, twigs and flowers by pollinating bees and other animals, and by pruning equipment. Badly infected trees to be singed.
  10. Apparently healthy rhododendrons can suddenly wilt and die due to root rot. Root rots can be hazardous to people and property when the roots of large trees are infected.
  11. The ash tree is this slide has poor vigor and a thin crown. The cause for decline is most likely a combination of environmental, cultural and pest factors.
  12. There are indicators in the landscape that aid plant managers in predicting disease outbreaks with reasonable accuracy. To capitalize on these indicators you must be familiar with and monitor the biology of host plants and pathogens.
  13. Some species or varieties of plants are more disease-prone than others. In some cases only specific parts of some plants are vulnerable to pest attack. Further, plants may be susceptible to pest attack only during a certain part of their life cycle. No matter the genetic predisposition to attack by disease, any plant that is stressed will be less able to resist and recover from disease. As a part of monitoring, keep an inventory of particularly susceptible host plants.
  14. Plant disease development is irregular largely due to variability in weather conditions. Rainfall, duration and frequency of dew, air and soil temperatures, and soil moisture are all factors influencing pathogen activity. Most pathogens benefit from moist conditions.
  15. Subtle differences in the landscape can result in dramatic variation in the severity of disease infection among plants. Microclimates commonly found in landscapes include low-lying, or windy areas, the southern or northern side of buildings, planting sites near a street, drive or parking lot, and the interior of dense plantings. Expect greater disease problems on plants where sir movement and light penetration is poor, and moisture is high.
  16. There is no way to entirely eliminate disease pathogens from infecting plants. Disease management efforts focus on preventing disease from developing in plants and lessening the effects. There are four categories of tactics to protect landscape plants from disease injury.
  1. Resistance. Select plant species, cultivars and varieties that are resistant to disease infection or injury.
  2. Avoidance. Create a landscape environment where conditions are unfavorable to disease development.

3. Elimination. Eliminate disease inoculum by destroying infected plants or plant parts and by using other sanitation practices. Some fungicides may reduce or eliminate the inoculum of some diseases.
  1. Protection. Make the pathogen ineffective before it can infect the plant. Most fungicides are protectants and timing applications is an important factor for obtaining control.

Let’s move on to a discussion about insect pests of ornamental plants
  1. Although it is a fact that the majority of landscape plant injury is due to cultural and environmental disorders, most people perceive and treat landscape pest management as a "bug problem". Of the 800,000+ insect species known, less than 3% are considered plants pests. However, those that are pest vary greatly in the way they feed, develop and reproduce.
  2. Insects feed on plant foliage, flowers, fruits, twigs, and roots. They injure landscape plants by sucking sap, consuming plant parts and boring through stems and wood. Some insects feed during only one stage of their life cycle, while others are destructive to plants during several of their life stages. Insect pests can be grouped by physical characteristics as in scientific taxonomy, or by their feeding habits and behavior.
  3. Be familiar with both the physical and behavioral characteristics of insects to help you identify and manage them. Listed here are several categories of insect feeding activities:

    4. -Piercing-sucking. Piercing-sucking insects feed on the sap of plants by puncturing stems, foliage, flowers, or fruit with needle-like mouth parts. Damage includes stippling and curling of foliage, loss of plant vigor and death. After feeding, aphids and other piercing-sucking insects excrete a sticky substance called "honeydew". Unsightly sooty mold will grow on the honeydew.

    Continued

    27. Continued

    -Leaf-chewing. Adult beetles and immature moths, butterflies, beetles, and sawflies make up the diverse group of leaf-chewers. These insects may be distinguished by the characteristic pattern left in the foliage from their feeding. Many are serious pests of ornamentals and shade trees.

    -Tent-and case-making. Some insects gather leaves and twigs or produce silk to construct a protective tent or case. Leaf rollers, leaf tiers, and casebearers attack many species of landscape plants. Bagworms, webworms, and tent caterpillars, are capable of totally defoliating plants.

    -Gall-forming. Galls affect the growth of developing plant tissues and are typically formed during late spring. Galls are often conspicuous, unattractive and permanent (for that season at least), but rarely cause more than aesthetic damage.

    -Root-feeding. Scarab beetle and weevil larvae (white grubs) are the two most important insect groups feeding on landscape plant and turf roots. Injury can be serious and management difficult as the grubs are protected down in the soil.

    -Boring. In most cases, it is the larvae of moth and beetle species that bore causing plant injury as they tunnel and feed inside plant roots, trunks and branches. Once underneath the bark, boring larvae are shielded from insecticides, as well as most other controls. Since most borers only attack plants that are in a weakened state, proper plant selection and care is the best defense against boring insects.

  4. Examples of piercing-sucking insects include aphids, leafhoppers, plant bugs, mealybugs, and thrips. We will see several of these insect types in the upcoming slides.
  5. Aphids are perhaps the most common piercing-sucking plant pest. They are small (1/4" or less) and come in a variety of colors: brown, black, green, yellow and white. Many feed on new, tender stems and foliage as shown here, but some species feed on roots.
  6. Scale insects can be serious pests, including pine needle scale shown here. Scales become immobile once they puncture the plant to feed. Note that there is no honeydew associated with pine needle scale.
  7. Magnolia scale is one of the larger scale insects found in the landscape. Here feeding injury includes honeydew.

 

 

 

32. Aphids excrete honeydew. Honeydew drips onto plants, furniture, and cars creating a real nuisance. The ants and sooty mold that feed on honeydew are also landscape nuisances. This linden leaf is so covered by sooty mole, its ability to photosynthesize is restricted.

33. Plant bugs can be found on many species of ornamentals. As they feed with piercing-sucking mouth parts, plant bugs inject saliva that is toxic to plant tissues. This results in bronzed leaf spots, or distorted new growth.

34. Leafhoppers also inject toxins as they feed. Feeding damage appears as white stippling or browning of foliage, or cupping and withering of leaves. The damaged leaves of this maple was caused by leafhoppers. The over 2,000 ornamental-feeding species of leafhoppers are 3-15 mm in size and come in a great variety of colors. Look for the greenish immature leafhoppers running sideways on leaf undersides.

35. Caterpillars are most commonly recognized leaf-chewing insects. While dozens of species feed without notice in a landscape in a landscape in a season, populations of any one of the leaf-feeders listed here can build to damaging levels.

36. The Eastern tent caterpillar is known mostly for its protective enclosure – its tent – considered unsightly in the landscape.

37. Sawfly larvae, like the pine sawfly shown here, look like caterpillars, but are the immature form of small, fly-like wasps. Like caterpillars, sawflies consume foliage and cause the most damage just before pupation. Damage often is significant because sawfly larvae are found in groups.

38. To the untrained eye, this injury appears to be due to a boring, rather than a leaf-chewing insect. Leaf miner eggs are laid inside of the leaf, and larvae chew the foliage between the outer layers. The blotches, or "mines", are actually dead or hollow areas inside the leaf. The oak leaf miner is a species of moth.

The birch leaf miner is a species of sawfly wasp.

39. Literally thousands of leaf beetle species feed on plants. The adults are often brightly- or metallic-colored like this Japanese beetle. Beetles range in size form 3-12 mm. The larvae may also feed on foliage with the adults.

40. There is no question that the damage on this yew was caused by a leaf-chewing insect. The notching pattern is characteristic of adult weevils.

The black vine weevil is a two-fold landscape pest. Injury from the leaf-chewing adult is more obvious, but much less serious than that done by the root-feeding grub.

 

 

 

41. The white grub shown here is the larvae of another landscape beetle pest. The Japanese beetle is a particularly serious landscape pest. Adults are voracious feeders that ruin rose blooms and defoliate many ornamentals. The grub is likewise a big eater that leaves large, rootless and dead patches in turf .

42. Some of the oddest-looking injury to ornamentals is caused by gall-forming insects. Fortunately, like this Maple bladder gall caused by a mite, galls typically have little effect on overall plant health.

43. A large population of spruce gall adelgid, on the other hand, can disfigure a tree enough to cause stunted growth.

44. Borers typically attack plants that are in an already weakened state. The feeding stage of borers is well-protected from the outside world and therefore they are difficult to control with external treatment. Borer infestation, such as bronze birch borer attacking birches, often is a very serious landscape problem.

  1. Most insects are tolerant of insecticides during part of their life cycle. During this time the insect is either inactive or is protected by a physical barrier. Example include:

    2. -Pupal cases of moths and butterflies.

    -Waxy coating covering adult scales.

    -Galls formed by adelgids and wasps.

    -Bark covering bark beetles and wood borers.

    -Leaf tissue covering deposited eggs or leaf miner larvae.

    -Soil covering beetle grubs and various overwintering insects.

  2. But, insects do have certain life stages vulnerable to controls. Insect management activities and susceptible life stages must coincide. When determining the need for ,and timing of insect control measures, consider these factors:

    3. -Life stage susceptible to management tactics

    -Damaging life stage(s)

    -Length of time feeding damage occurs

    -Rate of reproduction

    -Number of generations per year

    -Host tolerance to pest

    -Weather conditions

    -Presence of natural enemies.

     

     

     

     

     

     

  3. Because some aesthetic damage is tolerable, alternatives to pesticide use should always be considered for insect management in established landscape plants.

    4. Non-chemical Insect Controls

    -Improve plant vigor.

    -Encourage predators and parasites of insect pests.

    -Use plants resistant to insect pests.

    -Modify the environment to discourage insect pests.

  4. Remember, insecticides may be the most effective "manufactured" management tool, but they are secondary to natural enemies in limiting insect pests. Before carrying out insecticide applications, always consider the negative impact on beneficial organisms.
  5. Despite the controversy, concern, and criticism over insecticide use, chemical controls are a useful tool in IPM programs. Avoid problems:
  1. Monitor – apply insecticides only when and where needed.
  2. Protect beneficial organisms.
  3. Time insecticide applications to coincide with vulnerable life stages.
  4. Avoid preventive treatments except when intolerable damage is certain to occur.
  5. Use the least-toxic insecticides. Avoid broad-spectrum insecticides.
  1. Mites are similar to insects, but are more related to ticks and spiders. They are tiny in size – some species cannot be seen with the unaided eye.

    2. Mites feed by rupturing plant cells, inserting their mouth parts and drawing up cell contents. This feeding results in speckling that often has an overall cast of bronze, red yellow, white or brown. Spider mites spin light, delicate webs where they feed. Eggs and mites that are covered with webbing are somewhat protected from sprays. Gall mites cause rusting of foliage and disfiguration as they feed.

    Mites have many generations per season, so populations increase rapidly. The most severe injury is typically found in landscape "hot spots" – areas near pavement or building, or mulched with stone. Despite their small size, mites can be detected on plants by tapping the suspected branch over a white piece of paper. Dislodged mites will appear as tiny specks moving on the paper.

  2. Spider mites have 8 legs and are very tiny. First look for them on the underside of leaves. Heavy infestations can result in visible webs. Their feeding causes some plants turn bronze.

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  3. Nematodes are microscopic, worm-like animals found almost anywhere. Plant-parasitic nematodes feed most commonly on roots, but also foliage and stems. They use needle-like mouth parts (stylets) to puncture plant cells. Nematode-infested roots may have galls, lesions or rot. Above-ground symptoms include wilting, stunting, dieback, and lack of vigor.

    4. Because of their small size and nondescript top injury to the host, laboratory analysis may be necessary to diagnose nematode problems. Once diagnosed, it may be recommended to remove and destroy plants suffering from nematodes. Most nematicides are extremely hazardous and not easy to use in a landscape. Be sure to choose replacement plants that are not susceptible to the nematode pests.

  4. Snails and slugs are soft-bodied animals that leave large, irregular holes as they feed on young, succulent foliage. They mostly are attracted to herbaceous plants like hosta and cabbages
  5. Like other soft-bodied animals, snails and slugs search for moist, dark places in the garden. Discourage these mollusk pests by increasing light and ventilation around plants, and sanitation to remove snail habitat. Snails and slugs are active ant night; an shiny slime trail on plants and soil indicates their path. In addition to various home-made traps, snails and slugs can be limited with the use of baits treated with molluscicide.
  6. Several types of large animals harm ornamental plants. In the winter mice, squirrels, rabbits, voles and deer feed on the bark of ornamental trees and shrubs. Deer also injure the bark of trees the process of rubbing the felt off of antlers. Holes drilled by sapsuckers can seriously disrupt the vascular system of trees.
  7. Extensive feeding girdles, and kills stems and whole plants. The limb of this maple was stripped of its bark by squirrels. Rabbits chewed the lower limbs of this crabapple tree.
  8. When considering options to manage vertebrate pests, remember that nontarget wildlife must not be endangered. Physical barriers, live traps, repellents, and habitat removal should be used before poisonous baits. Know that trapping wildlife, except rate, mice, voles, moles, and chipmunks, is regulated by the Michigan Department of Natural Resources.
  9. The end. Good luck on your pesticide applicator certification exam. Have a great season.