3.3 Factors affecting forest Health.pptx

factor affecting plant health

1. Factors affecting forest health : Fire ; insect pests; vertebrate pests; invertebrate pests; weeds and pathogens

2. Forest Fire Fire is burning or rapid combination of oxidation of a substance characterized by heat, light and flame. A  forest fire  is an uncontrolled  fire  occurring in nature. Forest fire is an uncontrolled and freely spreading combustion which consumes the natural fuels of a forest Any wild land fire burning with natural fuels. Sometimes, the forest fire  is so large that it takes a long time for the  fire  fighting crews to gain control over the situation. This could result in massive destruction. After deforestation “forest Fire” is the most important cause of forest destruction. A single uncontrolled fire can ruin extensive areas The effects of fire are determined by the interaction of vegetation type, fire intensity, seasonality and fire history. Fire is an inevitable, periodic event in most of the forests that can have both positive and negative impacts on forest health and vitality.

3. Forest fires take place all over the world. Major fires happen every few years in the forests of the United States, Indonesia, Australia, India also in Nepal. Forest fires happen mainly in the summer and autumn. They are particularly destructive when there is a drought because branches and twigs die and dry out, creating plenty of fuel for the fire. Wind is a major factor. Some fires spread along the dead leaves and branches at the bottom of trees. Some fires spread when the leafy canopy catches fire.

4. Once a forest fire has started, many factors contribute to its spread and intensity. Fuel - such as leaves, needles, grass, branches, and logs Weather, including temperature, humidity, precipitation, and wind Topography, or landscape of the area, as steep slopes offer greater potential for increased fire intensity and more obstacles for fire fighting. An average of 19.8 million ha of forest are reported to be significantly affected annually by forest fire according to FAO.

5. On the basis of causative factors On the basis of causative factors forest fire are classified into 1.Natural fires 2. Accidental fires 3. Deliberate or intentional fires The natural causes of forest fires are as follows : Lightening Rolling of stones Rubbing of bamboos with each other . Volcanic eruptions too lead to forest fires. The lightening alone causes around 30 % of the forest fires in western countries.

6. Man made causes of Forest fires (carelessness) Leaving fires burning by cart man or travelers, lighted by them for cooking their mid day meal. Throwing of burning match stick, Bidi or Cigarette stumps in forest by grazers or other travelers. Throwing of fire carelessly after illicit collection of honey. Burning of grasslands in the villages and leave such fires spread in the forest. Accidental spread of fires while burning fire lines departmentally. Scaring away wild animals from near the villages

7. Man’s deliberate and intentional actions: Burning the undergrowth and grass to collect the minor forest produce such as horns etc. Fires are caused in Mahua forests to collect the petals and these in turn destroy the regeneration of previous years. To get a new flush of grass by burning dry grass in dry weather . Forest fires caused in the forest out of enmity with the forest officials. To destroy the stumps of illicitly cut trees in the forest areas.

8. Classification of forest fires on the basis of the place of action GROUND FIRE: Ground fire burns the herbaceous growth on the forest floor together with the layer of organic matter in various stages of decay, which cover the soil. A  ground fire  can occur in any conditions and is where coal, tree roots, slash, duff, humus and peaty layers lying beneath the litter or undecomposed portion of the forest floor or other materials ignite and burn under the ground.

9. These layers of organic material are either closely compacted or of a fine texture and are shut off from the wind and from oxygen supply in the air. Consequently a ground fire burns very slowly but persistently with instant heat and rather uniform destructiveness Such a fire may burn over several acres in a day .There may or may not much smoke , but there is practically no flame.

10. SURFACE FIRE Surface fires are those which burn on or near the ground in the litter, ground cover, underbrush, and reproduction. They are the commonest kind of fire and occur in all parts of the country. It is fire which not merely burns the ground cover but also the under growth and middle storey of the forest. Even the low trees and poles of the larger species are engulfed by surface fires. It causes considerable damage to the forest by destroying the young generation and even the pole crop of the favoured species.

11. Most of the fires in the plains are surface fires. The fire is so located as to be strongly affected by surface winds and there is an abundant supply of oxygen for purpose of combustion Hence surface fires are characterized by relatively rapid spread, abundance of flame and heat, but soon die out.

12. CROWN FIRE The foliage at least is consumed and the tree usually is killed through overheating of the cambium. Crown fires are restricted to species which have inflammable foliage. This usually occurs in coniferous forests during strong wind. Crown fires burn in the crowns of the trees. It is a forest fire which spreads through the crowns of the trees and consumes all or part of the upper branches and foliage. This is the most devastating types of fire which burns even the crowns of the tall trees. This type of fire causes immense loss of life and property.

13. Ground Fire Surface Fire Crown Fire

14. Damage caused by The Forest Fire DAMAGE TO THE TREES: The damage may range from slight fire scars at the base to complete consumption of the tree. Death is caused by the killing of the cambium or living layer between the bark and the wood. Baker states that a temperature of approximately 54 0c is sufficient to kill the cambium but lethal temperature lies between 65 0c and 69 0c. During the early part of the growing season, when cell division in the cambium layer is at its height, the cambium region is more sensitive to heat. Fires occurring early in the growing season are likely to kill a large percentage of the trees in a stand. Moisture content, thermal conductivity, and sensitivity as a consequence of anatomical structure may also differ with species.

15. ( DAMAGE TO THE TREES : Damage caused to the trees varies with species, age of trees, their condition and season. The species which have thick corky bark are comparatively less affected by the forest fires than the species with thin bark. The broad leaved trees are less affected by forest fires than the conifers. The age of the trees also affects the damage due to fire. Pole crops get damaged because of fire but the bigger diameter trees are relatively less affected . If the tree is very old and is dry and hollow in that circumstance it becomes more susceptible to fire, because once it catches fire it burns very fast and for long. The condition of the trees, whether it is very green or dry also affects the damage caused by the forest fire. If trees containing merchantable material are killed outright, they should be cut and utilized before the timber decays or is attacked by insects infesting dead trees. Tree with shallow root systems suffer more than the deep- rooted species Power of resistance to fire differs for each species of tree. These differences between species are due primarily to the character and thickness of bark.

16. (ii) DAMAGE TO REGENERATION : Fire damages the regeneration completely as most of the regeneration is completely wiped out in ordinary ground or surface fire. If the species possesses coppicing power regeneration in the form of seedling coppice appears again but even then, loss of growth does take place. Repeated fires may kill the small seedlings and then the regeneration may be lost completely. Even where small trees are only partly girdled by a fire their potential value is greatly reduced. Many years must elapse before the trees are merchantable. During this time insects and fungi have abundant opportunity to enter through the fire scars or elsewhere as a consequence of the weakened condition of the trees and frequently render them worthless by the time merchantable dimensions are attained. Fire in artificial regeneration areas of plantations, not only completely destroys the plantations but also results in wastage of money spent in raising the plantations. Destruction of seeds: Seeds are destroyed, adversely affected regeneration; only hard coated seeds remain and germinated.

17. (iii) DAMAGE TO SOIL: Forest fires in their action on the soil affect its physical properties more critically than its chemical properties. Physical properties of soils are influenced by fires through decrease in the humus content. A severe fire which kills most of the trees opens the forest canopy, burns off the litter, and exposes the soil to drying influences of sun and wind. The humus in the soil decomposes, and without litter or trees to furnish litter no more humus is formed. The soil on bare burned areas consequently deteriorates in physical condition . The forest fire leaves the soil bare to the action of natural elements i.e sun, wind and rain consequently soil erosion starts resulting in loss of top fertile soil.

18. Destruction of soil organic matter affects the soil structure adversely. Nitrogen reserves of the soil are depleted. The forest fire destroys the humus and soil micro flora which in turn affects the forest growth. Fire makes soil compact and impervious and their effect on clay is extremely bad as they get hardened and cracked. Light fire burning over the same ground every year consume the annual leaf fall and thus keep the ground bare of litter. Under these circumstances, when the humus in the soils once exhausted the soil deteriorates. The forest litter contains nutritive materials, principally nitrogen, calcium, phosphorus and potash. Last three remain in wood ashes but the nitrogen is volatilized and lost to the soil when the forest litter is consumed by fir e

19. Soil moisture loss Organic matter destroyed bulk density raised increased runoff/ reduced infiltration drier soil Ash and charred crust resulting from fire reduce micropores .

20. Effects on Soil

21. Damage to the productive power of the forest: 1.Injuries due to replacement of good by poor species 2.Injuries due to reduction in the density of stocking 3.Injury due to forced cutting or loss of the forest crop before financial maturity. Forest fire seriously affect the productive capacity of forest. Repeated fires degenerate a valuable evergreen forest into inferior deciduous forest or even grass land. Valuable species disappear and their place is taken by inferior fire hardy species. As a result of fire one forest type may be replaced by some other forest type. Density and increment of forest is reduced and this affects the yields. As timber become defective their value decreases. When a forest crop is killed before the end of the rotation, even though it is cut and salvage, it may happen that the mean annual growth of stand in quantity or quality is found to be less than it would have been if the crop had grown to maturity The productive power of the forest has been decreased in this way

22. ( iV) DAMAGE TO THE PROTECTIVE POWER OF THE FOREST: Forest can discharge its protective function when it is a forest in real sense i.e it has not only trees but also grasses, shrubs and small trees. Even ordinary fire burns down the ground cover and undergrowth completely and therefore it affects the protective power of the forest. Fire increases the flood havoc as it destroys the protective cover of the forest. Heavy rains on newly denuded slopes results in to devastating floods. When protective power of the forest is reduced, it causes increase in soil erosion and run-off.

23. DAMAGE TO WILD ANIMALS : Fires either directly or indirectly, cause the destruction of many birds, animals, and fish. The biggest effect fire has on wildlife is the change in their habitats. Wildlife habitats, like forests, are not static; they evolve and respond to disturbances as do other natural systems. Fire changes the proportion, arrangement, and characteristic of habitats across the landscape Forest fire results in to enormous loss to wildlife and birds. It burns not only eggs or young ones but sometimes bigger animals also. An indirect effect of fires upon wildlife is the destruction of food and cover upon which animals are dependent. As destruction of wild animals destroys a valuable component of environment, natural equilibrium is seriously affected with consequent adverse effect on vegetation itself

24. Invertebrates Invertebrate populations tend to decrease after a fire because eggs, food supplies, and/or shelter are destroyed. Flying insects are especially vulnerable because they are attracted to fire by heat or smoke and are incinerated in great numbers. Surface insect populations, such as grasshoppers, also tend to decrease. Other insect populations, especially bark beetles, increase after a fire, as trees damaged or killed provide large amounts of suitable habitat.

25. DAMAGE TO RECREATIONAL AND SCENIC VALUE OF PLANTATION : As forest fire destroys the greenery of the forest, it destroys its recreational and scenic value. Burned areas are relatively unattractive for recreational use, particularly recent burns. The forest no longer remains a fit place to stay and roam about, as the ground is littered with ash and blackened stems of shrubs and poles of trees make the entire place desolate. The fire reduces the moisture level and leads to ecological retrogression of the site. Community income from the tourist may be unfavorably affected as a consequence of injury to the scenery and recreational facilities caused by forest fires.

26. Injury to other Property Buildings, livestock, and property of all kinds are at times threatened by forest fires , and serious losses result. The principal loss is to property found within the forest or in small clearings surrounded by woods. Whole towns have been wiped out by forest fires (Currie 1929, Guthrie 1936)

27. Injury to Human Life Rarely in United States does a year pass without loss of human life as direct consequence of forest fires. The greatest loss of life on record in any one fire took place in the Peshtigo fire of October 1871 in Wisconsin, in which 1500 persons perished (Plummer 1912) In 2016 , 15 people were reported dead. In 2009 13 army men were killed in central region of Ramechhap

28. Effect of fire on air Releases CO 2 , H 2 O, CO, CH 4 , N 2 O, NH 3 , trace hydrocarbon, volatile organic compounds, ozone ( Crutzen & Goldmmer 1993) Black carbon, other aerosols

29. FOREST INSECTS PEST CLASSIFICATION BASED ON FEEDING MECHANISM

30. On the basis of mode of damage and feeding behaviour forest insects pests may be categorized as- foliage feeding insects – These can be of 2 type- Leaf sucking (Aphid and Bugs) and leaf feeding( Moths and Butterflies) flower/fruit/ cone/seed insects- Some of the insects feed on reproductive part of plant and limit their growth. Ex- Wasps. bark beetles- Bark beetles attack trees that are weakened or dying due to stress factors such as drought, disease, smog .Ex- Ips beetle FOREST INSECTS PESTS :

31. Plant galls are "abnormal" structures that develop in the cells, tissues, or organs of a plant when it is colonized by certain parasitic organisms such as bacteria, fungi, nematodes, mites, or insects.   These gall-makers are collectively known as cecidozoa .   They usually secrete enzymes or plant hormones that stimulate hypertrophy (over-growth) and/or hyperplasy (cell proliferation) in their host plant. Ex- Adelges abietis   A weevil is any beetle from the Curculionoidea super family of order coleoptera Their presence is often indicated by the granules of the infested item sticking together in strings, as if caught in a cobweb. Ex- fungus weevils ,leaf rolling weevils. Weevils- Many species of boring insects attack the , twig, trunk, stems, bark, buds and roots of woody ornamental plants . Some bore deeply into the wood many bo ( dogwood borer, elm borer and bark beetles). Ex- Acossus centerensis on Poplar. Boring -insects gall makers -

32. Defoliation is the removal of all or part of the foliage from the tree. Forest insects are the primary agents that can cause defoliation . Forest insect defoliators can be classified scientifically by the order of insect, such as Lepidoptera, Hymenoptera, Coleoptera , Orthoptera , and Diptera. Common names or examples of the forest insect defoliators of these orders are caterpillars, sawflies, beetles, walking sticks, and miners , respectively . The adult beetles are polyphagous feeders of foliage and damage seedlings of many forest species in forest species in forest nurseries and plantations. The infested leaves may dry up and drop.

33. Forest insect defoliators can be classified or described in several ways: defoliation pattern on individual leaves, structures that they create from which to feed, and time of the growing season that feeding occurs. Defoliation Pattern Defoliators create many patterns of defoliation on the individual leaf . Some insects completely eat the leaf blade leaving only the large veins . Some create a “shot hole” pattern by eating holes in the leaf blade . Other insects make “ leaf mines ” by eating the middle layer of the leaf . One group makes a “ skeleton” of the leaf by eating everything but the large and small veins.

34. Shot hole Leaf mine Skeleton

35. Feeding Structures Forest insect defoliators are also classified by the structures that they create and use while feeding. These structures range in size from large “tents” holding hundreds of insects, to individual structures containing a single insect . Ex - Forest Tent Caterpillar ( Malacosoma disstria ) Examples of these are webworms, leaf rollers, leaf tiers, bagworms, and casebearers. However , many defoliators do not make a structure. They are called “free feeders” and eat individually or in groups.

36. Tent Feeding( Feeding in large groups) Free feeders

37. Leaf roller Casebearers

38. Time of Feeding Forest insect defoliators can be classified as spring defoliators, spring/summer defoliators, or summer defoliators . Spring defoliators feed from bud break until mid- to late June . Spring/summer defoliators feed from late May or early June until July or August. Summer defoliators feed from late June or early July through September. Generally, the forest insect feeds only during one of the three periods, But there are a few forest insects that feed in two or more periods, such as oak sawflies.

39. How to Recognize Defoliation Generally, you will not notice that a tree has been defoliated until more than 25 percent of the leaves have been eaten. The first symptom will be a change in crown colour from green to yellow green then toward reddish brown. You may hear what sounds like rain in the woods even though it is not raining. This is the excrement of the insects falling through the forest canopy. You might also observe or mentally note that more light is penetrating the forest canopy or that something “looks” different about a tree or a forest. But, the best way to recognize defoliation is to observe the actual insect feeding on the foliage.

40. How to Recognize Forest Insect Defoliators Caterpillars (Lepidoptera) cause the most defoliation. Caterpillars are wormlike insects, from less than 1 inch to more than 3 inches long, with segmented bodies. They have one pair of legs on the 3 segments behind the head and one pair of Legs on 2 of the remaining body segments. Colour, markings, and degree of hairiness varies. Sawfly larvae (Hymenoptera) are also common defoliators. They look like caterpillars except that more body segments have a pair of legs. They feed together in colonies .

41. FOREST DAMAGE

42. Damage by defoliators: The damage to the forest is primarily done by the immature and not the adult stage of the insect. It is the caterpillars, larvae, maggots, and nymphs that defoliate the trees The extent of damage to a tree or forest depends on the amount of leaves eaten and the time of the growing season when defoliation occurs. Direct damage Such as growth reduction, twig dieback, and mortality, begins when more than 60 percent of the foliage is eaten. At this level of defoliation, the tree may be forced to refoliate by expending food reserves. The new leaves are smaller, lighter green, and not as efficient in photosynthesis. These secondary forest pests are the main reason that trees stressed from defoliation, drought, or other disturbances die 1 to 3 years later.

43. Indirect Damage – The loss of foliage can have negative impacts on the watershed value and indirectly lower water quality. Defoliation can alter wildlife habitat and change or shift wildlife composition. The nuisance of insects, especially overabundant caterpillars, also discourages forest recreation. Damage due to the time of defoliation Spring defoliators are more likely to cause mortality than spring/summer and summer defoliators. The amount of twig dieback and growth reduction may also be greater for spring defoliators. Spring defoliation occurs just when the tree has already expended food to form leaves.

44. In case of spring defoliation ,if the defoliation is greater than 60 percent ,the tree refoliates and even more food reserves are depleted. The new leaves do not totally replace food reserves, resulting in a weak tree that has a greater chance of dying. Trees that do not refoliate and simply use the damaged, less efficient leaves to produce food, are less likely to die, even though growth is reduced and twigs die back. Spring/summer and summer defoliated trees may not refoliate even if more than 60 percent of the leaves are eaten. By this time trees have already replaced the food used to form leaves at the start of the growing season. They are not as weak and have a greater chance to survive with less growth reduction and twig dieback.

45. Vertebrate pests Animals- As injurious to Forest i . Domestic animals Wild animals Rodents Birds Insects Domestic animals : Cows, bulls, buffaloes, horses, asses, sheep, goats, camels and elephants. Why grazing is allowed in Forests?: Live stock raising and forestry played role in country’s economy. It is difficult to separate land for each purpose. Hence, land is subject to mixed utilization. In forest, also many such areas are grass lands and need to utilize for grazing. Grazing is an important instrument in forest management. Unlimited and uncontrolled grazing has no place in forest management. Dis -advantage of Forest grazing: If the limit of grazing exceeded, physiological balance & tree growth is deteriorated. Size of live stock and size of available grazing area should be balanced. Unlimited or uncontrolled grazing is incompatible with Scientific Forestry .

46. Accessibility to grazing: Grazing in forests becomes confined largely to fringe of forests, bordering village and around sources of water. These peripheral regions results in the depletion of more palatable and nutritive grasses. Kinds of stock introduced: two kinds of stock Goats, camels and other animals which browse on herbaceous & prefer to ligneous plants. Goat is considered as destroyer of vegetation. Camel required 5 hectares area, otherwise incidence of browsing is severe. Cows, buffaloes, bullocks etc. which are selective feeders, prefer herbaceous and ligneous plants.

47. Effects on Vegetative: After fire, grazing is most influential factor, affecting forests. Causes retrogression through hardening of soil which leads xerophytic conditions Good palatable grasses are eaten first and lack of them shows over grazing Lopping for Fodder: Tree lopping for fodder is common for animal Husbandary . In cold season grass become tough and unpalatable, less nutrient and useless as fodder. Lopping of oak trees in western Himalayas, are common. Severe lopping may kill the trees, due to fungal infection, and inset borers. Acacia catechu attacked by Formes badius , cause heartrot . Pinus wallichiana attacked by Formes pini , cause heart rot.

48. Effect of grazing on soil: Hardening of soil. Manurial ingredients pass away by animals in the form of dung and urine. Over grazing denude soil and exposed to soil erosion. Effect of grazing on regeneration: Grazing compacting soil where germination and establishment of desirable species is difficult. Browsed seedling are stunted, branchy & malformed. Effect on wild life: Grazing by domestic animals has detrimental effect on wild life. Wild herbivores compete with cattle for food and water. Cattle carry diseases: Rinderpest , Anthrax, Septicemia etc. Out break of these diseases kill the deer, bison, elephants.

49. Advantages of Forest grazing : Control forest grazing is useful Reduction of fire hazards: grass is reduced which is prone to fire. Checking of low value species: Grazing and browsing to grass and low value species suppress their growth. Aid to natural regeneration: Regulated grazing exposed the mineral soil & mixing with humus in trampling seed into soil and enhance regeneration. Also help in disposal of seeds ( Acacia milotica ) pods are eaten by sheep and ejected seeds germinate rapidly.

50. Grazing laws: Number of cattle: . (b)Season of grazing: (c)Area of grazing: (d) Other considerations of grazing: Grazing fees: . (ii) Closure on Silvicultural reasons: Rotational closing Fodder Reserves:

51. Wild animals Carnivores keep the population of herbivores under control. Herbivores damage the forest. Antelops , bisons , wild buffaloes, Sambhar , Chital, blue bull and elephants. Elephants: Feed young branched & tender bamboos. Chital, Sambhar , antlers : Feed on saplings Black bears: damage deodar, spruce poles by strippling of their barks. Monkey: damage by eating growing buds , fruits and pulling seedlings. Chital and Sambhar : Brows sal Chital : Brows – Sterculia sp, Pterocaarpus sp. , Lagesstroemia sp. Terminalia Sp. Dipterocarpus and teak. Sambhar brows Gmelina arborea ; Acacia catechu is damaged by Elephant.

52. Rodents: Porcupines, hares, rats, squirrels and other rodents eat succulent shoots and germinating seeds; cut into bark and wood. Porcupine damage to semal and khair seedling and fleshy roots or girdle of plants. Rats damage nurseries and teak plantations. Protection against wild animals & Rodents . Fencing- Costly, so nurseries, regeneration area and selected areas are fenced. Trenches: For elephants, deep trenches 6 feet wide and 6 feet deep and 4 feet at base are dug. Earth is heaped on inner side and agave or babul is planted. Stone Walls: stone walls of 4 feet high and 3 feet wide are built for keeping out wild bores. Live hedges : By thorny Prosopis sp ; Pthecolobium sp., Euphorbia, opuntia , Agave, Acacia and by Saccharum .

53. Invertebrate pests Thousands of species of insects are found in our forests and rangelands, and many play an important role in pollinating plants, recycling nutrients, decomposing vegetation, and providing food for wildlife. They also occasionally can kill trees and impact forest health. Forest Health Protection surveys our forests to detect insect outbreaks, provides assistance to land managers to manage pests and develops tools for detection and management. Several native species, such as the southern pine beetle, several species of western bark beetles (mountain pine beetle, spruce beetle and Douglas-fir beetle), and spruce budworms have had significant impacts on forests. Pine Beetle Bark Beetles Spruce Budworms Molluses - Laevicaulis alte - a serious pest of neem seedlings (ii) Mites: Eutetranchychus orientalis – Neem , suck cell- sap from leaves Aceria pougamiae galll formation in Pongamia pinnata . Eriophyes prosopidis - gall formation in prosopis cineraria Tetranychus urticae - suck the cell –sap from leaves of Albizia sp.

54. Forest Pathogens Forest pathogens are often microscopic organisms that attack trees in ways that can be hard to see with the naked eye. Tree pathogens such as fungi, bacteria, phytoplasmas , virus, viroids , and higher parasitic plants can serve as disease agents and are normally considered part of a healthy forest. However, under favorable environmental conditions and presence of a susceptive host they can do significant damage to forest resources nationwide. One good definition for tree disease is any harmful deviation, caused by a persistent agent, impacting the normal functions of the tree. There are roughly five common tree problems highlighting the importance of pathogens in the forest. They include Wilts, Cankers, Rusts, Mistletoes, and Root Disease. Symptoms generated by their persistence can be identified on leaves, branches, trunks, or roots expressed as blights, galls, leaf spots, or witches brooms. Understanding the critical control points of their disease cycles is key to successful management.

55. PEST RECOGNITION There are four main groups of pest organisms: weeds, invertebrate animals, pathogens, and vertebrate animals. Never classify an organism as a pest until it is clearly determined to be one. Be certain any injury or observed damage is actually due to the identified organism and not to some other cause. Some plants, for example, can be damaged by factors in the environment. This damage may be mistaken for that caused by living pests. The first step in pest management is to accurately identify the pest. Once the pest is identified, applicators can learn about its life cycle, behavior, characteristic damage, factors that favor its development, susceptible life stage(s), and known control methods. Misidentification and lack of accurate information could cause pest control failure

56. Ways to Identify Pests To identify an organism, consult reference materials: identification books, Extension bulletins, field guides, and online identification keys that contain pictures and biological information. If you cannot pinpoint a specific plant or animal, take or send the specimen to a university diagnostic lab or a local pest management specialist. Collect several specimens, if possible. Ask the specialist to recommend the best way to collect and send samples. It may be difficult to identify small insects and most mites, nematodes, and plant pathogens. Accurate identification requires the use of a hand lens or microscope, special tests, or careful damage analysis

57. . Often the pest’s host (the animal or plant on which an organism lives) and location are important clues in making a correct identification . Information on the environmental conditions where you collect pests and the time of year of collection provide clues to the pest’s identity. Pest species have different physical forms depending on the life cycle stage or the time of year. Weed seedlings, for example, often do not resemble the mature plant . Many insect species undergo changes in appearance as they develop from eggs through immature stages to the adult form.

58. Characteristic Damage Pests may leave signs of their presence or damage that will help you determine what they are. Birds and rodents often build characteristic nests. The type of feeding damage and excrement can help you identify many insects. Burrows, gnaw marks, tracks, trails in the grass, and/or feces are often characteristic of certain mammals. Weeds may have unique flowers, seeds, or fruits or unusual growth habits. Fungi and other pathogens often cause specific types of damage, deformation, or color changes in host tissues.

59. WEEDS

60. Weeds comprise the most aggressive, troublesome and undesirable element of the world’s vegetation. Weeds are a group of herbaceous or shrubby plants

61. A  weed  is a plant considered undesirable in a particular situation, "a plant in the wrong place". The term  weed  also is applied to any plant that grows or reproduces aggressively, or is invasive outside its native habitat. Inspite of all the preventive measures taken before regenerating a forest crop, a lot of weeds appear on the forest floor much before the seedlings of the desired species appear and if not kept in check they kill the plant. The weeds may be either shrubs or grass. In the nursery and natural regeneration areas, heavy growth of shrubs make regeneration of the desired species extremely difficult. They have to be checked or else they cause considerable damage. The problem of weeds is also acute in forest nurseries where regular weeding have to be carried out for keeping the beds free from weeds

62. Weeds compete with productive crops or pasture, ultimately converting productive land into unusable scrub. Weeds compete with crops for space, nutrients, water and light. Smaller, slower growing seedlings are more susceptible than those that are larger and more vigorous

63. Types of Weeds Annual types Biennial types Perennial types

64. Adverse effect of weed : Matted roots of weeds hamper the establishment of regeneration Mechanical injuries to seedlings and saplings of favoured species in case of slow growing species Tend to use mineral nutrients essential for the growth of plants Immense competition for moisture, light and essential nutrients between weeds and young individuals of favoured species. Prevents light rain and dew from reaching the soil. Draws up precious moisture from below the surface and transpire it. On drying, increases the risk of fire. Serve as the hosts to fungi providing hosts and vectors for plant pathogens, giving them greater opportunity to infect and degrade the quality of the desired plants

65. Efficiency is reduced since costs are increased through cultivation, hoeing and spraying. Species choice may be limited. Some species may not compete effectively against heavy weed growth, and some weeds are parasitic on the species All types of crop products may be reduced in quality. Livestock products may bring lower prices or make it unmarketable. Weeds bring more problems in water-management for irrigation, drainage, recreation. Weeds reduce human efficiency through allergies and poisoning. Some times , certain weeds act alternative host of insect pest and rust diseases.

66. Presence of Premna and Vitex in teak forests facilitate increase of Hyblaea puera as they are its alternate host plant. A dry humus is produced by some weeds which is not suited for many forest species

67. The properties of weed species The knowledge gained from the study weed biology under given agro ecological conditions represents the basis in choosing the appropriate measures for their control. Compared to cultivated plants, weedy plants show considerable plasticity in relation to numerous ecological factors. One of the most important weed traits is the expressed adaptation ability. Another important weed trait is the pronounced resistance to unfavourable environmental conditions (drought, moisture, wind etc.). Many weeds are resistant to plant diseases and pests. Also, one of the weed traits is the periodicity of germination. In addition, many weeds produce an enormous quantity of seed, which makes it easier for them to spread and expand in space.

68. Weed problem in Plantation Controlling or eliminating weed competition is an essential component of plantation establishment ( Bey et al. 1976). Plantations are commonly established on abandoned agricultural fields with an existing seed bed and rootstock of desired plants.

69. Regardless of the origin or species of weeds, they will provide competition with planted seedlings for nutrients, moisture, and light. If weed competition is unmanaged, it will result in reduced seedling growth, vigor , and survival. High densities of weeds may also provide food and habitat for mammals that will damage or destroy seedlings through girdling and browse (Erdmann 1967). Regardless of which system or combination of systems is implemented, weed control should be applied for the first 2 to 3 years of plantation establishment, or when the trees have reached a height that will allow them to grow free of competing vegetation

70. The density of grass can be reduced only by allowing the shrubs to grow and suppress it. In man made plantations, fire danger resulting from the presence of grass is reduced by raising agriculture crops in interspaces . When it is not possible ,this is achieved by harrowing the grass down. Some times Sesbania and Crotolaria are also raised in the interspace to suppress grass.

71. Weed control in forestry There are numerous measures and procedures for weed control in forestry today, but, in order to fight weeds successfully, they should consist of different care and control measures. Some of the weed control measures are :

72. Methods of Weed Control Manual Mechanical Chemical Biological Cultural weed control

73. Preventive measures The main goal of preventive measures is to prevent weed distribution. Preventive measures in forestry weed control include: - Control by sowing only pure crop seeds, which prevents spreading of weeds over sown surfaces

74. Mechanical measures Mechanical measures for combating weeds include basic treatment such as ploughing, disking, tilling etc. Also regular measures in forest nurseries and plantations are hoeing and farrowing, undertaken during the greatest part of the vegetation period and especially emphasised during the entire spring and in early summer. one of the methods of weed suppression in forestry is also the pruning of shoots and stump shoots. However, this weed suppression method is relatively expensive due to intense labor and if repeated pruning is required depending on the weed species present. Concerns about increasing pesticide use have been major factors for research in physical weed control methods.

75. Chemical Chemicals that are used to kill weeds are called herbicides or weedicide.

76. Soil application Soil surface application:   Herbicides are usually applied to soil surface to form a uniform herbicide layer. The applied herbicides, due to their low solubility may penetrate only few centimeters into the soil. Weeds germinating in the top layers are killed due to incidental absorption of herbicides. eg . triazines , ureas and anilide

77. Soil incorporation Some herbicides are applied to soil surface and incorporated into the soil either by tillage or irrigation for their effectiveness. eg . volatile herbicides  viz ., aniline and carbamate Sub-surface application : Perennial weeds like  Cyperus rotundus  and  Cynodon dactylon  are controlled by injecting herbicides to the lower layers of the soil at several points.

78. Herbicides Herbicides are used in forestry to manage tree-species composition, reduce competition from shrubs and herbaceous vegetation, manipulate wildlife habitat, and control invasive exotics ( Shepard et al., 2004). Unlike agriculture, the use of herbicides in forestry began much later and generally the application of herbicides in forestry was based on experiences from intensive agricultural production. The results of research in agriculture are applied in forestry with major or minor delays. Due to the lack of labour , high labour costs, and large areas, producers are more often interested in the use of herbicides. Use of herbicides in forestry decreases weediness , particularly at the initial stages of development of forest nursery plants, when the effect of weeds on plants is the greatest; at the same time, much better economic efficiency in the production process is achieved. Also, possible mechanical damages to the nursery plants can be avoided, and it happens very often that any kind of mechanical treatment is prevented in early stages of plant development due to high soil humidity.

79. Mulches The covering of soil with a variety of materials such as straw, stubble, polyethyelene films, and others, to prevent the emergence of weeds is utilized on smaller areas, mostly in forest nurseries. Polyethylene films of varying colours and thickness are most often used. This type of weed control is efficient for annual weeds but has no effect on control of many perennial weeds, and can be expensive compared to other methods used to fight weeds. Many types of mulches have been tried including: sheets of plastic, newspaper, plywood, various thicknesses of bark, sawdust, sand, straw, and even large plastic buckets.

80. Biological weed control Biological measures of weed control are based on the application of natural weed enemies such as insects, fungi, viruses, and bacteria in order to prevent their dissemination, and thus spreading. There are numerous examples of successful biological weed control. Application of pathogenic fungus, Chondrostereum purpureum , is used to control beech, yellow birch, red maple, sugar maple, trembling aspen, paper birch, and pin cherry Cultivated plants can be protected from some weeds, but not from all of them. It is impossible to destroy weeds completely because the biological agent depends upon the weed for survival.

81. Cultural Cultural weed control methods include the use of fast-growing plants to suppress weeds, and mulching. Closer spacing of trees reduces the amount of weeding that is required over the medium term because canopy closure occurs faster, thus leading to the shading out of weeds