Insect Management In Commercial Forest Management

Pabasara Gunawardane

Insects Pests Diseases

Kingdom :AnimaliaPhylum :ArthropodaClass : Insecta

Classification

Around 30 orders worldwide

More than one million different species of insects have been identified, but some experts believe that there may be as many as 30 million insect species in the world that have yet to be discovered and identified.

Dominant Orders Of Forest Pest Insects

• Coleoptera (beetles)• Lepidoptera (moths and butterflies)• Hymenoptera (ants, bees, and wasps)• Hemiptera (bugs)• Isoptera (termites)• Orthoptera (grasshoppers and crickets)

The diversity of forest insects is also reflected in their feeding habits.

• Leaf feeders• Sap feeders• Stem feeders• Flower, nectar, pollen, and seed feeders• Dead-wood feeders

Functional Diversity: The Feeding Guilds

Plantation Species in Sri Lanka

• Teak - Tectona grandis (Verbenaceae)

• Eucalyptus

• Mahogany - Swietenia macrophylla

• Sandalwood – Santalum album

• Aquilaria

Tectona grandis• Well known for its versatile timber

• Possesses several qualities - lightness and strength, drying without warping and splitting, easy workability and attractive appearance

• Plantations of teak are estimated to occupy an area of 5.7 million ha worldwide

Insects in Teak

174Species

137Leaf Feeders

16Sap Feeders

14Shoot/Stem Feeders

5Root Feeders

3Seed Feeders

Nair et al 2007

Defoliators Hyblaea puera (Lepidoptera: Hyblaeidae)

• Defoliator insects cause severe defoliation and, hence, reduce growth rate

• Outbreaks of these insects may occur 2 or 3 times during the growing season

Skeletonizer Eutectona machaeralis (Lepidoptera: Pyralidae)

• Its larva feeds on the green leaf tissue between the network of veins, leaving the skeleton of veins intact• Partially damaged leaves are not shed and even the fully skeletonized leaves are retained by the tree for a long time

Stem borers Zeuzera coffeae (Lepidoptera : Cossidae)

• The most important stem borer in young teak plantations• The larva bores into the pith of the stem of saplings and ejects the frass through holes made on the stem

Stem borers Xyleutes ceramicus (Lepidoptera : Cossidae)

• Commonly called the teak bee hole borer• Found in older Teak plantations• The larva of this moth bores into the wood of living Teak trees

Whitegrubs Whitegrubs are the immature stages of some beetles of the family Scarabaeidae (mostly of the subfamilies Melolonthinae and Rutelinae)• They live in soil and feed underground on the roots of seedlings, grass etc.• Holotrichia (syn. Lachnosterna) consanguinea and H. serrata (Melolonthinae) are the common species found in Teak nurseries in India and Sri Lanka• The larvae bore into the fleshy taproot of Teak seedlings and cause their death

Eucalyptus species (Myrtaceae)• Eucalyptus is a widely planted tree genus in the tropics• The adaptability of eucalypts to a variety of site conditions and their fast growth are major characteristics•The global area under eucalypt plantations is at 10 million ha

Insects in Eucalypts

920Species

Nair et al 2007

Root feeders Defoliators Sap suckers Borers

The most common pest problem of exotic eucalypts is mortality of saplings caused by root-feeding termitesPostelectrotermes militaris (Kalotermitidae) is found on the heartwood of living trees of Eucalyptus sp. in Sri Lanka.

Eucalyptus Gall Wasp has been reported in Sri Lanka in 2010.

Swietenia species (Meliaceae) Produces one of the world’s best furniture timbers Swietenia macrophylla is the most widely distributed and planted both in indigenous and exotic locations

Swietenia mahagony is also raised in plantations, but to a much lesser extent

The plantations cover 151 000 ha worldwide

Mahogany Shoot Borer Hypsipyla robusta (Lepidoptera: Pyralidae)

• Saplings are the most susceptible to Hypsipyla attack• Tunneling of the leading shoot kills the terminal growth, resulting in the development of lateral shoots which may also be attacked, causing a bushy top and loss of tree form, in addition to growth loss• It is suggested that the relatively low level of attack in Sri Lanka may be due to good overhead shade where the trees have been planted.

Sandalwod (Santalum album)

• Commercially and culturally important plant species• Sandalwood oil extracted from the heartwood has high market demand • Due to the high value and the demand, there is a growing attention at present in establishing sandalwood plantations

Insects in Sandalwood

150+Species

60Leaf Feeders

92Sap Feeders

6Stem Feeders

5Bark/Deadwood Feeders

3Seed Feeders

Remadevi et al 2012

Insects in Sandalwood Sandalwood seedlings in the nurseries are subjected mainly to the attack by defoliators and sap suckers

Cryptothecia cramerii (Psychidae: Lepidoptera) cuts off young plants

Stem borers – Zeuzera coffease (red borer) Indarbela quardinotata (bark-feeding caterpillar) and Aristobia octofasiculata (heartwood borer) are some of the pests causing considerable damage to living trees

Agarwood (Aquilaria Species) Agarwood (Family -Thymelaeaceae) is one of the most prized non-timber forest product traded in the international market

The establishment of forest species producing agarwood is gaining attention at international and local levels

Insects in Agarwood In agar plantation no such serious pests and diseases have been observed Heortia vitessoides - a leaf-eating caterpillar is considered to be the most destructive pest causing damage by complete defoliation of agar plantations

The intensity of attack is more in the trees grown in open than under shade

Pest control

• Commonly used term for attempts to limit the damage caused by pests

• Tried to kill the pest insects using chemical or other means

• it was not easy to kill off the insects; they reappeared when the effect of the insecticide waned or developed resistance to the chemicals

Pest Management• Planters realized that pests need to be controlled only if they cause economic damage

• The term ‘pest management ’ was therefore coined to indicate management of the pest population to limit it to a tolerable level

•The emphasis was on regulating the population size, not killing all the pest insects, which was impracticable anyway

Historical Pest Management• Traditionally, forest managers in the tropics have ignored insect pest problems• Main reason was the lack of scientific researches• Research in tropical forest entomology is about a century old• A sound foundation of basic knowledge on insects associated with forest trees has been built up over time• But, very few practical problems have been addressed

Integrated Pest Management (IPM)• The concept of ‘integrated pest management ’ emerged in the 1970s• It envisaged the use of all the available techniques in an integrated manner to reduce the economic damage caused by pests with the least ill effects on the environment

• IPM aims at regulating all the pest species including insects, pathogens and weeds in a crop production system

•IPM marks a change in human attitude or philosophy, from supremacy over nature to acceptance of an ecologically compatible strategy to contain the pests

Tools of Integrated Pest Management• Monitoring (scouting)

• Identification

• The threshold level

• Management Strategy – (Do nothing, Cultural management, Mechanical management, Pesticides)

• Evaluation

Monitoring (scouting)• Monitoring (scouting) forests and newly established plantations will help detect problems early, while there is still time to take action• A representative sample of trees can be checked for signs and symptoms of insect and disease problems• All parts of the tree should be inspected from top to bottom and from branch tips to trunk• Depending on the pest, the use of traps or microscopic examination may improve the information gathered by visual examination

Identification• Identification of pests and the diagnosis of pest damage are key elements of IPM• What kind of pest is present?• What stage of the pest is present?• What is the size of the pest population?• How much damage has occurred?• How much damage is likely to occur if no control measures are taken?• Does the pest or damage require immediate attention, or can control measures be postponed until the trees are near harvest?

Threshold Level• The threshold level - the point at which the pest or its damage becomes unacceptable• The threshold level may be related to the beauty, health, or economic value of the tree crop• Once the threshold level has been reached, determination of the type of control procedure is needed• Several factors are considered here (The size of the pest population, the kind of damage the pest is causing, and the control measures that are available and the cost effectiveness of potential controls)

Management Strategy • Decision on management (control) strategies• Do nothing - pest does not damage the crop value or the crop value is so low

• Cultural management - manipulates the environment to make it more favorable for the plant and less favorable for the pest (good site selection, planting resistant varieties, or selective pruning)

Mechanical management - Some measures exclude or remove the pest from the habitat (Mechanical traps, screens, fences, and nets can remove the pest or prevent access by the pest)

Management Strategy • Biological management - Biological controls include the

beneficial predators, parasites and pathogens that kill pests• Pesticides - Pesticides are a very important tool in IPM when

large pest populations threaten high-value trees - Knowledge of the pest’s life cycle, selection of an appropriate pesticide, proper timing of the application, and use of the right application equipment will improve coverage and effectiveness

Evaluation

• The results of management strategies are evaluated• This information will determine whether any follow-up

treatment is needed and will improve the management strategies for the future

• Sound IPM practices pay off both economically and environmentally

• Preventive measures - aim to keep pest populations at low densities and not allow them to develop into outbreaks• In the case of teak defoliator outbreaks, destroying the early epicenter populations during the pre-monsoon period can prevent at least part of the subsequent large-scale outbreaks• Retention of plant species that support alternative hosts of pest insects• Reduce pest build-up by enhancing natural enemy action• Use of pest-resistant trees

Two approaches are available for pest management

Remedial measures Aim to reduce the pest population level by killing the insects by one means or other• Use of insecticides - control of root-feeding termites of eucalypt saplings, where the insecticide is mixed with the soil to kill the termites that might attempt to penetrate to the tap root - insecticidal treatment of nursery soil to control ants and whitegrubs or mixing of insecticide with seeds while in storage - insecticides are applied to the insects and the trees after the infestation is noticed• Biological control with predators and parasitoids

Use of transgenic trees - An emerging method of pest management is use of transgenic or genetically modified trees which possess genes conferring insect resistance

Natural outbreaks of virus diseases are common in many forest insects Causes sudden collapse of population outbreaks as in the case of the teak defoliator Hyblaea puera

Such disease epizootics are usually caused by baculoviruses Use of Semiochemicals (behaviour-inducing chemicals)

Existing management methods for Mahogany shoot borer • Mixed or enrichment plantings• Wider spacing• Varying tree density • Provision of shade• Promoting vigorous tree growth• Encouraging natural enemies• Leaving weed rows between young plantations• Few systemic insecticides like carbofuran and Deltamethrin are occasionally used. But these insecticides have limited prospects in today’s pest management practices due to environmental concerns

Existing management methods for Termites

• Several termiticides containing active ingredients: bifenthrin, chlorfenapyr, cypermethrin, fipronil, imadacloprid and permethrin are used• New methods of termite control are always being developed by researchers• Plant derived natural products, entomopathogenic fungi are some of the alternative methods

Constraints To Forest Pest Management• Small number of forest entomologists compared to the large number of pest problems• Lack of adequate training of entomologists in applied research and in the principles and techniques of pest management• Inapplicability of sophisticated pest management methods employed in developed countries, such as ultra-low volume aerial application of insecticides, aerial release of biocontrol agents, computer-based pest prediction and alert systems, due to technological and economic constraints• In most tropical countries forests are predominantly government owned, and forest pest management has low priority relative to the more pressing agricultural pest problems

Recommendations• Increasing the research and monitoring of pest outbreaks• Reformation of the forestry research institute to develop suitable plant species• Establishment of rules and regulations when importing plant species• Conducting more research on biological treatments• The ability to recognize beneficial biocontrol organisms, combined with cultural and mechanical controls, may allow to reduce, delay, or eliminate pesticide treatment of a minor pest problem

References Nair, K. S. S , (2007) Tropical Forest Insect Pests, Cambridge University Press

Nair, K. S. S, (2001) Pest out breaks in tropical forests, Center for international forestry research

Mohd Farid Mamat , (2011) Costs and Benefits Analysis of Aquilaria Species on Plantation for Agarwood Production in Malaysia

Remadevi O.K. (2012) Pests and diseases of sandalwood plants in nurseries and their management

Sandy Perry, (2000) Forest Pest Management, Michigan State University

Howard F. W. (2014) Mahogany shoot borer, University of Florida

Apichart Kaosa-ard (2010) Overview of problems in teak plantation establishment, Forest Resources Department, Chiang Mai University, Thailand

Pest problems in forests available at http://shodhganga.inflibnet.ac.in/bitstream/10603/6175/4/04_chapter%201.pdf as at 0220 hr. 25.08.2015

Indian Council of Forestry Research and Education, Dehradun. Sandal (Santalum album Linn.). Dehradun, Forest Research Institute. 9p.