From BugwoodWiki

Authors: Dave J. Shetlar, Ohio State University and Frank Hale, University of Tennessee

Contents 1 Pest management vs. pest eradication 2 What IPM is not 3 What IPM is 4 Monitoring 5 The control options 5.1 Cultural controls 5.2 Chemical Controls 5.3 Biological controls

Pest management vs. pest eradication

Managing insects and mites that attack our urban ornamental plants has generally relied on the use of pesticides. Whether this is good or bad is beyond the scope of this discussion, but we must ask whether alternative controls are available. Before we can consider the alternatives, we should review our current concept of pest management. Pest management as opposed to “eradication” implies that some pests will always be around. It is the goal of pest management to keep the pest populations down to a level where damage is not overly evident. In field crops, this has generally been termed an economic threshold level. In urban ornamentals, the aesthetic threshold level (the population of a pest that causes noticeable, unacceptable visual damage) is the term to be used.

Another common term used is integrated pest management (IPM), which is the selection, integration and implementation of pest control (biological, chemical or cultural) based on predicted economic, ecological and sociological consequences. In other words, when we use a pest control we must consider the cost both to the ecosystem and human society. Using the IPM approach, three important concepts must be accepted:

1. No single pest control method is always used. All of the control options — biological, chemical and cultural — must be considered. Chemical control is used only when needed.
2. Monitoring (sampling) of the pest is constantly needed to evaluate the status (not present, present but not causing aesthetic damage, present and causing aesthetic damage, etc.) of a pest population.
3. Therefore, mere presence of a pest is not a reason to justify action for control.

There has been considerable misunderstanding about IPM, IPM control options and the underlying concepts. Perhaps a look at what IPM is or IPM is not will aid our understanding of these concepts.

What IPM is not

1. IPM is not a biological control program, though biological control is a useful option. However, biological control is only one of the options. We also have to consider chemical, cultural and other controls.
2. IPM is not an organic program, though organic materials can certainly be used if they do not cause economic, environmental or sociological problems.
3. IPM is not a pesticide-free program, because the chemical control tactic may be warranted. Generally, IPM programs have reduced chemical controls (pesticides) but not eliminated them. It is not necessarily the goal of an IPM program to reduce or eliminate pesticides.
4. IPM is not the least or most expensive method of pest management. Usually, the cost of pest control remains close to original costs. Monitoring and sampling costs are traded for scheduled pesticide applications.

What IPM is

1. IPM is a decision-making process. Each plant, each year and each habitat are slightly different and programmed controls will not address these differences. Thus, monitoring must be performed and decisions must be made.
2. IPM is a system of pest management decisions based on ecological, economic and sociological values.
3. IPM is a process of pest monitoring and sampling. We must know the status of a pest and whether it really needs a control action or not.
4. IPM is a process that considers all of the control options.

Monitoring

Monitoring pest activity and population levels is the key to successful IPM. Unfortunately, most feel that monitoring must be a complicated and time-consuming process where someone must constantly watch each and every plant. This is simply not true. Monitoring of pests in nurseries and landscapes can be done in a multitude of ways — from visual inspection to using temperature-dependent (degree-day) developmental models. Another method of solving the seemingly impossible task of monitoring pests in complex settings is the concept of KEY PLANTS and KEY PESTS:

1. Key plants are trees, shrubs and flowers that are known to have perennial pest problems. As an example, birch trees often get leafminers, aphids and borers, while red oaks rarely get significant pests.
2. Key pests are those that cause significant damage or may kill trees, shrubs or perennial flowers. These key pests often have special times (windows of opportunity) that they are susceptible to controls. Aphids or galls in oaks are rarely significant enough to warrant controls, while peach tree borers in ornamental plums need special attention.

The control options

IPM uses a variety of control options — biological, chemical, cultural and other controls. These are our alternatives and we must understand the benefits and limitations of each option. Since we are dealing with ornamental landscape plants, most of the pest problems are a direct result of poor horticultural maintenance. In other words, plants placed in urban habitats or pushed during nursery production that are not suitably adapted are the ones most likely to be severely attacked by pests. Therefore, let us look at the cultural control option first.

Cultural controls

The cultural control option should be our first consideration as an alternative in landscape tree and shrub IPM. Cultural controls in field crops have generally included sanitation, crop rotation, tillage, host plant resistance/tolerance, regulatory control and mechanical/ physical destruction. If we look at these techniques, we may wonder how these relate to ornamentals in nurseries or landscapes. Though we use different terms, these techniques are commonly used and need to be emphasized more.

1. Sanitation helps remove inoculum or hiding areas of pests. Pruning, raking of leaves and destruction of heavily infested plant stock are sanitation techniques useful on our urban landscapes and nurseries.
2. Crop Rotation is generally used in field crops (i.e., corn rotated with soybeans), but should be considered for ornamental tree and shrub production. Many nursery producers rotate growing areas by planting different types of stock after a rotation. This seems to help reduce attacks by borers and root-infesting diseases. We also need to realize that most trees and shrubs in urban landscapes are limited by space, which reduces their vigor with time. Therefore, if a plant has begun to reach its limitations, it should be replaced with a smaller, better-suited one.
3. Tillage in field crops exposes resting pests and breaks up the soil for better air and water movement. In ornamental trees and shrubs, aeration and mulching are analogous.
4. Host Plant Resistance uses plants that are less susceptible to pest attack (tolerance), nonpreference (antixenosis) or produce actual toxins (antibiosis) that kill or stop pest growth. Trees and shrubs with resistance properties are well known though poorly utilized. In fact, damage can be reduced with the use of resistant plants. For people concerned with the use of pesticides, this is a major option to be considered.
5. Mechanical/Physical techniques are as simple as crushing the pest under foot to using large industrial vacuum sweepers to suck up pests. In our landscape plantings, we need to constantly remind ourselves that simple pruning or crushing of pests is preferable to chemical spraying. We are all guilty of spraying an entire juniper hedge for bagworms when only three or four bags were seen, which could have been easily picked off and crushed. Likewise, we tend to “Rambo” spray tent caterpillars in the spring when we could just reach in, roll up the nest with the caterpillars inside and dispose of the mess in a bag.
6. Regulatory Control is a legal method of restricting movement of contaminated plant material. Unfortunately, this technique is rarely effective, even though we know that most pest problems arrive on infested plant material. Therefore, we should pay special attention to new plantings that may have pests and plant stresses developed from the transplanting process.
7. Good Horticulture is one of the simple but commonly ignored methods of pest management. In other words, a “healthy” plant can generally fend for itself against insects, mites and diseases. Therefore, one of the most important control alternatives that we can use is tending to the proper needs of landscape plants. We need to match the correct trees and shrubs to the typical alkaline, hardpan clay soils of our landscapes. Not to do so causes plant stress, which allows pests to gain the upper hand.

Chemical Controls

Probably our second most useful control option in ornamental plant IPM is chemical control. Unfortunately, we have overused and misused this option, so most citizens are beginning to cast a weary eye to its use. Chemical control to most people means pesticides, though other chemicals such as attractants and pheromones are increasingly important in our IPM practice. Even if pesticides are our principal weapon, we need to understand that not all pesticides are created equal. In IPM, we want to use the ideal pesticide — a material that only kills the target pest. Unfortunately, we do not have these “silver bullets.” Most of the pesticides that are currently used have short residual life spans (this reduces accumulation in the environment), are more selective (this reduces the chance of killing nontarget animals) and are used at lower rates (this reduces the total chemical “load” used). Because of these characteristics, we need to be able to better target our applications to achieve satisfactory control.

Another general public misconception about pesticides is that “natural” pesticides are better than “synthetic” pesticides. IPM does not make this distinction. Using pesticides in IPM is evaluated on economic, ecological and sociological impacts together. In other words, there are “natural” botanical insecticides (i.e. nicotine sulfate with an LD50=55 and a known carcinogen) that are much more toxic and have more adverse effects than some “synthetic” organic insecticides (i.e. acephate with an LD50=866). In short, chemical controls used in IPM should be selected on their total attributes.

By knowing that we do not have “ideal” pesticides, whether natural or synthetic, we must use great caution to limit their adverse effects. Generally, this means that we should only target sprays to those individual plants or blocks that need it — not cover sprays. General cover sprays (spraying everything in the landscape or nursery whether needed or not) tend to cause several problems.

Cover sprays often tip the balance of control in favor of the pest. As incredible as this seems, cover sprays usually kill beneficial insects and mites (predators and parasites) better than they kill pests! Since pests usually have good reproductive ability, they “rebound” faster than their natural controls. This causes what we call pest resurgence and secondary pest outbreak.

Cover sprays tend to cause development of resistance. Pests and potential pests often develop resistance to pesticides when they are under constant pressure from a specific pesticide. In other words, a few insects on a plant may not cause significant damage, but if we constantly spray these insects, we force them to develop resistance. Then, when they reach damaging levels, our pesticide is no longer effective.

A more recently identified problem with general cover sprays of pesticides has been identified to be enhanced degradation. Because most of our current pesticides are organic compounds (i.e., containing carbon, hydrogen and oxygen), microbes are able to use the chemicals as foods or nutrients. Generally, these microbes are beneficial in aiding in the removal of pesticides from the environment. However, when constantly “fed” through general cover sprays, these microbes gain the ability to degrade pesticides more rapidly than normal. In summary, if the chemical control option, is to be used, we need to use target sprays only when needed.

The chemical control option should be considered a limited resource. As with all limited or scarce resources, we need to conserve what we have. Many of the chemical companies are no longer developing traditional pesticides. The cost of discovery, development and registration is simply too high. Therefore, we must conserve what we have and guard carefully the few new products that become available.

Most people believe that chemical control merely means pesticides. The chemical control option also contains repellents, attractants and pheromones, and desiccants. It is easiest to discuss these by their chemistry and activity:

1. Chemical Pesticides - are chemicals that directly kill the pest.
   1. Inorganics are pesticides without carbon, which can be natural earth minerals or synthetic compounds. Examples are:

      1. Diatomaceous Earth

         glass-like remains of single-celled organisms, diatoms, which scratch insect cuticle or puncture gut cells. Acts mainly as a desiccant and is rarely useful in landscapes unless combined with an insecticide like pyrethrin.

         Sulfur

         an ancient control for insects and mites.

         Sodium Fluoaluminate (=Kryocide, Cryolite)

         an earth mineral (or synthetic) that forms sharp, glass-like particles that puncture insect gut cells if ingested. Since it is a stomach poison, it does not adversely affect beneficial predators and parasites. Good only against leaf-feeding caterpillars, sawflies and beetles.

   2. Oils are petroleum- or plant-based hydrocarbon chains that have insecticidal activity. Toxicity appears to be caused by suffocation and/or membrane disruption. Examples are:

      1. Summer Oil

         a highly refined mineral oil used on green plants at a 0.5-2.0 percent rate.

         Dormant Oil

         a slightly less refined mineral oil or summer oil used at a 2.0-4.0 percent rate when plants are in winter dormancy. When used in winter, it has a minimal adverse affect on beneficial insects.

         Citrus Oil

         raw oil or separate constituents (e.g, d-Limonene) that have insecticidal properties at low dosages. Usually combined with other insecticides such as soaps.

   3. Fatty Acid Salts or Soaps are synthetic hydrocar bons using an ion, usually potassium or sodium, to join together fatty acid chains. Fatty acid chains containing six to 10 carbons have insecticidal properties. Insecticidal soaps apparently disrupt cell membranes. Soaps tend to be good at controlling soft-bodied insects such as aphids, mealybugs, soft scales, caterpillars, beetle larvae and spider mites.
   4. Microbial Toxins are molecules produced by bacteria, fungi, protozoa and other microbes that are toxic. Toxins like Bt endotoxin are relatively low in toxicity to mammals, while botulism toxin is one of the most toxic molecules known. These toxins are used by extracting the microbe or using whole organisms. Examples are:
      1. Bacillus thuringiensis (Bt) — a bacterial product containing both endotoxins and spores that are active on a variety of insects. See Biological Control below.
      2. Avermectin-B (=Abamectins, Avid) — a powerful toxin derived from Streptomyces fermentation.
      3. Chitin (=Clandosan) — the chemical that makes up the exoskeleton of arthropods (insects, crustaceans, etc.) and nematodes. By adding chitin to the soil, microbes produce toxins (ammonia) and/or produce digestive enzymes that destroy the cuticle of insect and nematode pests. Field results in landscapes have not been consistent in efficacy.
   5. Botanicals are plant extracts, usually alkaloids, that have insecticidal properties. Most people believe that since these are “natural” products, they are “safer” than other pesticides. Many of these chemicals have not been fully tested and many have striking adverse affects on mammals. Many cause severe allergic reactions (i.e. pyrethrin and sabadilla), have high toxicity (nicotine) or are even suspected carcinogens (nicotine). Examples are:
      1. Pyrethrin is derived from a specific species of chrysanthemum originally grown in Iran. The natural product is mainly an irritant to insects and is usually mixed with piperonyl butoxide (PBO) or rotenone to provide better kill of insects. Some people are allergic to the compounds.
      2. Nicotine is an alkaloid derived from tobacco that has high toxicity and is a suspected carcinogen.
      3. Neem or azadirachtin (Bioneem, Azatin, Neemazad, Neemix) is an interesting botanical derived from an Asian tree grown in India. Neem is used as a general cleaning chemical and is found in toothpaste. It seems to act as a systemic with repellent and growth-regulator effects on insects and mites.
   6. Synthetic Organics are synthetic compounds containing carbon and are usually synthesized from petroleum products. This is the group most people refer to when they mention pesticides. Because of the diversity and number of materials in this group, no attempt will be made to cover these compounds.
      1. Organochlorines (=Chlorinated hydrocarbons) usually have long residual life spans in the environment. This quality has caused most to be banned because they end up in the food chain or cause damage to non-target organisms.
      2. Organophosphates usually have short residual life spans. They are often stated as being related to nerve gas. Compounds in this group range from category I to III in toxicity and are generally neurotoxins. The EPA toxicity categories and accompanying hazard signal words for pesticide labels are toxicity category I, “Danger” and “Poison”; toxicity category II, “Warning”; toxicity category III, “Caution”; and toxicity category IV, “Caution.” EPA toxicity category I is the most toxic, while IV is the least toxic.
      3. Carbamates may have long or short residual life spans and range from category I to III in toxicity. Most are neurotoxins.
      4. Pyrethroids are synthetics that look and act like the botanical pyrethrins. They range from category I to III in toxicity, though most are in categories II and III.
      5. Insect Growth Regulators (IGR) are synthetic chemicals that look and act like insect hormones. They are often metabolism-modifying organo phosphates and carbamates with very low toxicities to mammals or other non-target animals.
      6. Spinosyns are fermentation derived metabolites from a newly discovered species of bacteria. The only commercially available insecticide in this class is considered a “reduced risk” product by the EPA (“Caution” hazard signal word on label) because of its low levels of toxicity to mammals, beneficial and other non-target species. The mode of action is a unique mechanism that is active on the insect’s nervous system nicotinic acetylcholine receptors. Exposure may occur by either ingestion or contact.
      7. Chloronicotinyls are a new class of insecticides. Imidacloprid is the only commercially available active ingredient in this class. It is a broad-spectrum systemic insecticide that is effective at very low use rates. The “Caution” hazard signal word appears on the labels. The mode of action is similar to that of nicotine in which nicotinic receptors at certain nerve endings are stimulated. The difference is that the chloronicotinyls are extremely selective at stimulating nicotinic receptors in insects but not those in vertebrates. Also, very little imidacloprid is absorbed through the skin into potentially sensitive tissues of vertebrates.
2. Attractants and Pheromones are compounds that attract a pest in search of food or another of the species (aggregation and sex pheromones). Most of the compounds in this group have not been used effectively to reduce pests but are used in traps to sample pest activity. Examples are:
   1. Geraniol/Eugenol is the attractant “floral scent” used in Japanese beetle traps. These traps do not reduce beetle damage or grub populations. In fact, evidence exists that plants near traps may sustain more damage.
   2. Disparlure is the sex pheromone attractant for gypsy moth males. It is a powerful sampling tool but has not been successful in disrupting mating.
   3. Clearwing Moth Borer Pheromones is a mix of sex pheromones attractive to several borers such as the dogwood, lilac/ash, rhododendron and peach tree borers. These traps allow for precise timing of larval controls.
   4. Pine Tip Moth Pheromones are sex pheromones for various pine tip moths. These traps determine the starting point for degree-day models for predicting larval control windows.
3. Desiccants are materials that cause the insect pests to lose water faster than they can replace it. Since insects are very small, this water loss is rapidly lethal. Unfortunately, most desiccants must be kept dry, so outside usage is limited. Examples are:
   1. Silica Gel is the same drying agent used in packing or flower drying and can be ground to a powder to dust onto insects.
   2. Diatomaceous Earth acts like a desiccant when dusted on the exterior of insects. The sharp edges of this product abrade away the thin wax waterproofing coat on the exoskeleton of insects.

Biological controls

Biological control is the use of parasites, predators and pathogens (diseases) to control pests. We have to realize that in the urban landscape and nursery, there are a multitude of beneficial insects and mites that can prey on pests. In many cases, these naturally-occurring beneficials will do a good job of controlling the pests if we do not disturb the system too much. As stated above, we usually disrupt this system by overusing pesticides that kill the beneficials better than the pests. On the other hand, there are occasions where we can actually increase these biological controls. The classical way to implement biological controls is through introductions, conservation and augmentation.

1. Introductions of exotic parasites, predators or diseases are made when foreign pests become established. This is an attempt to establish some of the checks and balances found where these pests are naturally controlled. Occasionally, foreign biological controls are found that may better control native pests. Many of these organismas are commercially available.

1. Conservation is the use of other control tactics, usually pesticides, so they have the least adverse affect on predators and parasites. It can also be the providing of habitat or food needed by the biological control organisms to improve their survival. In the urban landscape or nursery, we can use targeted sprays on those specific plants where pests are getting the upper hand. We can also plant flowers that provide nectar and pollen to feed the adults of many of the parasitic insects.
2. Augmentation is usually the rearing and release of biological control agents. Many of the organismas used in this way are commercially available. Unfortunately, this technique is usually expensive and we must use those biological controls that fit into the definition of a “good” biological control.

What is meant by a “good” biological control? Not all predators, parasites and pathogens are useful in their ability to be used in pest management. Useful ones have the following characteristics:

1. High Reproductive Potential — they must be able to keep up with the high reproduction of the pests.
2. Good Mobility — they must be able to search out the pests or come into contact with the pests.
3. Host-specific — they should not be generalists that may adversely affect other, sometimes beneficial, organisms.
4. Persistent— they should have the ability to exist when pest populations become low and remain from season to season.
5. Easily Reared or Encouraged — this will allow them to be inexpensive and competitive with other controls.
6. Tolerant of Other Controls — to fit into a true IPM system, they need to be tolerant of cultural and chemical controls.

To illustrate these concepts, let us look at a praying mantis versus a lady beetle. The praying mantis has one generation per year; eats anything in sight (including each other and other beneficials); usually ignores small insects such as aphids, mites and scales; often does not survive the summer to lay another egg case; and is sensitive to any pesticide. Therefore, praying mantids do not qualify as a useful biological control. On the other hand, lady beetles have many generations per year, they only eat a narrow range of pests (usually they are aphid, mite or scale specialists), usually overwinter well and can often withstand some of the softer pesticides, especially soaps and oils. Therefore, lady beetles easily qualify as a useful biological control.

Unfortunately, we often think that we have to actively introduce predators and parasites in our urban landscapes. Because most of these animals already exist, we merely have to be able to recognize them and avoid using cover sprays of pesticides.

Predators you should learn about are:

1. Lady Beetles are commonly sold as adults and are useful control agents if properly handled. The adults need to be fed honey (resembling aphid honeydew) in a cage (to suppress a strong urge to fly away) before release in the garden. Larvae are often mistaken for pests because they look like leaf beetle larvae or some other pests (e.g., the “mealybug destroyer” lady beetle larva looks like a mealybug).
2. Green Lacewings are not to be confused with the lace bug pest. The larvae feed on aphids, scales and mites. Eggs are purchased and sprinkled where small pests are noted to be active. The larvae must search for the pests because they do not have wings.
3. Ground and Rove Beetles are active predators present in most soil/turf habitats. Both the adults and larvae feed on a wide variety of pests, but are highly intolerant of pesticides.
4. Syrphid Flies (=Hover Flies) are common yellow and black flies that have voracious larvae (maggots) that eat aphids.

Parasites are insects (often called parasitoids) with larvae that feed on the inside or outside of their host, usually killing or sterilizing it. Some common parasites you should learn about are:

1. Trichogramma Wasps (=Egg Parasite Wasps) are microscopic (usually less than 0.02 inch long) and lay their eggs in the eggs of other insects. They are usually very host-specific and generally limited to butterfly or moth (caterpillar) pests.
2. Ichneumonid and Braconid Wasps are small wasps that commonly attack caterpillars and aphids. The larvae usually emerge from the dying host and spin small-white or yellow cocoons.
3. Tachiniid Flies are generally medium-to-large flies that lay eggs on caterpillars or various leaf-feeding beetles. The eggs hatch into maggots, which feed on and eventually kill the host insect.

Pathogens can cause diseases that kill insects. They are usually bacteria, virus, fungi and protozoa. Insect pathogens are fairly ideal in that they are host-specific. They are also non-infective to vertebrates. Examples are:

1. Bacteria have been the easiest of the pathogens to use because they can often be reared “in vitro” (in artificial culture) and form spores fairly resistant to adverse environments. Examples are:
   1. Bacillus thuringiensis (Bt) - has several strains that produce toxins lethal to various insect groups (and are thus technically a chemical control). The most common types are:
      1. Bt ‘kurstaki’ — that affects only young caterpillars.
      2. Bt ‘israelensis’ — that affects aquatic fly larvae such as mosquitos and black flies.
      3. Bt ‘tenebrionis’ — that affects some leaf-feeding beetles.
   2. Bacillus popilliae (= white grub milky disease) — has one strain available that kills Japanese beetle grubs.
2. Fungi have been identified, but are difficult to use because the spores are easily dried out or need high moisture and/or water to germinate. An example is:
   1. Beauveria spp. have been identified infecting a wide variety of insects including bugs and beetles. A commercial strain, Naturalis - OTM, is available for indoor and outdoor use on a variety of ornamental plants.
3. Viruses are common pathogens of insects, but are one of the most difficult to use because they require living insects to grow. Recent development of insect tissue culture has allowed for rearing of some of the virus strains, but the only commercial product is Nuclearpolyhedrosis Virus (NPV) — for gypsy moth control under the trade name of Gypcheck™.
4. Entomopathogenic Nematodes are a group of tiny parasitic roundworms that carry a bacterium lethal to insects. Once the nematode gains entry into an insect, it regurgitates the bacterium, which paralyzes and kills the insect. The nematode then feeds on the reproducing bacteria. The most commonly mentioned species are:
   1. Steinernema carpocapsae, which has several strains good at attacking insects that live in the upper soil or on the soil surface. Biosafe™, Vector TLTM and Scanmask™ are commercial preparations.
   2. Heterorhabditis spp. are better at attacking insects that live deeper in the soil. This group can also bore through the insect cuticle.

In summary, there are multiple alternative control methods that can be used in the urban landscape. Integrated pest management provides a framework in which to use all of the alternatives in a systematic fashion. Of most importance is the idea that we must monitor for pest problems and then select the best targeted control available.

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