Revision Date: 11/1/2004 Dewey M. Caron, Extension Entomologist BI-15 IPM for Homeowners We generally rely on a pesticide to keep insects and mites from attacking our ornamental plants and turf. Because we may not detect a serious pest before it becomes a problem or the insect/mite may transmit a plant disease pathogen, use of a pesticide often is the easiest and surest means of achieving a good looking, healthy landscape. It is obvious that we are not capable of eradicating all the potential harmful insects. One reason we do not want to do this is because of the interconnectedness of plants and animals in our ecosystem. What is our alternative then to enjoying a relatively pest free and good looking landscape? For homeowner and professional alike is is IPM. IPM stands for INTEGRATED PEST MANAGEMENT. Pest management, as opposed to pest eradication, implies that some pests will always be around. Our goal is to manage these populations of pests, and to keep their populations down at a level where damage can be tolerated. This level we can call an economic injury level or in the urban environment an aesthetic threshold level . We strive to keep the pest population below a point where id does not cause noticeable, unacceptable or monetary losses to plants in our environment. A good definition of IPM is that it is the selection, integration and implementation of a mixture of pest control strategies (biological, cultural and chemical) based on predictable economic, ecological or sociobiological consequences. In other words, we attempt to solve insect/mite pest problems keeping the cost to both ecosystem and human society in mind. We do not rely on a single pest control scheme and we don't always look to a chemical pesticide as the solution. In actual practice, IPM is a decision making process. Monitoring or sampling is important because we need to know not just that a pest is present but also if the population is increasing or decreasing, where it exists in the environment, and if a control might be warranted. Our decisions are: IF we need pest suppression treatments WHEN we need them WHERE we need them, and WHAT mix of control tactics to use. http://ag.udel.edu/extension It is the policy of the Delaware Cooperative Extension System that no person shall be subjected to discrimination on the grounds of race, color, sex, disability, age, or national origin. I ntegrated P est M anagement ( IPM ) uses a combination of strategies to manage pest populations. It is not biological control although biological control is often a useful tactic. IPM is not an organic program although once again we may integrate organic materials into our control tactic. IPM is not anti-pesticide but we generally hope to reduce chemicals as we mix our control tactics. Monitoring The success of an IPM program hinges on good monitoring . Early pest detection often allows for the use on nonchemical controls. By monitoring, you reveal the exact location and size of the pest population. By analyzing data collected by monitoring, you will be better able to predict when a recurring problem might occur and more efficiently manage that problem. Scouting is a key element in IPM. We scout, or simply look at on a regular basis: • to monitor pest population levels • to determine when a pest is present • the life stage(s) present • how many are present (the population level). Scouting takes time and scouts must be knowledgeable in what to look for. As with many things, a little training and some experience help make scouting easier and more accurate. We scout in a number of different ways. Some monitoring of plants in the urban landscape is necessary since we need accurate and timely information to use to determine the need for control. We generally key our visual inspections to “windows” of time when a certain pest is likely to be present. We can refine these windows by using Growing Degree Days (GDD) which is very reliable as a predictor of pest insect activity and by observing indicator plants. When we scout, we examine plants and the environment for pests, plant damage and conditions that would contribute to problems. If pests or damage are found, we estimate the relative population levels, damage levels and distribution of pests or damage. We note the general vigor of the plants. Some common indications of pest activity on woody plant parts include egg-laying scars, borer holes, insect frass, pitch, gummosis, fungal fruiting bodies, cankers and galls. Indications of pest activity on foliage include leaf-margin notching, irregular holes, leaf tattering, stippling, bronzing, streaking, necrosis, honeydew deposits, leaf mines, insect frass and galls. Beating is an alternative method of monitoring. To scout using this technique, place a white paper or cloth under the plant or plants and tap or beat the foliage. Beating is very useful to detect spider mites, thrips, lace bugs and aphids. The insects that fall onto the white paper can be easily seen, IDed, and counted. . Traps are often a useful monitoring device. Traps are most often used by professional IPM scouts. Different traps are designed to catch specific pests. By placing and monitoring traps, an IPM scout can determine whether a pest is present, the population level and the location of the infestation. A common trap used by homeowners is the Japanese beetle pheromone trap. Most homeowners don't really need to catch Japanese beetles in a trap to know when the pest is present. All you have to do is look at your roses or on other plants around the home or garden. The traps do help determine the level of the beetle population. Careful records from one season to the next and information from sources such as extension or industry that are conducting on-going monitoring programs can greatly assist the scout. By conducting timely scouting and keeping good records, a homeowner can greatly reduce and highly refine his/her pest control program. Keys to Monitoring In any mixed landscape there are key plants key locations key pests around which we center our scouting. We scout these plants/sites and look for the specific pest. A key plant is an aesthetically desirable or functionally important plant in a landscape that is most susceptible to insect, disease and/or cultural problems. Unless you live on an arboretum, you should have relatively few key plants to deal with. For key plants you should identify key pests. Key pests are those that are usually present, usually damaging, and therefore usually requiring control on your key plants. It may take a little research to determine the pests you need to worry about. Of course the ideal is to grow species and cultivars of plants that are relatively pest free. If you are planning a new landscape or replacing plants in your current landscape remember to consider pest tolerance as part of your selection criteria. Following scouting we should have answered the questions: • Is a pest present? • What type of pest is it? • Where is the pest population located? Now you have the major decisions: • Should I control the pest? • What pest control method should I use? • When should I apply the pest control? • How can I insure pest control effectiveness? . Insect/Disease IPM In the IPM approach we use an integration of three general control options – CULTURAL, CHEMICAL, and BIOLOGICAL controls. Cultural Controls Using a cultural control option should be our first consideration in Landscape IPM. Cultural control tactics include sanitation, crop rotation, tillage, host plant resistance/tolerance, and mechanical/physical destruction. In landscape IPM most of the pest problems are a direct result of poor horticultural practices or insufficient/improper landscape maintenance. Plants that are not suitably adapted are the ones most likely to be attacked by pests. If we plant our urbanscape and then fail to adequately manage and care for the plants, they may become stressed and more likely to be attacked. A healthy plant can generally fend for itself against insects, mites and diseases. In practice for our lawn this means matching the correct turfgrass cultivars for sun or shade, mowing them correctly, fertilizing when and at proper levels as needed, insuring that thatch is controlled, avoid killing off the normal component of soil creatures and keeping the soil as open as possible. For trees and shrubs or our other plantings, the principles are the same, though our management details may differ. Here in practice is how we use cultural controls: Sanitation is probably the most important cultural control tactic we can employ in the urbanscape. Sanitation helps remove disease inoculum or pest insect hiding places. Sanitation means starting and staying disease free. Sanitation takes away the harborage locations that many pest insects need as alternatives during their life cycle. Sanitation is smart urban management and it helps maintain the aesthetic value of our environment. Crop rotation is ideally used in the agricultural sector. It is rotating corn with soybeans but it should also be considered for the urban environment. Turf renovation and replacement of stressed trees and shrubs can greatly reduce insect/disease pressures and improve our management practices. We must realize that most trees and shrubs in our urban plantings become space limited with time. This reduces their vigor. If a plant or planting has reached or has begun to reach its limitation, consider rotation with smaller, better suited alternatives. Host resistance uses plants which are less susceptible to pest attack (tolerance). This may be due to physical characteristics of the plant such as stickiness or hairiness or it may be chemical such as protective chemicals that may be distasteful or toxic to insects that may feed on the plant (antibiosis). We generally know the turf varieties and plants and shrubs that exhibit tolerance or antibiosis but we too infrequently utilize these alternatives. We could greatly reduce our insect and disease problems in the home landscape by simply changing to plant varieties that are most host resistant. . Mechanical/physical techniques can be as simple as crushing pests under foot or using barriers and/or traps for potential pests. If we find infestations at an early stage, we can prune out or pick off pest individuals and discard them. This can be very effective for bagworms when numbers are low or in mid season as the new bags are forming. Removing the unsightly and disfiguring webs of tent caterpillars or fall webworms is effective control. Prune out and destroy small infestations of quince rust, insect galls, cedar-apple rust galls and tip borers of evergreens. Mulch keeps weeds down. Screening can keep insects and birds off plants and protect ripening fruit. Various traps may reduce populations of destructive insect like yellow jackets or Japanese beetles or help us attract beneficials like soldier bugs. Opportunities are limitless if we regularly monitor and keep ahead of potential problems. Chemical Controls Probably our most common control option in landscape IPM is chemical control. Chemical control to most people means pesticides though other chemicals such as attractants and pheromones are increasingly important in our landscape IPM programs. Even if pesticides are our principal weapon, we need to understand that not all pesticides are the same. In IPM programs, we seek to use the ideal pesticide – a material that only kills the target pest. Thus many of the pesticides which are currently used are: * short residual life spans – this reduces accumulation in the environment * more selective – this reduces the chance of killing non-target animals * used at lower rates - this reduces the total chemical “load” used Because of these characteristics, we are able to better target our applications in order to control pests. By knowing that we do not have “ideal” pesticides, we must use great caution to limit their adverse effects. Generally this means that we should only do target sprays to those individual plants which need it – not cover sprays. General cover sprays (spraying everything in the landscape whether needed or not) tends to cause several problems. Cover sprays may tip the balance of control in favor of the pest. Cover sprays may 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 increase 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 be causing significant damage, but if we constantly spray these insects we are creating selection pressure that can lead to developing resistance. Then, when the now-resistant bugs reach damaging levels, our pesticide is no longer effective. A more recently identified problem with general cover sprays of pesticides is enhanced degradation. Since 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 general cover sprays are used repeatedly, these microbes degrade these pesticides more rapidly than normal and they are less effective. Classification of Pesticides: • INORGANICS are pesticides without carbon which can be natural earth minerals or man- made compounds. Examples are: • Diatomaceous Earth – glass like remains of single celled organisms, diatoms, which scratch insect cuticle or puncture gut cells. Inorganics act mainly as a desiccant and are rarely useful in landscapes unless combined with an insecticide like pyrethrum. • Sodium Fluoaluminate (= Kryocide, Cryolite) – an earth mineral (or man-made) which forms sharp glass-like particles which 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. • OILS are petroleum or plant based hydrocarbons which have insecticidal activity. Toxicity appears to be caused by suffocation and/or membrane disruption. Examples are: • Horticultural Oil – a highly refined mineral oil used on green plants at a 0.5-2.0% rate. • Dormant Oil – a slightly less refined mineral oil or horticultural oil used at a 2.0-4.0% rate when plants are in winter dormancy. When used in winter, dormant oils have minimal adverse affect on beneficial insects. • FATTY ACID SALTS OR SOAPS are man-made hydrocarbons using an ion, usually potassium or sodium, to join together three fatty acid chains. Fatty acid chains containing 6-10 carbons have insecticidal properties. Insecticidal soaps apparently disrupt cell membranes. Soaps tend to be very good at controlling soft bodied insects such as aphids, mealybugs, soft scales, caterpillars, beetle larvae and spider mites. • MICROBIAL TOXINS are molecules produced by bacteria, fungi, protozoa and other microbes which are toxic. Toxins like Bt endotoxin have relatively low 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. Bacillus thuringiensis (Bt) is a bacterial product containing both endotoxins and spores which are active on a variety of insects. (See Biological Control below.) • BOTANICALS are plant extracts, usually alkaloids, which have insecticidal properties. Most people believe that since these are “natural” products, they are “safer” than other pesticides but this is not the case. Some cause severe allergic reactions (i.e., pyrethrum and sabadilla), have high toxicity (nicotine), or are even suspected carcinogens (nicotine). Examples of botanicals are: . • Pyrethrum (LD50=200) 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 or rotenone to provide better kill of insects. Some people are very allergic to them. • Rotenone (= Cube, Derris) (LD50=132) is an alkaloid from roots of a tropical plant. It is highly toxic to fish and was used originally by South American Indians to collect fish from lakes and rivers. • Nicotine (LD50=55) is an alkaloid derived from tobacco with high toxicity. It is a suspected carcinogen. • Neem (Azadirachtin, Margosan-O) (LD50=3000) is an interesting botanical derived from an Asian tree grown in India . Neem is used as a general cleaning chemical and is found in tooth paste. It seems to act as a systemic with direct toxicity and it has growth regulator effects on insects and mites. Field results have been inconsistent. • SYNTHETIC ORGANICS are man made compounds containing carbon. They are usually synthesized from petroleum products. This is the group most people refer to when they mention pesticide. Because of the diversity and number of materials in this group, no attempt will be made to cover these compounds here. Biological Control Biological control utilizes the 3 P's - Parasites, Predators and Pathogens (diseases) to control pests. We have to realize that in the urban landscape, there is a multitude of beneficial insects and mites which 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. The classical way to implement biological controls is through introductions, conservation and augmentation. To be effective, a biological control agent should be: • host specific in eating a pest species • able to keep up with pest population explosions • compatible with other control methods We often think that we have to actively introduce predators and parasites in our urban landscapes. Since most of these animals already exist, we merely have to be able to recognize them and avoid using cover sprays of pesticides. Two familiar biological control agents are preying mantids and ladybird beetles. The preying mantid has one generation per year, eats anything in sight (including each other and other beneficials), usually ignores the small insects such as aphids, mites and scales, often doesn't survive the summer to lay another egg case and is very sensitive to any pesticide. Therefore, preying mantids are not very useful in 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. • Some common predators which you should know are: • Lady Beetles – are commonly sold as adults. They are a useful control agent if properly handled. The adults need to be fed some honey (to resemble aphid honeydew) in a cage before release in the garden to suppress a strong migration urge. Larvae are often mistaken for pests because they look like leaf beetle larvae or are mistaken for pests. • Green Lacewings – are not to be confused with lace bugs which are pests. The larvae feed on aphids, scales and mites. Eggs are purchased and sprinkled in areas where small pests are noted to be active. The larvae must search for the pests because they do not have wings. • 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 susceptible to pesticides. • Syrphid Flies (=Hover Flies) – are very common yellow and black flies which have voracious larvae (maggots) which eat aphids. • Parasites are insects (insect examples are often called Parasitoids ) with larvae which feed on the inside of their host, usually killing or sterilizing it. Some common parasites which you should know are: • Trichogramma Wasps (- Egg Parasite Wasps) are microscopic in size, usually less than 0.5 mm long. They lay their eggs in the eggs of other insects. They are usually very host specific and generally limited to butterfly or moth (caterpillar) pests. • Tiphiid and Scoliid Wasps – are fairly large insects which attack white grubs. Unfortunately they usually cause alarm because of people's fear of being stung as the adults search just above the turf. • Ichneumonid and Brachonid Wasps – are small wasps which commonly attack caterpillars and aphids. The larvae usually emerge from the dying host and spin small white or yellow cocoons. • Insect pests are also attacked by a variety of diseases, which we call Pathogens , caused by bacteria, virus, fungi and protozoa. When an insect is infected with these agents, it is usually killed. Insect pathogens are ideal in that they are very host specific and are also very non-infective to vertebrates. Examples are: • BACTERIA – have been the easiest of the pathogens to utilize because they can often be reared “in vitro” (in artificial culture) and form spores fairly resistant to adverse environments. • Bacillus thuringiensis (Bt) – there are several strains which produce toxins lethal to various insect groups. The most common types are: 1) Bt “Kurstaki” – which affects only young . caterpillars; 2) Bt “Israelensis” – which affects aquatic fly larvae such as mosquitoes and black flies; and, 3) Bt “Tenebrionis” – which affects some leaf feeding beetles. • FUNGI – Several fungi have been identified but they are difficult to utilize because the spores dry out easily or need high moisture and/or water to germinate. Beauveria spp. and Metarrhixium spp. are the most commonly identified species. Unfortunately, there are no commercially available fungal products in the United States , though some exist in Europe . • VIRUSES – There are several common viral pathogens of insects but they are 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. • ENTOMOPHAGOUS NEMATODES – These are a group of tiny parasitic roundworms which carry a bacterium lethal to insects. Once the nematode gains entry into an insect it regurgitates the bacterium which paralyzes the insect. The nematode then feeds on the reproducing bacteria. The most commonly sold species is Steinernema carpocapsae which has several strains, good at attacking insects, which live in the upper soil or on the soil surface. Biosafe and Scanmask are commercial preparations. Another group, the Heterorhabditis spp., are better at attacking insects which live deeper in the soil. This group can also bore through the insect cuticle. At present, nematodes have been inconsistent in their activity and further research is needed to improve their performance. Weed IPM Weeds, like diseases or insects, lend themselves to I ntegrated P est M anagement ( IPM ) strategies. A variety of methods are available for weed management in landscapes. Physical control techniques like hand weeding can be used to control existing vegetation. Hand weeding by direct pulling of weeds or hoeing is time-consuming and expensive but may be the preferred method if weeds are scattered at the site. Since weeds can root back into the soil as shoot fragments and weeds typically tolerate a degree of desiccation, avoid bringing soil up from deeper in the soil profile, as this carries additional weed seeds to the soil surface, which can then germinate. Weed seed generally needs moisture and sunlight for germination. Mulches are a mechanical control commonly utilized in landscapes for weed control. Mulches may serve moisture conservation and other reasons too. Use a 2 to 4 inch depth of mulch. Deep layers of mulch can lead to very wet, poorly aerated soil under the mulch, promoting such disorders as root rots. Piling mulch up against the trunk of a tree can cause rotting of the trunk if it stays moist. When remulching a site, rouge out existing mulch and use a shallow layer so as not to exceed a 4 inch depth. Use mulch that is free of weed seed, rhizomes or tubers. Weeds easily spread through contaminated mulch. Use mulch that has been properly composted. “Sour mulch” can damage landscape plants. Sour mulch will have a penetrating odor like sulfur, vinegar or ammonia, and will have a low pH (under pH 4). . A variety of organic mulches (pine bark, hardwood bark, pine straw, etc.) can be used in the landscape. Organic mulches generally provide good short term control of annual weeds like crabgrass. As organic mulches break down, however, they become a good growing medium for weeds. Organic mulches generally will not control perennial weeds like bindweed, yellow nutsedge or bermudagrass. Rock mulches (lava rock, white marble chips, etc.) provide better control of annual weeds than organic mulches. Like organic mulches, rock mulches will not control perennial weeds. If using rock mulch, consider placing a landscape fabric underneath it. The fabric will act as a soil separator, preventing rock pieces from sinking into the soil as it prevents soil from moving above the rock layer, which would bring weed seed to the surface. Black plastic (solid polyethylene) has been used underneath mulches to improve weed control. Black plastic provides excellent control of annual weeds, and will suppress perennials. However, black plastic lacks porosity, restricting air and water movement. For this reason, black plastic is not recommended for long term weed control in landscape beds. Landscape fabrics, also called geotextiles or weed barriers, have been developed to replace black plastic in the landscape. Landscape fabrics are porous, allowing water and air to pass through the material, overcoming the major disadvantage of black plastic. Placing a landscape fabric under mulch results in greater weed control than when mulch is used alone. There are differences in the weed-controlling ability among the landscape fabrics on the market. Fabrics with more open space allow greater weed penetration both downward and upward from beneath the material than more closed fabrics. Chemical Weed Control You should initially use a herbicide to control perennial weeds prior to fabric installation. Use a shallow mulch layer (about 1 inch depth) to thoroughly cover the fabric, thus preventing photodegradation. Deeper mulch layers may encourage weed growth in the mulch layer. Maintain the mulch layer above a fabric free of weeds. Use of rock mulch above a landscape fabric has given greater weed control than fabric plus organic mulch combinations. Herbicides can be used to improve weed control in a mulched landscape. Grasses germinating from seed can be easily controlled with a preemergence application of one of the available grass herbicides. Controlling broadleaf weeds from seed can be somewhat harder, although there are a few broadleaf herbicides that can be combined with a grass material for broader- spectrum weed control. Annual and perennial grasses can be controlled selectively through application of a postemergence grass herbicide. Yellow nutsedge can be controlled using certain preemergence herbicides, or through careful application of an appropriate postemergence chemical. Control of perennial broadleaf weeds and perennial monocots such as wild onion is very difficult in landscapes. Often the only option for chemical control is careful application of a nonselective herbicide. .