What is integrated pest management(IPM)? And What are the tools of IMP?
Integrated Pest Management (IPM) has been a valuable tactic in pest management programs around the world but has undergone a resurgence in recent decades that parallels the development of IPM as an accepted practice for pest management.
A brief historical perspective of Integrated Pest Management follows the interaction of pests with biological control, chemical control, physical control and with the various elements of integrated pest management. Existing implementation, as well as potential uses of this bio-chemo-physio control in IPM are also considered.
Tools of the Integrated pest management (IMP)
- CULTURAL CONTROL
- MECHANICAL OR PHYSICAL CONTROL
- CHEMICAL CONTROL
- BIOLOGICAL CONTROL
1. CULTURAL METHOD
A variety of cultural practices such as management of cropping patterns, soil, crop residue, and non-crop vegetation are used in the management of insect pests. These practices in some cases can be manipulated to enhance natural enemies of insect pests. In general, these approaches are aimed at increasing the density of resident natural enemy populations or communities to increase their effectiveness in pest suppression. culture control is major tool in integrated pest management.
It has long been recognized that perennial cropping systems such as orchards are more favorable to natural enemies and IPM because of the habitat stability they provide. Habitat stability can also be provided institutions where crop cycles overlap throughout the year in a substantial portion of the landscape so that individual fields are not too far apart for enemies to move between them. Although there are several examples of harvest modification to allow for conservation of benefits such as strip harvesting, pruning and relay cropping or intercropping.
Crop rotation is a foundation for pest management in some cropping systems, dissociating pest populations from continued food supply from one year to the next. Although not common, crop rotation can also affect populations of beneficial such as ground-dwelling rove beetles. Placement of rotated crops in relation to prevailing wind direction and previous years crops may influence the ability of parasitoids to locate and colonize the new crop.
The increased vegetational diversity provided by intercropping was proposed byRoot (1973) as a possible means to reduce pest discovery and retention in crops, and to enhance natural enemy populations and activity. Intercropping studies in the literature noted that pest densities were reduced by 56% of cases, increased by 16%, and not affected by 28%. Natural enemy activity in intercropping reported increased pest mortality due to natural enemies in 70% of cases, lowered mortality in 15%, and no effect in another 15%. The responses of both pest and beneficial insects to intercropping are not well understood, because the underlying mechanisms at the behavioral level have not been well studied. An understanding at this level is important to develop intercropping systems with more predictable outcomes.
Trap crops are deployed to intercept dispersing pests before they can enter the main crop, allowing control measures to take place in a smaller area. Natural enemies invariably follow these pests and may be affected as well. These effects may be positive, where natural enemy populations are able to build upon concentrated pest populations and then move into the main crop, although this does not necessarily lead to increased pest reductions in the main crop. The trap crops may also act as a sink for insect pest populations as a result of increased natural enemy activity. However, control measures taken for pests in trap crops have the potential to negate these positive effects by eliminating natural enemies as well. Even if control measures are used in traps crops, the main impact of trap cropping on beneficial insects may be the reduction in pesticide usage in the main crop resulting in the conservation of beneficial insect populations.
Cover crops are employed in crop production systems for a variety of reasons including soil fertility, erosion control, and in some cases, pest management. In several agricultural systems, cover crops have been shown to disrupt the behavior of pest insects and reduce their abundance. It is less clear row cover crops influence natural enemies, and as a result the pest insects they attack. For example, cover crops have been shown in some studies to enhance natural enemy populations in cotton while other studies have found no effect. Buckwheat (Fagopyrum escalentum Moench) has been shown to enhance natural enemy activity in crops as diverse as cabbage and grapes, but in very few cases have effects on pest densities been associated with this enhancement. When mulched, cover crops can provide microhabitats favorable to insect natural enemies and increase their numbers. There does not appear to be any study that links the enhancement of natural enemy populations by cover crops with economic suppression of insect pests.
2. MECHANICAL OR PHYSICAL CONTROL
Tillage is the primary means of disturbance in agroecosystems and is central to many agricultural practices such as preparation of seedbeds, incorporation of organic material and fertilizer, and suppression of weeds and some diseases and insects pests. Tillage practices can have significant influences on arthropod populations, including natural enemies, and in turn pest management. A significant amount of research has been directed toward understanding the influence of reduced tillage systems on arthropods, including natural enemies. In some cases, conservation tillage has been shown to increase natural enemy populations while in others they were either not affected, or reduced.
Much of the work dealing with soil-dwelling insect natural enemies has focused on carabid beetles (Coleoptera: Carabidae), which are significant generalist predators in annual row-crop agricultural systems. Tillage affects carabid populations through direct mortality from tillage events, or indirectly through loss of prey resources and changes in microclimate. Shearin et al. 2007 reported that entomophagous carabid beetles were more sensitive to tillage than herbivorous220 D. Orrcarabids. While diversity and abundance of carabids appears to be favored by reduced-tillage, there are examples where entomophagousbeetles are significantly more abundant in conventional tillage systems.
The interpretation of the results of these studies is complicated by the sampling method employed. Populations of carabids are usually sampled with pitfall traps with trap catches expressed as activity-density. However, there are significant constraints to using this method, and care should be taken when designing studies and interpreting results. In addition, dispersal of beetles between experimental plots may mask treatment effects. More work appears to be needed to gain a clearer understanding of the effects of tillage on ground-dwelling arthropod natural enemies. What is less clear, and needs even more work perhaps, is the link between population changes in enemies from tillage practices and suppression of target insect pest populations.
Tillage has also been found to affect foliage dwelling arthropod predators as well as parasitoids either directly from soil disturbance, or indirectly by altering weed communities. This is especially important where natural enemies pupate in the soil. For example, an outbreak of cereal leaf beetle, Oulemamelanopus(Coleoptera:Chrysomelidae), in Canada was linked to a change in tillage practices that killed parasitoids of the beetle overwintering in the soil. In addition to tillage, other practices used to manage crop residues can affect natural enemies. Several studies have shown that leaving crop residues behind, in cases where there is no good pest management (or other) reason to remove them through tillage or other means, can conserve populations of parasitoids and predators.
2.TRAPS AND BARRIERS
Traps and barriers are frequently employed in IPM programs to either reduce pest numbers directly or deny them access to crops. However, there are cases where they may have side effects on beneficial organisms that may interfere with pest management.
Semi chemicals, including pheromones and kairomones, are commonly utilized in host-finding by natural enemies such as parasitoids. They may have the potential for manipulating populations of natural enemies to benefit pest management. These same semi chemicals in turn can have non-target impacts on natural enemies when traps employing them are used in IPM programs.
In mass-trapping efforts or even monitoring with traps such as colored sticky traps, attraction and effect on natural enemy populations should be considered prior to implementation. Electric traps, using ultraviolet light as an attractant killed almost exclusively non-target insects, rather than the targeted biting flies, with approximately 13.5% of the catch predatory and parasitic insects. Mesh size of insect barriers require testing to determine the size that excludes pest but does not also exclude natural enemies that may be attacking other pests in a cropping system.
The use of UV blocking films has potential for use in IPM programs against insect pests in greenhouse crop production, through interference with insect visual receptors and behavior. However, these films also have the potential to interfere with biological control, and more studies examining effects on natural enemies should be undertaken.
In the 1980s and ’90s vacuum systems became popularized for management of insect pests organically, and a few systems are still available for this purpose. Studies conducted to date have not demonstrated any negative impact on beneficial insects in crop field treated with the vacuums.
3.CHEMICAL CONTROL AND PESTICIDAL USE
Probably the most common pest management activity that negatively impacts beneficial organisms in agroecosystems is pesticide application. Although herbicide use can influence both pest and natural enemy populations, this section will focus on insecticide effects since they are so much more significant. Pesticide products used for pest management in agriculture have been changing so that use of the oldest and most toxic cyclodienes, carbamates and organophosphates is slowly decreasing worldwide. For example, in the United States between 1992 and 2000, the use of these materials had declined by 14% (by weight of active ingredient), even though overall agricultural pesticides had not declined in that same period (GAO, 2001). However, these materials still retain a 50% worldwide market share. Synthetic pyrethroids, with their vastly improved mammalian and avian toxicity profiles, now account for 20% of global insecticide sales.
1.SIDE EFFECTS ON NATURAL ENEMIES
Studies examining the side effect of pesticides on natural enemies have been reviewed several times. These side effects are manifested in several different ways. Indirect effects include habitat destruction, and damage to nesting, oviposition, resting, and mating sites. Direct lethal effects of insecticides are the most well-known and have typically been estimated by determining a median lethal dose (LD50) or median lethal concentration (LC50) that enemies are directly exposed to. Sublethal effects of insecticides on beneficial arthropods include deleterious side effects of direct pesticide exposure on physiology and behavior. The physiological effects extend to general biochemistry and neurophysiology, development, adult longevity, fecundity, sex ratio and immunology, while behavioral effects extend to mobility, navigation/orientation, feeding behavior, oviposition behavior, and learning performance.
In addition to direct lethal and sublethal effects, insecticides may also lead to pest population resurgence, often attributed to the removal of a target pests natural enemies by the application of broad-spectrum insecticides. Taking sublethal effects of pesticides into consideration when choosing pesticides for an IPM program can result in great improvements in natural enemy performance. In some cases, sublethal doses of pesticides have been shown to have favorable effects on arthropod physiology and/or behavior, a phenomenon known as hormoligosis. Although hormoligosis has been reported in a beneficial arthropod, the predatory mite Amblyseiusvictoriensis(Womersley), this phenomenon appears very uncommon for natural enemies andlikely of little widespread value in the integration of chemical and biological controls.
2.MODIFICATION IN PESTICIDAL USE METHODS
Because of the widespread use of pesticides in agricultural systems, it follows that modifications of pesticide use practices are probably the most commonly implemented form of conservation biological control. This approach has long been considered an important component of integrated pest management programs. The use of pesticides can be modified in a variety of ways to minimize their impact on natural enemies. These include treating only when economic thresholds dictate, use of active ingredients and formulations that are selectively less toxic to natural enemies, use of the lowest effective rates of pesticides, and temporal and spatial separation of natural enemies and pesticides. While the concepts behind modifying pesticide use are relatively straight forward, implementing these modifications is not necessarily straight forward. One obstacle is that the primary source of information regarding IPM is probably extension services, yet at least in the United States, there are a variety of competing sources from which growers can get information regarding pesticide use.
The practice of IPM has been shown under large-scale field conditions to be favorable to beneficial insects. Furlong et al. (2004) determined the impact of IPM practices at different farms on beneficial insects in Brassica crops in the Lockyer Valley, Australia. Their study clearly demonstrated increased natural enemy abundance and diversity, as well as significantly greater predator and parasitoid efficacy at farms practicing IPM compared with farms that frequently treated with insecticide.
3.SELECTIVITY CRITERIA OF THE PESTICIDES IN USE
The use of selective pesticides is perhaps the most powerful tool by which pesticide use decisions can be modified to favor natural enemies (Hull and Beers, 1985), and the one most readily available to growers. Selecting the best insecticides for pest management that have minimal impacts on beneficial can be challenging.
To assist in this effort, a variety of databases and ranking systems have been developed which incorporate insecticide toxicities to non-target species and other information such as human toxicity and environmental contamination potential.
These systems can be used to compare the relative impacts of different pesticides on non-target organisms and to estimate probable effects on non-target environments. However, they have rarely been used to consider insecticide impacts on predators and parasitoids in the crop environment at a landscape level.
In an effort to make this process more user friendly a Beneficial Disruption Index (BDI) was developed by Hoque et al. (2002) to provide a generalized measure of insecticide impacts on beneficial arthropods in Australian cotton crops. This index was tested by Mansfieldet al. (2006), who concluded that the BDI is an effective measure of insecticide impacts on beneficial insects in Australian cotton crops.
Pesticide exposure of natural enemies may also be reduced by applying materials only where they are needed within crop fields. Coll (2004) reviewed the future potential for reducing the negative impacts of pesticide use on natural enemies through the use of precision agriculture technologies.
4.RESISTANCE TO NATURAL ENEMIES
Efforts have been made over the last several decades to develop natural enemies that are pesticide-resistant with the goal of better integration of chemical and biological control. Genetically manipulated arthropod natural enemies have been used only a few times in IPM programs. Only one transgenic arthropod natural enemy has been released on an experimental basis (i.e. with only a molecular marker), a transgenic strain of the predatory mite Metaseiulus occidentalis (Nesbitt) (Acarina: Phytoseiidae). While this approach may have the potential for improving resistance to pesticides, as well as other traits of natural enemies, a variety of scientific, regulatory, and political issues remain to be resolved before transgenic arthropod natural enemies can be used in practical pest management programs. Meanwhile, traditional selective breeding programs attempting to develop pesticide-resistant strains of beneficial insects continue to be explored. While some authors have advocated the use of resistant beneficial insects in IPM programs, it could be argued that this approach is counter-productive to the goals of IPM because it could encourage more pesticide use as with herbicide-resistant soybean cultivars.
Consumers are becoming a driving force in determining pest management practices, with retailers increasingly requesting horticultural or agricultural practice standards from farmers. Public opinions on pesticides have become polarized, with measures such as organic agricultural production gaining popularity. Global sales of organic produce are rising approximately 20% per year, with 97% of that market in North America and Europe. However, approximately 70% of organic production occurs outside of North America and Europe, primarily in Oceania and Latin America, meaning the effects of this organic demand will not be restricted to western countries. However, organic production still only represents a small fraction of total agricultural sales, which means that synthetic pesticides can be used on the vast majority of agricultural production, and remain a critical component of IPM programs worldwide.
4. BIOLOGICAL CONTROL
Natural enemies have been utilized in the management of insect pests for centuries. However, these last 100 years have seen a dramatic increase in their use as well as our understanding of how they can better be manipulated as part of effective, safe, pest management systems. Recent advances in molecular systematics are shedding new light on the classification of groups of beneficial insects such as the Hymenoptera, and delivery of this information on the internet makes it quickly and widely available (e.g. The Tree of LifeWeb Project at http://tolweb.org). Recent advances in the study of beneficial organism behavior and reproductive biology are revealing surprising complexities in the life histories of these organisms. Understanding this complexity should lead to potential new methods for their manipulation.
Despite the long history of utilizing natural enemies, it wasn’t until 1919 that the term biological control was apparently used for the first time by the late Harry Smith of the University of California (Smith, 1919). There has been debate regarding the scope and definition of biological control brought about by technological advances in the tools available for pest management. Each of these approaches has been used to varying degrees in integrated pest management programs.
1.SUCCESS RATE OF BIOLOGICAL CONTROL
From 1890 through 1960, approximately 2300 species of parasitoids and predators were introduced in approximately 600 different situations worldwide for suppression of arthropod pests. The overall level of establishment of these natural enemies was calculated to be 34%, with complete suppression of target pests occurring in 16% of situations, and some level of pest suppression achieved in an additional 42% of situations. These rates have apparently not increased over the last 100 years, although the percentage of successful projects that are complete successes has reportedly risen since the 1930s. A more recent analysis has shown that the percentage of agents that establish is between 20 and 55%, and the percentage of introductions contributing to success falls within the range of 5 ± 15%.
Because importation biological control has historically been targeted primarily towards exotic pest species, it is particularly suited as a integrated pest management tactic for exotic invasive pests. This approach continues to play an important role in this area. An example is the recent successful control of glassy-winged sharpshooter in the South Pacific. However, because these agents are exotic, there is the possibility of non-target impacts.
Benefits provided by importation biological control far outweigh the few negatives resulting from occasional cases of non-target impacts. Simberloff and Stiling (1996) argued that the few documented cases of non-target impacts, compared with the number of natural enemy introductions, may have been more the result of a lack of monitoring and documentation than a lack of actual impacts. This suggestion may be supported by the database on non-target effects of importation and augmentation compiled by Lynch and Thomas (2000). These authors found that from the relatively few cases where data had been collected in biocontrol projects, there appeared to be a number of non-target effects, although these were primarily from very early importation efforts and were mostly relatively minor.
There is one example of a biological control agent that became a widespread and well-known pest following its release. The ladybeetle Harmonia axyridisPallas(Coleoptera: Coccinellidae) was released in North America and Northwest Europe as a predator of aphid pests. However, it has become not only a threat to native biodiversity and possibly ecological services through intra-guild and inter-guild predation, but also a noxious household pets, and minor agricultural pest.
Although importation biocontrol has been practiced for more than 100 years, there has only been one documented case of a target pest developing resistance to a biological control agent. The introduced larch sawfly, Pristophoraerichsonii(Hartig) (Hymenoptera: Tenthredinidae), improved its defenses against the parasitoid Mesoleiustenthredinis Morley (Hymenoptera: Ichneumonidae), after the parasitoid was introduced into Canada for suppression of the pest. This suggests that importation biological control is a highly sustainable practice for the management of insect pests in integrated pest management.