Dr. Richard Freeman
This guide provides instruction on designing and implementing an ecological pest management system, which should provide the foundation for any integrated pest management system. The intended audience includes horticultural operations, small-scale farmers and gardeners. The guide is applicable to a variety of environments, urban, exurban and rural. This guide is still in DRAFT status, so please excuse the errors. Please see the author’s note at the end of this guide.
Introduction
Urban horticulture generally lacks the benefits of complex, high-functioning ecosystems. These severely simplified, novel ecosystems lack robust biodiversity on all scales, from microbes to mammals, so that only a few species in each trope dominate the landscape as pests (organisms that interfere with management objectives). Because biodiversity is so fundamental to suppressing pests without severe ecosystem disruption (pesticide use), the sustainable urban horticulturist must design and build this biodiversity.
A sustainable urban horticulture requires augmenting any plant types managed for production with a substantial representation of plants that will attract and nurture arthropodic pest enemies while repelling arthropodic pests. With a basic understanding of the ecology of pest management, also known as conservation biological control, common pests, pest enemies and the ecosystems that support pests and pest enemies, the horticulturist can design and implement a horticultural ecosystem that will significantly reduce pest problems while maintaining productive operations.
This guide provides a framework for designing and implementing and ecological pest management plan with reference to arthropod control. Future editions will discuss pathogens and microscopic pests. For clarification, the guide continues to refer to the reference example.
Section 1 gives a brief overview of conceptual basis for ecological pest management (EPM). Section 2 describes some horticultural practices the manager can institute for EPM.
Section 1. The Ecology of Pest Management
Through evolution, plants have developed various defense mechanisms to protect themselves against herbivores, from displaying pubescence and emitting volatile oils (eg. terpenoids) to signaling availability of resources to carnivorous predators to “false advertising” of such resources. Thus, a plant in a natural setting with dense biodiversity and full trophic and functional representation generally produces well, especially with careful management.
Ecosystem production depends upon biodiversity and diverse associated functional services, in the rhizosphere and in the aerial ecology. In the container, a full trophic web provides diverse nutrient pathways and protection from pathogens. In the surrounding atmosphere, a full trophic web provides pollination and protection against pests. As noted in the introduction, diverse ecosystem composition, structure and function interrupts resource concentrations, confusing and distracting pests with terpenes (aromatic compounds exuded by plants as secondary metabolites produced for plant defense), visual blocking, masking and shading, and physically blocking and diverting pests from their target plants.
Likewise, ecosystem biodiversity confers floral benefits upon pest enemies, which have a primary role in suppressing pest populations, especially in agricultural contexts. As noted in the introduction, pest enemies, especially insects, require several resources to survive and reproduce, many of them provided by plants. Insectary plants are highly important to pest enemies, providing them with the nectar, pollen, alternative prey and hosts and shelter.
1.1. Nectar
Many adult pest enemies, especially parasitoids, require floral and or extra-floral nectar as a primary source of energy, especially the flying insects (parasitoids and syrphids) as well as minerals and water. Nectar is the most highly sought resource for most pest enemies. Floral nectar, which is exuded through nectaries at the base of the corolla, is a carbohydrate-rich syrup made of sucrose and its derivatives, glucose and fructose, other sugars, various amino acids and proteins, lipids, vitamins, mineral ions, alkaloids, ethanol, eugenol, and methyleugenol. Different parasitoid taxa have evolved preferences to specific concentrations characterized by nectars from different plants.
Extra-floral nectar, exuded from various parts of some plants, mostly contain “oligosaccharides, fructose, glucose and sucrose” and a wide range of secondary metabolites. Because extra-floral nectar is independent of inflorescence, it is available over longer time periods and is thus an important source of nutrition for many parasitoids and other pest enemies, including hymenopteran parasitoids and the predatory larvae of Chrysoperla florabunda Fitch (Neuroptera: Chrysopidae).
Floral architecture varies among plant species in accessibility to parasitoids, with nectaries ranging from partially concealed to fully exposed. To access floral nectar, the parasitoids must be able navigate the floral architecture, which varies from among flower species.Flower geometry and size determine accessibility in relation to a given pest enemy, which may or may not be able to access nectar if head width is larger than the corolla opening and mouth parts are too short, or if a tubular corolla is too narrow for the pest enemy species’ abdomen. A different species may have access to the same flower. For example, hymenopteran parasitoids often have mouth parts too small to access partially-concealed and concealed nectaries.
Flowering plants also must be within traveling distance of parasitoids and predators, which varies. Some species of wasp parasitoids in the Ichneumonidae family, which have the largest body sizes among the parasitoid Hymenoptera, can fly beyond 80 meters searching for nectar.
Likewise, the molecular composition of the nectar must be palatable to the pest enemy. Nectars are diverse and some are more or less palatable to any given species than are others.
1.2. Pollen
Some adult pest enemies require or opportunistically eat pollen as an important source of protein, energy, vitamins and minerals, especially for reproduction, and many will opportunistically consume it. Pollen availability improves the longevity and fecundity of several parasitoids, including several Syrphidae (Diptera) and several parasitoid wasps. Studies found that corn pollen increased longevity among some species in both the Braconida and Mymaridae parasitoid wasp families of the Hymenoptera order. However, many parasitoids are not adapted to eating pollen.
In addition to the parasitoids, minute pirate bug, Orius minutus Linnaeus (Hemiptera: Anthocoridae) and predator mites Amblyseius cucumeris and A. fallacis eat pollen.
1.3. Alternative prey
Many of these insects, especially the flying parasatoids that oviposit inside their host prey, require alternative prey or multiple hosts for oviposition.
1.4. Shelter
Natural pest enemies use flowers and other plants for several forms of shelter, including shade (cooling and humidity), ovipositing (egg-laying), hiding from predators, as windbreak and for overwintering.
In addition to the immediate floral benefits, to build abundant populations, many pest enemies require access to relatively undisturbed areas with grasses, perennial herbs and forage and woody perennials. Ecosystems complex in structure, composition (species richness) and function are highly beneficial to these pest enemies.
The distance pest enemies can travel and the space they require vary by species, as do the flowers and other plants they choose for floral benefits. The knowledge base in this regard is still growing and evolving, but some reliable patterns have emerged. The following section mentions the primary pest enemies and some of the flowers they associate with. In addition, some flower families are known to attract numerous pest enemies and taxa, though definitive species-to-species relationships have not been established.
Section 2. Pest enemies
Pest enemies take the form of predators, parasites and disease-causing organisms. These organisms and their pest prey form a generalized “pest-natural enemy complex” that opportunistically feeds on whatever prey is abundant, slowing if not suppressing pest outbreaks. This guide focuses on the predators and parasites.
2.1. Predators
Predators are generalists that feed on a wide range of prey and include insects and arachnids. These arthropodae are usually larger than their prey, and in immature or mature form they attack pests at all developmental stages. For energy and protein supplement, they depend upon pollen and nectar, and flowering plants are important to their survival, vigor and reproduction. Generally, predators cannot suppress an established infestation.
2.1.1. Arachnids
From the arachnids class, several spiders and mites prey upon other arthropods, including pest species, though this guide will not discuss them in detail. Of primary interest are insect pest enemies, primarily among six orders: Diptera (flies), Coleoptera (beetles), Hemiptera (bugs), Hymenopotera (wasps), Neuroptera (lacewings) and Odonoptera (dragonflies). These insects are widely abundant on relatively undisturbed sites not subject to pesticide use.
2.1.2. Syrphids
Prominent among pest predators are the syrphids, or hoverflies, members of the Syrphidae family in the Diptera (fly) order. Roughly one third of the species in this family are zoophagous (consuming other animal organisms), mostly the aphidophagous (consuming aphids) family, Syrphinae. Syrphid larvae feed aggresively on aphids and aphid larvae and other insect larvae. Adults require pollen for proteins related to sexual maturation and nectar for energy expended on flight. Flower-visiting flies, including syrphids, most commonly seek nectar is especially important to the larger species, while some smaller species eat mainly grass pollen as adults. Syrphids will also rely on honeydew for sugars. Syrphids generally prefer warm, dry weather, will not fly in cold, wet weather and prefer to oviposit in proximity to aphid populations, near flowers and sheltered from wind. Syrphids are also important pollinators.
Syrphids are specific to the flowers from which they can obtain nectar due to physical anatomy, specifically tongue length, so depth of length of the corollas of florets is an limiting characteristic in flower choice. Syrphids and other flower-visiting flies recognize floral rewards by color and scent, and they can learn to associate new flower colors with floral rewards.
Syrphids acquire SNAP benefits from several flower species. Members of the Apiaceae family are prominent, for example, coriander (Coriandrum sativum), but syrphids also frequent others. Buckwheat (Fagopyron esculentum), tansy phacelia (Phacelia tanacetifolia) and sweet alyssum (Lobularia maritima) are especially important to syrphids, as well. Other syrphidae insectary plants include hairy vetch (Vicia villosa), chamomile (Matricaria chamomilla), yarrow (Achillea millefolium, especially white, pink, and red varieties) (Angelica archangelica), annual baby’s breath (Gypsophila muralis), bishop’s weed (Ammi majus), coxcomb (Celosia cristata), Queen Anne’s Lace (Daucus carota), native buckwheats (especially Eriogonum grande var. rubescens, Eriogonum giganteum, and Eriogonum latifolium var. rosea), and annual clary sage (Salvia horminum var. ‘Marble Arch’). Syrphids also rely on several flowering aromatic herbs, including lemon verbena (Lippia citriodora), oregano (Origanum vulgare), common culinary sage (Salvia officinalis), culinary thyme (Thymus vulgaris) and spearmint (Mentha spicata).
2.1.3. Lacewings
Larvae of the green lacewings (Chrysopidae) and brown lacewings (Hemerobiidae), families within the order of Neuroptera, prey upon soft-bodied insects like aphids and caterpillars. Larvae also opportunistically feed upon nectar and pollen. While adults of some lacewing species prey upon insects in addition to nectar, pollen and honeydew, adults of others rely only on these sugar resources.
Lacewings are opportunistic foragers that find floral benefits from a wide range of plants including perennial shrubs, grasses and a wide range of flowers.
2.1.4. Minute pirate bugs
Minute pirate bugs (flower bugs), prey upon a range of arthropod pests, which constitute the Anthocoridae family in the insect order Hemiptera (true bugs), prey upon a wide range of pests, including mites and small insects such as thrips, aphids, psyllids, small caterpillars and eggs. Anthocorids also consume pollen, nectar and plant juices to prolong longevity in the absence of prey.
Anthocorids seem to prefer flowers with deeper and wider coollas than do other pest enemies, and they can access flowers with flag type corollas, such as found with plants in the Fabaceae family. Some taxa find SNAP benefits from Asteraceae plants (see Figure 9.5 ), especially sunflower (H. annuus) and cosmos (Cosmos bipinnatus).
2.1.5. Lady beetles
Larvae and adult lady beetles (Coccinillidae family, order Coleoptera) feed on a wide variety of pests, especially aphids but also scales. In the absence of prey, they will consume nectar and pollen to sustain life, but will not attain the necessary nutrients for reproduction with these floral resources. However, with abundant prey, nectar and pollen enhance development and reproduction in Coccinillidae. Of the two, pollen is probably the more important resource.
2.1.6. Miscellaneous predators
Various Coccinillidae species seem to frequent flowers based on one of two habitual patterns. Adults and juveniles of some species glean resources from flowers that are common hosts to aphids. Others glean from plants with abundant floral resources, such as Tripleurospermum inodora (L.), Myosotis arvensis (L.), Leucanthemum vulgare (Lamarck), Daucus carota (L.), and Verbascum thapsus (Mullein), Lamium purpureum (L.) and Plantago major (L.). All species seem to favor yellow flowers.
Other notable predators include bigeyed bugs (Geocoris spp., Hemiptera: Lygaeidae), damsel bugs (Nabis spp., Hemiptera: Nabidae), and ground beetles (e.g., Bembidion spp., Coleoptera: Carabidae), all of which will prey upon spider mites and Lepidoptera (moths).
2.2. Parasitoids
Parasitoids – parasites that kill their prey – are mostly specialists that feed on a narrow range of species, though some are generalists. For energy and protein supplement, they depend upon pollen and nectar, and flowering plants are important to their survival, vigor and reproduction. Parasitoids also depend upon honeydew for energy, though it is lower in nutritional quality than nectar.
Parasitoids begin their life cycle when adults oviposit directly into pest bodies or near them from where larvae attach themselves. Most parasitoids prey only as larvae, and as adults they tend to be smaller than their hosts. Only female parasitoids suppress pests. Parasitoid adults are highly sensitive to chemical cues and are thus efficient host locators even when pest populations are small.
Hundreds of parasitoid species and dozens of families can reside in an agricultural field, and usually dozens of species are present and suppressing pests. Often, two or three key species are responsible for most pest suppression. Though the parasitoids can be ubiquitous, these organisms are highly sensitive to pesticide use and require diverse vegetation to survive and thrive. In addition, parasitoids generally do not have a wide range of dispersal.
Most parasitoids are in the Diptera (flies) or Hymenoptera (wasps) insect orders. Within the Diptera order, most parasitoids are in the Tachinidae family.
2.2.1. Diptera
2.2.2. Hymenoptera
Within the Hymenoptera, most parasitoids are within the Chalcidoidea, Ichneumonoidea, and Proctotrupoidea super-families and the braconid family.
As larvae, hymenopteran parasitoids feed on their pest hosts, which are usually highly specific. As adults, most Hymenoptera depend upon plant sugar from nectar for energy, though some synovigenic females also consume host haemolymph to provide protein and lipids for egg maturation. (Synovigenic adult females develop eggs during their lifetime; provigenic adult females carry mature eggs from eclosion.) However, sugar is essential to adult Hymenoptera survival and is key for successful reproduction and fecundity, especially leading up to oviposition. Some Hymenoptera species are specific to hosts with high-sugar diets, so the search for hosts and sugars in the same locations. Aphidophagous Hymenoptera, which prey on aphids, provide a prominent example and often feed off honeydew, the sugar-rich syrups exuded by their hosts. Other Hymenoptera species with hosts consuming less sugar, search for hosts and sugar in different locations, partitioning their energy and time between tasks. Larger Hymenoptera spend less time on individual flowers (residence time) than smaller Hymenoptera.
Hymenopteran parasitoids typically have short mouths compared to Diptera species, and thus are unable to access floral nectaries in many flowers accessible to other Hymenoptera and Dipteran parasitoids. Members of the Ichneumonidae family seem to prefer flowers in the Apiaceae family, though they access others, also. However, the Ichneumonids are relatively large Hymenoptera, which usually lack elongated mouth parts. Thus they cannot access flowers and florets with narrow, tubular corollas, as with many Asteraceae and Fabaceae, nor plants with well concealed nectaries, like members of the Convolvulaceae family. These Hymenoptera depend upon plants with exposed, accessible floral nectaries or extra-floral nectaries or plants associated with honeydew from aphid infestation. On the other hand, the members of the smaller Braconidae family do exploit plants with narrow, tubular corollas as can others in the Cynipoidea, Chalcidoidea and Proctotrupoidea families. Likewise, very small wasps such as found in the Aphelinidae and Trichogrammatidae families can access nectar from Phacelia spp. and Eryngium in the Apiaceae family.
Hymenoptera are able to adapt searching patterns to optimize opportunistic resources, such as nectar, from a new food source, because they are capable of associative learning.
Flowers with exposed, accessible floral nectaries provide SNAP benefits to many taxa of Hymenoptera. Some examples include most species in the Apiaceae family, buckwheat (Fagopyron esculentum) and sweet alyssum (Lobularia maritima (L.)). Hymenoptera also rely upon extra-floral nectaries for nectar requirements. Examples include cornflowers, sunflowers (Helianthus spp.) and some vetches (Vicia spp., Fabaceae family).
In a study of an agricultural field, researchers found visiting frequency from Hymenoptera highest among ten flowering species in three families. Within the Apiacea family are Pastinaca sativa, Heracleum maximum, Sium suave, Oxypolis rigidior, Cicuta maculata and Perideridia americana. Within Asteracea are Solidago canadensis, Aster pilosus and Eupatorium serotinum. Cassia fasciculata is from the Fabaceae family. Other research on Hymenoptera have found them obtaining nectar from some of the larger species in the Apiaceae family, including Daucus carota, Heracleum sphondylium, Angelica sylvestris and Oenanthe crocata.
and flowers providing SNAP benefits
Section 3. Plants that provide SNAP benefits to pest enemies
Plants produce terpenes (isoprene-based aromatic compounds) and pigments in flowers to signal and attract pest enemies via smell and sight and to guide them to SNAP benefits, especially nectar and pollen. Some plants will “advertise” resources without producing them in order to entice pest enemies to visit and provide pest suppression or pollination services without having to expend energy to produce nectar and pollen specifically useful to these pest enemies. Floral signaling varies between different species.
Some flowers are highly specific to certain pest enemies, while others attract hundreds of species. For example, several plants in the Apiaceae family provide SNAP benefits to a multitude of pest suppressors. Prominent plant families contributing floral benefits include Apiaceae, Asteraceae and Polygonaceae, but others like Boraginacea offer them, also.
3.1. Apiaceae
Most species in the Apiaceae family, which form umbel flowers, provide nectar and pollen to several pest enemies. Daucus carota, Heracleum sphondylium, Angelica sylvestris and others.
Oenanthe crocata provide nectar to hymenopteran parasitoids. Researchers have found that that dill (Anethum graveolens L.) and coriander (Coriandrum sativum L.) flowers are compatible with the head morphology of some species of ladybeetles (Coleomegilla maculata, Coleoptera: Coccinellidae) and green lacewings (Chrysoperla carnea, Neuroptera: Chrysopidae).
3.2. Asteraceae
Several members of the Asteraceae family, which form composite flowers (pseudoanthiums), provide nectar and pollen to several pest enemies. Sunflower (Helianthus annuus) provides SNAP benefit to several pest enemies, including predators of thrips (Thysanoptera). Marigolds general increase predators and parasitoids in some food crops.
3.3. Polygonaceae
Several plants in the Polygonaceae family provide nectar and pollen to several pest enemies. Buckwheat, Fagopyrum esculentum provides floral benefits to several pest enemies, including predators of thrips (Thysanoptera). Buckwheat improved longevity, fecundity and sex ratio of at least one species of parasitic wasp (Dolichogenidea tasmanica) in the braconid family.
3.4. Boraginaceae
The Boraginacea includes several genera that provide SNAP benefits, including Phacellia spp. Phacelia tanacetifolia in strips among farm fields has increased abundance of syrphid flies and other aphidophagous predators and reduced aphid populations. However, Phacelia’s deep corolla makes the nectar unavailable to some short-tongued insects, such as some syrphids. Some hymenopteran parasitoids feed off Phacelia as well.
3.5. Brassicaceae
Allysum flowers have extended longevity for female parasitoids in the Braconidae family.
3.6. Mixed selections
A flower mix containing the list below significantly increased adult abundance of
hoverflies with aphidophagous larvae (Diptera: Syrphidae), ladybeetles (Coleoptera: Coccinellidae) and and lacewings (Neuroptera: Chrysopidae).
Anethum graveolens L. (Apiaceae)
Anthemis arvensis L. (Asteraceae)
Anthriscus cerefolium Hoffm. (Apiaceae)
Bellis perennis L. (Asteraceae)
Calendula arvensis L. (Asteraceae)
Camelina sativa (L.) Crantz (Brassicaceae)
Centaurea cyanus (Asteraceae)
Coriandrum sativum L. (Apiaceae)
Fagopyrum esculentum Moench (Polygonaceae)
Papaver rhoeas L. (Papaveraceae)
Sinapis arvensis L. (Brassicaceae)
Section 4. Overview of Ecological Pest Management
Engineering, maintaining and preserving biodiversity is fundamentally important to pest management. Robust, sustained systems exhibit high functional diversity, which suggests high trophic and taxonomic diversity. Generally, with smaller organisms such as arthropods, nematodes and microbes, more species representation is beneficial. The vast majority of the smaller organisms are not significant pests and are thus beneficial to ecosystem production by either eating pests or decomposing organic detritus. In concert with designed and “planned biodiversity,” this “associated biodiversity” will generally deter the small minority of pest species that are present, keeping damage well within management thresholds.
Ecological pest management involves altering and manipulating habitats to enhance populations of pest enemies, suppress pests and promote plant resilience and pest resistance. (Plant resistance is a plant’s ability to withstand or avoid disturbance-induced stress; resilience is its capacity to recover from disturbance stresses.) In the most general terms, ecological pest management involves two major components: designing and creating complex, biodiverse floral ecosystems through careful selection and spatial arrangement of plants and building biologically robust, healthy soils and HCMs that provide optimal conditions for vigorous plants.
This section will introduce the two guiding concepts to ecological pest management — the bottom-up approach and the top-down approach. It then introduces some easy-to-implement practices that apply these complimentary guiding concepts.
4.1. Two Ecological Models
The bottom-up half of EPM involves growing plants that confuse and distract pests, while the top-down approach involves growing plants that attract and support pest enemies.
4.1.1. Bottom-up EPM
The confuse-and-distract approach is considered “bottom-up” because it works at the lowest tropic level, the autotrophic level, to manage pest organisms at the next tropic level, the herbivorous pests (which are heterotropes). Plants can also physically block pests, especially light, winged pests like thrips and aphids, from migrating between crop species. All the techniques listed below in the Top-down EPM section are completely suitable and adaptable to bottom-up strategies.
4.1.2. Top-down EPM
The practice of promoting pest enemies to suppress pests is a “top-down” approach because it works at the third and fourth tropic levels to suppress organisms at the second tropic level. The top-down approach involves several techniques that provide SNAP benefits to the pest enemies. Primary among these techniques are growing complex gardens and interplanting with SNAP-providing plants, sowing blocks and strips with SNAP-providing plants, establishing corridors and reserves, building beetle banks, providing supplementary resources and introducing banker plants. In establishing these landscape elements, careful flower selection is fundamentally important, to assure that the elements will provide SNAP benefits to the most important pest enemies. Random plant diversity has little benefit and can inadvertently exacerbate pest problems.
4.2. EPM practices
Several practices will provide substantial SNAP benefits and encourage an active pest-enemy ecology.
4.2.1. Complex Gardens and Interplanting flowers
ConclusionGrowing complex gardens, while maintaining careful attention to operational flow and work efficiency, is effective in preventing pest infestation. Planting permanent polycultures, which are assemblages of plants selected on the basis of their ecological functions, can provide a full complement of SNAP benefits. Interplanting flowering plants among horticultural plants to attract native pest enemies into a crop zone is an effective technique for suppressing pests. Designing polycultures requires selecting plants based on management objectives, plant form (above and below ground), function, phenology (development timing) and environmental requirements and arranging them spatially to optimize their functionality. Because designing for multiple factors introduces complexity, designers often begin with simple polycultures of three or four plant selections.
4.2.2. Blocks and strips
Horticulturists can plant blocks and strips, which are areas within the crop area sown with flowering plants that provide abundant SNAP benefits. Researchers recommend sowing blocks and strips on at least 10% of the total crop zone. When feasible, blocks and strips should have a variety of perennial plants.
4.2.3. Vegetational Corridors
Another important top-down technique is providing corridors to and from nearby reserves and other refugia. an important practice in promoting and maintaining populations of pest enemies. Reserves are semi-wild and wild sites with abundant perennial plant species and relatively permanent plant structures (woody perennials, perennial grass and forage fields). Corridors are areas that provide safe passage from reserves to crop zones. Pest enemies use these areas during non-cropping seasons, for some reproduction and for transit into and out of the crop zone.
4.2.4. Beetle banks
A technique similar to providing reserves and blocks is to build beetle-banks, which are low mounds planted with perennial grasses to support propagation of all predators, including the minute pirate bugs, voracious polyphagous predators. These zones provide vegetation that pest enemies can use for over-wintering, locating alternate prey, ovipositing, and finding refuge when migrating. When feasible, perennial grasses are beneficial for beetle banks.
4.2.5. Hedge rows
Building hedge rows of perennial herbs and shrubs provides physical barriers to pests and they provide overwintering habitat for predators. When practical, hedge rows are a valuable tool for an urban or suburban setting.
4.2.6. Reserves
Establishing nearby on-site or off-site reserves with abundant perennial woody and herbaceous perennials provides important overwinter habitat and other floral benefits to predators and parasites. Reserves are also appropriate zones for locating trees that will control micro-climate conditions less conducive to pest populations.
4.2.7. Cover crops
Whenever possible, cover any bare soil, with a cover crop that will provide SNAP benefits and benefit soils as well.
4.2.8. Artificial supplementary resources
Horticulturists can also create provide artificial supplementary resources. Researchers have used “artificial nesting structures for the red wasp Polistes annularis” to intensify predation. Likewise, providing artificial food supplements made from hydrolyzate, sugar and water increased ovipositing in green lacewings and increased populations of predatory syrphid fly, lady beetle and soft-winged flower beetle populations. (Nicholls 2004) Others have used a honey-water and sucrose solution to increase longevity of a parasitic wasp, Cotesia plutellae Kurdjumov, Hymenoptera: Braconidae).
4.2.9. Banker plants
Another technique involves introducing controlled populations of targeted pests, usually aphids, and pest enemies via banker plants, flowering plants that provide SNAP benefits to the pest enemies. Banker plants are obviously appropriate only when a pest problem is already established in a greenhouse so that introduced pest populations only reach background populations, enough to maintain vigor in pest enemies until they have access to pest-infested horticultural plants.
4.2.10. Flower selection
When creating these landscape elements, plant and flower selection is fundamentally important. The practitioner should design elements and select plants with reference to the pests of most concern and to known and unknown relevant pest enemies native to the site.
Identifying and profiling pest enemies requires a bioassay process similar to bioassaying herbivorous pests. Procedures range in sophistication, from field assays to semi-field methods to laboratory techniques. Field techniques usually involve identifying, counting and recording pest visits and behavior on target flowers in the natural or semi-natural environment. Studying pest visits is more effective for larger pest enemies because they generally have shorter residence time. When possible, determining whether or not the pest enemy is feeding on nectar and/or pollen is important. Studying the smaller insects via visit counts is more difficult because they have longer resident times per flower. Thus, field techniques often involve counting individuals on sampled flowers, usually by vacuuming the flowers to obtain specimens or shaking them on a white surface and collecting with an aspirator and counting. The practitioner can augment field studies with local bioassays others have published if they are available. Though field assays are fraught with methodological problems, they can provide a general inventory of the on-site beneficial fauna and pests.
Having determined the species composition of some of the prominent pest enemies on-site, the designer identifies the target pest enemies, those species that will best meet management goals, generally (long-term) and in regard to specific problem pests. The next step involves creating profiles for the target pest enemies based on published scientific literature, including morphology, phenology, physical preferences (temperature, light, moisture, etc.) and ecological preferences – especially flower species known to provide SNAP benefits.
In the absence of specific flower species to match the target pest enemies, the horticulturist can select species known to provide benefits to taxonomically proximate species – starting with pest enemies in the same genus and proceeding to those in the same family. In the absence of known plant species, genera or families to match a pest enemy, the practitioner can choose plants known to be attractive to a wide variety of pest enemies, known and unknown.
Likewise, in the absence of a pest enemy identification process, the practitioner can lure unknown native species with flowering plants known to attract a multitude of taxa. For example, a multitude of parasitoids rely on a few known members of the Asteraceae or Apiaceae families, such as wild parsnip, wild carrot and buttercup.
4.2.11. Sequential flowering
In context of both targeted and general flower species, horticulturists should select flower species with over-lapping, successive inflorescence periods to provide SNAP benefits during the entire crop cycle. At any given time, more than one species should be blooming. Early-flowering varieties are especially important to establishing pest enemy populations before pest populations can establish themselves. Late season flowers are also important because they provide nutritional resources when pest enemies are preparing for autumn diapause.
Conclusion
EPM presents substantial costs from foregone opportunity, labor and materials. The 10% set-aside removes 10% of growing space for the targeted crop or crops. Likewise, managing that 10% entails equal costs, at least, of managing the same area in crop space.
The direct benefits include a stable, optimal production, if other factors are functioning well, and thus a reduction of direct and indirect pest management costs. Common direct pest management costs generally arise from labor, material production losses from pest damage, biological stress and stress induced by management actions, for example, heating or moisture variations or chemical stress from pesticide use. Product degradation from pests and from pesticides also introduce pest management costs. Indirect costs include the long-term degradation of biodiversity on or near the site from pesticide applications, including many of the terpene-based essential oil suspensions.
Indirect benefits can include diversified harvests or commercial crop offerings from flowers, herbs and fruits grown in SNAP benefit areas, increasing biodiversity on the site, and beautiful landscapes. In addition, depending on diverse crop taxa and varieties leaves the gardener less susceptible to crop failure. Generally, even under harsh conditions, the gardener will get a harvest from the majority of crops.
Cautionary Note: Pesticide use, including certified-organic pesticides, will kill friendly arthropods.
Author’s Note
This guide is in draft form. It includes no foot notes or references and it contains significant omissions. Anyone interested in republishing using the content in this guide should first contact me, the author, Richard Freeman, to gain permission.
This paper makes reference to the scientific research of several authors. For those interested in obtaining a final version with footnotes, please contact me. I am also interested in co-authoring a final version of this paper.
https://www.designedecosystems.com/contact
The information I present is for educational purposes and I am not liable or responsible for anyone’s use or misuse of this information.
