Crop susceptibility to pest damage may be influenced by differences in plant health mediated by soil management ~ New England Vegetable and Fruit Conference, Manchester, NH
biological weed control ,what is bio-control of weed ,how biological control of weed works ,advantage of biological weed control ,methods and agents of biological weed control
AUTHORED BY: JOHANNA ELSENSOHN AND KELLY SEARS
By 2050, the world’s population is estimated to exceed 9 billion people. A challenge to this rising food demand is that crops will have to be grown on the same or less land as today. Additionally, global climate change is causing considerable uncertainty in the ability of the current food production system to adapt to an unknown future.
To address these issues sustainably, scientists from many disciplines have been investigating ways to increase crop yields and prepare for a changing climate. Considerable effort has focused on enhancing the traits of the crop plants themselves, to enhance their growth, make them resistant to disease, or tolerant to environmental stressors like drought or high salinity conditions. Conversely, a growing area of research is looking at how microorganisms, such as bacteria and fungi, influence these plant characteristics.
The relationship between plants and microorganisms is well known. However, researchers are still working to understand the full complexity and extent of interactions between the two groups. We have seen that microbes are important for plant nutrient acquisition, plant growth and protection against disease. Certain types of bacteria are commercially available and used to increase yields and decrease fertilizer use (Farrar et al. 2014).
Biological Control of Weeds in European Crops
`
For more information, Please see websites below:
`
Organic Edible Schoolyards & Gardening with Children
http://scribd.com/doc/239851214
`
Double Food Production from your School Garden with Organic Tech
http://scribd.com/doc/239851079
`
Free School Gardening Art Posters
http://scribd.com/doc/239851159`
`
Companion Planting Increases Food Production from School Gardens
http://scribd.com/doc/239851159
`
Healthy Foods Dramatically Improves Student Academic Success
http://scribd.com/doc/239851348
`
City Chickens for your Organic School Garden
http://scribd.com/doc/239850440
`
Simple Square Foot Gardening for Schools - Teacher Guide
http://scribd.com/doc/239851110
biological weed control ,what is bio-control of weed ,how biological control of weed works ,advantage of biological weed control ,methods and agents of biological weed control
AUTHORED BY: JOHANNA ELSENSOHN AND KELLY SEARS
By 2050, the world’s population is estimated to exceed 9 billion people. A challenge to this rising food demand is that crops will have to be grown on the same or less land as today. Additionally, global climate change is causing considerable uncertainty in the ability of the current food production system to adapt to an unknown future.
To address these issues sustainably, scientists from many disciplines have been investigating ways to increase crop yields and prepare for a changing climate. Considerable effort has focused on enhancing the traits of the crop plants themselves, to enhance their growth, make them resistant to disease, or tolerant to environmental stressors like drought or high salinity conditions. Conversely, a growing area of research is looking at how microorganisms, such as bacteria and fungi, influence these plant characteristics.
The relationship between plants and microorganisms is well known. However, researchers are still working to understand the full complexity and extent of interactions between the two groups. We have seen that microbes are important for plant nutrient acquisition, plant growth and protection against disease. Certain types of bacteria are commercially available and used to increase yields and decrease fertilizer use (Farrar et al. 2014).
Biological Control of Weeds in European Crops
`
For more information, Please see websites below:
`
Organic Edible Schoolyards & Gardening with Children
http://scribd.com/doc/239851214
`
Double Food Production from your School Garden with Organic Tech
http://scribd.com/doc/239851079
`
Free School Gardening Art Posters
http://scribd.com/doc/239851159`
`
Companion Planting Increases Food Production from School Gardens
http://scribd.com/doc/239851159
`
Healthy Foods Dramatically Improves Student Academic Success
http://scribd.com/doc/239851348
`
City Chickens for your Organic School Garden
http://scribd.com/doc/239850440
`
Simple Square Foot Gardening for Schools - Teacher Guide
http://scribd.com/doc/239851110
Age structured populations, habitat and niche, niche types, diff bw fundamental and realized niche, niche width and overlap, competitive exclusion principle, resource partioning and its types, character displacement.
"Bio - Warfare During Host Pathogen Interactions in Indigenous Crop Plants" b...Md. Kamaruzzaman
This is a analysis of some collected information of the subject of my M.S. theory semester. Course title was Plant Pathogenesis and Genetics of Plant Pathogens
1. Microbes are everywhere!
There are more microbes in a teaspoon of soil than there are people on earth. In fact, according to this Ohio State article, “Soils contain about 8-to-15 tons of bacteria, fungi, protozoa, nematodes, earthworms and arthropods.
2. Losing Soils
President D. Roosevelt once said, “a nation that destroys its soils destroys itself. Forests are the lungs of our land, purifying the air and giving fresh strength to our people.” Yet despite its importance, we have lost about half of the topsoil on the planet over the last 150 years. According to University of Sydney Scientific Director, Dr. John Crawford in an interview in Time Magazine, “a rough calculation of current rates of soil degradation suggests we have about 60 years of topsoil left. Some 40% of soil used for agriculture around the world is classed as either degraded or seriously degraded.”
3. Fertilizer Factories & Shields
“Microbes are like mini Fertilizer factories,” explains Dr. Robert Neidermyer, Holganix Director of Plant & Soil Science. For example, microbes like Nitrogen Fixing Bacteria and Phosphorus Solubilizing Bacteria release nutrients locked in the soil and make them available to the plant. Fungi like Mycorrhizae, travel across large swaths of soil to hunt down nutrients and water for plants. Further, having a diverse amount of bacteria and fungi allow the microbes to help protect plants from harmful pathogens.
4. Largest Organism On Earth
Mycorrhizae Fungi form synergistic relationships with trees. In exchange for sugars excreted by the plant, mycorrhizae produce thousands of linear miles of “hyphae” in soil to mine nutrients and water for plants. In fact, the largest organism on earth is a 2.5 mile-wide Honey Mushroom (Armillarea ostoyae).
5. We Are More Bacteria Than Human
Humans are about 95% bacteria and 5% human. The consortium of all microbes that live on and within humans is called our MicroBiome.
Isolation and characterization of fungi associated with spoiled tomatoesResearchWap
The study examined the various fungal pathogens associated with tomatoes spoilage as well as their preliminary taxonomic grouping up to genus level. 25 samples of the spoiled tomatoes were collected from five locations within Gwagwalada area council. Locations include: Passo Village, Gwagwalada market, Phase III, New Kutunku and Dagiri. The same prevalence rate(100%) was recorded for all tomato samples purchased in all locations.
Age structured populations, habitat and niche, niche types, diff bw fundamental and realized niche, niche width and overlap, competitive exclusion principle, resource partioning and its types, character displacement.
"Bio - Warfare During Host Pathogen Interactions in Indigenous Crop Plants" b...Md. Kamaruzzaman
This is a analysis of some collected information of the subject of my M.S. theory semester. Course title was Plant Pathogenesis and Genetics of Plant Pathogens
1. Microbes are everywhere!
There are more microbes in a teaspoon of soil than there are people on earth. In fact, according to this Ohio State article, “Soils contain about 8-to-15 tons of bacteria, fungi, protozoa, nematodes, earthworms and arthropods.
2. Losing Soils
President D. Roosevelt once said, “a nation that destroys its soils destroys itself. Forests are the lungs of our land, purifying the air and giving fresh strength to our people.” Yet despite its importance, we have lost about half of the topsoil on the planet over the last 150 years. According to University of Sydney Scientific Director, Dr. John Crawford in an interview in Time Magazine, “a rough calculation of current rates of soil degradation suggests we have about 60 years of topsoil left. Some 40% of soil used for agriculture around the world is classed as either degraded or seriously degraded.”
3. Fertilizer Factories & Shields
“Microbes are like mini Fertilizer factories,” explains Dr. Robert Neidermyer, Holganix Director of Plant & Soil Science. For example, microbes like Nitrogen Fixing Bacteria and Phosphorus Solubilizing Bacteria release nutrients locked in the soil and make them available to the plant. Fungi like Mycorrhizae, travel across large swaths of soil to hunt down nutrients and water for plants. Further, having a diverse amount of bacteria and fungi allow the microbes to help protect plants from harmful pathogens.
4. Largest Organism On Earth
Mycorrhizae Fungi form synergistic relationships with trees. In exchange for sugars excreted by the plant, mycorrhizae produce thousands of linear miles of “hyphae” in soil to mine nutrients and water for plants. In fact, the largest organism on earth is a 2.5 mile-wide Honey Mushroom (Armillarea ostoyae).
5. We Are More Bacteria Than Human
Humans are about 95% bacteria and 5% human. The consortium of all microbes that live on and within humans is called our MicroBiome.
Isolation and characterization of fungi associated with spoiled tomatoesResearchWap
The study examined the various fungal pathogens associated with tomatoes spoilage as well as their preliminary taxonomic grouping up to genus level. 25 samples of the spoiled tomatoes were collected from five locations within Gwagwalada area council. Locations include: Passo Village, Gwagwalada market, Phase III, New Kutunku and Dagiri. The same prevalence rate(100%) was recorded for all tomato samples purchased in all locations.
http://www.williamhenry.com/materials/ | William Henry combines naturally beautiful organic materials and innovative man-made alloys in their men’s jewelry and accessory collection. Learn more about the fascinating materials they use in the following presentation.
Effect of plant nutrition in insect pest management: A review kiran Bala
Nutrition concerns the chemicals required by organism for its growth, tissue maintenance, reproduction and necessary to maintain these functions. It may determine resistance or susceptibility to pests. Among several plant nutrients, only 17 are essential for proper growth and development of plants and each nutrient plays important role in their growth. These nutrients are required by insects for their growth, tissue maintenance, reproduction and energy. They fulfill their requirements through feeding on plants. Nitrogen has positive effects on individual insect performance, probably due to deposition-induced improvements in host plant chemistry. These improvements include increased nitrogen and decreased carbon-based defensive compound concentrations. Potassium provides high resistance against insect– pests. High levels of potassium enhance secondary compound metabolism, reduce carbohydrate accumulation and plant damage from insect pests. Phosphorus also decreases the host suitability to various insect-pests. Secondary macronutrients and micronutrients like calcium, zinc and sulphur also reduce the pest populations. Among mineral elements, silicon is involved in plant resistance against insect pest damage. The indirect effects of fertilization practices acting through changes in the nutrient composition of the crop have been reported to influence plant resistance to many insect pests. The need for more healthful foods is stimulating the development of techniques to increase plant resistance to phytophagous insects.
This PPT gives a detailed information about
1.Introduction to Organic Farming
2.Review of Literature about Organic Farming
3.Materials & Methods used to establish an "Organic Kitchen Garden"
4.Implementation
5.Observation & Results
6.Conclusion
Trichoderma is a filamentous fungus that is widely distributed in the soil, plant material, decaying vegetation, and wood. It belongs to the family Hypocreaceae. They have high potential for colonizing their habitats and have various applications in food industry, agriculture, as a biocontrol agent with mechanism involving antibiosis, competition, mycoparasitism, promotion of plant growth, solubilization and sequestration of inorganic plant nutrients, inducing resistance and inactivating pathogen’s enzymes and also as a source of transgene. The major driving force for investigation of biocontrol with Trichoderma is sustainability. As a plant symbiont and effective mycoparasites, numerous species of this genus have the potential to become biofungicides. the extensive studies on Trichoderma, including its diverse physiological traits available, is still progressing and making these fungi versatile model organisms for research on both industrial fermentations as well as natural phenomena. Jasmine Chughasrani | Abhishikta Dasgupta | Rutuja Das "Applications of Trichoderma- A Review" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-5 | Issue-2 , February 2021, URL: https://www.ijtsrd.com/papers/ijtsrd38341.pdf Paper Url: https://www.ijtsrd.com/biological-science/botany/38341/applications-of-trichoderma-a-review/jasmine-chughasrani
AnswerThe trophic interaction between microbes and plants is impo.pdfaradhana9856
Answer:
The trophic interaction between microbes and plants is important.
Plant growth-promoting rhizobacteria (PGPR) are group of micro-organism that increasingly
appreciated for their contribution to primary productivity through promotion of growth and
triggering induced system registance.
By triggering plant defense, PGPR can make an important contribution to biocontrol of pests and
pathogens. The interactions increasing order of complexity, starting with single micro-organism
to other organisms that are present in the soil such as nematodes, fungi, earthworm or protozoa
and other soil dwelling organisms in the rhizosphere.
In the rhizospheres, bacteria can have direct beneficial or harmful effect on plant. However there
are also important indirect feedback interaction between plant roots and soil bacteria and other
micro-organisms. For example root-released exudates promote bacterial growth. In turn plant
growth stimulated by bacterivores (those eat bacteria) who liberate nutrients. Plant roots, bacteria
and other microbes interact in complex food web to form a multi-trophic complex interaction
between plants and bacteria.
In maintaining sustainable agriculture, the enhancement of environmental quality and natural
resources occurs. Sustainable agriculture focus on prucing livelyhood communities. Successful
sustainable production in healthy soil is an ecologically sound practice that have little or no
adverse effect on natural ecosystem. To reverse the damage of natural communities, renewable
natural resourses are protected and recycled.
Solution
Answer:
The trophic interaction between microbes and plants is important.
Plant growth-promoting rhizobacteria (PGPR) are group of micro-organism that increasingly
appreciated for their contribution to primary productivity through promotion of growth and
triggering induced system registance.
By triggering plant defense, PGPR can make an important contribution to biocontrol of pests and
pathogens. The interactions increasing order of complexity, starting with single micro-organism
to other organisms that are present in the soil such as nematodes, fungi, earthworm or protozoa
and other soil dwelling organisms in the rhizosphere.
In the rhizospheres, bacteria can have direct beneficial or harmful effect on plant. However there
are also important indirect feedback interaction between plant roots and soil bacteria and other
micro-organisms. For example root-released exudates promote bacterial growth. In turn plant
growth stimulated by bacterivores (those eat bacteria) who liberate nutrients. Plant roots, bacteria
and other microbes interact in complex food web to form a multi-trophic complex interaction
between plants and bacteria.
In maintaining sustainable agriculture, the enhancement of environmental quality and natural
resources occurs. Sustainable agriculture focus on prucing livelyhood communities. Successful
sustainable production in healthy soil is an ecologically sound practice that have littl.
Palestine last event orientationfvgnh .pptxRaedMohamed3
An EFL lesson about the current events in Palestine. It is intended to be for intermediate students who wish to increase their listening skills through a short lesson in power point.
Honest Reviews of Tim Han LMA Course Program.pptxtimhan337
Personal development courses are widely available today, with each one promising life-changing outcomes. Tim Han’s Life Mastery Achievers (LMA) Course has drawn a lot of interest. In addition to offering my frank assessment of Success Insider’s LMA Course, this piece examines the course’s effects via a variety of Tim Han LMA course reviews and Success Insider comments.
Operation “Blue Star” is the only event in the history of Independent India where the state went into war with its own people. Even after about 40 years it is not clear if it was culmination of states anger over people of the region, a political game of power or start of dictatorial chapter in the democratic setup.
The people of Punjab felt alienated from main stream due to denial of their just demands during a long democratic struggle since independence. As it happen all over the word, it led to militant struggle with great loss of lives of military, police and civilian personnel. Killing of Indira Gandhi and massacre of innocent Sikhs in Delhi and other India cities was also associated with this movement.
Embracing GenAI - A Strategic ImperativePeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
How to Make a Field invisible in Odoo 17Celine George
It is possible to hide or invisible some fields in odoo. Commonly using “invisible” attribute in the field definition to invisible the fields. This slide will show how to make a field invisible in odoo 17.
2024.06.01 Introducing a competency framework for languag learning materials ...Sandy Millin
http://sandymillin.wordpress.com/iateflwebinar2024
Published classroom materials form the basis of syllabuses, drive teacher professional development, and have a potentially huge influence on learners, teachers and education systems. All teachers also create their own materials, whether a few sentences on a blackboard, a highly-structured fully-realised online course, or anything in between. Despite this, the knowledge and skills needed to create effective language learning materials are rarely part of teacher training, and are mostly learnt by trial and error.
Knowledge and skills frameworks, generally called competency frameworks, for ELT teachers, trainers and managers have existed for a few years now. However, until I created one for my MA dissertation, there wasn’t one drawing together what we need to know and do to be able to effectively produce language learning materials.
This webinar will introduce you to my framework, highlighting the key competencies I identified from my research. It will also show how anybody involved in language teaching (any language, not just English!), teacher training, managing schools or developing language learning materials can benefit from using the framework.
Macroeconomics- Movie Location
This will be used as part of your Personal Professional Portfolio once graded.
Objective:
Prepare a presentation or a paper using research, basic comparative analysis, data organization and application of economic information. You will make an informed assessment of an economic climate outside of the United States to accomplish an entertainment industry objective.
Instructions for Submissions thorugh G- Classroom.pptxJheel Barad
This presentation provides a briefing on how to upload submissions and documents in Google Classroom. It was prepared as part of an orientation for new Sainik School in-service teacher trainees. As a training officer, my goal is to ensure that you are comfortable and proficient with this essential tool for managing assignments and fostering student engagement.
Instructions for Submissions thorugh G- Classroom.pptx
The Soil Food Web and Pest Management
1. The Soil Food Web and Pest Management
Mary Barbercheck, Department of Entomology,
501 ASI Building, Penn State University, University Park, PA, 16802
Tel. (814)863-2982 meb34@psu.edu
New England Vegetable and Fruit Conference, Manchester, NH December 13-15, 2011
Many agricultural production practices affect insect populations. Crop susceptibility to
pest damage may be influenced by differences in plant health mediated by soil
management. In general, soil management that replenishes and conserves organic matter
and enhances the abundance and biodiversity of beneficial organisms creates an
environment that promotes plant health. Crop rotation and preservation of beneficial
insects through the reduction of insecticide use can reduce pest pressure.
Increasingly, research has demonstrated that the ability of a crop plant to resist or tolerate
pests is tied to the physical, chemical, and biological properties of soil (Phelan et al.,
1995, 1996; Altieri and Nicholls, 2003; Zehnder et al., 2007). Soils with high organic
matter and active soil biology generally have both good soil fertility and complex food
webs. Soil organisms are involved in many beneficial processes, e.g., decomposition and
nutrient cycling, carbon sequestration, maintenance of plant diversity, bioremediation,
and biological control. In this paper, I will focus on how two key functions of the soil
food web, decomposition/nutrient cycling and biological control, affect pest management
in agricultural systems.
The Soil Food Web
All of life can be thought to operate in a food web based trophic groups. Trophic groups
are defined by what an organism eats. Food webs are composed of many food chains depicted as a linear sequence starting from a species that eats no other species, e.g.,
decomposers and producers (plants), and ends at a species that is eaten by no other
species in the chain, e.g., predators. The “structure” of a food web is the composition and
relative numbers of organisms in each trophic group. Food web complexity is a
characteristic of both the number of species and the number of different species in the
soil. The foundation of the soil food web is organic matter. The lower the level of
trophic group, the more heavily it relies on its nutrition from soil organic matter.
Management practices can alter the diversity and complexity for interactions in the soil
through effects on organic matter. For example, crop type, tillage practices, residue
management, pesticide use, and irrigation can alter the structure and complexity of the
food web.
Bottom-Up Control: Plant Quality from an Insect’s Point of View
From the plant-feeding insect’s point of view – the insect is at the center of the food
chain – below it are the food it feeds on - plants - and above it, animals that feed on the
insect, – natural enemies. What regulates insect populations to determine whether a
plant-feeding insect will reach damaging levels? Characteristics of an insect’s food are
considered “bottom-up” factors. Characteristics that influence the natural enemies of
insects are considered “top-down” factors because of the position of these factors in
relation to the plant-feeding insect in the plant-insect-natural enemy food chain.
151
2. Many kinds of insects feed on plants, although not all plant-feeding insects are pests.
Even when a known insect pest is present in the environment with a crop, there are many
factors that influence whether or not an insect will choose to eat, and potentially damage
a plant. Insects use chemical smell and taste cues to help them recognize host plants,
and can differentiate plants based on their odors and tastes. The chemistry of the plant
determines its appeal to an insect.
Chemical cues from plants that insects use to determine the suitability of the plant as a
resource fall into two broad categories: primary and secondary metabolites. Primary
metabolites are compounds synthesized by plants for essential functions, such as growth
and development. Examples of primary metabolites include carbohydrates, lipids,
proteins, and nucleic acids. A key component of proteins and nucleic acids is nitrogen.
Secondary metabolites are compounds produced in metabolic pathways other than those
directly involved in growth and development and are not considered essential to the plant.
Many thousands of secondary metabolites have been isolated from plants, and often
contribute to their distinctive colors and flavors. Some secondary metabolites are toxins
for insects, and are called plant defense compounds because they can interfere with an
insect’s metabolism, often by blocking specific biochemical reactions. The higher the
concentration of these chemicals in the insect’s diet, the less nutrition the insect can gain
from eating plant tissues. These defensive chemicals are usually most effective against
non-adapted specialists on other plant species and generalist insects that feed across plant
types. Plant defensive chemicals include alkaloids, cyanogenic glycosides and
glucosinolates, terpenoids, and phenolics.
These defensive chemicals often render a particular plant species unsuitable as a food
plant for particular insect species. However, in some cases, insect species have evolved
mechanisms to overcome the defensive function of particular secondary metabolites and
are be able to exploit them as a food resource.
The Effects of Fertility Source on Plant Quality
Soil organisms play a key role in decomposition and release of plant-available nutrients
from soil organic matter, a process called mineralization. As organisms decompose
complex materials, or consume other organisms, nutrients are converted from one form to
another, and are made available to plants and to other soil organisms.
The way that soil fertility is managed affects insect-plant interactions by altering plant
quality as a resource for plant-feeding insects. Soil fertility in agricultural systems is
mainly accomplished through applications of synthetic fertilizers, crop rotation, cover
cropping, and the application of plant and animal materials. Healthy, vigorous plants that
grow quickly are better able to withstand pest damage. However, over-fertilizing crops
can increase pest problems through changes in nutrient and chemical composition of crop
plants. Specifically, increasing soluble nitrogen levels in plants can decrease their
resistance to pests, resulting in higher pest density and crop damage. For example,
increased nitrogen fertilizer rates have been associated with increased soluble N in plant
tissue and large increases in numbers of mites, aphids, thrips, and other plant feeding
insects.
Practices that promote an increase of soil organic matter and a gradual release of plant
nutrients through decomposition and mineralization do not generally lead to excessive N
levels in plant tissues. Therefore, in theory, do not promote increases in insect pest
152
3. populations. In general, organic fertilizers such as animal and green manures contain
nitrogen sources that are released over a longer time scale than the pulsed and readilyavailable nitrogen in synthetic fertilizers.
Bottom-Up Control of Insects: Soil fertility and Brassica pests
Plants in the Brassica (cole crop) family are rich in sulfur containing compounds called
glucosinolates. These compounds play a defensive role in Brassica – insect relationships
and have a negative effect on generalist plant-feeding insects, although some insect
species are able to tolerate or detoxify some glucosinolates. Staley et al. (2010) applied
organic and synthetic fertilizer treatments at two nitrogen concentrations each to cabbage
(Brassica oleracea var. capitata cv. Derby Day), and measured their effects on the
abundance of plant-feeding insects and plant chemistry. The organic treatments included
a green manure (white clover, Trifolium repens var. Milvus) for the low-nitrogen
treatment (approx. 100 kg nitrogen per hectare), while the high- nitrogen treatment
included both green and animal manures (organic chicken manure to provide approx. 200
kg nitrogen per hectare in total). The two synthetic fertilizer treatments included a
conventional high fertilizer treatment (ammonium nitrate at 200 kg nitrogen per hectare)
and a conventional low fertilizer treatment (ammonium nitrate at 100 kg nitro- gen per
hectare).
The most common plant-feeding insects found were the cabbage aphid, Brevicoryne
brassicae (a cole crop specialist), the green peach aphid, Myzus persicae (a generalist
plant-feeder), and the diamondback moth, Plutella xylostella (a cole crop specialist). The
cabbage aphid was more abundant on organically fertilized plants, while the green peach
aphid had higher populations on synthetically fertilized plants. The diamondback moth
was more abundant on synthetically fertilized plants and preferred to oviposit on these
plants. Nitrogen concentration was greater for conventionally fertilized than organically
fertilized cabbage. Glucosinolate concentrations were up to three times greater on
cabbage plants grown in the organic treatments, while foliar nitrogen was maximized on
plants under the higher of the synthetic fertilizer treatments. The varying response of
insect species to these strong differences in plant chemistry demonstrates that the
response of plant-feeding insects to level and source of fertility is complex.
Top-Down Control of Insects: The Soil Food Web and Biological Control
Complex food webs foster populations of beneficial organisms that can help keep pest
organisms in check. The exploitation of the predators and parasites, or natural enemies,
to control pest insects is called biological control. Natural enemies include predators,
such as birds, lady beetles and lacewings, that consume a large number of prey during
their whole lifetime; parasitoids whose immature develops on or within a single insect
host, ultimately killing it; and pathogens - disease-causing organisms including bacteria,
fungi, and viruses that kill their insect host. Many natural enemies can be purchased, but
it may be more economical to use a conservation approach – i.e., create conditions
through management that attract and retain these beneficial organisms. Some common
biological control organisms associated with the soil include ground and rove beetles,
spiders and harvestmen, insect-parasitic fungi, and insect-parasitic nematodes.
Biological control of pest insects may be enhanced by reducing disturbance, such as
reducing tillage and pesticide use, by creating refuges from these disturbances, and
153
4. providing alternate food resources for the natural enemies (e.g., nectar and pollen from
flowering plants). Crop residue may provide habitat and/or food resources for beneficial
arthropods, and diversity and abundance of arthropod predators are greater under no-till
in comparison to conventional tillage. Organic cropping practices, and cover cropping, in
particular, may conserve and increase the activity of natural enemies.
Managing for Diversity and a Functional Soil Food Web
To exploit the benefits and services of soil organisms, such as bottom-up and top-down
control of insect pests, some goals of soil management should be to improve the physical,
chemical and biological properties of soil. This is mainly achieved through additions and
conservation of soil organic matter, as the base resource for the soil food web
Adding plant diversity to a production system in space and time can help break
pest cycles. Plants in the same family tend to have similar pests. Crop rotation, planting
a series crops from different plant families in the same space in sequential seasons, helps
deter the build up of pests that can occur when one crop species is planted continuously.
Crop rotations that include sod, cover crops, and green manure crop provide benefits in
addition to providing pest management in annual and perennial crops, including:
maintenance or improvement of soil organic matter content; management of plant
nutrients; and erosion control. Spatial crop diversity can be achieved through crop
rotation and various forms of polyculture, e.g., strip cropping, multiple cropping, or
interplanting of plant species or varieties. A general effect of polyculture is a spatial
mixing of crops, which can slow the build-up and spread of pests during the growing
season.
Literature Cited
Altieri, M. A., and C. Nicholls. 2003. Soil fertility and insect pests: Harmonizing soil and
plant health in agroecosystems. Soil Tillage Research 72: 203–211. (Available online at:
http://dx.doi.org/10.1016/S0167-1987(03)00089-8)
Phelan, P. L., J. F. Mason, and B. R. Stinner. 1995. Soil-fertility management and host
preference by European corn borer, Ostrinia nubilalis (Hübner), on Zea mays L.: A
comparison of organic and conventional chemical farming. Agriculture, Ecosystems and
Environment 56: 1–8. (Available online at: http://dx.doi.org/10.1016/01678809(95)00640-0)
Phelan, P. L., K. H. Norris, and J. F. Mason. 1996. Soil-management history and host
preference by Ostrinia nubilalis: Evidence for plant mineral balance mediating insectplant interactions. Environmental Entomology 25: 1329–1336.
Staley, J.T. A. Stewart-Jones, T. W. Pope, D. J. Wright, S. R. Leather, P. Hadley,
J. T. Rossiter, H. F. van Emden, and G. M. Poppy. 2010. Varying responses of insect
herbivores to altered plant chemistry under organic and conventional treatments. Proc. R.
Soc. B 277: 779–786
Zehnder, G., G. M. Gurr, S. Kühne, M. R. Wade, S. D. Wratten, and E. Wyss. 2007.
Arthropod management in organic crops. Annual Review of Entomology 52: 57–80.
154
5. Additional Resources
Altieri, M. A., C. I. Nicholls, and M. A. Fritz. 2005. Manage insects on your farm: A
guide to ecological strategies. Sustainable Agriculture Network Handbook Series Book
7. National Agricultural Laboratory, Beltsville, MD. (Available online at:
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