Soil Pests & Diseases
By Lazystrain
Soil is a living organism made up of billions of microbes and bacteria.
The cosmology of soil life is therefore such a vast subject that we can only really cover the very basics of soil science here in this issue of Treating Yourself.
As highly advanced ecosystems, all healthy soils naturally support a variety of quantum beings and microorganisms.
Most of these soil organisms, as we shall discover, often remain completely invisible to the naked eye, while others are more easily observed and recognized.
In the majority of cases, most of these soil organisms are total-ly beneficial to plant life and should always be encouraged in any healthy garden.
Several of the more hardcore soil organisms may, how-ever, be considered garden pests as and when they become established. Gardeners therefore aim to discourage unwanted soil species from reproducing before they can establish themselves and become totally uncontrollable. Telling soil-friendly centipedes from root-destroying millipedes or harmful mushrooms from friendly fungi isn’t always easy and often involves a keen eye for observation. The importance in identifying soil species before applying methods of biological control, therefore, cannot be over-stressed in this article, especially within the context of the medicinal herb garden.
Soil Microorganisms
Microorganisms are an essential ingredient of any soil or compost. These soil organisms are often so small that millions of microbes can inhabit the surface of a single seed. These microbes consist
of bacteria and protozoa, each of which specializes in a specific task. Most of these quantum beings are 100-per-cent garden friendly. For example, azotobacter fix nitrates on to root hairs and soil particles in exchange for plant sugars and residual salts. Likewise, some fungi microbes latch on to harmful nematode worms as gar-den-friendly parasites. Mycorrhizae fungi release hor-mones into the soil that help to prevent the spread of plant diseases and are believed to enhance plant growth.
Where or when soil conditions are unhygienic, however, due to the use of infected organic materials and/or the introduction of a stagnant supply of water, then harmful bacteria gradually start to persist in the soil. The use of non-treated water, for example, often poses a serious threat to outdoor soil sites, since untreated water carries a host of anaerobic bacteria (several of which are toxic to humans). Once irrigated on to outdoor soils, these harmful bacteria thrive during the autumn and in spring months, when conditions are warm. Several of these anaerobic microbes further support and co-exist along-side primitive algae species, such as liverworts, mosses, and fungi, the presence of which encourages the spread of further pests and diseases throughout the garden and wider environment.
Soil Fungi
Fungi can be sexual or asexual in character, meaning that once established, they can be difficult to control or eradi- cate. Soil fungi themselves are
the fruits or flowering bodies of subterranean spores collectively, mycelia are made up of many hyphae. These hyphae string themselves together underground, allowing the colony to travel across soil sites as rhizomorphs. For most of the year, these spore colonies go completely unnoticed. However, once the moisture and the temperature of a soil site reach an optimum level for a prolonged period of time (usually during autumn and spring), then specific spores start to flower into the fruiting bodies we
call mushrooms and toadstools.
Once established, these fungal spores obtain carbon compounds from carbonaceous food sources found within organic matter, soil, and compost. Since fungi do not themselves contain chlorophyll, they must co-exist along-
side other organisms that do. For example, many algae species provide certain fungi with foodstuffs in exchange for mineral salts and moisture. The presence of residual salts and excess moisture, especially within uncultivated soils, therefore strengthens the possibility of inheriting
unwanted algae and fungal species to begin with.
Soil Invertebrates
Soil invertebrates have no backbones and can easily burrow into soils to make a home. In contrast to fungi species, which require stagnant soil conditions, most terrestrial invertebrates thrive in soils that are well cultivated, free draining, and rich in soil nutrients. Common soil pests outdoors often include ants, beetle larvae, grubs, nematodes, millipedes, spider mites, wee-vils, and woodlice/wood bugs. Likewise, winged soil pests often include ground-dwelling hornets, wasps, and bees, to name but a few.
Several insect species build nests for their larvae under-ground. Others simply lay their eggs in the soil, and they later become serious pests as they hatch into hun-gry larvae. For example, the larvae of beetle grubs, cut-worms, and leather jackets all feed on the young roots of plants in the soil subsurface. The best ways to control these soil invertebrates is often to remove them visibly by hand during cultivation and/or the regular rotation of surface soil. Another way is to encourage friendly pred-ators, such as songbirds, toads, and frogs, into the gar-den; they will happily and naturally eat up unwanted insects.
In truth, most insect pests do as much good as they do harm in the garden, usually serving a dual role as garden friends and garden foes. Even the most hardcore soil invertebrates, like millipedes and nematodes, actually help out in the garden by improving the overall soil structure, breaking down organic debris, and helping to control other unwanted soil pests in the process of their own life cycle. It is only when an insect species begins to feed directly on a plant’s root system, and/or when plant life starts to deteriorate in the garden, that any soil inver-tebrate can really ever be considered a pest.
A Brief Note on Earthworms
Adding earthworms to outdoor soil sites (and compost bins) is an ancient practice. As and when earthworms burrow down into the ground, they improve soil drainage and soil aeration. During autumn and spring, earthworms come up into the topsoil to break down organic debris, dragging dead leaves and twigs back down into the ground below. These organic materials then get broken down to form a mineral-rich compost that helps to improve soil condition.
Each day, an earthworm makes its own weight in worm casts. These worm casts contain high traces of (N) nitro-gen, (P) phosphorus, (K) potassium, and (Mg) magne-sium. Earthworms also attract a special type of (Ca) cal-cium-loving bacterium, which fixes vitamin B12 into the soil as the worm travels. These added elements in turn help to improve the overall health and flowering poten-tial of plants. Likewise, in time, earthworms help to cul-tivate the land, turning heavy soils into smaller particles that are easier to work by hand.
Typically, earthworms prefer warmer soil conditions that are free draining, with a pH around 6.5. It is easy to make a worm farm at home using a few old buckets. Worms can be liberally fed on a variety of uncooked kitchen waste, broken eggshells, and shredded paper, until a nice worm-cast compost is produced. This worm-cast compost can then be added to compost teas and/or fed directly to the base of plants to help improve growth.
Biological Soil Control
In order to control outdoor soil sites, we must first grasp a basic understanding about the local pest species that are already living there and their potential impact on the garden environment. Once these factors have been addressed, a course of soil management can be planned throughout the year. Winter is often the best place to start: Winter is a gardener’s best friend when it comes to con-trolling unwanted soil pests and diseases. In winter, ground frosts help to sterilize the soil. Winter kills off any overpopulated invertebrate colonies and helps to reduce the spread of fungal diseases and spores. It is advisable to add animal manure to outdoor gardens prior to winter frosts arriving (or at least before the last frost has passed). This helps ensure that any harmful organisms in the manure itself have been killed off. A healthy and natural balance of soil microbes and soil invertebrates will then slowly start to establish during the months of spring.
Spring usually brings rain. The water content of outdoor soils often reaches near full capacity at this time of year. As water levels slowly start to recede, soil organisms (good bad) start to multiply – ground. At this stage, we want to free up the surface depth heavy soils and improve ready for planting. Green manures, which help retain water content in soil, can be added at this stage. By refreshing old soils in winter and spring, gardeners ensure a soil site is always rich in available healthy, and in peak condition, ready for planting at any time in the season.
Summer brings with it insects. Insects producing lar-vae begin to make homes in the ground as the soil starts to dry out. Parent insects also start laying their eggs below ground at this time in preparation for next season’s larvae. Friendly soil microbes are work-ing flat out in summer, providing plant root systems with NPK nutrients and other complex compounds in exchange for plant sugars. Harmful bacteria are also clubbing together and lying dormant, getting themselves warmed up and ready for an outburst fol-lowing heavy rainfall in autumn.
Fall/Autumn is the time of the year when the soil really comes alive. Soil conditions are wet and humid, which promotes major fungal activity. Mycelia have multiplied in such numbers under-ground that they start looking to fruit out over ground into mushrooms and toadstools. In turn, these fruits will produce spore that will establish new colonies. All visible fungal infections and spore, like Botrytis or Gray Mold, are best removed by hand and burned on a fire to prevent further infection in the garden.
Fungal sprays containing benomyl or carbendazim (and
sulfur) can be used during the early stages of Botrytis or Gray Mold infection
several weeks prior to harvest to help prevent bud rot. However, this is NOT an
option available to organic gardeners. Organic methods of reducing the
environmental con-ditions that mold species favor include the following:
reducing humidity, reducing watering, increasing air-flow (where possible), and
removing all dead or decaying leaf debris from the garden.
After Thoughts
All soils (indoor and outdoor) contain microscopic beings (tiny creatures whose existence we can barely comprehend, let alone see). Sadly, many gardeners notice the symptoms of damage in their plants without ever acknowledging the presence of the problem, pest, or disease in the soil. Likewise, using chemical fungicides and pesticides to treat symptoms that naturally occur does not acknowledge the causes. It is all too easy to go to the store, buy a bottle of chemicals, and apply them to a soil site without thinking about the process behind it (thousands of people do so every year with relative success).
However, with a soil management plan in place, most sites (indoors and outdoors) can be turned around organically without using anything other than common sense. It is important to remember that friendly bacteria prefer free-draining soil conditions with good aeration at all times in the season; and that unfriendly bacteria thrive within over-watered, uncultivated soils that are humid, especially in spring and fall/autumn. Likewise, soil invertebrates dislike soil that is kept under regular cultivation.
From a medicinal marijuana perspective, it is important that we grow herbal medicines that are free from harmful chemicals, many of which cause further free-radical damage when consumed. This is especially the case where herbal cannabis is ingested as medicine. Likewise, from an ecolog-ical perspective, it is often less stressful to find an organic solution to the cause than fighting the infection with a lack-luster remedy. Treating soil life with the same degree of care, judgment, and respect as we do plant life is perhaps the second step toward growing cleaner organic medicine for ourselves.
Keep medicating!
