Good growing practices to control pests and diseases

My old colleagues and friends still scratch their heads and laugh at me. Many decades ago I carried a very important key. It opened the door of a triple bay storage shed, stacked with numerous horticultural chemicals. With tireless regularity, I applied these to control the pest and disease organisms which attacked the various plants under my care. One morning, I woke up and said no more. I had been studying the organic approach to insect and disease control quietly for several years, but remained uncertain how to make the necessary changes on the estate. In the end, we agreed to embrace organics with a sink or swim approach. I readily admit this was more than challenging for an initial few seasons.

There were several steps to establish a working organic environment. We commenced a thorough evaluation of local conditions, determining the prevalence of various plant diseases, insect pest, and predator species. Success then depended upon choosing the set of control procedures which were most suitable for replacing our dependence on the chemicals. Many of the control procedures were labour intensive and required considerable amounts of research and fine tuning to accommodate the specific requirements of our garden. Fortunately, I was mentored by a well respected pioneer of the organic approach. His detailed and objective journal records revealed significant progress by the commencement of the third season. I make some point of this because the incremental achievements and overall success had been almost buried amidst my elevated expectations and desire to achieve positive results in the shortest amount of time.

Constant learning

Approximately four decades later, I’m still learning the importance of self restraint and patience. Thankfully, I’m no longer tempted to abandon organics and spray my plants with chemicals to facilitate a hasty solution for insect and disease problems. As my original mentor once explained, the organic approach is about creating balance between healthy soils, and the biological ecosystems which include garden plants, and the various organisms which seek to destroy them. I suppose it’s a theory which accepts opposing influences rather than attempting to eliminate one side of the equation. Adopt this mindset and you’ve basically found the road heading towards practical organic solutions. From then on, proceed to accumulate relevant knowledge, remain calm and be prepared to stay the course.

Risks to plant health

Despite common misperception, the influence of pest and disease organisms does not represent the major risk to plant health. When statistically measured, the most negative impact on plants is bad weather, followed by poor husbandry and management. Basic errors associated with watering, feeding, and overcrowding are directly responsible for more losses than any combination of disease or pest. Having clarified this, it is important to acknowledge that plant resilience and immunity may be progressively weakened by any sequence of negative events. For example, an immature plant receiving poor management combined with unfavourable seasonal conditions will be more vulnerable to pest and disease problems than an established specimen which is well managed and unaffected by inclement seasonal factors. These observations support the organic philosophy of providing plants with the best available conditions and resources to enable them to naturally resist disease and predation.

Approaches to pest and disease control

There are several popular strategies and remedies available to assist the organic gardener to control insect pests and disease. The most effective approach is to build an integrated system which mimics the checks and balances occurring in nature. An integrated system should combine the fundamental aspects of plant husbandry with a selection of preventive and remedial strategies. Effective plant husbandry involves the strict maintenance of garden hygiene, the provision of healthy soils and growing conditions, in addition to the selection of plant varieties exhibiting some natural resistance to locally prevalent disease and nuisance insect organisms.

Disease and insect problems are less likely to affect gardens where basic hygiene and quarantine rules are practiced. Many garden resources such as soil, seeds, or plant cuttings are capable of transmitting disease or pest infestation when introduced from affected areas. Aside from restricting their entry, the best protective measure is to quarantine any risk associated materials introduced to the garden. Where practical, a quarantine area can be designated, preferably one offering a degree of physical isolation from the rest of the garden. By applying a strict observation period of several weeks, the likelihood of detecting any outbreak is increased along with the opportunity for containing and destroying the culprit. The risk can be further minimised or eliminated by obtaining plants and other stock with certified disease free status.

Wind, birds, insects, and other animals are also capable of spreading plant disease. Symptoms may occur on any part of an affected plant include mottling, discolouration, wilting, and holes or notches in the foliage. Regular observation and inspection is essential throughout the garden, to ensure that minor infestations can be controlled or eliminated before they become established. With experience and research, it is possible to gain basic understanding of the life cycle and behaviour of the organisms causing damage to plants. This effort is usually rewarded with practical results such as earlier detection and more effective control strategies.

Suitable conditions

In order to support the natural health and resilience of plants, it is important to consider the most fundamental aspects of their growth and development. Selecting an appropriate site, one which provides the required sunlight, temperature and soil conditions is critical. The ability to accomplish this for some of the less common plant species can depend on specialist knowledge and practical skills which are sometimes obtained only through initial error and persistence. Healthy and vigorous plants depend upon their growing medium to provide a complex range of nutrients. Compared with their wild cousins, many cultivated plants are less equipped to compete with other species for their water and nutrient requirements. In practice, they may require their own dedicated site where they benefit from enriched soils with adequate drainage characteristics. The nutrient cycle of cultivated gardens can be improved by the practice of crop rotation and the provision of complex organic soil conditioners.

Plant selection will ultimately determine the success of strategies used to control nuisance insect and disease organisms. By selecting strains containing a natural resistance, organic plant breeders have carefully developed their own varieties which are resistant against the pest and disease organisms which most commonly affect the species. Examples include carrots with superior resistance to whitefly, potatoes less affected by blight, and a lesser susceptibility to fungal infection for tomatoes and vine fruit. In many instances, it makes sense to choose these hardy varieties, particularly where climate or soil conditions are likely to contribute to plant stress.

The widespread use of synthetic pesticides is a relatively recent phenomenon, with its technological foundation emerging from the development of chemical weaponry during the Second World War. By comparison, remedial and preventive strategies available to organic practitioners are based on modification of various agricultural applications which were once widely used to control insect and disease problems among edible crops and other plants. Companion planting, beneficial predators, physical barriers, and organic sprays are all considered to be common or essential practice within integrated systems of pest and disease management. These organic methods of control will be slower and their results less dramatic, compared with most of the currently available chemical treatments. The main advantages of the organic methods include environmental safety, protection of bio-diversity, and their contribution to healthy soils and a sustainable approach to gardening.