Mother Earth Gardener

Compost Teas for Protection and Control

Brew up some insecticidal liquid soap spray.

The use of blasters in conventional agriculture to apply insecticides, fungicides and herbicides.
Photo courtesy of NRC (1989). ‘Agricultural Age’. In NRC (1989) Alternative Agriculture. Committee on the Role of Alternative Farming Methods in Modern Production Agriculture’, National Research Council. p.123.

Pesticides have come a long way in the last few decades from the reckless attitudes towards nature and all the environmental wreckage that entailed, towards a grudging acceptance to working in more harmony. Many of the synthetic pesticides hawked by the global agri-business trade have been outlawed and no safe synthetic alternative currently exists. Because of this, greater attention has again been directed to botanicals, namely plant extracts, that tend to be less destructive and linger less in the environment.2 A home brewed botanical pesticide can have a novel advantage over something industrially produced, because a substance from natural sources possesses a greater range of active compounds which are harder for a pest to evolve a resistance to than a single lab produced chemical.

Today the organic grower works spade by spade with the chemical grower, so many of the problems that beset the chemical grower are transferred to the organic grower’s fields. The chemical grower’s plan is high risk in that they grow single crops of the same cultivar. The preoccupation with detrimental regimes of pest control can be seen as an aspect of this scene. If the particular conditions are suitable for a pest it has more potential for growth in a field that has only a single crop and in principle the same applies to crop diseases. The grower is constantly waging a losing battle as pests gradually develop a resistance to the current brand of pesticides. From the point of view of agri-business this situation is ideal; it could be said that they are waging a winning battle with another business opportunity every time the current round of pesticides become redundant or are found to be environmentally unsound.

If the organic grower lived in a world where there was no chemical grower there might be no need for this chapter. The idea of attempting to surgically remove a pest is against the philosophy of organic growing where a balance is struck between a diversity of organisms. The organic grower would have fewer concerns about pests and crop failure because the ecology of the crops is inherently more resilient. The grower will have a different set of concerns, such as issues over productivity and challenging the false perception that all unblemished, uniform produce is healthy. If something goes wrong with one crop they will have crops of other cultivars that have not been stricken. If a particular pest attempts to ravage a crop it will be in less devastating numbers than a pest that has found ideal conditions in a vast single crop. In organic growing, natural enemies linked to a particular pest are nurtured and any pest that is starting to get out of control will soon be brought back in check with an influx of predators. For instance, the life cycle of the ladybird is intimately linked to the emergence of aphids with ladybirds seeking out areas where aphids may be prevalent such as in a nettle patch or a stand of yarrow. If all the wild patches have been removed to squeeze in a few more crops then another safety net has effectively been removed.

A further interesting example of a natural balancing mechanism is the way the wolf spider will expand their numbers where there is abundant prey and then regulate their own population by cannibalism when they run out of food.

Unfortunately even if you are a dedicated organic grower you still have to deal with factors outside your control in the best way you can. You may be near a farmer’s field for instance or your site may be next to a grower that has built up a whitefly problem from growing brassicas on the same spot for decades and has unwittingly killed all the whiteflies’ natural predators. The philosophy of tackling the symptoms rather than the causes can lead the grower down an often unnecessary cycle of destruction with spiralling pest numbers and costs. Desperate situations sometimes require desperate measures and many of the recipes in this chapter should only be used in an absolute emergency. To mitigate this issue the ingredients and preparations chosen are those that have minimal impact on beneficials and still leave the plant edible to humans.

I concentrate on preparations that have an excellent track record as botanical pesticides, have ingredients that are easy to get hold of and can be cultivated locally. The pests and diseases that may beset a plant are too numerous to mention in a single chapter so I will only note some of the most important ones, where there is a good indication that the preparations here can have an impact. Towards the end of the chapter I describe two teas that initiate a ‘Systemic Acquired Resistance’ (SAR)3 which is an intrinsic natural process that exists in an enormous range of plants. Basically if a plant is attacked, a defence mechanism is triggered which operates within the whole plant. These teas initiate these responses without the attack.

When investigating pesticides you will come across the terms target and non-target. This simply means that some preparations target a specific problem taxon, for instance spider mites, and some are less specific, being non-target and hitting a broader spectrum of organisms. You will also come across pesticides that are systemic and non-systemic. All this means is that systemic pesticides go into the plant and non-systemic pesticides stay on the surface.

The concept of half-lives is sometimes used with regards to how persistent a pesticide is after it has been applied. If a particular pesticide has a half-life of three days its effectiveness will halve every three days. So if you have 100% effectiveness on the moment of application, your pesticide will be 50% effective after three days, 25% after six days and so on. The point of using half-lives is that products can linger a very long time in negligible quantities and this kind of information can make more sense when judging a product’s safety. It’s unfortunate that with regards to applications of pesticides to the soil, half-lives can be misleading and should only be treated as a rough estimation because their pathways rarely follow such a predictable pattern as there are a considerable number of confounding factors such as weather conditions, runoff and the amount of organic matter in the soil.

The foliar preparations presented here use liquid soap combined with water as described below. The reason for this primarily is that the soap solution acts as a wetting agent which helps the preparation stick to the surface of the plant considerably better than just water alone, which makes it stay longer on the plant and enhances the impact.

A note of caution must be added for this chapter that although almost all the preparations here are derived from natural locally available sources, it does not necessarily mean that they are harmless so some degree of care is needed, the extent of which will be noted in each case.

Soapwort (Saponaria officinalis) growing wild in North East England.
Photo by Eric Fisher, Permanent Publications

Making liquid insecticidal soap with soapwort

(Saponaria officinalis)

Soap sprays have an insecticidal effect on their own with nematocidal properties and are indicated to affect the breathing apparatus of insects. A further feature of soap sprays is that they can help protect the plant against infection by wiping clean the feeding apparatus of certain pests when they penetrate the plants with their mouth parts. Depending on your level of engagement with self-sufficiency you may want to produce your own liquid soap. A method for one such solution is described here. Alternatively you can go to your local pharmacy and obtain an enema soap which works fine. Under no circumstances use washing up liquid because the chemicals it contains are too harsh and definitely not a product for organic growers. Finally, if you like bees, it is best during flowering time to spray in the evening when the bees have gone back to their hives.

Soapwort was one of the staples of the cottage garden and is popular today for its beauty and heady fragrance. It was brought over to the UK during the Middle Ages by Franciscan and Dominican monks from Northern Europe as ‘a gift of God intended to keep them clean’.4 Later the plant was taken to America by the Puritans. Its main active compounds are saponins which are mildly toxic. Today soapwort is important industrially for making halva and the head on beer. It is a vigorous perennial herb and grows up to a metre high. For our purposes the soapy compounds of saponin makes a useful wetting agent as a base for other preparations in this chapter. The added benefit is that saponin compounds have excellent insecticidal properties in their own right;5 in a recent study aphids and caterpillars were killed or disrupted by saponins.6

It is very important to use soft water for this preparation; hard water interferes with the process, therefore rainwater is ideal. When preparing liquid soap for up to 10 litre sprays you only need a standard sized cooking pan because the final solution is to be diluted 1 part liquid soap to up to 5 parts water/pesticide solution.

Pulverise the soapwort roots and finely chop the whole plant, roots and all. Half fill your pan (2.5 litres capacity) with the whole soapwort plant and fill up with water. Bring to a boil then simmer for 30 minutes or until the solution becomes viscous. Allow to cool and then strain using panty hose. You are now in the possession of a very useful and versatile liquid.

More from Compost Teas for the Organic Grower:

Cover courtesy of Permanent Publications

Excerpted with permission from Compost Teas for the Organic Growerby Eric Fisher, published by Permanent Publications and distributed in the USA by Chelsea Green Publishing, 2019.

  • Published on Aug 5, 2020
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