Healthy and robust plants are less attractive to pests and diseases, however weak and malnourished plants are attacked more easily. At the same time, healthy plants are better equipped to deal with the attack, while the weak will be less able to cope. Early detection of the problem is a major factor in its eradication.
In outdoor cultivation, we can count on the help of certain plants. For deterrence of cannabis pests, companion plants such as Nasturtium, Chinese Carnation, basil, wormwood and sage can be planted to form a micro-balanced and self-regulating ecosystem. Generally, flowers and herbs help ward off pests and attract beneficial insects to our garden.
Let’s look at some more methods for the treatment of the 5 most common pests in the South African climate. We always aim for ecological solutions, as cannabis is a product intended for human consumption.
Spider mites
Spider mites are tiny arachnids, often less than 1 millimetre in size, that infest various plants. These pests are known for their ability to reproduce rapidly, leading to severe infestations if not managed promptly. Spider mites feed on plant sap by piercing plant cells with their mouthparts, causing damage that appears as tiny yellow or white spots on leaves. Over time, this feeding can lead to leaf discolouration, wilting, and even plant death. Spider mites thrive in hot, dry conditions and are commonly found on the undersides of leaves, where they spin fine webs as they feed and reproduce.
What to do:
A simple homemade remedy to control spider mites involves using a mixture of water and mild liquid soap. Combine two tablespoons of liquid dish soap with one quart of water in a spray bottle. I add a teaspoon of cayenne pepper too. Shake the mixture well and spray it directly onto the affected plants, ensuring to cover the undersides of the leaves where spider mites are likely hiding. The soap solution works by suffocating the mites and disrupting their cell membranes. The pepper will act as a deterrent, helping get rid of the mites. For best results, apply the solution in the early morning or late evening to avoid harming beneficial insects and to minimize the risk of leaf burn from sunlight. Reapply every few days until the infestation is under control.
We have the options here of help from certain organic products and predatory insects:
The most effective red spider mite predators are Phytoseiulus persimilis, and Amblyseius californicus which can be bought online. Always follow the retailer’s directions closely. We must remember that if we use live predators we should, under no circumstances use pesticides too, even organic ones. Notably, temperatures above 26 degrees and low relative humidity favour their proliferation.
Well-known organic remedies include wettable sulfur, potassium soap, pyrethrins, neem, or natural products that have extracts of cinnamon, camomile or wormwood.
White fly
Whiteflies are small, winged insects that belong to the family Aleyrodidae. They are typically found on the undersides of leaves and are known for their white, powdery wings. Whiteflies feed on plant sap, extracting nutrients and weakening the plant. This feeding process can lead to yellowing of leaves, stunted growth, and a general decline in plant health.
Additionally, whiteflies excrete a sticky substance called honeydew, which can attract sooty mould, further harming the plant and reducing its ability to photosynthesize effectively.
What to do:
Both for early detection and for eradication, chromatic traps (sometimes also called ‘cues’) are a good call. These insects are attracted to the color yellow, and become stuck in the traps.
Good organic remedies include neem, pyrethrum and other medicinal plants (such as Nasturtium, Marigold, Onions and Garlic) are also effective.
A homemade remedy to control whiteflies involves using a mixture of water, liquid dish soap, and neem oil. In a spray bottle, combine one quart of water with one tablespoon of liquid dish soap and one teaspoon of neem oil. Shake the mixture well and spray it onto the affected plants, focusing on the undersides of the leaves where whiteflies congregate. The soap helps to suffocate the insects, while neem oil acts as a natural insect repellent and disrupts the life cycle of the whiteflies. Apply this solution in the early morning or late evening to avoid harming beneficial insects and to prevent leaf burn. Reapply every few days until the whitefly population is under control.
As the most effective remedy we have some natural predators – in this case, the very effective Encarsia Formosa wasps, Macrolophus (also good for spider mites) or Amblyseius swirskii, which stands out amongst others for its effectiveness and resistance to high temperatures.
Caterpillars
Caterpillars are the larval stage of butterflies and moths, belonging to the order Lepidoptera. These larvae are typically elongated, soft-bodied, and segmented, with varying colours and patterns depending on the species. Caterpillars are voracious feeders, primarily consuming leaves and other plant parts, which can lead to significant damage in gardens and agricultural crops. As they feed, they create holes and ragged edges on leaves, weakening the plants and affecting their growth and productivity. Some caterpillar species can also burrow into fruits and stems, causing further harm to the plants. Caterpillars cause great damage outdoors and in the greenhouse or polytunnel. They are difficult to combat and can leave growers defeated.
What to do:
Spotting them early and taking preventative action would be the ideal way of going about them. Once they get going, you can lose crop overnight without seeing any damage… Until it is too late and buds are falling off from the plants.
A homemade remedy to control caterpillars without using bacteria involves a mixture of water and chili pepper. To make this solution, blend two fresh chili peppers with one quart of water until smooth. Strain the mixture through a cheesecloth or fine mesh to remove any solid particles, then pour the liquid into a spray bottle. Add a few drops of liquid dish soap to help the solution adhere to the leaves.
Spray the chilli pepper solution onto the affected plants, focusing on areas where caterpillars are present. The capsaicin in the chilli peppers acts as a natural deterrent, making the leaves unpalatable to caterpillars. Be sure to apply the spray in the early morning or late evening to avoid harming beneficial insects and to prevent leaf burn from sunlight. Reapply every few days or after rainfall until the caterpillar population is under control.
Another way is pheromone trapping. Pheromones are chemicals produced by females to attract males. They consist of a trap for adult butterflies and moths; males are attracted to pheromone tablets and poisoned, thus disrupting the reproductive cycle and preventing Caterpillar proliferation.If you are growing in a greenhouse, it is worth using fabrics or nets.
Another weapon is Bacillus thuringiensis, a bacterium that attacks the digestive system of caterpillars causing them to die of starvation. However, we recommend a selective use of them because many applications may have residual effects on our buds. Steinernema carpocapsae is another predator, a microscopic roundworm that lives in the soil, and is an entomopathogenic nematode.
Powdery mildew
Powdery mildew is a common fungal disease that affects a wide variety of plants, characterized by white or greyish powdery spots that form on the leaves, stems, and sometimes flowers and fruits. This disease thrives in warm, dry climates and can spread rapidly, covering entire plant surfaces if not controlled. The powdery coating can block sunlight, reducing photosynthesis and weakening the plant. Infected leaves may become distorted, turn yellow, and eventually drop off, leading to reduced plant vigour and yield.
What to do:
Fungi are very, very difficult to combat, once they appear, both outdoors and indoors. It is possible to take preventive measures such as proper ventilation and humidity control, and good spacing between plants. As for treatments we have with sulfur, horsetail, nettle extracts, cinnamon, and Propolix. There are also specific microorganism extracts which inhibit the growth of the fungus.
A simple homemade remedy to control powdery mildew involves using a mixture of baking soda and water. Combine one tablespoon of baking soda with one quart of water in a spray bottle. To enhance the effectiveness, add half a teaspoon of liquid dish soap, which helps the solution stick to the leaves. Shake the mixture well and spray it onto the affected plants, thoroughly covering all surfaces, including the undersides of leaves. The baking soda alters the pH level on the leaf surface, creating an environment that is inhospitable to the powdery mildew fungus. For best results, apply the solution in the early morning or late evening and reapply once a week or after rain until the powdery mildew is under control.
Botrytis
Botrytis, commonly known as grey mould, is a fungal disease that affects a wide range of plants, especially in cool, damp conditions. It is caused by the fungus Botrytis cinerea, which produces greyish-brown, fuzzy spores on the surfaces of infected plant tissues. This disease can affect leaves, stems, flowers, and fruits, leading to soft, rotting areas that may be covered with the characteristic grey mould. Botrytis can spread rapidly, particularly in humid environments, causing extensive damage to crops and ornamental plants by promoting decay and inhibiting growth.
Also very difficult to combat and prevent. Spores of all fungi, float in the air and spread very quickly. Botrytis is perhaps the most difficult fungus to fight.
What to do:
Trichoderma harzianum is a natural fungicide which colonizes the root, can act as a protective barrier act minimizing the spread of pathogenic fungus. Other options include Bacillus subtilis or Bacillus velezensis, bacterias that slow the spread of Botrytis. Wormwood extract and thyme are also useful for preventing this.
Once Botrytis is detected, manually or with scissors, remove the infected buds, place them quickly into a bag and throw them away. Remove the entire plant if it is too affected in order to minimize its spread.
We see that insects in general are a little less difficult to combat, because their life cycle, although very fast, is much slower than that of fungi. However, the best way to prevent significant loss is to closely observe your plants, as early detection is always the best control tool. If you take care of your plants they will take care of you.
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