Tips for the Three Main Infestations in Your Garden

There is nothing more frustrating than putting in all the work of growing a garden, only to have a bunch of insects come in and eat your crops down to nothing, harvesting aphid-infested vegetables, or facing the sudden death of your seedlings in the seed tray.

Pests are always a symptom of something more fundamental that is going on in your garden. In fact, by the pests showing up, you can be sure there’s been something going on for a while. Growing organically requires a very different mindset than that of the commercial gardener. It is not about poisoning weeds, bugs, and simply eliminating diseases—no, it’s about creating and supporting a healthy ecosystem where what’s beneficial keeps what’s harmful in check, the health of the soil provides the nutrients and living relationships your plants need, and the plants can thrive and be filled with both flavour and nutrition.

Stressed Plants Lure Pests

Unhappy plants nearly always end up either having pests or becoming sick. Healthy and robust plants transform simple sugars (which they gain through photosynthesis) into complex carbohydrates, making them so healthy for us to eat. This conversion is much more difficult to accomplish for sick and stressed plants, and more of the simple sugars remain available for insects. Of course, the sweeter the food, the more bugs swarm to the plant!

In this case, as we might be used to, we spray the crop. Sure enough we chase the fast-food customers away, but unless the menu of our “restaurant” changes, the customers will come back as soon as they can to enjoy some more.

So the key to successful organic farming is to have a holistic view on the garden. When dealing with vermin and illnesses, the focus is on (1) healthy soil, (2) building up strong and undisturbed plants and seedlings, and (3) controlling pests and diseases.

The following pyramid shows how much we can do to protect our crops and how little the usual “spraying-part” of all measures actually is.

Thou Shalt Not Kill

Have you ever heard of the thought that when we are fighting against insects and diseases, we are actually killing living beings? How do you deal with that?

Ellen White actually writes about this and she says that if we don't do anything about it pests can harm, even kill, us!

“There are those who say that nothing, not even insects, should be killed. God has not entrusted any such message to His people. It is possible to stretch the command “Thou shalt not kill” to any limit; but it is not according to sound reasoning to do this. Those who do it have not learned in the school of Christ.

This earth has been cursed because of sin, and in these last days vermin of every kind will multiply. These pests must be killed, or they will annoy and torment and even kill us, and destroy the work of our hands and the fruit of our land. In places there are ants [termites] which entirely destroy the woodwork of houses. Should not these be destroyed? Fruit trees must be sprayed, that the insects which would spoil the fruit may be killed. God has given us a part to act, and this part we must act with faithfulness. Then we can leave the rest with the Lord.” 3SM 329.1&2

“Those who advance the theory that vermin should not be killed know not of what they speak. There is nothing of this order in the teachings of Christ. It is not the Spirit of God that brings such theories as this to the mind. They originate with Satan who prepares every idle tale he can devise for the itching ears which cannot distinguish between truth and fiction. Discard all such theories for your own good and for the good of those with whom you associate. Those who go to such extremes do great harm. They bring the truth into disrepute. They place principles which are as precious as gold on a level with fables. Men might better let the fables rest in the silence of the grave than to speak and teach those things which have no foundation in the Word of God.” 20MR 338.5

A reassuring thought for me is that pests are so numerous that it is impossible to eradicate them. We probably kill more creatures with our poor lifestyle and the chemicals we use daily than with a few pesticides that we keep as natural as possible....

“God has given no man the message, Kill not ant or flea or moth. Troublesome and harmful insects and reptiles we must guard against and destroy, to preserve ourselves and our possessions from harm. And even if we do our best to exterminate these pests, they will still multiply.”—Manuscript 70, 1901 (The Review and Herald, August 31, 1961.)

Snails & Slugs

Who doesn’t know these animals? Snails and slugs are often seen as the “bad guys.” Despite their slow movement, they are quick eaters and play an essential part in cleaning up your garden debris. There are also “good guys”: tiger slugs, grove snails, and burgundy snails. They mainly munch on lichens, algae, mosses and withered plant parts. Tiger slugs also love to eat the eggs of other slugs; that’s a great benefit.

The most common measure against slugs is handpicking them at dusk. Some people create a designated “sacrificial bed” for these critters. Some of their favourite plants are growing there so it makes it easier. Whether you water your garden in the evening also plays a role—if you do, you’re actually encouraging slugs to come out and feast in your garden. Even your choice in mulch can make a difference. If you use fine bark mulch, they will not enjoy coming to your plants. Consider using wool too; slugs try to avoid crawling over this coarse texture.

There is also the option of creating beer traps. I have never personally tried that but it seems that slugs are attracted to yeast. To create a beer trap you need a shallow container filled with 3-5 cm of beer, set out in a high snail-traffic area. Best is to bury the container slightly, so that the rim is level with the soil. Empty and refill the trap every day or two as needed.

If nothing works anymore and you are afraid of losing your seedlings, you can create some collars from plastic bottles (cut into rings) and put them around each individual plant. Another good method is to build a broad copper tape around your bed. Slugs and snails do not like to crawl across it because it creates a biochemical reaction that feels like an electrical shock to them.

Slugs are a favorite food of many different predators. Encourage birds, snakes, lizards, frogs, toads, and ground beetles to make a home in your garden (consider using the idea of a beetle bump). The best help at my parents’ home was ducks! I remember the difference it made after just a few weeks. There are still some slugs around but it is no longer a plague.

There is one more notable predator of slugs—the larvae of fireflies. You can encourage them to make your garden their home by letting your grass grow a little longer, have wood piles laying around, and turning off all porch lights and other garden lights. This larvae attack the adult slug by injecting it with a numbing chemical, disabling it.


Powdery mildew and downy mildew are collective names for one significant group of fungi that comprise many different species. Each species specializes in a particular host plant.

Powdery Mildew

"Legume: Powdery mildew" by Plant pests and diseases is marked with CC0 1.0

Powdery mildew is considered a so-called "fair-weather fungus". It spreads primarily during typical Indian summer weather, i.e. dry and warm conditions. The fungus does not penetrate into the surface of the plants. You can recognize an infestation by a wipe-able, initially off-white, coating on the leaves that later turns brown. The affected leaves will eventually turn completely brown, dry out and wither away.

To prevent powdery mildew, it is important to leave enough distance between each plant during the planting process. This allows more sunlight to reach the leaves—sun is the number one enemy of fungal diseases! If the powdery mildew is already somewhat advanced, cut off and remove the infested leaves to get rid of as many fungal spores as possible.

Overhead watering during a dry summer additionally helps; although this is debateable, I think it's worth a try. Be mindful however, that it is better to do this in the morning, so that it is not too wet in the evening and you then catch the downy mildew too. Also, avoid giving too much nitrogen to the plants in late summer because a lot of soft leaf mass promotes fungus.

You can also spray the plants with a mixture of milk and water in a 1:5 ratio. Make sure the milk is raw, not boiled, otherwise it contains significantly less microorganisms....If the disease is advanced, you can increase the ratio of milk and water to 1:1.

Another way to combat powdery mildew is to treat it with a mixture of baking soda (max. 50g), 3-4 tablespoons of canola oil, and five liters of water. The baking soda produces a weak alkaline reaction when combined with water and the harmful fungus does not like that very much. Instead of baking soda, potassium hydrogen carbonate (or potassium bicarbonate) can be used; that increases the effect. The rapeseed oil also contains phosphatidylcholine (lecithin) that mainly acts as a repellent and plant protection. This mixture must be applied to the affected plant leaves every two weeks. If you’re early enough, you can also dust the plants with a thin layer of algal lime. Its high pH prevents the harmful fungal spores from germinating.

A natural, beneficial insect against powdery mildew is, you won’t believe it, the ladybug. The larva immediately attacks the fungus and, after about two weeks, pupates. A week later, the ladybug hatches and continues to fight the powdery mildew!

Downy Mildew

Downy mildew fungi grow mainly in cool and damp weather conditions. They thrive well in spring as well as autumn, when there is less sunlight available. This fungus, which isn't actually a fungus but a mock fungus related to algae, deeply invades the plant tissue. You can recognize an infestation on the underside of the leaf by a gray or gray-purple fungal turf. On the upper side of the leaf you will see several yellowish spots. Over time, the leaf will die.

Most home remedies that you can use for powdery mildew should also work for downy mildew. The problem is that downy mildew grows on the underside of the leaves, so it’s more challenging to evenly coat the affected areas; and since this practice isn’t usually done very accurately, it’s immediately deemed to be ineffective.

One other option for powdery mildew is tansy tea (the recipe is described below). Horsetail broth is also used against fungal diseases (scab, powdery and downy mildew, gray mold, late blight, etc.; also against mite infestation) because of its high silica content. It is best to apply it regularly from spring to summer, on dry and sunny days, on at-risk crops, as a preventive measure. In case of acute danger, spraying should be done on three consecutive days. Soak 100 g of fresh (15 g dried) field horsetail in 1 liter of water for 24 hours. Boil the broth on low heat for about 30 minutes and let it cool. Strain it as you would strain tea and dilute the broth with water in a ratio of 1:5.

What I also find very helpful is garlic. Either I use garlic tea or a garlic oil extract, which is practical to have on hand. For garlic tea: cut 50 g of garlic into small pieces or use a garlic press; cover with 1 liter of boiling water, let sit at room temperature for about 24 hours and then infuse with water in a 1:5 ratio; spray on the affected plants and the surrounding soil.

For garlic oil extract: press or chop 100 g of garlic with the peel, mix the garlic with 3 Tbsp of canola oil and let sit covered for 24 hours; strain the liquid and make sure to crush the remaining pulp to extract as many active ingredients from the garlic as possible; add 1 Tbsp of soft soap to the mixture, whisk together, combine with 1 liter of water and store in the fridge until needed (it will keep for at least 1 month). Upon usage, make sure to spread this broth 5% diluted; that means you need 100 ml of it for 2 liters of water.


In vocational school, my teacher, when asked where aphids come from, said that that’s determined by a higher power. Actually, most of them are transmitted via the soil and they reproduce extremely quickly in favourable conditions. They prefer warm and humid weather. There are over 800 different species of aphids and they reproduce differently, but common to all of them is that they multiply terribly fast—a new generation in about one week! They only lay eggs in autumn, otherwise they reproduce by means of asexual reproduction.

Aphids are prey to many predatory insects. One of them is the hoverfly. Many flowers and herbs such as marigolds, borage, zinnias, cosmos and nasturtiums, attract hoverflies and ladybugs.

"Ichneumon wasp"

Ichneumon flies parasitize aphids by laying their eggs directly into them. You can easily settle them in your garden. To do this, you need to set up a tree trunk in which you drill holes all around for their lodge. Setting up birdhouses for titmice is also valuable because, especially for blue tits, aphids are a main food source.


The larvae of the lacewing also eat aphids. The lacewing feels at home if there are natural hedges in your yard and the autumn foliage remains throughout the winter. There are also lacewing boxes painted red where they can find good shelter.

In addition, you can plant herbs like lavender, savory, marjoram, thyme, rosemary, hyssop and sage, among your vegetables. Either the aphids will avoid these plants because of their smell or flock to the crops they find attractive, like nasturtium, leaving the others free.

A well-known remedy against aphids is soft soap. Dissolve 30 grams of soft soap in 1 liter of water and spray this solution directly on the plants. It is best to use potassium soap because linseed oil and potassium hydroxide in combination have an anti-parasitic effect. But to be honest, I am somewhat hesitant to use soft soap because I'm not so sure what it does to my soil and the little critters there...

I know from experience that the aforementioned garlic extract repels aphids. But it's important to note that not every plant tolerates the oil well. I've had some not-so-great experiences with sweet bell pepper plants. A spot test is certainly wise before spraying everything ;)

Black tea helps as it contains tannins. This preparation requires 3 tea bags for ½ liter of water.

Oregano tea is another option: 10 g of dried oregano to 1 liter of water is used to drive away the pests; strain the mixture, cool, and dilute with water in a 1:3 ratio. Against black bean aphids, you can also make a rhubarb leaf broth. Boil 200 g of rhubarb leaves in 1 liter of water for 30 minutes; strain, cool, and spray undiluted. The tansy tea is very effective too. Just 15 grams of the dried plant, or 150 g of the fresh plant, brewed in 10 liters of water makes an effective tea. Poured on the soil or sprayed on the leaves, this bee-friendly plant protection works wonders. Be sure to keep this tea away from children because tansy is poisonous.

Lastly, there’s one thing that draws my attention more and more: Diatomaceous earth. It is a natural substance from sedimentary rock, created by fossilized algae called diatoms. This material works alternately to poisoning or smothering the insects. Instead, it absorbs the aphids, lipids (a waxy fat) and they a dehydrated to death within 48 hours. Insects are defenseless against it because there are no chemicals to which they can build up an immunity. Additionally, its roughness is a deterred. To apply, simply dust the ground around your plants or sprinkle it on the foliage. Due to its dried nature, diatomaceous earth must be reapplied after rainfall.

And with that, happy gardening! :)


Pest and Disease Control by Darren Greenfield & Timothy Hyde

Common Pests and Diseases by Bob Gregory



Four Season Harvest by Eliot Coleman, p. 122-123; 143-150

The New Organic Grower by Eliot Coleman, p. 172-189

Insect Disease & Weed Control I.D. Guide by Linda Gilkeson


Picture sources:

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