How to Prevent and Get Rid of Aphids Naturally

Aphids are sap-sucking pest insects that every gardener deals with at some point. Unfortunately, these are one of the most destructive pests. Having some ‘tools’ in your pest management toolkit for getting rid of aphids quickly is essential. So, let’s take a look at who they are, why they are such a problem plus how to prevent aphids and minimise the damage with practical science-backed strategies to get rid of aphids naturally. I’ve lost plenty of plants to aphids so I’m sharing what really works and why.

Aphids – Who are They?

Aphids (Hemiptera: Aphididae) are tiny insects that clone themselves and feed on plant juices. They literally suck the nutrient-rich sap and life out of your plants. There are over 5000 species in various colours from green to pink and black!

How to Prevent and Get Rid of Aphids Naturally

In small numbers, they’re not always a problem on mature plants. Especially if you have natural predators in your garden like hoverflies, parasitic wasps or ladybirds. If these hungry omnivores are residents in your garden, they will often seek out and enjoy aphid dinner, taking care of minor numbers.

Why are Aphids Such a Problem?

However, aphids generally are a BIG problem. They may be tiny but can do a LOT of damage in just a few days. Colonies with thousands of aphids can build up VERY quickly. How’s that possible? To be blunt, their highly successful reproductive rate happens because female aphids don’t waste time or energy on looking for a male partner, courtship, sex, or laying and incubating eggs! Sorry boys, not needed here as aphids are primarily asexual. In most species, males are rare or absent! Males don’t get much attention until cold weather when they’re occasionally required to fertilise eggs as a backup plan! Even then, mother aphids control their population by laying eggs that morph into males when necessary!

Aphid colonies are started by a stem mother who flies to a new food source location. She carries live babies and gives birth on arrival to start the new colony.

Aphids are female cloning experts that take a shortcut. Mother aphids give birth to multiple live female nymphs rather than eggs. Not only are all these daughters born hungry, but also ready within days to produce their own look-alike families! There’s no time buffer for you to miss their arrival before the exponential population explosion gets out of hand. A gardener’s nightmare, right? Take a look at this video to see how quickly this scenario unfolds.

How Do You Know if You Have an Aphid Problem?

If you notice tiny dots on your plants, curled leaves or discolouration, check carefully. Look on the undersides of leaves, stems, on flowers and new lush bud or tip growth. Aphids are really good at hiding. Especially the tiny nymphs. They are masters of camouflage, often blending in with the same colour of the plant they are on. A magnifying glass may be helpful to locate them.

How Do Aphids Feed, Move and Multiply So Fast?

Aphids have two main goals in life. Eat and reproduce! They feed on plant sap to convert nutrients into aphid biomass as fast as possible. This enables them to duplicate themselves sooner. They devote their short lives and energy to eating, motherhood and finding the next host plant. So essentially these wingless, sedentary insects are continually pregnant and giving birth. They don’t waste energy on exercise! They only move to locate more sap on the host plant or hide from natural enemies – and maybe you.

Mature adult aphid with wings

Mature adult aphid with wings – Image source

If one plant gets too crowded with aphid clones, they walk to the next. So the cycle starts again.

Winged aphids have a different role. Adult aphids fly to locate new host plants and establish new colonies. They take off with embryos inside and give birth when they find their next plant victim. Aphids just keep coming back with new versions of themselves. If you eliminate most of them, it only takes one single aphid to repeat the nightmare. Sounds like an alien horror movie, right? They’re definitely a pest to take seriously.

What Damage Do Aphids Cause?

When aphids feed, they disturb the balance of the plant’s growth hormones. Leaves wilt, wither, yellow, and dry out. Aphids prefer new shoots and buds to older leaves. Buds may not open at all or produce distorted flowers. Aphids also transmit plant viruses.

After feeding, they secrete honeydew (a sugary substance). This food source often attracts ants who act as bodyguards for a sweet reward. It’s a win-win relationship.

Ant receives sweet honeydew reward from an aphid for security services

Ant receives a sweet honeydew reward from an aphid for providing security services – Image Source

The ants keep potential predators like ladybirds away and get paid with free food. Sticky honeydew covers the leaf creating the perfect growing environment for black sooty mould to develop. This, in turn, slows and stops photosynthesis so the plant can’t produce energy to grow. It’s a domino effect. Forewarned is forearmed!

So, one small dot on your plant can have serious consequences! A single aphid can lead to other diseases and plant death. If ants are present as guards, you have to remove them too. That’s why you need to act fast to prevent and control aphids.

Host Plants and Aphid Species

If you grow any vegetables, fruit or citrus trees, roses, perennials or annuals, it’s likely you’re going to encounter at least one species of aphid sap suckers! Most aphid species look for hosts of a particular plant genus, but others are generalist feeders. They’re not fussy about which plants they eat whereas others target specific plant family groups. Onion aphids, for example, are specialist aphids that feed on host plants (HP) in the onion family. Have you ever noticed those black bugs on your leeks, onions, chives, spring onions and garlic? They’re common in spring.

Severe infestation of onion aphids Neotoxoptera formosana on shallots

Severe infestation of onion aphids Neotoxoptera formosana on shallots – Image source

Neotoxoptera formosana is one of these species. It’s a global pest insect that sucks nutrients from the onion (Allium) family including onions (Allium cepa); shallots (Allium ascalonicum); spring or green onions (Allium fistulosum); garlic (Allium sativum); garlic chives (Allium tuberosum); chives (Allium schoenoprasum); leeks (Allium porrum) and Chinese onions (Allium chinense).

Research studies (Pickett et al., 1992; Pickett & Glinwood, 2008) show onion aphids can detect their preferred host plants in the Allium family by scent using olfactory cues. Aphids use their sense of smell to identify their host species by the unique aromatic airborne plant volatile compounds (volatiles) released by the leaves. They move directly towards the odour source, kind of like using GPS. Or pet dogs that magically appear in the kitchen when they smell their favourite food!

Two sulphur-containing compounds that are characteristically found in Allium plants are diallyl disulphide and dipropyl trisulphide (Hori, 2007). Since both these compounds are relatively uncommon among other plant taxa (Webster, 2012), aphids can accurately target the onion family. Amazing huh? That’s why you’ll see specific aphid species on thousands of different plants. Read on to find out how to use this to your advantage.

Natural Pest & Disease Management
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How to Prevent and Get Rid of Aphids Naturally

So what can we do to prevent and minimise aphid damage? I use a few key strategies and principles because you need more than one tool in your toolkit. From my experiences with black onion aphids on members of the onion family over the years, I’ve adapted my gardening practices.

7 Preventative Pest Management Strategies for Aphid Control

How do you avoid an aphid infestation on your plants? These are some science-backed suggestions for you to consider.

1.       Be observant. It’s much easier to tackle a dozen aphids when they first arrive than a major infestation problem in plague numbers. Check your plants daily if possible. As the weather warms up in spring, you can expect aphids to become more active with all the new growth to feed on. Early detection and intervention will help. If you see a few, don’t wait a week to do something about it! Act quickly.

2.       Maintain plant health and watering. Weak nutrient-deficient plants are a magnet for pest insects. Keep up the soil moisture, nutrients and mulch. Strong, healthy plants have a better chance of resisting attack. Studies have found plants with adequate bioavailable phosphorus and potassium have higher resistance to aphid populations. Water in dry times so plants can access nutrients in the soil. Drought or heat-stressed plants release chemical cues that insects pick up on. If your plants are showing signs of wilting or leaf discolouration, check nutrient availability. Foliar spraying with seaweed can also help strengthen cell walls and encourage earthworm activity.

Foliar feed plants with liquid seaweed to strengthen and protect against pest attack

Foliar feed plants with liquid seaweed to strengthen and protect against pest attack

3.       Avoid excess nitrogen. An imbalance of too much nitrogen can create a flush of new sappy growth. The allium family is particularly vulnerable. Whenever I’ve applied nitrogen-rich organic fertiliser pellets and watered them in, within 24 hours, aphids appear. Like magic. Every time. Scientific studies confirm excess nitrogen fertilisers attract aphids and other sap-sucking pest insects like whiteflies. You can’t go wrong with slow-release compost and worm castings. Nature’s food with a balance of nutrients.

4.       Practice biodiversity. Aphids use scent cues. They are attracted to the volatile compounds your host plants release. So, avoid planting large numbers of the one plant family all in one spot. It may look pretty to have a row of onions or broccoli and make crop rotation in garden beds easier. However, this just spotlights your crops making it easy for aphids to find them. Instead, spread them around the garden. Interplant alliums as beneficial companions near other plants like beets, brassicas, carrots, cucumber, dill, lettuce, potatoes, roses, spinach, strawberries and tomatoes. The scents and diverse leaf shapes of other vegetables and herbs can also help make it more difficult for the aphids to find them. Win-win!

“Solid blocks of the same plant variety, though easy to seed and harvest, act as an ‘all you can eat’ sign to insect pests and diseases. Harmful bugs will stuff themselves on this unbroken field of abundant food as they make unimpeded hops from plant to plant and breed to plague proportions.” – Toby Hemenway, Author – Gaia’s Garden

5.       Plant flowering species that attract aphid predators. Aphid natural enemies include omnivorous hoverflies, ladybirds, lacewings and their respective larvae, plus predatory wasps. These beneficial insects also dine out on nectar from many flowers as a supplementary food source. They eat meat and veg! So, try growing herbs and flowers like oregano, dill, buckwheat, sweet alyssum, nasturtiums and bachelor buttons in your garden prior to spring when aphids generally are most problematic. You’ll have your friendly predatory ‘armoured guards’ ready to take care of these unwelcome aphid guests on arrival. Early intervention can keep the pest-to-predator ratio in balance. Insect-eating birds that feed on aphids include wrens, silvereyes, willy wagtails, finches, honeyeaters, pardalotes and some sparrows. Make your garden bird-friendly with habitat and water!


A Silvereye feeding on aphids on a Red Russian kale plant

6.       Interplant with strongly scented herbs like rosemary and pennyroyal. The volatile organic compounds (VOCs) in these non-host plants have been found to help mask the odour of alliums and repel aphids of various plant species. (Hori, 1996). Keep in mind though, you need to maintain your herb health as well. The production of these volatile compounds that help repel aphids is often dependent on moisture availability. Research studies (3) show rosemary, for example, decreased the release of VOCs after a four-day water deficit. Pruning can also help increase the release of VOCs. So you can encourage plants to provide a protective role at critical times in spring.

7.       Cover your crops. Obviously, if you use exclusion insect netting or crop protection bags, aphids will find it hard to access their host plants.

Exclusion Insect Netting for Crop Protection
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Companion Planting – How to Confuse and Lose Aphids

This is a complex area of pest insect and plant interactions. Research studies vary widely in their findings. However, some of the science-backed findings regarding companion planting are interesting and give us the confidence to use plants as part of our integrated pest management (IPM) toolkit. Evidence-based research shows many companion plants have been found to work in several beneficial ways. (more…)

How to Control Garden Pest Insects Naturally

Do you panic when you see an insect you don’t recognise in your garden? Do you assume it’s a pest causing damage? If so, it may help to understand WHY insects attack plants. I also share a toolbox of natural and organic strategies to help prevent and control the damage.

How to Control Garden Pest Insects Naturally - why they attack plants + organic and natural strategies to prevent and control damage

Firstly, a reality check! Don’t expect a pest-free garden. Even the healthiest gardens still get pest insect visitors. It’s more important to focus on creating a healthy balanced ecosystem. Aim for a productive harvest rather than a zero-tolerance policy!

There will be more beneficial predatory insects and pest controllers in residence with the right elements in place, than those causing damage. You need both – in balance.

If your garden is new, has few flowering species or has poor quality soil, it may be a different story. If you have a horde of herbivores eating your plants, don’t give up! Give it a little time and nature will restore the natural equilibrium. Read on to learn how.

Let’s colour in the picture so you know why the pest insects are there and what to do about it.

How do Pest Insects Damage Plants?

Some insects suck the sap out of plants or chew leaves, while others bore into the roots, seeds or stems. You can tell if you have some unwanted visitors in your garden by the visual damage. You won’t see underground pest insects. However, you WILL be able to observe the evidence they’re in residence by the appearance of your plant aboveground.

Why do some Plants Attract Pest Insects?

Pest insects target plants that are minerally deficient. They are indicators of an imbalance. Weak malnourished plants are magnets for herbivorous insects. They are a CLUE you need to change something.

Pest insects often target nutrient-deficient plants

Pest insects often target nutrient-deficient plants

Professor Philip Callahan, the author of Tuning into Nature, observed that insect antennae enable them to sense a variety of environmental signals. He also found that plants emit infrared radiation (not visible to us). What’s really interesting is these signals vary depending on the nutrient levels inside the plant. He notes “A sick plant actually sends forth a beacon, carried in the infrared, attracting insects. It is then the insect’s role to dispose of this plant deemed unfit for life by nature.”

Survival of the Fittest

So, ‘pest’ insects are actually Nature’s ‘garbage collectors’. Their role is to remove ‘rubbish plants’ and help strong healthy plants survive! They leave plants with optimum nutrition levels alone. What can you learn from this? Grow nutrient-dense food and insect pests won’t bother your plants.

If you have a lot of pest insect problems in your garden, look at your soil health as a first step. Then, cultural practices like watering, feeding and position. It’s far easier to implement preventative strategies than deal with a big outbreak.

Pest insects select plants with a nutritional imbalance of one or more nutrients. They don’t have the pancreatic enzymes necessary to digest complex carbohydrates in healthy plants. Untouched plants are a clue you are meeting their needs. (more…)

What is Damping Off and How to Prevent It

What is Damping Off?

Definition: ‘Damping off’ is a condition caused by pathogens that destroy seeds before germination or very young seedlings. The term refers to the outcome – weakened or dead seedlings or seeds. The seedling stem rots and the young plant collapses or seeds fail to germinate.

What is Damping Off and How to Prevent It - Symtoms, Causes & Treatment

Is it really that serious? Yes, unfortunately! Damping off can affect up to 80% of seedlings. So, if affected, you could lose a significant number of plants. Research has found that “even a very low population density of soil-borne pathogens can lead to severe epidemic development.” (1)

What Causes Damping Off?

So, who are the little rotters responsible for this sad end to your plant ‘toddlers’ or seed ‘babies’?

There are over a dozen culprits of soil-borne disease-producing organisms – different species of fungi and fungus-like organisms called ‘oomycetes’. They live in soil and transfer to a seed or seedling when conditions are favourable. Some pathogens are carried inside seeds or on the seed coat. However, only a few are commonly associated with damping off.

Firstly, let’s meet a few pathogens and their tongue-twisting names! They include Pythium species, oomycetes like Rhizoctonia solani, Phytophthora, Fusarium and Aphanomyces cochlioides.

More importantly, where do they hang out? Wet or overwatered soil, particularly in cool temperatures or cloudy conditions, provides favourable conditions for oomycetes called ‘water moulds.’ Why? Clearly, because they require water to multiply and spread. Phytophthora and Pythium species are both parasitic oomycetes.

Difference Between Pythium and Phytophthora - Pathogen Comparison

However, if you have warm, dry soil conditions, Rhizoctonia and Fusarium can thrive and are usually the most likely offenders. Rhizoctonia attacks seedlings causing them to collapse. A dry brown discoloured stem is often a clue.

This fungal pathogen thrives in soils with poor fertility (nutrient-deficient) and insufficient moisture. The brassica family of vegetables including broccoli, rocket, kale and cabbage seem most susceptible to this pathogen. Making your own seed raising mix just before sowing seeds may prevent this fungus from ‘priming’ itself to infect the emerging crop.

What are the Two Types of Damping Off?

Damping off affects both seeds and seedlings. So, what evidence should you look for?

  1. Pre-emergence: Seeds rot in the seed raising media before germinating or emerging above the soil level. Your seeds never appear to germinate. So, you may be left wondering what went wrong.
  2. Post-emergence: ‘Newborn’ seedlings that have recently germinated wilt, collapse quickly or die from soft rot in the stem. They usually fall over at the soil level. Woody seedlings may start to weaken and wither while still erect, but baby roots may decay soon after. The infected stem looks soft, brown and water-soaked. A bit of a sad story really, isn’t it? It’s devastating for new ‘plant parents’!

What are the Symptoms of Damping Off?

Damping off in Seedlings:

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Imitate Nature for Higher Yields & Less Pests

Get Hundreds of Free Workers AND an Abundant Harvest!

Want less pests in your garden? To help achieve a balance between pests and predators, I’ve found that imitating natural ecosystems can be a useful pest management strategy to use.

 

Imitate Nature for Higher Yields and Less Pests

Facilitating natural predator-pest relationships in your garden is a way to harness hundreds of free workers to help manage insect imbalances. An example is the ‘aphid banquet’ on the menu for this ladybird’s lunch!

How to Work with and Imitate Nature

Whilst ‘having a relationship’ with birds, lizards, frogs and insects may not be on your To Do List, seeking a ‘win-win’ outcome by working with these creatures in your garden can help you:

  1. Achieve a higher crop yield (by encouraging more Pollinators); and
  2. Minimise insect damage to your edibles (by creating an unwritten ‘Workplace Agreement’ of sorts with Pest Predators – one that offers the kind of job perks that are an incentive for them to get to work in your garden)!

I’ve learned the benefits of ’employing’ hundreds of workers in my garden. Even though I don’t know them all by name, they still turn up regularly for work, never ask for a raise, are reliable in undertaking their jobs and save me hours of hard labour. In this article, I’ll share with you what my end of the agreement entails and how you can negotiate a similar arrangement at your place.

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