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Nematodes

SERIES 20 Episode 10

A single teaspoon full of well-composted soil can contain hundreds of thousands of different species of organism and up to half a kilometre of fungal threads. But in Jerry’s Brisbane garden, as well as the usual worms, bacteria and fungi that any healthy, organically rich soil plays host to, Jerry has encountered what is actually a common summer pest — the Root Knot Nematode.

About nematodes

Nematodes are also known as ‘Eel Worms’ and they’re colourless, microscopic worm-like animals. Scientists have described about 20,000 species and some specialists estimate there could be over a million. Most of these are harmless to plants, and some are even beneficial. But the Root Knot Nematode is a plant parasite.

Recognising you have a problem with nematodes is not always easy as they work undercover or, more specifically, underground. When young nematodes burrow into plant roots their feeding stimulates the production of tumour like growths and these inhibit the plant’s ability to take up water and nutrients. The result is a weak plant, reduced growth and productivity, and plants also become susceptible to secondary fungal infections and to sudden wilting.

Symptoms

You may notice that even with moist soil your plants still wilt, turn yellow, and may eventually even die. If your garden is infected with nematodes, you may not notice their presence during the cool seasons because their populations peak during summer, and by that stage, when you notice plants wilting, it’s too late to do anything about that particular crop.

Identification

If you think your plants are infected, dig up a plant, rinse the soil off the roots and inspect them. Nematodes present as tumour-like growths on the roots, which may be tiny or take over the entire root system. Remember that beans and peas fix their own nitrogen in the soil, which is stored in small growths similar to nematode tumours, so check other plants in your garden first before diagnosing from legumes.

Plants affected

Many plant species are affected by this particular nematode, but it mostly causes damage to the following plants:

* The solanaceae family, which includes potatoes, eggplant, capsicum, chilli and tomatoes.

* Cucumbers, melons and pumpkins.

* Strawberries, peaches, bananas, grapes, passionfruit, pineapples, pawpaw.

Controlling nematodes

Create a rich organic soil by adding compost, manures and mulches. These encourage beneficial nematodes which attack the pest species.

Practice crop rotation. Don’t make life easy for nematodes by planting the same crops in the same soil, year in, year out. Vary your crops and make it difficult for nematodes to really enjoy living in your garden.

If your plants are affected, don’t put the roots in the compost heap — drop them into a plastic bag and put them in the garbage.

Sow mustard seed as a green manure. When crops have been cleared broadcast mustard seed over the surface, rake it in, water it, grow it to 45 centimetres high and then dig it in. If the soil is moist, the mustard will decompose and release chemicals known as ‘isothiocyanates.’ This is the chemical that gives mustard its hot flavour and it’s that chemical that fumigates the soil and helps control nematodes.

While no infected garden will ever be entirely free of these pests, Jerry says, «Don’t worry. With some careful observation and some simple organic gardening techniques, you can look forward to abundant harvests for years to come.»

Transcript

JERRY COLEBY-WILLIAMS: You wouldn’t necessarily think so, but a single teaspoon full of well composted soil like this is a seething metropolis. It can contain up to 200 000 different species of organism and up to half a kilometre of fungal threads. And all of these creatures are living together, competing with each other for water, nutrients and space.

But here in my Brisbane garden, as well as the usual worms, bacteria and fungi that any healthy, organically rich soil plays host to, I’ve encountered what is actually a common summer pest but one you may not know much about. The Root Knot Nematode.

Nematodes are also known as ‘Eel Worms’ and they’re colourless, microscopic worm-like animals. Scientists have described about 20,000 species and some specialist estimate there could be over a million. Most of these are harmless to plants. Some are even beneficial. But the Root Knot Nematode is a plant parasite.

Recognising you have a problem with nematodes is not always as they work undercover, or more specifically, underground. What happens is young nematodes burrow into the roots and their feeding stimulates the production of tumour like growths and these inhibit the plant’s ability to take up water and nutrients.

So the result is a weak plant, reduced growth and productivity and plants become susceptible to secondary fungal infections and to sudden wilting.

If your garden is infected with nematodes, you probably won’t even notice their presence during the cool seasons and that’s because their populations peak during summer and by that stage, when you do notice plants wilting, it’s too late to do anything about that particular crop. The difficulty is knowing if they’ve got them at all. And the only way to do that is to dig the plants up, rinse off the soil off the soil like I’ve done with this kohlrabi and check. And I can see that this has got nematode infection. It’s not bad. That’s why the plant has grown really well. But in severe cases, these roots, these fibrous roots wouldn’t be able to be seen at all. It would be just tumour-like growth and perhaps the plant would completely rot and die.

So which plants are most affected by the Root Knot Nematode? Well, the Solanaceae or potato family and that includes some of our favourite food plants. Things like eggplant, capsicum, chilli and tomatoes, and that’s in fact where I first discovered what nematodes were doing in my garden.

They were growing beautifully one week, and the next week, they were going yellow and wilted, even though the soil was moist. Now there are some other things, some surprises that occurred. Like this Ceylon Spinach, totally unrelated to the potato family and yet that got nematodes as well. Now, there’s one group of plants that we can be comfortable about growing in nematode infected soil and that’s the peas and beans. The legumes.

Like this Snake Bean. These do produce nodules on their roots and you mustn’t confuse them with nematodes. This is natural. This is what they do. They put nitrogen into the soil and if you look closely, you can see they’re clean and rounded. They’re not tumour shaped as the nematodes cause on other plant roots, so you can grow these in nematode infected soil. And that brings me back to the bed.

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Everything I’m growing in here, apart from the Ceylon Spinach, is not going to be affected by Root Knot Nematodes. I’m resting my bed to reduce their population.

Often you can eat crops that that have been affected by nematodes, but if you do have that situation, get rid of the roots. Don’t put them in the compost heap, drop them into a plastic bag and put them into the garbage.

No the secret to living with nematodes, which I practice here involves a couple of strategies. Firstly, organic rich soil. By putting in compost, manures and mulches, you can encourage beneficial nematodes to attack the pest species. And practice crop rotation. Don’t make life easy for nematodes by planting the same crops in the same soil, year in, year out. Vary your crops and make it difficult for nematodes to really enjoy living in your garden.

There is one other, newly confirmed technique for controlling nematodes and that involves this — sowing mustard seed as a green manure. Once you’ve cleared the crops, you just broadcast mustard seed over the surface, rake it in, water it, grow it until it’s 45 centimetres high and then you dig it in and something very special happens. If the soil is moist, the mustard will decompose and it releases a chemical known as ‘Isothiocyanates.’ We all know what it tastes like. If you’ve eaten mustard or horseradish, it’s the same thing that gives them their hot flavour and it’s that chemical that fumigates the soil controlling nematodes. And we’ve got the CSIRO to thank for that 21st Century solution to nematodes.

While no infected garden will ever be entirely free of these pests, don’t worry. With some careful observation and some simple organic gardening techniques, you can look forward to abundant harvests for years to come.

STEPHEN RYAN: I’m with Jerry on that one. Looking after your soil is definitely the key to a great garden.

Still up in Queensland, Colin’s found a wonderfully peaceful spot that’s an oasis for native plant lovers.

www.abc.net.au

Garden Myths — Learn the truth about gardening

Nematodes and Marigolds

Companion planting is a standard recommendation for growing vegetables. One of the most commonly recommended plants for this is the marigold, which is supposed to be good for preventing various pests from eating the vegetables. I will limit the discussion in this post to using marigolds to reduce or eliminate nematodes in the garden.

Root knot nematodes on carrots

Nematode – What is it?

Nematodes are microscopic worms that live in soil and other places. All soil has them in varying amounts, and there are many different types. Unless you take a soil sample to a lab you will not know which type you have or how many you have. Some nematodes cause problems in the garden, but many are beneficial. For example, nematodes are used to kill June bugs in lawns.

The nematodes being discussed here invade plant roots and cause various deformities in the roots. That can be a real problem in root crops like beets and carrots since they affect the part of the plant we want to eat. But nematodes also affect other plants like tomatoes. When tomatoes are infected, the nematodes make the plant weaker resulting in a poor crop.

Some damage is always present, but in most cases it is so minor that we don’t even see it. In severe cases you simply can’t grow certain crops.

Nematodes and Marigolds

Many web sites and gardening books promote the idea that marigolds will reduce or eliminate the amount of nematodes in the soil. If this happens, then you no longer have a nematode problem. Seems simple enough. Plant some marigolds in your vegetable garden and you eliminate nematodes.

There is some validity to this idea so it is not a complete myth. The problem is that the real truth of the matter has been vastly exaggerated and over simplified.

How do Marigolds Control Nematodes?

Based on my research, scientists are not really sure. Marigolds do produce compounds that are nematicides, a compound that kills nematodes. It is possible that these are released into the soil and that the nematodes in the vicinity of the roots are killed. Field testing does not support this hypothesis.

A more plausible explanation is that marigolds act as a host for the nematodes. The nematodes actually invade the marigold roots in the same way they invade a tomato root. The difference is that once the nematode is inside the marigold root, the natural nematicides of the plant kills the nematode and prevent it from breeding. Over time the population of nematodes decreases.

None of this has anything to do with the marigold fragrance which does not attract nematodes, nor does it repel them–that is a myth.

Does Companion Planting Work?

Stated another way, will marigolds, planted along side of other vegetables, control nematodes? The key words here are ‘planted along side’. The answer is NO. This has been tested scientifically many times and it just does not work. Your garden may look pretty, it may smell nice, but this practice does not prevent nematodes from invading your crops.

Best Cultural Practice

If you decide to use marigolds to control nematodes you should follow these steps. Plant the marigolds in the exact spot where you will be growing the vegetable. Grow them there for at least 2 months and some references suggest 4 months. After 2 months, you can remove them, or dig them into the soil and then plant your vegetable crop. This will control the nematode problem, provided you are planting the right kind of marigold – see below.

The marigolds attract nematodes and as they invade the marigold root, the number of nematodes is reduced. When the vegetable is planted right after the marigold, it grows in an area that does not have many nematodes and therefore you see less damage to the vegetable crop. To make this work the marigold needs to be in the “same” spot as the vegetable. A foot one way or the other makes a big difference and that is why growing the two plants side by side does not work.

If you are located in climates with shorter growing seasons, for example much of the northern hemisphere, you don’t have a long enough growing season to dedicate 2 months to marigolds. You are out of luck.

Which Marigold Works Best?

You might know that there are a number of different types of marigolds, both species and cultivars. It turns out that each type has a different effect on nematodes and the effect depends very much on the type of nematode. That is right, to have any effect you need to match the right type of marigold to the nematode growing in your soil. How do you figure that out? You need to have your soil analyzed at a lab. Unless you are prepared to do this, you have no idea which marigold to plant.

If you are not prepared to have your soil tested, don’t bother trying to use marigolds to control the nematodes. It’s probably not going to work.

Marigold Facts

The following are some facts related to the use of marigolds in fighting nematodes.

  • Most modern day tomatoes have been breed to be nematode resistant–one reason for not using heirlooms.
  • Protection lasts one season or for one crop. Nematodes multiply quickly and will return.
  • Marigolds do not draw nematodes away from crop plants. They are simply one of the possible hosts.
  • Digging the marigolds in is good for the soil, but it does little to help the nematode problem. The natural nematicides are only found in living plant tissue. However, the extra organic matter might encourage natural nematode predators to prosper.
  • The effectiveness of marigolds is temperature dependent. Some marigold types work better at higher temperatures, and some work better at lower ones.
  • Marigolds are a magnet for thrips and spider mites which could be as big a problem on vegetables as the nematodes.
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www.gardenmyths.com

Nematodes

Please note: This content may be out of date and is currently under review.

Nematodes are common soil pests that affect plants. The aboveground symptoms of disease caused by nematodes can be difficult to detect, and may be often confused with symptoms of nutrient deficiency. Typically, plants do not thrive, are paler than normal, and may wilt in the heat of the day. Affected plants are often dwarfed, with small leaves. Sometimes, when infected plants are growing in moist, fertile soil, or during cool weather, the aboveground parts can still appear healthy.

X12_4190 Root symptoms.jpg

Types of nematodes

There are numerous soil-inhabiting nematode species, but not all are harmful to plants. This information sheet deals only with plant-parasitic nematodes. Within this group, some nematodes spend their life within the plant roots. These are endoparasitic. Others are ectoparasitic, and only their stylets (hollow spears used to puncture roots) enter the plant to extract nutrients from the roots or root cells. Plant-parasitic nematodes have many hosts and are seldom plant-specific.

Root knot nematodes

Root knot nematodes (Meloidogyne) are the most damaging species in the home garden. These nematodes have a very wide host range, affecting more than 2000 plant species worldwide. Root knot nematodes enter the roots as larvae, causing the plant roots to form galls or knots, and there may be excessive root branching. Underground organs such as potato tubers or carrot taproots may be damaged and become unmarketable. The nematode larvae mature in the roots, where they mate. The female adults enlarge, remain in the roots, and lay eggs into an egg sac that exudes into the soil. The eggs hatch and the young larvae go on to infect more roots.

Plants are damaged because the galls or root knots block the transport of water and nutrients through the plant. Nematode feeding sites in the roots can also provide entrance for other disease-causing organisms, like fungi or bacteria, leading to increased plant damage. Nematodes are a greater problem where conditions favour them, such as a long growing season, sandy soil and if plants are under water or nutrient stresses.

Root lesion nematodes

Although they are present in home gardens, where they can affect fruit trees, roses and turf, root lesion nematodes (Pratylenchus) are more damaging to broad-acre crops like cereals. Root lesion nematodes use the stylet to puncture roots and enter the cells. They move through the root, piercing cells, extracting cell contents, and leaving behind a trail of both cell-killing metabolites and eggs. Root cell death results in browning and lesioning of the roots. These lesions can rapidly coalesce, resulting in browning of whole roots. Individual lesions may fully encircle a root. These nematodes also damage feeder roots and root hairs, further reducing a plant’s effective extraction of water and nutrients from the soil. The overall effect is a weak, shallow root system with many dead or dying areas. When the soil dries out, root lesion nematodes become inactive and survive in a dry form in the soil or in root tissue of old crops. As the soil moistens, the nematodes become active again and reinfect the fresh roots of the new crop.

Cause

Many nematodes occur naturally, at low levels, in most soils. Most plant-parasitic nematodes enter the garden through infested soil or infested transplants. Once nematodes are present, they are almost impossible to eliminate, but their damage to plants can be reduced. Inspect the roots of transplants before placing them into your garden, whether they originate from a reputable dealer or a neighbour. This will help to keep your garden clean. Successive growth of plants that host the nematodes will lead to an increase in their population.

www.agric.wa.gov.au

Organic Slug & Snail Control

By Andy McIndoe • February 4th, 2015

10 Best Ways To Control Slugs and Snails Organically.

There is no doubt that slugs and snails are the gardener’s worst enemy in many parts of the world. These voracious slimy creatures are able to devour several times their own body weight of your favourite plants in just one meal.

They seem to appear from nowhere when the weather is mild and damp. Overnight they appear from neighbouring vegetation, under stones, under the rims of plant pots, a thousand hiding places.

It is therefore no wonder that so many different ways to attempt to control them have evolved over the years.

Fifty years ago most gardeners kept a drum of table salt at the ready to pour on to the offending creatures as they appeared. Salt was sprinkled around newly planted seedlings.

Of course it dissolved instantly causing potential harm to soil and other wildlife. If you live near the coast you may well use seaweed around the garden which many claim is an effective barrier.

Wood ash may be deterrent for a while. Like many “natural” remedies, it seems to work in some gardens and is totally ineffective in others. Some slugs seem to be deterred by coarse grit spread around plants. Other slugs and snails cross intrepidly. Maybe it’s a bit like walking over hot coals.

Of course the ideal method of natural slug and snail control is to encourage enough natural predators to inhabit your garden: frogs, birds, hedgehogs and the like. This can only be successful if your other slug control methods are harmless to them.

Traditional slug pellets contain metaldehyde which is harmful to wildlife. It is worth mentioning that birds, amphibians and mammals are unlikely to eat the pellets, however they will eat slug and snail corpses and that’s where the real harm is caused. So what are the top 10 alternative natural remedies?

1. Coffee Grounds.

Coffee grounds spread round plants you want to protect do deter slugs and snails.

Some swear by this method and coffee grounds are not a resource we are short of considering the number of coffee shops that have sprung up everywhere in the past quarter of a century.

No good for those of you using pods in your espresso machines; but ideal for those still using cafeterias.

2. Beer Trap

Slugs love beer, apparently. A container such as a margarine tub or large yogurt pot sunk into the ground so the rim is at or just above soil level, filled with beer acts as a slug trap.

The slugs are attracted, fall in and drown; a great way to go. What of those that don’t like beer? They are still eating your lettuces.

3. Eggs shells and sea shells.

These are effective for a while when spread in a barrier ring around precious plants. If you live by the coast, near a sandy beach with bivalves you may have access to sea shells.

If using egg shells you will need to eat a lot of eggs to keep the average plot slug free.

4. Diatomaceous earth (DE).

This is an interesting one and popular in some parts of the world. Diatomaceous earth is the finely ground fossil remains of freshwater prehistoric diatoms.

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It is used in various grades to kill bedbugs, cockroaches and food grade DE is used to kill internal parasites. As an abrasive powder inhalation is to be avoided.

Slugs can’t cross it but it does need to be replaced after rain; no good to me I fear. Some say perlite works in the same way: worth a go.

5. Copper tape.

Slugs can’t cross copper, so copper tape acts as a barrier. You can use a ring of it around an individual plant, however it works best to protect plants in pots.

A ring around the pot, just below the rim prevents the slug from getting at the plant in the pot. There are copper impregnated mats too that you can stand pots on.

These are successful until the plant grows; its leaves touch a neighbouring plant and the slugs and snails use it as a bridge.

6. Slug repellent plants/Slug attractive plants.

Garlic, Lawn Chamomile, chives. Some plants repel most slugs and snails and these may have a deterrent effect when planted alongside or used to make an extract.

Many gardeners swear by garlic as a natural pest control. Some say chives are effective it the leaves are tied around vulnerable plants; sounds fiddly.

You can of course plant something that is more attractive to slugs and snails. Lawn chamomile seedlings are reputed to be irresistible.

The slugs go for them and you wait in ambush, pop them in a jar and deport them.

7. Recycled wool waste pellets.

Shoddy, wool waste is a by-product of the wool manufacturing process. This is turned into pellets that you spread around the plants as a barrier.

They swell up and reveal nasty little fibres that are irritant to slugs. Over a period of time the pellets degrade and act as a plant food. I’ve used this one and it is effective when protecting newly planted seedlings and emerging perennials.

8. Nematodes.

Biological control of slugs and snails is effective in small gardens if carried out with care early in the season. Basically you water on a solution of nematodes (microscopic worm).

These penetrate the slug, infect it and kill it: not a pleasant thought but organic and effective. You usually buy from mail order and storage and usage instructions must be followed if it is going to work.

9. Wheat bran/Corn Bran.

Small piles or rings of wheat bran or corn bran are eaten by slugs and snails and they cause desiccation and death. Totally organic and if wildlife eat the corpses they are getting extra nutrition.

This method has had great following. Disadvantage: you need to replenish regularly in rainy weather. Advantage: buy it from the health food store.

10. Nature Friendly Slug Pellets.

Organic Slug Pellets are based on Iron phosphate rather than metaldehyde. If you want an off-the-shelf, easy solution that is simple to use, these are probably your best bet.

They are approved for use in organic gardening and have soil association endorsement. Use sparingly: not like granular fertiliser.

They are not completely non toxic to other animals. They can kill earthworks and there have been some reports of dogs becoming ill after ingestion them. But they are still a safer alternative to metaldehyde.

There are so many more possibilities, and I know you will have your suggestions: please post them below. Let’s keep to the passive solutions like these: no violence. However, I do understand why gardeners get so emotional about slug and snail damage.

If you try or have tried any of these do let us know what you think.

www.learningwithexperts.com

Strawberry Plant Protection: Tips On Protecting Strawberries From Insects

We had a strawberry field in our backyard. “Had” is the operative word here. I got fed up with feeding every bird and pest in the neighborhood, so I had a conniption and removed them. Might there have been a better method of protecting the strawberries from insects? Probably. I was too impulsive and should have looked into strawberry plant protection. So here we are, learning how to protect strawberry plants from pests.

How to Protect Strawberry Plants from Pests

There actually are many ways of keeping pests away from strawberries, some of which I really did use….to no avail. The birds were the most obvious intruders. There are lots of things you can do to repel birds. Noise scares them off, but it’s so, noisy. Fake predator birds will do the trick sometimes but, interestingly, our fake eagle is covered with bird manure. A scarecrow works in corn fields, right? I didn’t want to erect an entire person, so we did something else. We hung old CDs from twine hanging along the gutter line under which the strawberries resided. It worked.

Once the birds were gone, you’d think I could heave a sigh of relief, right? Nope, now it was the bugs’ turn. The pests are attracted to the succulent berries via their sweet aroma. Following that line of reasoning, the obvious thing to do would be to distract them with another more scintillating odor. Herbs are often co-planted around crops to confuse pests. Try planting:

If nematodes are your problem, try planting marigolds as a method of strawberry plant protection. The nematodes are attracted to the marigold roots and invade them. Then the natural nematicides in the marigold’s roots kill the nematode and prevent it from breeding. So the numbers of nematodes will be naturally reduced.

While you’re planting marigolds, plant other flowers nearby. They will attract beneficial insects such as lacewings, parasitic wasps, ladybugs and spiders that like nothing more than supping on some of the less welcome pests.

Try organic methods of pest control when protecting strawberries from insects and other pests. Organic methods for keeping pests away from strawberries might involve hot pepper spray, rotten eggs, blood meal, castor oil, orange peels, soap and human hair. Apparently, soap or human hair placed in a mesh bag and hung on a tree branch at deer height will keep the deer away from the strawberries. Blood meal mixed into a gallon or water or an Epsom salt spray will keep the rabbits from eating young berry plants.

Make your own insecticidal soap with 4 tablespoons of dish soap to 1 gallon of water. Fill a spray bottle and douse the aphids. Ladybugs in the garden can also help with these pests.

The biggest offenders in my garden were the slugs. We tried the beer trap. Fill a container with beer and place it (or several of them) around the strawberries. Dig a hole so the container’s lid is level with the soil. The slugs fall into the container of beer and drown. Copper strips can also be placed around the perimeter of the garden to deter the slugs. Diatomaceous earth is another tool in your arsenal. The gritty powder cuts into soft bodied pests like slugs.

Lastly, using a floating row cover to keep pests from nibbling on your berries is probably one of the best ideas. This lightweight fabric covers the plants but allows them access to light, air and rain. Secure the edges of the row cover with stakes or heavy rocks or bricks to keep flying insects out. Remember to uncover the berries for at least 2 hours per day to allow the bees a chance to pollinate them.

www.gardeningknowhow.com

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