Tuesday, September 22, 2009

Nematode talk

I was at a community garden workshop run by Janet Millington and Sonia from transition towns - Sunshine coast on the weekend. In our conversations nematodes came up as a major issue in alice Springs. Many people didn't know what they were or how to keep them out so i thought i'd go through it here
Nematodes are microscopic unsegmented worms. There are many types - some are helpful in th egarden and some aren't. The ones we are talking about here are ectoparasites of plants roots. They latch on to the fine roots of plants and start sucking the goodies out. in the process of doing this the roots develop callus or nodules but gradually many of the fine roots are lost. this reults in plants not being able to take up minerals or water. Plants with nematodes will not crop heavily and will wilt easily in the summer. When you pull them out of the ground they will have distorted nodulated roots and very few fine roots. these nodules are almost succulent and when they dry out they are harder to recognide so try to do this with fresh roots.

What do you do about them?

First you need to establish that you have them and the description above should help you to do this. Plants luke tomatoes, cucumbers, zucchini are very susceptile so if they are not doing well you may have to investigate further.

NOTE: some people may muse that if you have nematode problems your soil must be badly balanced, have an underlying problem etc - so you can solve those problems and you don't need to worry about nematodes. If there is such a solution i have not found it, but even if there was it would probably be a whole lot more work. and in my experience this is a turn off for people wanting to grow vegies so much better to keep them out and make your life a whole lot easier.

If you don't have them you want to keep them out! you do this by observing some quarantine rules in your garden.
TOOLS: If you or anyone lese brings in garden tools or wheelbarrows into your garden make sure they are washed - preferably not on your property. all dirt should be removed - wire brushes etc.

PLANTS: Don't accept plants from anyone that have been dug up from someones garden. Even plants that haven't been dug up may have been sitting on soil or have contact with soil. Take cuttings and root them yourself or take seeds and grow them yourself.

MANURE: folklore has it that if you pick up horse manure from the racetrack you may end up with nematodes. They way this probably happens is that when the horse owners pick up th emanure in yards, they also pick up some dirt and this ends up in a manure pile. If you have no choice compost the manure you get in an open heap that heats up to high temperatures for a number of days.

cow manure from the stock yards is a good choice. the cows are confined in yards which no vegetation grows, thus there is no opportunity for nematodes to breed. the cows are fed hay and produce manure which is then scraped up. You should always try to compost your manure anyway to get a more balanced product that is better for plants - and it kills nematodes and other pathogens.
My experience and that of others is that we have had no indication of anyone bringing nematodes home in cow poo
having said that - bringing anything into you yard has some risk attached.

If you already have them what do you do?
there are two ways of coping with nematodes. one way is to manage them with lots of organic matter, compost and green manure crops. you can still produce some reasonable crops of most things.
Your other strategy which you also might try is to find vegetables that are resistant to nematodes and grow more of these. Eg instead of trying to grow silverbeet - grow Amaranth in the summer and kale in the winter. Grow snake beans instead of green beans and grow sweet potato instead of normal potatoes. I have found that more often tropical vegatbles will be resistant and vegetables that have not been highly domesticated - although okra is an exception. ( you can obtain lists of more nematode resistant crops)
Asparagus is unaffected by nematodes - so make sur eyou have some of it!
i use both of these strategies and still gave a productive garden. In the summer i can grow sorghum as a green manure crop an dthen plant into it(after its dug in) in Jan or feb.

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