The ABC’s Gardening Australia program on June 20th told gardeners how to identify plants affected by bacterial wilt but, unfortunately, did not tell them how to eliminate the disease.
Bacterial wilt (Ralstonia solanacearum) is a serious soil disease that can, like Fusarium and Verticillium wilts, spread throughout the garden on boots, gardening tools, and infected plant material and seeds. It grows best in temperatures of between 30 and 35° C. and the bacterium requires both heat and moisture to multiply. Consequently, it is more commonly found in areas with wet summers.
It can affect the entire tomato family, the banana family (including Heliconia), onions, papaya, ginger, mung beans, cashews and peanuts. Like the fungal wilts, it affects the water-conducting tissue of plants and causes rapid wilting. Diagnosis can be determined from a section of stem pruned from near the base of a suspect plant. Immediately after pruning the stem, suspend it in a glass of clean water for several minutes. Milky threads will begin to leak from the stem and the water will quickly become white if Bacterial wilt is present.
Remove all plants, tubers and weeds from infected beds and destroy them, or dispose of them in a sealed plastic bag. Any remaining plant material can infect future crops of susceptible varieties – do not compost this material.
Raising beds to 20 cm or more can help deter this disease. After working on affected beds, wash boots and garden tools and allow them to dry in direct sunlight.
Bacterial wilt often occurs in conjunction with root knot nematodes. These pests can be eliminated by growing a green manure bio-fumigant.
Allowing a fallow of at least 18 months will also help, especially if soil in the bed is kept dry. This can be achieved by covering the bed with clear plastic, anchored around the edges. This process is called solarisation and it works best in warmer months, as bacterial wilt pathogens cannot survive in temperatures over 41° C.
After solarisation and bio-fumigants, grow a green manure of corn or maize and dig it into the topsoil. This will restore organic matter to soil and encourage the growth of beneficial mycorrhiza fungi. Bacterial wilt is more likely to occur in soil that is low in nutrients and organic matter, and has a high pH. Before growing crops in the treated beds, add plenty of complete organic fertiliser and as much compost as you can spare. Also check that soil pH is in the 6.5-7.5 range. Avoid growing susceptible crops in the treated beds for at least 3 years after diagnosis of the disease. Maintaining organic cultivation methods and practicing an adequate crop rotation will help prevent recurrence of this disease.

Soil fungi that affect the water-carrying parts of plants cause wilt diseases that can affect a wide range of vegetables, grains, and ornamentals. Fruit trees can also be affected.
Wilt diseases are commonly caused by not practicing a proper crop rotation. Adding organic matter to soil helps to limit soil-borne diseases because the beneficial fungi in organic matter out compete the pathogens. Avoid using glyphosate because it has been shown to affect the microorganisms in soil that assist in keeping diseases under control.
To find out which fungus is affecting your plants, pull out (if possible) one of the affected plants and cut open the stem near the roots.
If it’s Fusarium wilt, the inside of the stem (in most plants) will be pink to reddish brown. In beans, the inside of the stem will be dark brown with reddish roots. According to research recently published by the US Department of Agriculture, Fusarium diseases are becoming a serious problem in GM crops that have been engineered to be glyphosate-resistant. The research found that glyphosate exuding from the roots of this type of GM crops stimulates Fusarium fungi in soil. In wheat, these fungi cause Fusarium Head Blight. Fusarium produces several toxins in plants that are not destroyed by cooking. These become a health problem when present in large quantities. One type causes vomiting. Another type causes cancer and birth defects, while a third type of toxin is lethal. It is important to act to prevent the establishment of Fusarium in garden and agricultural soils.
If it’s Verticillium wilt, the outside of the stem appears normal but the inside of the stem will be dark brown to black. This disease is more common where drainage is poor. Improve drainage and control weeds. Give any unaffected plants in the bed a drink of seaweed extract tea as potassium and trace elements in this tea assist in building resistance to disease.
TREATING FUNGAL WILT DISEASES
Remove all weeds and affected plants and burn them or dispose of them in a sealed plastic bag. Do this carefully, as spores can be spread by shoes, and gardening tools. Wear rubber boots and wash them and all tools after working in infected soil. Then dry these in direct sunlight.
Bio-fumigation
When soil temperature is 14° C. or higher, grow a green manure crop of bio-fumigants such as Green Harvest’s BQ Mulch, yellow mustard, or radish. The peppery members of the Brassica family produce good quantities of glycosinolate that breaks down in wet soil to produce a gas that is effective against fungal pathogens and nematodes. Slash the green manure before it flowers, and hoe it into the topsoil. Then water the bed and cover it thickly with mulch.
Solarization
Recent Spanish research has shown that, during summer, solarization is effective in treating these diseases. Place clear plastic sheets over irrigated beds and leave them in position for a minimum of 2 months.
Then grow a green manure crop of corn or maize and slash it when it is knee high and dig it into the topsoil. Wilt diseases are more common where soil is low in broken down or decomposed organic matter, and bio-fumigation will also affect beneficial mycorrhiza fungi in soil. Replacement of organic matter through green manures and as much compost as you can spare will encourage the re-establishment of mycorrhiza and other beneficial fungi and bacteria that can control soil pathogens when organic cultivation methods are used.
You will also need to practice a long crop rotation for different plant families until your soil is free of disease.

Plant varieties for sowing and planting are fairly similar for both June and July in most climate zones. Some areas are finding conditions colder than usual for this time of year, and vegetable growing will have to be adjusted to suit local conditions. Brussels sprouts and cauliflowers perform best in areas with cold winters and the cooler conditions may help cropping in marginal areas. Peas and broad beans should be sown at a time that will avoid frost damaging the flowers (see Broad beans and peas). Sowing times are more flexible when sowing peas or broad beans as a green manure because these crops are cut down as soon as the plants start to flower.
The following planting guide is an abbreviated list for vegetables, fruit trees and some culinary herbs that can be planted in June or July in Australia and New Zealand. A comprehensive monthly guide that includes planting times for the entire garden, as well as when to fertilise, prune, weed, take cuttings or divide plants, can be found in my book Easy Organic Gardening and Moon Planting.

WARM CLIMATE – South of Rockhampton
Before the Full Moon, cabbage and grains can be sown direct, and suitable lettuce and spring onions can be sown or planted out in June or July. A green manure crop of barley, chick pea, red clover, broad bean (faba bean), field pea, or triticale can be sown in June, and red clover can be sown in July. English spinach, peas and radicchio can be sown in the last week of June. Silver beet and tomato can be sown in a cold frame in July.
During Full Moon phase, radish can be sown direct, and asparagus and rhubarb crowns, fig, pecan and pistachio can be planted in June and July. In June, kiwifruit vines can be planted out, and Jerusalem artichoke tubers can be sown in July. Beetroot can be sown in a cold frame in July. Seed potatoes can be sown north of Brisbane in June, and from Brisbane southwards in July.

WARM CLIMATE – Rockhampton northwards
Before the Full Moon, bush and climbing beans, cabbage, open Chinese cabbage, chamomile, coriander, grains, lettuce, mizuna, rocket, silver beet, sweet corn and tatsoi can be sown direct, and pumpkin, spring onion, summer squash, tomato, watermelon and zucchini can be sown or planted out in June or July.
A green manure crop of barley, lablab, or triticale can be sown in June, and lablab or corn as a green manure in July if irrigation is available. Capsicum and eggplant can be sown in a cold frame in the first week of July.
During Full Moon phase, beetroot, radish, turnip, fig, pistachio can be planted in June and July. Avocado and banana can be planted in July.

TEMPERATE CLIMATE
Before the Full Moon, English spinach can be sown in June in all areas, and also in July in frost areas. In frost-free areas, lettuce and spring onions can also be sown during June and July. A green manure crop of broad bean (faba bean) or field pea can be sown in June and July. In suitable areas, broad beans and peas can be sown during the last week of June and the first week in July – choose dwarf broad beans for July planting.
During Full Moon phase, garlic, mid season onion, radish, asparagus and rhubarb crowns, fig and pistachio can be planted during June and July. Kiwifruit vines can be planted in June, and Jerusalem artichokes tubers and seed potatoes sown in July.

COOL CLIMATE
Planting is extremely limited during June and July. Before the Full Moon, English spinach can be sown, as well as a green manure crop of broad bean (faba bean) or field pea. Broad beans and peas grown as a vegetable can be sown during First Quarter phase (see post on when to sow Broad beans and peas for your local climate).
During Full Moon phase, mid and late season onions can be sown in June, and late season onions can be sown in July.
Asparagus and rhubarb crowns can be planted in June, also deciduous fruit trees and vines where frosts are not severe, and herbaceous perennial crowns can be planted in July. In cold areas that receive winter rain, it is better to delay sowing seed potatoes until August.

Hi everyone. Well, I had to replace my computer today as my old one had a very poor prognosis, but I’m back on line again and will catch up with my posts tomorrow.
Last weekend I had the opportunity to attend Greenfest in Brisbane as a guest of the Biological Farmers of Australia (BFA). I’m sure you are familiar with their logo of the germinating seedling that appears on many certified-organic products. Greenfest was very well attended and is is most encouraging to see so many people interested in organic produce and sustainability.

This is just to let Lyn’s readers know that her computer has crashed and so she’ll be offline for the next week or so until it has been repaired.

Apologies for any delays in response to comments or emails.

Occasionally, I receive e-mails from readers who are confused about which gardening or climate zone they live in. Australia has been divided into as many as eight different gardening zones because of the huge variations in temperature and rainfall across our continent. Altitude variations or geographical features within each zone will modify temperatures and rainfall patterns, breaking up the eight zones even further.
To complicate the issue, climate change is resulting in evolving milder winter conditions in some areas and longer, harsher winters in others. Last summer, extreme heat or rain events played havoc with a lot of gardens across Australia, and the extent of further changes related to extreme weather events is impossible for anyone to accurately predict.
However, Australia can be divided into three basic gardening or growing zones; Warm, Cool, and Temperate (as indicated in the diagram below). The zone divisions are based on the types of plants that will grow in a moderately irrigated garden in each zone
Within these basic zones, altitudes and geographical features gardens at higher altitudes will be cooler than those at sea level in adjoining areas. Sea breezes can provide a milder climate for coastal areas than those a few kilometres inland. Gardens where cold air can flow downwards will be less damaged by frost than gardens in valleys or where solid walls block the escape of cold air. These variations are known as local microclimates, and gardeners may have to make minor adjustments to what they can grow each month according to local conditions, and evolving microclimates brought about by climate change.
New Zealand has a more constant climate and can be divided into temperate and cool zones. Frosts do occur, and snow falls on the mountains, but New Zealand is not subject to hot winds from a parched inland. New Zealand is a very suitable place for growing an extensive range of species from Europe, North America, and the cooler parts of Asia.

WARM CLIMATE ZONES
These are frost free, or may experience some frosts in inland areas during their short winters, and are not suitable for plants that require a defined period of chilling. Warm zones are suited to warmth-loving Australian natives and plants, including fruits and vegetables, from warmer areas of the world. December, January, and February can be too hot for gardening in a lot of warm zones, and some warm zones experience distinct wet and dry periods requiring conventional vegetables and some annuals to be grown at different times to other zones.
The Tropic of Capricorn runs through the northern states of Australia from Rockhampton and Longreach in Queensland, just above Alice Springs in the Northern Territory, and crosses the West Australia coast between Carnarvon and Exmouth. In areas from Rockhampton northwards, tropical coastal conditions allow an entirely different style of gardening, while in drier areas high temperatures and lower water availability make gardening quite a challenge. Winter temperatures in areas within the Tropic of Capricorn can be higher than summer temperatures in some Cool Zones, and common vegetables from temperate areas can only be grown during winter months. Consequently, I have divided this zone into two sub-sections.
Warm zones:
All of Queensland (except for the southern highlands),
Northern Territory,
North coast of NSW above Coffs Harbour,
Northern West Australia,
Northern South Australia.

COOL CLIMATE ZONES
These are areas where low temperatures occur for long periods. Frosts are common in winter and can continue into spring. Snow occurs in some areas. Cool zones are suitable areas for growing many European, Asian, and North American plants that require a period of winter chilling. Many of the fruits and vegetables we are familiar with come from cooler climates. They, and frost-hardy Australian natives, grow well in Australian cool zones, but frost-tender plants, and plants which require a long period of warmth to flower or fruit are unsuitable for these areas.
Australian cool zones:
All of Tasmania, and the ACT,
Southernmost part of South Australia including Mt Gambier,
Around Albany in Western Australia,
Most of Victoria (except for Melbourne and Benalla areas),
Far south coast of NSW,
NSW tablelands and highlands.
New Zealand cool zones:
The interior of the North Island,
The entire South Island.
(However, within these areas, protected local microclimates along the coast as far south as Christchurch can be regarded as cool temperate areas, extending the planting range.)

TEMPERATE CLIMATE ZONES
These, strictly speaking, are all areas on earth between the Polar Regions and the Tropics of Cancer and Capricorn. Although winter frosts occur in some temperate zones, soil warms quickly in spring. The areas of Australia not listed above can be considered temperate zones, because an extensive range of Australian and New Zealand natives, and decorative plants, vegetables, and fruits from temperate regions around the world can be grown in these areas. January to late February can be too hot for a lot of gardening activity in some Australian temperate zones, but mild autumn weather usually extends from March through May.
Minimum temperatures within metropolitan areas of Sydney, Adelaide and Perth are similar and tend to be slightly higher than those in surrounding areas. Melbourne’s minimum temperature is only slightly lower, and gardeners in Melbourne may find that they can grow many temperate climate plants in protected gardens.
On the North Island of New Zealand, North and South Auckland areas, Hamilton, most of the west coast to just above Wellington, the Bay of Plenty area, and the east coast to Hastings are temperate zones.

A month ago, Graincorp announced that they will mix GM and non-GM canola varieties together from now on. The Rudd Government promise that GM canola would be separated from conventionally-grown canola in Australia has been broken after only one growing season. This comes as no surprise to those of us who know that no other country has been able to successfully separate the two.
Australian grown Monsanto’s RoundUp tolerant GM canola will be mixed with conventional, Triazine Tolerant and Clearfield canola varieties in bin CSO1, which will sell unlabelled in domestic and export markets. If growers require their canola to be labelled GM-free, they will have to pay for testing and storage in a separate bin.
A perusal of the FSANZ’s labelling requirements for GM foods and ingredients allows an incredible range of exemptions, and relies largely on the honesty of suppliers and processors to ensure that GM additives are correctly labelled. There is no post-marking testing.
Our current regulations regarding GM foods and ingredients are another broken election promise by Kevin Rudd, who stated on November 6, 2007, that:
“Labor will ensure accurate information on GM products is provided to consumers and the community. Labor will establish a meaningful labelling regime that enables consumers to make informed choices about what they are buying.”

If you are not happy about your family eating GM foods, and want GM foods and ingredients clearly labelled, please sign the petition at:
www.truefood.org.au/ourrighttoknow

Some nurseries are advertising bare-rooted roses for sale. This is just a reminder to, if possible, avoid purchasing bare-rooted roses before the end of June, as roses that have been lifted before they are fully dormant do not usually grow well.
Potted roses can be planted as soon as they are dormant, if your area is not prone to severe frosts.
For rose planting guide-lines see: here
And
Planting shrubs and vines

For gardeners undecided about whether to adopt organic cultivation methods, perhaps reading my article in the May issue of Mindfood magazine may help you to decide.
You can read it here:
http://www.mindfood.com/at-organic-gardening-environment-flavours-garden.seo

As anyone who has had a vigorous, productive pumpkin vine emerge from an old compost heap will know, pumpkins l-o-v-e compost. If you are a pumpkin enthusiast, and live in an area with cold winters, you can prepare for pumpkin growing now.

Choose a sunny spot in the garden where you want to grow pumpkins next spring, and where the vine will have room to spread (but not the same spot where you grew them this year). Get a bag of horse manure and other compost ingredients, mix the ingredients together and pile it directly onto the soil where you will sow pumpkin seed.

Dampen the heap and cover it with black plastic but, and this is the important part, uncover the pile weekly and turn it to keep it aerated. Keep the heap just damp and the heat absorbed by the black plastic will help the materials break down over winter to about the quarter of the size of the original heap. Compost made from a mixture of ingredients will provide a full range of nutrients that pumpkin vines need for healthy growth. Soil under the heap will improve in structure, allowing better root penetration. Immediately after frosts in spring, you can sow seed directly into the compost to get your pumpkin vine off to a flying start, and you should get a very good crop.