Cocoons on Brassicas

If you come across a cluster of small, yellow cocoons on leaves of Brassica vegetables – don’t spray them or feed them to the chooks. They do not belong to garden pests. (See photos below.)
These cocoons are, in fact, the pupation stage of a very small, black wasp. This wasp belongs to the Braconidae family. Braconids are parasitic wasps and very beneficial insects to have in your garden.
The female adult wasps, which are barely 5 mm long, lay their eggs in caterpillars of the Cabbage White Butterfly, which feeds on the leaves of stressed broccoli, Brussels sprouts, cabbage, cauliflower, horseradish, kale, radish, rocket, swedes and turnips.
The wasp larvae then feed on the caterpillars from the inside until they are ready to pupate. (Sounds gruesome, doesn’t it.)
They each then spin a small cocoon on the remains of the caterpillar, and hatch out two or three weeks later to repeat the cycle.
Adult wasps feed on nectar from flowers. It is worthwhile growing some nectar-producing plants to encourage these useful pest predators.
cocoons12 newwasps1

Wireworms

Jeanette is having trouble with wireworms in her potato patch and where she has grown yams.
Wireworms are larvae of Click Beetles. The larvae are shiny, brownish cylindrical creatures with 6 legs close to the head. They can grow to about 3.5 cm long, and are fond of eating roots, fleshy stems and tubers.
Wireworms can increase to pest proportions where sufficient crop rotation has not been practiced. The adults shelter in weeds or vegetable litter in and around garden beds.
To get rid of the adults, clear the garden area of weeds, old plants and mulch. You can then get the adults to shelter under a plank or bag laid on a garden bed. Early each morning, collect and destroy the beetles until it is obvious you have numbers under control.
Dig a 3 – 5 cm layer of compost into the top 15 cm of affected beds, or add plenty of organic fertiliser and grow a green manure crop to slash and dig into the topsoil when it is knee high.
Don’t grow yams, potatoes or carrots in that area again for at least four years. Rotate crops, starting with a legume, on a regular basis to prevent a build up of these pests in soil. (See Crop rotation )
Keep weeds under control and apply enough organic fertiliser to keep plants growing vigorously, and they should cease to be such a nuisance for you, Jeanette.

Growing apples in NSW

A reader has asked if he can grow ‘Pink Lady’ apples in Morisset NSW and, if so, does he need a second tree for pollination? Good question, Malcolm!
As a general rule, except for areas of high altitudes, apples are not grown commercially in latitudes of less than 33.00° South because most varieties of apples require 1000-2000 hours of temperatures lower than 10° C. in order for the flowering buds to mature properly through winter. Poor maturation of flowers buds results in flower drop, which reduces the number of fruit. However, a slight shortfall in chilling days is not as critical in the home orchard. In the backyard, the variety of apple and the microclimate of the property will also have an influence on the success of the apple crop. A property on sloping ground where cold air can drain away will stay warmer on winter nights than a property in a valley where cold air pools at night and night temperatures will be lower and take longer to rise through the day. Morisset is a lovely spot near the shores of Lake Macquarie. It has a latitude of 33.11° South, which is borderline for successful apple growing.

‘Pink Lady’ – has been listed as a relatively low-chill variety. This excellent apple, which was featured on ABC’s Landline program recently, was developed in Australia as the ‘Cripps Pink’ is crisp, with a thin skin and sweet flesh. It is also an attractive, late-maturing variety that has a bright pink blush on a yellow background, and well worth remembering when choosing an apple variety to grow.
I would think you have a reasonably good chance of success with this variety Malcolm, especially if you can situate the tree where it has a bit of shelter from hot afternoon sun. This will allow soil and air around the tree to stay a bit cooler in winter months and prevent sunscald of the fruit during summer.
Most apple varieties require a pollinator for successful fruiting. The pollinators for ‘Pink Lady’ are: ‘Granny Smith’, ‘Delicious’, ‘Gala’ and ‘Fuji’. In your area Malcolm, I would choose either ‘Granny Smith’, which performs well in warmer areas, or ‘Fuji’, which is another low-chill variety.
Low-chill apples
Apples and pears require longer chilling than peaches (700-800 hours). For gardeners who yearn for their own apple trees but live in an area with mild winters, ‘Sundowner’, a sibling of ‘Pink Lady’ requires even less chilling than its “sister”. It also needs a long, hot summer and autumn. ‘Granny Smith’, an excellent cooking apple, was bred in Sydney. It likes a warmer climate and can be grown in northern NSW (and some parts of Queensland). ‘Anna’, a variety developed in Israel, requires only 450 hours of chilling, and ‘American Dorset Golden’ requires only 250 hours of winter chilling. ‘Fuji’, developed in Japan, also does well in areas with mild winters.
Please remember though, when selecting low-chill varieties of fruit trees, that areas with mild winters may also have wet summers, and prolonged rainfall can result in a waste of your hard work by spoiling the crop. Also remember that plants grown in unsuitable climate conditions for their variety will become stressed, and stressed plants attract pests and disease.

Some varieties of fruit trees require particular methods of pruning. The Complete Book of Fruit Growing in Australia by Australian author Louis Glowinski is a handy reference for pollinators and pruning information of fruit trees, but it does not give organic cultivation or pest control information.
Pruning and Training by Christopher Brickell is a UK book with detailed information on pruning different types of fruit trees.

Fungal wilt diseases

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.

Cabbage white butterfly

These flirtatious little butterflies can be destructive to stressed Brassica plants.
Sowing dill seed between brassicas can deter these pests as the aroma from dill confuses them. If you see these butterflies around your brassica plants, attach the plastic clips from packaged bread to the edges of some of the leaves as a pest deterrent. They look as though pests are already laying eggs on those plants. Use white clips for butterflies, beige for cabbage moth.
If your plants have been attacked, squash any green caterpillars or feed them to the chooks. They often hide along the mid ribs of leaves making them difficult to see. Check daily for newly laid CWB eggs (bright yellow dots – usually on the backs of leaves), and brush them off. Also check for newly hatched larvae – these appear as fine green threads hiding under the leaves, and can look like leaf veins.

White cabbage butterfly or cabbage moth attack is a sign that either:
1) Your plants could do with more water. Brassicas need thorough, regular watering – not a daily sprinkle. Mulching the bed reduces water loss and encourages horizontal movement of water through soil.
2) You have been a bit mean with the complete fertiliser when preparing the bed. Brassicas prefer a humus rich soil to provide a good supply of fertiliser. If they are not making steady growth, a side dressing of compost (under mulch) or applications of complete fertiliser, applied as a tea, can correct the problem. Or, they are missing some essential trace elements that you can supply with a drink or two of good quality seaweed extract tea (such as Acadian, Natrakelp or Seasol).
3) You have added enough fertiliser but the soil is too acid or alkaline for the plants to absorb what they need for pest resistance. If it is a case of too acid – and this can be remedied with an application of dolomite or agricultural lime. If you suspect acidity, apply a handful per square metre of bed and water it in. Avoid using hydrated lime on beds that contain plants as it can burn plant roots. If your soil is too alkaline, the addition of elemental sulphur will reduce alkalinity.
However, if they are making a total mess of your plants, apply Dipel while waiting for soil conditions to improve. Dipel will kill the caterpillars without killing good insects.

Bean Fly

Although bean crops in most areas are close to the end of their productive life (April-May), some gardeners in warm climates are having problems with bean fly.
The best way to avoid bean fly is to have plenty of compost in the bed where you grow your beans so that they will have a full range of nutrients available to them. These pests tend to attack plants that are low in potassium. A drink or two of seaweed extract tea can help bean plants that have been attacked because it has plenty of potassium, as well as trace elements that plants need for good health. But don’t overdo the seaweed as too much can “lock out” some other nutrients.
Also, hill up soil around the main stem of the bean plants to encourage them to send out more roots along the stem above the damaged area just above ground level. Mix some compost through the hilled-up soil. Plants can be saved this way. Also, allow a three year break between growing crops of beans in the same soil.
Bean fly love warm, humid weather. In these conditions put out some yellow sticky paper traps to alert you to their arrival, and hopefully catch some of the adults before they lay eggs. Also look out for fine lines on leaves and stems indicating where the larvae have tunnelled to reach the base of the stem. Stems of affected plants become swollen, cracked and reddish in colour.
Organic sprays are not really effective because the larvae that do the damage are protected by plant cells. A good fertilising and watering routine will help your plants avoid these pests.

Aphids

Pieter has had a severe aphid infestation on his zucchini plants, and applying a dishsoap/water spray not only killed the aphids, it also killed the plants. He wants some tips on a better way to deal with aphids.

Aphids are fairly easy pests to get rid of without resorting to chemical pesticides. Aphids have a lot of natural predators, but the sprays will also kill these, resulting in more intense pest infestations in future.
Moderate infestations of aphids can be blasted off plants with a jet of water from a hose or a spray bottle set to ‘stream’. For plants with hairy leaves (such as zucchinis) apply water early in the day so that leaves can dry before night. If you blast them with water before serious damage occurs, predators will be able to control any escapees.
Severe infestations can be removed with a soap spray, but not with detergent or bathroom type soap, which has a caustic soda base. The soap used in soap sprays to kill pests has a potassium base, and is available from nurseries, or can be purchased by mail order from Green Harvest. ‘Natrasoap’ does not leave a residue on plants, nor will it burn leaves if used in temperatures below 30° C.
In order to prevent future infestations of aphids, avoid overdoing nitrogen fertilisers because aphids are pests that are attracted to a flush of soft, sappy growth that excess nitrogen, or erratic watering, produce. Controlling weeds in the growing area can also help prevent aphid attack. Many weeds are host plants for aphids, allowing a large colony of pests to establish before you notice them. As aphids can carry viruses for which there is no cure, prompt removal of these tiny pests is advised.

Tomato problems

From e-mails I’ve received, it appears that some gardeners are having problems with their tomato plants. When tomato plants become water-stressed in prolonged hot, dry conditions that are affecting some parts of the country, they are prone to attack by fruit fly, heliothis moth caterpillars (corn earworm) and blossom end rot.
Blossom end rot is caused by calcium deficiency, and is not a disease. Like us, plants need a good balance of calcium and magnesium to form a strong structure. Calcium and magnesium are required for growing tips of plants as well as fruit production and, if there are not enough of these nutrients to go around, growing tips will get priority. Calcium deficiency can occur in several different ways.
Most commonly, it occurs when soil is too acidic (soil pH less than 6) and there are insufficient calcium ions in the soil. Rarely, it also occurs in extremely alkaline soils (soil pH above 9) where calcium becomes insoluble, and plants are unable to absorb it.
In soils with a suitable pH of 6 – 7.5, erratic watering can cause it, as plants are unable to absorb nutrients from dry soil, when needed.

To avoid this problem, ensure that your tomato, capsicum or chilli bed has a suitable soil pH before planting out seedlings. See Changing soil pH. If your soil is slightly too acidic, and the problem has already occurred, you can raise soil pH slightly by dissolving a generous handful of dolomite (a mixture of calcium and magnesium) in a full watering can, and apply this around the root area (under mulch) of each plant – one full watering can per plant. If you know that your soil has plenty of magnesium, use agricultural lime instead. This treatment will take several weeks to work, so good bed preparation is worth the effort.

Tomatoes will benefit from being protected by a thick layer of mulch to reduce fluctuations in soil moisture, and a thorough soaking (under mulch) two or three times a week during dry weather, rather than a light daily watering. Avoid overhead watering of tomatoes.
Hot days increase transpiration (water loss) from plants in the same way we perspire to keep cool. Setting up a light shade cloth canopy over the tomato bed will reduce water loss from plants and help prevent water stress and sun scald on fruit. Tomatoes will ripen under light shadecloth in hot weather. A soil feeding of seaweed extract ‘tea’ can also help plants build resistance to adverse conditions, including drought.
Mosquito netting over plants will serve two purposes. It will prevent attack by Heliothis moth and fruit fly, and provide a light shade for the plants. Modern tomato varieties do not require insects for pollination. If older varieties cease to set fruit, flowers can be hand pollinated with a dry watercolour paint brush.
In some areas, the netting may be enough to slow transpiration, without the shade cloth. All fruit affected by grubs or caterpillars should be collected and fed to the chooks, or placed in a sealed black plastic bag and left in the hot sun. This will kill the larvae and break the breeding cycle. Never compost fruit that contains grubs.

Squash, melon and cucumber problems

A problem I am frequently asked about is why do immature fruit of the Cucurbit family become soft or discoloured, and fail to mature. The squash or Cucurbit family includes chokoes, cucumbers, grammas, gourds, pumpkins, rockmelons, squash, watermelons, and zucchinis.
If your cucurbit plant is producing small fruit that yellow and fall off before maturity, or turn mushy at the end furthest from the stem, it does not have a disease, or a pollination problem. Your plant is deficient in calcium. Calcium deficiency also causes blossom end rot in tomatoes and capsicums.
Like us, plants need a good balance of calcium and magnesium to form a strong structure. Calcium and magnesium are required for growing tips of plants as well as fruit production and, if there are not enough of these nutrients to go around, growing tips will get priority. Calcium deficiency can occur in several different ways.
Most commonly, it occurs when soil is too acid (soil pH less than 6) and there are insufficient calcium ions in the soil. In soils with a suitable pH of 6 – 7.5, erratic watering can cause it, as plants are unable to absorb nutrients from dry soil, when needed.

To avoid blossom end rot, ensure that your cucurbit (or tomato/capsicum) bed has a suitable soil pH before planting out seedlings. See Changing soil pH. If your soil is quite acidic, and the problem has already occurred, you can raise soil pH slightly by dissolving a generous handful of dolomite (a mixture of calcium and magnesium) in a full watering can, and apply this around the root area (under mulch) of each plant – one full watering can per plant, or two around large vines such as pumpkin and watermelon. If you know that your soil has plenty of magnesium, use agricultural lime instead. This treatment will take several weeks to work, so good bed preparation is worth the effort.
Where erratic watering is the problem, mulch around your plants to reduce fluctuations in soil moisture, and water plants thoroughly once or twice a week, rather than giving them a light watering every day. Pumpkin vines require a lot of water to produce a good crop.

Green vegetable bugs

Karen is new to organic gardening and is wants to know what to do about the green vegetable bugs that are attacking her tomatoes.

The green vegetable bug is a sap-sucking pest. They use weeds as hosts and attack vegetable plants that are stressed in some way. Of the chemical sprays required to kill these bugs, one will poison any birds that eat the bugs, and the other is deadly to bees and other beneficial insects. It can also metabolise in humans to a more toxic chemical, and is currently under review.
Chooks show no interest in eating these bugs. The best way to get rid of these organically is to put some methylated spirits into a soup tin or similar container. Put on gloves to protect your hands from any smelly juice they excrete and use a stick to knock them into the tin. Then get rid of weeds and plants that have finished bearing to prevent these pests continuing to breed.
To prevent further attacks (and this is the most important part of the treatment) have a look at why your tomato plants are stressed, and correct the problem. Some gardeners find it difficult to understand that pest and disease attack are only symptoms of unsuitable conditions for a particular species, but it is true. I noticed yesterday, that similar bugs are attacking some silver beet plants we have. We decided after picking the first of this silver beet that we did not like this variety as much as ‘Fordhook’ and decided to just feed the plants to the chooks, a plant or two at a time. Consequently, the silver beet did not receive the same attention as the other vegetables and, before long, these bugs moved in. The bugs are not attacking other vegetables that are receiving normal care.
When pests attack plants, the answer is always in the soil. It may be too dry or poorly drained. If water is in short supply in your area, hill up your tomatoes about 5 cm at a time. They will produce more roots along the stem and allow them to access water more efficiently. Tomato plants need a deep watering (under mulch) several times a week in dry weather, rather than a light daily watering.
Or, the plants may be short of the nutrients they require to produce pest-deterring pheromones. If you have skimped on fertiliser, after a thorough watering, give each plant a light feed of complete poultry-based fertiliser and a drink of seaweed extract tea.
Or, the soil may be too acid or alkaline for the plants and the nutrients they require can be locked out and unavailable to the plants. This can be difficult to determine without testing, except that, with tomatoes symptoms of phosphorus deficiency (purple colouring under leaves and slow growth) are a clue that soil is too acid or alkaline if you have applied adequate complete fertiliser. If soil is too alkaline, put some well-rotted horse or cow manure under the mulch around the plants. If soil is too acid, water in some dolomite or lime around the base of each plant. See Changing soil pH.