This ugly little creature is the larva of the leaf-eating ladybird. Stressed plants in prolonged hot, dry conditions attract these pests. The larvae become almost black as they reach pupa stage. Both adults and larvae of leaf-eating ladybirds are particularly fond of the Solanum family (tomato, potato, eggplant) and the melon or squash family where they do a lot of damage to leaves.
The adult leaf-eating ladybird has 26 or 28 spots in rows across its wing covers. They are slow moving and drop to the ground when disturbed. In summer, if you see the adults on leaves in your garden, be sure to look under the leaves for their eggs. Remove small leaves containing eggs and, on large leaves, use a knife to scrape the eggs into a container. As I dislike spraying my garden, I just squash the adults and larva with a gloved hand.
Unfortunately, the damage done by these ladybirds and their offspring have resulted in many gardeners spraying other species of ladybirds that are voracious pest predators. Both adults and larvae consume a considerable quantity of pests such as aphids, scale and mites, and one type of ladybird feeds on fungus. Peter Chew and his family have an excellent website, Brisbane Insects and Spiders, where gardeners can easily identify which creatures are beneficial to their gardens and which are pests, and includes a Ladybird Field Guide.
The photo below shows both larva and pupa stages of the 28-spotted ladybird.
A reader wanted to know what what is causing yellowing of new leaves in her potted, dwarf lemon tree. From the photos she e-mailed, it does look like this tree has an iron deficiency, as yellowing is showing in the young leaves. This can be caused by a number of conditions:
a) potting mix (or soil) that is too alkaline from excess bio-char or calcium in the mix or fertiliser containing a lot of poultry manure b) cold and wet soil or growing mix c) if there is a build up of fertiliser salts from synthetic fertilisers, or d) where there is an excess of potassium from synthetic fertilisers or over-use of seaweed liquid fertiliser.
The first thing to do is check that your pot has ample drainage. Large pots should not sit directly on a hard surface. While smaller pots usually have ample drainage holes around the sides at the base of the pots, large pots often have only one large hole in the base and this can easily become blocked resulting in poor aeration and/or a concentration of fertiliser salts if synthetic fertilisers have been used. Large pots should have pieces of tile placed under the pot to allow a small space between the base of the pot and the verandah or paving. If you notice crusting around the top of the soil line (fertiliser salts), flush the plant with clean water, once drainage has been improved.
The next step is to check the pH of the mix with a test kit. A suitable pH is important to all parts of your garden as the pH in soil or mix controls the availability of nutrients. Test kits are very economical to use and readily available from larger nurseries. If you find that the pH is above 7.2, you could repot the tree using an organic-registered potting mix as organic matter is an important source of iron. However, to do so may result in the loss of this crop of fruit.
The addition of flowers of sulphur (elemental sulphur) is the usual way to reduce pH in soils, but it is easy to overdo this in potted plants. You can apply iron chelates (the form of iron in organic compost) to the mix in the pot at the recommended rate. Citrus trees do not absorb iron chelates well through foliar spraying. Or, you can fertilise the tree with a weak solution of Multicrop’s Ecofish. This is an organic-registered liquid fertiliser that contains soluble iron and has a low pH, qhich will help to reduce the pH in the pot. Ecofish contains iron, manganese, sulphur and zinc (trace elements needed by citrus). Manganese deficiency is also caused by high pH or poorly-drained soil.
The warm, dry weather has enouraged this small native beetle (Monolepta australis) to move into gardens. As their common name suggests, these yellow beetles have a bright red stripe across their shoulders and a red spot on their wings. They arrive in a large swarm and choose one or two stressed plants to feed on. We have noticed that they frequently choose plants with white flowers. Although these beetles are only 6mm long, their sheer numbers enable them to skeletonise small to medium shrubs in a very short time before moving on to another property. Monoleptas are difficult to control because sprays that will kill the beetles will also kill beneficial insects visiting plants at the same time.
If the plant being attacked is not too large, you can get rid of these beetles by using a stick to knock them into a container of soapy water. Because of their fondness for the colour white, many beetles will drown themselves in a white container full of water left near the target shrub. (Don’t add soap to this water or it will kill bees that stop by for a drink.) The only way to protect your garden from attack by these beetles is to keep shrubs watered during dry spells, and keep the garden surface mulched to prevent moisture loss through evaporation.
Agricultural lime or elemental sulphur are recommended to modify soil pH to a range that suits healthy growth of particular plants. A reader recently asked me if “Lime Sulphur” was suitable to use around roses in her organic garden.
‘Lime Sulphur’ or ‘Lime Sulfur’ is a fungicide/pesticide formed from reacting calcium hydroxide (made from adding water to quicklime) with sulphur. It is usually applied when roses are dormant as it can burn foliage.
Hydrated lime is very reactive and should not be used where plants are growing. Lime Sulphur solution is quite alkaline (pH 10.5–11.5) and corrosive. Gloves, goggles, face masks and protective clothing must be worn as the pesticide is very irritating to the eyes, skin and respiratory passages. See the Material Safety Data Sheet for this product.
Plants are affected by diseases when they cannot get enough of the elements (including sulphur) they need for a healthy immune system either from inadequate fertiliser, or an unsuitable soil pH (because pH controls the availability of different nutrients to plants), or soil that is either too dry for the roots to absorb the nutrients, or is waterlogged and very acidic.
Although some sources state that Lime Sulphur fulfils requirements of organic gardening groups, the ‘Australian Certified Organic Standard 2010‘ lists Lime Sulphur as a restricted product and notes that it has a potential impact on beneficial insects.
My advice is to maintain a moderate amount of well-made compost in your topsoil, where compost holds all nutrients (including sulphur) close to plant roots; adjust irrigation and soil pH, and provide suitable amounts of complete organic fertiliser. In the meantime, if your plants have a serious fungal problem, I suggest you use Organic Crop Protectants’ organic-registered ‘Eco-fungicide’. It won’t damage your plants or your soil, and it is kind to beneficial insects.
Cabbage white butterflies have had a lovely time with my broccoli this year. There are several conditions that make brassicas very attractive to these pests and the brown cabbage moth. See Cabbage white butterfly.
My problem was that I inadvertently added some very alkaline compost to that area of the garden, (See recent post on Compost pH) and it is taking a while for the soil to get back to a neutral pH.
After spending a week or so removing eggs, squashing tiny caterpillars, or feeding larger ones to the chooks, I remembered a tip someone gave me long ago to deter these pests but have not needed to use before. The tip was to slip the plastic clips that seal loaves of sliced bread onto the edge of some of the Brassica leaves. White seals to deter the C W butterfly and beige ones for cabbage moth. The theory being that the adult butterflies and moths will “think” that eggs are already being laid on these plants and they look for another food source for their larvae.
My broccoli plants are looking healthier already and I have not found any more eggs under the leaves, but I don’t know if the seals are working or the pests are no longer present in our area. Has anyone else tried this tip?
Nematodes that damage roots in the vege patch, are minute worm-like creatures, also known as eelworms. The female nematodes penetrate plant roots causing lumps to form on the roots, which affect the water-carrying ability of the roots. (These are not to be confused with the nitrogen–fixing lumps that form on the roots of legumes, see Fixing nitrogen). Root knot nematodes are more likely to occur in warm climates in soils that are low in organic matter, especially where a proper crop rotation has not been practiced.
Each female nematode can lay up to 2000 eggs, and numbers can multiply quickly. Give affected plants a foliar feed of seaweed extract tea. Seaweed contains plenty of potassium that helps to strengthen cell walls and improves plants’ resistance to pests and promotes root growth. Remove all weeds. Some weeds are hosts to these pests and can transfer viruses to plants.
Affected plants must not be allowed to become water-stressed. Badly affected plants will have to be removed. Make sure the soil is damp so that soil clings to the roots. Place plants (with attached soil) into a garbage bag. Seal the bag, leave in hot sun for a few days, then place it in the garbage. Do not compost these plants. Once the crop is harvested, proceed with methods for prevention (see below).
Allow 3 years between growing any member of the tomato/potato or melon/cucumber families in the same patch of soil. During this break, grow a green manure that is a ‘bio-fumigant’. ‘Bio-fumigants are green manures that release a gas that is toxic to nematodes. They are grown to knee height and chopped up and mixed through top soil, then covered with mulch. Green Harvest have seed for BQ Mulch (sown in cooler months) and cowpea (sown in warmer months) that control nematodes. Indian or brown mustard (Brassica juncea) and non-GM rapeseed (Brassica napus) are also effective bio-fumigants. Forget marigolds, they are more effective against northern hemisphere nematodes. During the 3 year break, brassicas or corn can be grown in the treated bed, if you have limited garden space.
When preparing beds, add a 5 cm layer of organic compost to the bed surface and cover it with organic mulch. Beneficial organisms in compost are pest nematode predators, and mulch keeps compost damp to allow microorganisms to work on restoring soil to health.
A reader has asked about powdery mildew on zucchini plants and fungus-eating ladybirds: Hi. Wonder if you can sort this. 1. Most fungi need moisture and organic material. This seems to be supported by my zucchinis which seem to get worse powdery mildew when I get water on the leaves. I have read that they like dry weather. Is there evidence for either opinion? 2. Some people say that the ladybirds that feed on this mildew spread it by carrying spores, others reckon they are a controller, eating the fungus down. What is the evidence please for either of these? Many thanks, Barb
Powdery mildew is likely to occur on stressed plants in humid weather when temperatures are between 11-28° C. and, once established will continue to affect the plants even if weather becomes dry. Avoid wetting leaves whenever possible Barb. However, because they like low-humidity weather, it doesn’t mean that they are drought tolerant. Zucchini and some other members of the cucurbit family (melons and squash) produce a lot of foliage and need plenty of water and fertiliser. An efficient way to water this group of plants without wetting the leaves is to put a large drink container (with the base and cap removed) neck downwards near the roots so that all the water goes directly to the root area where it is needed, (see photo). Keep topping up the container until it empties slowly.
The yellowish ladybirds with 26 or 28 spots are the only pests of the ladybird family. They eat the leaves of stressed plants of cucurbits. The beneficial fungus-eating ladybird and larvae can be clearly distinguished from the pest in the photos below. From the far left is the ‘Fungus-eating ladybird’, then the leaf-eating ’26 spot Ladybird’ that damages plants. Next is the larva of the ‘Fungus-eating Ladybird’, which also eats fungus and, last of all is the prickly larva of the ’26 spot Ladybird.
Rather than blame the fungus-eating ladybird for spreading the disease, gardeners should check that their plants have sufficient water and nutrients to avoid stress, and the soil pH is suitable for them to absorb what they need for healthy, disease-resistant growth. Also see Powdery Mildew for treatment of this disease.
If new leaves on Camellia plants become thick and very pale green or pink, and the underside of the leaf starts becoming white – the plant is suffering from ‘Camellia leaf gall’. This is a fungal disease that affects tender new growth of Camellia sasanqua (and sometimes Camellia reticulata), especially in very humid or wet, shady conditions. Fungal diseases are a sign that growing conditions are stressing your plants and their immune system is compromised. There is no organic or chemical treatment for this disease. However, an application of seaweed extract tea will help to strengthen the cell walls of the affected plants and make them more resistant to disease.
But, first the affected growth must be removed, preferably before the undersides of leaves develop white spores. You will need a baked bean tin containing about 5 cm of methylated spirits to sterilize secateurs blades, and a large garbage bag for the prunings. Prune off all affected growth (swish the open secateurs in the spirits often while pruning) and place it directly into the garbage bag. Also collect in the bag any fallen leaves as they can harbour the fungal spores that will activate this disease again when conditions are suitable. Seal the bag and put it in the garbage if you are unable to burn the leaves. Do not compost them. Then give the soil around the plants a drink of seaweed extract at the recommended strength, and protect the soil surface with 3–5 cm of fresh mulch. Make sure your camellias are watered when the top centimetre of soil is dry, but afford watering the foliage. Also give the plants an annual application of compost or complete organic fertiliser and seaweed extract tea in late winter.
See below, how affected new growth appears, and close-up of affected leaves.
Many parts of Australia are experiencing flooding, while West Australia is experiencing extremely hot weather with bushfires in the south, so looking after the garden is the least of their problems. My sincere sympathy to all those affected by these extreme weather events, many of whom are facing heart-breaking work to rebuild their lives.
For those of us who are fortunate enough to still have gardens, the prolonged wet conditions provide the perfect conditions for downy mildew to flourish. A set of three conditions (10:10:24) is necessary for downy mildew to establish – a minimum of 10 mm of rain, a temperature higher than 10 degrees Celsius, and foliage that stays wet for more than 24 hours. It is also more likely to affect plants that are stressed for some reason, and where there is poor air circulation. This group of fungal diseases produce pale green or yellow spots on the upper side of leaves, and white-grey furry patches on the underside of leaves of a wide range of plants, including cucurbits, the cabbage family, lettuce, onions, peas and grapes (starts as oily spots). Different species of the fungi infect different varieties of plants, so that downy mildew on your cauliflowers does not mean that other vegetables in your garden will be affected.
The best thing you can do is remove badly damaged foliage and dispose of it in a sealed plastic bag – compost it! Then give soil around affected plants a drink of seaweed extract tea at the strength advised on the label. A good potassium content in seaweeds strengthens plants cell walls helping plants to build resistance to diseases.
Spray remaining leaves with 100 mls milk in 900 mls water (to make 1 litre of spray), and add a good pinch of bi-carbonate of soda (baking soda) for every litre of spray. Full cream milk works best because the fat content helps the spray stick to the leaves, and full cream, organic milk is even better (according to some gardening gurus) – if you can spare it. Milk and bi-carb are not fungicides, but they produce unsuitable conditions on leaf surfaces for the fungi’s survival. Spray leaves early in the day, and repeat every four or five days until mildew clears.
Downy mildew tends to disappear as weather becomes drier because it needs constant humidity. However, powdery mildew needs high humidity, but not wet weather, to establish and will continue to flourish after weather becomes drier. Powdery mildew is caused by an entirely different genus of fungus and treatment for that disease can be found here.
P.S. When spraying – be careful to avoid these tiny fellows below – the adult and larva of the Fungus-eating Ladybird.
Another post about roses this morning, but this is a problem that can affect the entire garden. Amy in WA is having trouble with ‘twenty-eight parrots’ nipping leaves and new growth from her treasured rose bushes. I understand how annoying some parrots can be as sulphur-crested cockatoos used to bite through the stems of my flowering flag irises and leave the garden littered with damaged flowers.
Twenty-eight parrots are a sub-species of the very inquisitive Port Lincoln parrot that inhabits south-western and central Australia. Amy has tried a variety of methods of deterring these pesky parrots and is now resorting to netting the roses but wants to be able to access the plants.
To be effective in protecting foliage and crops from large birds, the netting will have to sit at least 20 cm clear of the foliage and be strongly supported. We have found that hoops of 49 mm flexible irrigation pipe are very effective supports for netting (and shadecloth), and allow access to crops for watering, progressive harvesting, feeding etc. The arches are left in position permanently so that plant protection can be provided quickly when needed.
To make the hoops, measure across the area you want to protect and add 40 cm to the width (20 cm clearance each side) to give you the width (diameter) of the arch. Use a calculator to multiply this measurement by 1.6. The result is the measurement of an arch of that width. Add 75 cm to that measurement to allow for slipping the ends of the arch onto wooden garden stakes as shown in the photo. For example, if the bed is 120 cm wide, adding 40 cm gives you a width of 160 cm. Multiplying 160 by 1.6 equals 256 cm; adding 75 cm equals 331 cm, but 330 cm, or 3.3 m. is close enough. Pipe is cut into 3.3 m for each hoop.
If you also want to make shadecloth covers for beds see: Sun and heat protection
P.S. Someone advised me that attaching a large ‘red nose’ (these were produced for vehicles for ‘Red Nose Day’) to a fence near the irises would keep the cockatoos away as they think there is a large eye watching them – and it worked! They didn’t bother my garden again. These ‘red noses’ are no longer available but you could try painting an old basketball bright red, or using a red balloon on a string.