Community Event – Warrandyte Food Swap

I’ve been asked to promote a free local community event in Warrandyte, Melbourne, Victoria, Australia – the Warrandyte Food Swap!

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Warrandyte Food Swap

Join us for the 3rd Birthday Celebration

Sat 6th October 2018

9am – 10am

Warrandyte Community Garden

Live music, fresh produce, free seeds, and most of all….friendly faces

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"Flashback from last years birthday celebrations.  This year we celebrated new baby Lachlan, 2 university graduations, woofing in Canada, a plum role in the outback, winter in the Scottish Highlands and spring on a Qld beach.  Along the way we enjoyed great produce, luscious greens, tomatoes, cumquats, lillypilly, macadamia, turned grapefruit into conserve, chilli into ripper salads, all the time sharing stories enjoying community.   A big shout out to Glenn and Chris for their constant support.  Come and join us October 6th at 9am"

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Small-Space Intensive Tomato Growing

tomato-plants-vining-string-support

Want to grow lots of tomatoes in limited spaces, even containers? Ever wondered how the commercial hydroponic growers pack in as many plants as possible in their growing areas? By understanding the way tomatoes grow, we can select the right plants and utilise their growth habit for maximum production in the smallest of spaces.

 

Determinate Versus Indeterminate Tomatoes

Tomato varieties are classified into two categories based on their growth habit, determinate and indeterminate.

Determinate tomato varieties are known as ‘bush tomatoes’, they grow into a self-supporting small bushes up to 1.2m (4’) tall that don’t need staking, They grow to their full size, then produce flowers at the ends of all their branches (shoots), producing all the tomato crop at once.

Indeterminate tomato varieties are known as ‘vining tomatoes’, they grow very long stems around 2m (6’) tall which branch heavily and require staking or tying to a support to keep them off the ground, Flowers are produced along the sides of the branches (shoots), and the plants will continue to grow until the cold weather arrives.

 

Growing Indeterminate Tomatoes as Columnar Plants

Since indeterminate tomatoes flower alongside any new shoots that emerge, and continue growing after flowering, their continuous productivity makes them ideal plants for intensive growing systems.

A plant’s available growing energy can either go into vegetative growth (leafy green growth, basically leave and branches), or flowering and fruiting productive growth. We can direct the plants growth into flowering and fruiting simply by preventing the growth of new shoots (branches) by pruning them off.

Unlike determinate bush tomatoes which fruit at the ends of their branches and therefore need branches to fruit, indeterminate tomatoes don’t. A stem and leaves will do the job.

tomato-indeterminate-growth-habit

 

As we can see in the picture below, cutting off the new shoots (branches) growing from stem does not affect the flowers, as the flowers are produced on the stem.

indeterminate-tomato-pruning-shoots

If we prune off all new shoots (branches), we end up with a tall plant that is comprised of a stem with leaves along its length and flowers emerging from it –  basically a columnar (tall and narrow) tomato plant, the ideal shape for intensive plantings where many plants are fit into a small space!

indeterminate-tomato-stem-shoot

Don’t throw away any shoots that are pruned off, they can be very easily turned into new tomato plants! Just put them in a bucket with some water in the bottom, and locate in a protected area exposed to morning sun only.

tomato-cuttings-bucket

In a few days the cuttings will put out roots!

tomato-cutting-roots

 

Hydroponic-Style Supports for High Density Plantings

When tomato plants are pruned to be tall and narrow, they can space them quite closely, even in containers.

Pictured below are three tomatoes planted side-by-side in two self-watering containers, supported by strings attached to an overhead frame. The pots are 70cm (28”) wide, with the tomatoes spaced around 25cm (10”) apart, quite an effective use of space!

tomatoes-self-watering-containers

To support tomatoes on strings, as they do in hydroponic setups, attach hydroponic tomato clips (as pictured below) to the base of each tomato plant, then tie the string to the top of any overhead support, then wind tomato stem around the taught string.

image
Hydroponics tomato clip – plastic clips which hold string to base of tomato plant stem just above soil level

 

hydroponic-string-support
Hydroponic string support, constructed of thick galvanised wire, attaches to overhead frame

 

hydroponic-string-support-tree-tie
Hydroponic string support fastened to overhead support using plastic tree tie strip

Here is a tomato stem supported on a string, the stem is just wound around the string as it grows, and any new shoots (side branches) are pruned off. This maintains the narrow shape as the tomato grows upwards only.

indeterminate-tomato-string support

Using such a setup, it’s possible to grow tomato plants extremely closely, and it’s cheaper than using wooden stakes. The plastic string lasts several years, and is extremely cheap to replace.

I constructed my support frame out of square aluminium sections that connect with plastic fittings which just push together, all purchased from a local hardware store. Since these materials don’t rust or crack, they can withstand the weather and last almost indefinitely.

There is no limit to what can be used as an overhead support to attach the strings to. Two wooden tomato stakes in the ground with at third lashed to the top to form an inverted ‘U’-shape will work perfectly well in a garden bed.

For spacing, I’ve used a distance of 45cm (18”) between plants in the ground in garden beds, and in my experience this provides plenty of air circulation to prevent diseases. When planting in the ground, I always remove all leaves off the bottom 30cm (12”) of the tomato plant once it’s tall enough, as this prevents soil splash from the rain reaching the leaves which causes that all too familiar disease where to bottom leaves dry out and the infection slowly spreads upwards. Using a thick layer of mulch also helps considerably in preventing this problem.

In conclusion, we can exploit the growth habit of indeterminate tomatoes and borrow some tricks from hydroponic tomato growers to create high density, high productivity planting in the smallest of spaces. If you like experimenting and trying something different, I recommend trying these ideas out. Traditional tomato growers can still stake up and prune indeterminate tomatoes into columnar shapes this way to squeeze way more tomatoes into a garden bed than was ever possible!

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Gardening Calendar (Australian Temperate Climate) – September

It’s September, the beginning of spring, the time of new life and renewal! The weather is starting to warm up, but there are still cold days, rainy weather and winds to contend with.

Early spring is the best time to mulch garden beds, as the soil is still moist and is slowly warming up.

This month is the last chance to plant bare rooted deciduous trees and shrubs, as they need time to establish before the summer heat arrives. Container grown ones with well developed roots can be planted right through spring.

Things to Do This Month:

  • Plant evergreen shrubs and trees (this includes citrus trees).
  • Relocate evergreen shrubs – they can now regrow their roots during the mild weather.
  • Last chance to plant bare-root deciduous trees, shrubs and vines (otherwise wait till autumn).
  • Feed all fruit trees if you didn’t do so last month.
  • Clean up old growth in perennial herbaceous plants to make room for new growth.
  • Propagate plants by taking cuttings or layering (both ground layering and air layering).
  • Divide perennials, such as chives.
  • Tie canes of brambleberries to wires before the vigorous growth commences in early spring.
  • Plant passionfruit.
  • For seedlings raised indoors in August, harden off by slowly increasing sun and exposure to outside temperatures for 7 to 10 days before planting out.
  • In ponds, begin feeding fish small amounts of food often, so food is not left over to pollute water.

Vegetables and Herbs to Sow:

Sow in September   Harvest (weeks)
Amaranth** ds 7-8
Asparagus d 2-3 years
Asparagus Pea d 8-11
Basil s 10-12
Beetroot ds 7-10
Broccoli ds 10-16
Burdock d 17-18
Cabbage ds 8-15
Cape Gooseberry ds 14-16
Capsicum s 10-12
Carrot d 12-18
Celeriac s 14-28
Celery s 17-18
Chicory d 16-24
Chilli s 9-11
Chives ds 7-11
Climbing beans** d 9-11
Coriander d 30-45
Corn Salad d 5-8
Cucumber d 8-10
Daikon d 8-10
Dill d 8-12
Dwarf beans** d 7-10
Eggplant s 12-15
Endive ds 10-11
Fennel d 14-15
Globe Artichokes s 42-57
Horseradish d 16-24
Jerusalem Artichokes d 15-20
Kohlrabi d 7-10
Leeks ds 15-18
Lettuce ds 8-12
Luffa s 11-12
Marrow* d 12-17
Mint s 8-12
Mustard greens d 5-8
NZ Spinach s 8-10
Oregano s 6-8
Parsley ds 9-19
Parsnip d 17-20
Peas d 9-11
Potato d 15-20
Pumpkin* ds 15-20
Radish d 5-7
Rhubarb d 12 months
Rocket d 21-35 days
Rockmelon* ds 10-16
Sage d 18 months
Salsify d 14-21
Shallots d 12-15
Silverbeet ds 7-12
Snow Peas d 12-14
Spring onions d 8-12
Squash* d 7-8
Sunflower ds 10-11
Sweet corn** ds 11-14
Tomatillo s 10-14
Tomato ds 8-17
Turnip d 6-9
Winter Savory s 6-10
Zucchini* ds 6-9

Key:
d = sow directly into ground
s = sow in seed tray
ds = sow directly into ground or seed tray
*= frost tender
**= sow after frost

Download printable PDF version of Gardening Calendar (Australian Temperate Climate) – September

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The Difference Between Soft and Hard Mulches

garden-mulches

Hard woody mulches or soft non-woody straw-like mulches, what’s the difference?

They both work equally well as garden mulches to  moderate soil temperature, reduce water loss from the soil through evaporation, conserve soil moisture to reduce the need for watering, inhibit weed seed germination and suppress the growth of weeds.

Selecting the right kind of mulch is important, as it can make a huge difference to the quality of your soil over time!

Typically, woody mulches take longer to break down, usually around two years, as compared to six to twelve months for the soft non-woody mulches. But there’s more to consider than longevity, namely what happens when the mulches do break down, the ecological process of soil building and the carbon cycle.

 

The Carbon Cycle

Nature recycles everything! We’re all familiar with the water cycle, where rain falling from the sky soaks into the soil, the water is taken up by plants and transpired through their leaves back into the air as water vapour, which forms clouds and repeats the process. Well, there are cycles for all soil nutrients too, including carbon. Mulches are carbon-rich materials, so when they break down, they release carbon back into the soil. If there’s a carbon cycle, that would logically suggest that the carbon can move, and may possibly not stay in the soil.

Carbon_cycle
The Carbon Cycle – Diagram adapted from U.S. DOE, Biological and Environmental Research Information System (http://earthobservatory.nasa.gov/Features/CarbonCycle/)

When we look at the carbon cycle, we can see that carbon does indeed leave the soil naturally through microbial respiration and decomposition (as carbon dioxide), or through made made changes to the environment. That said, soil carbon is not all the same, and depending on the form of carbon we’re talking about, it may leave the soil very easily or it may be extremely stable and stay in the soil for a very long time.

 

Soil Organic Carbon – Labile and Stable Forms

Organic materials are essentially materials which contain carbon, the building block of all life on this planet. All living things are carbon-based life forms, us included! Soil is one of the most complex ecosystems on the planet, extremely rich and diverse in life, so it’s no coincidence that it contain a very wide range of organic materials, each with different chemical and physical properties.

Soil organic carbon in its various forms is generally divided into two major categories, labile carbon which decomposes relatively rapidly (days to years) and stable carbon which takes much longer to decompose (many years to decades to centuries). There is a further category of stable carbon, such as biochar, referred to as recalcitrant carbon which can last much longer, and may persist in soil for centuries to millennia.

Labile soil carbon is composed of small pieces of plant material 0.05–2 mm in size, as well as living organisms and the remains of dead organisms, all of which can break down relatively easily, serving as an energy source for soil organisms, and therefore able to be recycled through the carbon cycle.

Stable soil carbon is composed of much finer particles of organic matter that are either physically protected within clay for example, or are in a chemically-stable persistent form such as soil humus. In case you’re wondering, humus is ‘the black stuff in soil’, it’s essentially decayed organic matter which is very finely broken down and resistant to further breakdown, and it plays a very important role in the retention of moisture and nutrients in the soil.

When organic materials break down and decompose, what is basically happening is that soil microorganisms are breaking them down to use them as food, as an energy source. Since labile soil carbon materials break down more easily than stable ones, soils with more labile organic carbon will have a larger population of soil microorganisms feeding on them, and they will release more nutrients as a result of the decomposition process.

Now that we’ve made that distinction, it’s important to discuss which mulch materials create labile soil carbon, and which ones create stable soil carbon and a nice, dark, rich, long lasting humus.

 

Stable Soil Organic Carbon and Lignin

All woody plant materials contain lignins, complex organic (carbon-containing) compounds which play an important role in providing structural support of plant cell walls, particularly in wood and bark.

Chemically, lignins are cross-linked phenolic polymers – polymers are simply large molecules made up of smaller molecules repeatedly chained together. Plastics are synthetic polymers, and as an example, polystyrene is made up of many (Greek poly-, “many”) styrene molecules linked together. A cross-link is a chemical bond that links one polymer chain to another, creating a stronger structure.

Due to their chemical structure, lignins are rigid, and very resistant to decomposition and breakdown.

Bark contains more lignins than wood, and that would make sense as you would want the outside of a living tree to be resistant to decay! Therefore, mulches made of tree bark are higher in lignins than mulches made of tree wood alone, but both, when completely broken down into fine composted matter, create a dark, rich humus that is high in lignins, and therefore high in stable soil organic carbon.

 

Soil Carbon – Slow in, Slow Out, or Fast In Fast Out?

Woody mulches break down quite slowly, eventually releasing their lignin-rich humus, which is a stable soil carbon, into the soil. Since bacteria cannot readily break down stable organic soil carbon, it can last in the soil for years, decades or centuries. Over time, the soil will become darker and richer, improving soil quality.

biomat mulch
Woody mulches create a stable soil organic carbon – slow in, very slow out.

 

Gardeners who use non-woody mulches in their gardens during the start of the warm season usually notice that by wintertime the mulch will have all broken down back into the soil, depending on seasonal humidity levels.

Non-woody mulches include all the soft mulches, such as straw, lucerne, sugar-cane, and pea-straw, as well as any non-woody plant material that you may chop-and-drop on the soil surface. Non-woody plant material which is composted or buried in the soil acts in the same way, it breaks down very quickly, adding carbon the to soil very fast, because these are labile soil carbon materials.

Microorganisms are able to feed on labile soil carbon materials, and If we look at the the carbon cycle, just like us, they can engage in aerobic respiration, using oxygen and organic matter to produce energy, releasing the waste products water and carbon dioxide, the latter of which returns as a gas to the atmosphere, where it can be taken up by plants during photosynthesis.

straw-mulch
Non-woody mulches create a labile soil organic carbon – fast in, fairly fast out.

 

In Summary

Non woody mulches break down faster and more easily, adding to the pool of labile organic soil carbon, which is available to bacteria. The carbon enters the soil quickly, and leaves just as easily – Fast in, fast, out.

Woody mulches contain lignins, these compounds are complex organic polymers which provide structural support in the cells of woody plants and trees, and are resistant to breakdown and decomposition. Once woody plant material breaks down into the soil, the lignins remain, strongly binding the carbon for a very longer time, forming rich, dark soil humus. It takes a while for woody material to break down, and once the stable carbon is in the soil, it will remain there for a very long time – Slow in, slow out.

So, what should we use in our gardens, woody or non-woody mulches? The answer is WWND! (What would Nature do?)

In Permaculture, we emulate natural ecosystems, because Nature has perfected the process of soil-boiling and plant growing! What happens in Nature? We can look, observe and learn!

On forest floors we have a mixture of branches, bark and whole fallen trees supplying the stable soil organic carbon. These materials favour soil fungi and create a very stable, persistent soil humus.

We also have fallen leaves, and lots of other non-woody plant materials which supply the source of labile soil organic carbon, which favours soil bacteria, and the release of nutrients which become available for plants to use.

By adding both stable and labile soil organic carbon, we can enrich the soil and create a stable soil ecology which supports the growth of healthy and vigorous plant life, and that is what we should aim for.

In practical terms, we can take a Permaculture solutions thinking approach and get creative, here are a few suggestions which I use in my own garden.

  • If your garden beds use straw mulches, prune any woody shrubs and trees, chop up or mulch the woody material, lay it on the soil (and also add fertiliser and compost if you want to practise no-dig gardening), then cover with straw mulch.
  • If your garden beds use woody mulches, before replenishing the mulch, push aside any remaining mulch and dig compost into the soil, or empty your compost bin contents on the soil surface (and also add fertiliser if you want to practise no-dig gardening), and then add new woody mulch to the top.

In Permaculture, we look to Nature for inspiration, and to science for the explanations!

 

References:

  1. Soil Quality Fact Sheets Labile Carbon http://soilquality.org.au/factsheets/labile-carbon
  2. A Comparison of Landscape Mulches: Chemical, Allelopathic, And Decomposition Properties by Mary L. Duryea, R. Jeffery English, and L. Annie Hermansen
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Apple Tree Diseases – Crown Gall

crown-gall-apple-tree

Crown gall is a bacterial disease caused by Agrobacterium tumefaciens (syn. Rhizobium radiobacter), which produces tumour-like swellings on the bark of trees and plants. It can infect a wide range of dicotyledonous (broad-leaved) plants, particularly members of the Rosaceae (rose) family such as roses, raspberries, almonds, cherries, peaches, pears and apples.

These disease-causing bacteria live in the soil and only enter fresh tree wounds (less than 24 hours old), which are often caused by insect and frost damage, mechanical damage from mowers and lime trimmers, pruning, or transplanting damage.

Crown gall bacteria are able to detect the various phenolic compounds which wounded dicotyledonous plants release as chemical signals in their defence and repair process, enabling them to home in on the wounds and infect the damaged plant cells.

They don’t just infect the plant though, the Crown gall bacteria insert some of their own bacterial DNA into the plant cells, altering their functioning and causing them to produce unusually large amounts of plant hormone, which in turn stimulate the plant cells to multiply and enlarge, leading to tumour or gall formation.

 

Crown Gall Identification

The galls can form on both the roots and the trunk of a tree, and they can also form at graft unions or at the base of the trunk at the root crown, just below soil level. The bacteria can spread into branches through pruning cuts and other damage.

Identification of crown gall is made more difficult by the fact that the appearance if the galls changes over time. Galls start off light-coloured, soft, and spongy, then become rough and corky with an irregular surface and a hard woody interior, and as they mature, they turn dark brown and woody. Some galls will disintegrate over time and others may remain for the life of the plant.

Galls grow in size over time, affecting the growth, health and vigour of the plant. Galls impede the flow of water and nutrient movement in the plant, as they effectively cut off the bark in the site of infection. Reducing the flow of water and nutrients in a plant causes slow growth, stunting of the size of the plant, deficiency symptoms such as chlorosis and a decline in the overall health of the plant. If galls grows large enough to extend right around a branch or trunk, they can girdle (ring-bark) the tree, causing decline and possible death of the tree, depending on the location of the damage.

Crown gall may kill a very young apple tree by girdling the stem, while a mature apple tree may be able to tolerate it and remain productive.

 

 crown-gall-apple-tree-close-up
Crown gall infection on apple tree

 

Crown Gall Life Cycle

The crown gall bacterium Agrobacterium tumefaciens can persist in the soil in decomposing plant debris for long periods of time, it  may live saprophytically (living on dead organic matter) in soil for up to two years. It can only proceed in its life cycle if it finds fresh wound to infect and form galls. Without wounds on trees and plants, no galls can form.

These bacteria mainly live in the outer portions of primary galls, which can break off and fall to the soil, spreading the bacteria. The centre part of the gall is dead and contains no bacteria. Secondary galls may also form without any bacteria present on other parts of the plant or around other wounds. Crown gall bacteria can overwinter both in the galls and in the soil, and reinfect any plant wounds they come in contact with, completing the disease cycle.

 

Crown Gall Control and Treatment

There is no known cure for crown gall disease, and the best control is prevention.

If there are not too many galls, the branches and parts of the trunk where the tumours occur can be pruned off and destroyed – do not compost infected plant material!

When pruning, disinfect pruning tools between cuts. Use either a solution of 70% alcohol and 30% water, or a 10% bleach solution (1 part bleach with 9 parts water).

If the tree is too heavily infected, the recommendation is usually to dig up, removing as much of the roots as possible, and to destroy all infected plant material.

 

For prevention of crown gall disease:

  • Avoid wounding trees in any way, especially during transplanting. 
  • Don’t replant susceptible fruit trees trees in an area where crown gall infections have occurred.
  • Cover young trees during extreme frosts with hessian or geotextile fabric as a frost cover to prevent frost damage.

 

Biological control agents exist for preventing crown gall in apples and many other fruit trees, as well as berries and ornamentals (but not grapes). A non-pathogenic (non-disease causing) strain of the same bacterium (Agrobacterium radiobacter strain 84) has been used to protect plants against infection by crown gall bacteria in the soil. Plants are dipped into a suspension of the protective Agrobacterium radiobacter strain 84 at planting time to keep plants free from disease. This biological control cannot cure plants which ae already infected .

Some suggest removing existing galls with a sharp pruning knife, destroying the infected plant tissue and treat the wound with a chemical control.

Researching chemical eradicants of crown gall, most research literature mentions a variation of this statement:

Eradication of crown gall using creosote-based compounds, copper-based solutions, and strong oxidants such as sodium hypochlorite are transiently effective. The chemical eradicant application procedure is labor intensive and therefore costly both monetarily and to the environment. The superficial treatments are ineffective against systemically infected plants. Generally, chemicals are rarely used for control of crown gall.”

The references are vague in respect to the chemicals mentioned, so to provide further detail, I had to do a lot of time consuming and fairly unproductive literature searches.

  • The creosote based chemical compounds are a mix of 2,4-xylenol (0.463%) and meta-cresol (0.466%), sold in a commercial product known as Gallex, it’s pretty toxic and not something you would want contaminating the soil.
  • The copper-based solutions refer to copper fungicides such as copper oxychloride, which seems to show the best results of the copper compounds from my searches of the literature.
  • The strong oxidants such as sodium hypochlorite refers to common household bleach, read the ingredients on the label and it should be listed there.

What they’re saying is that cutting away the gall and spraying with these chemicals may or may not be effective. What is clear from research is that applying copper and bleach-based bactericides reduce many A. tumefaciens populations on the surface of plant cells.

Want to try a safe chemical control? You can cut away the gall, mix up some copper oxychloride fungicide or a 10% bleach solution and spray the cleaned up wound area, it may not eliminate the crown gall disease but may stop it spreading.

 

References:

  1. New Mexico State University, Extension Plant Sciences – Featured Diagnosis: Crown Gall (Agrobacterium tumefaciens)
  2. North Dakota State University, NDSU Extension – Crown Gall, Agrobacterium tumefaciens by Esther McGinnis
  3. The Microbial World: Biology and Control of Crown Gall (Agrobacterium tumefaciens) by Jim Deacon, Institute of Cell and Molecular Biology, The University of Edinburgh
  4. Mikiciński, Artur & Sobiczewski, Piotr & Berczyński, Stanisław. (2012). Efficacy of fungicides and essential oils against bacterial diseases of fruit trees. Journal of Plant Protection Research. 52. 10.2478/v10045-012-0075-7.
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Organic Control of Curl Grubs in Lawn

ID00033Curl grubInsectaColeopteraScarabaeidaelarvaKRPDMCC23/07/2002
Curl Grub larvae (credits – CSIRO Australia scienceimage)

If you’ve ever been digging in the garden and discovered plump, pale coloured grubs beneath the soil that curl up into a “C” shape when disturbed, these are Curl Grubs.

Curl grubs are the larvae of various species of cockchafers or scarab beetles (family Scarabaeidae). Depending on where you are in the world, these curl grubs can be the larvae of the Japanese beetles, African black beetles, Christmas beetles, June beetles, Brownish cockchafers, Blackheaded pasture cockchafers, Black soil scarabs and several others. Once these larvae go through their life cycle beneath the soil and emerge as beetles, they’re relatively short lived, living for 1 to 9 weeks. The female beetles can lay 20-40 eggs in the soil, from which new curl grub larvae will emerge.

 

Identifying Curl Grubs

It’s fairly easy to identify curl grubs, they have white, pale cream or greyish-white soft bodies, with 6 legs, and a small hard brown, yellowish brown or reddish brown head. They vary in size and can grow to a size of  4mm to 60 mm long. When resting or disturbed they curl up into a C-shape, hence their name. Their rear end is enlarged and has a grey tinge from the faecal matter in their hind gut which is visible through their bodies.

The natural habitat of scarab beetle larvae is grasslands, where they feed on organic matter and plant roots. In large numbers, curl grubs can be very destructive, damaging lawns, gardens and plants in pots by feeding directly on the roots or cutting roots off as they forage for organic matter.

They are most active during mid spring to mid summer, and usually will only feed in the warmer months, but if winters are mild they may continue feeding throughout the year. Being most active during the hotter weather, they damage plants when they are most likely to be heat stressed, causing them to wilt and not respond to watering, eventually drying out if the root damage is extensive. Most curl grubs are active just below the soil, feeding within 1 to 2 cm of the soil surface.

Curl grub damage in lawns is quite distinct – during late summer and early autumn, irregular brown dying patches of lawn will appear, which can easily be lifted off and peeled  away like carpet from the soil surface, as the roots have been eaten away.

Curl grubs will feed on the roots of a wide range of plants, but not those of the legumes family such as beans and peas.

 

Assessing the Curl Grub Problem

It’s important to point out that having curl grubs in your soil does NOT mean you have a curl grub problem! As a general rule, a healthy lawn can tolerate up to five curl grubs per square foot.

If you want to check if you have a problem with curl grubs, dig up one square foot (30cm x 30cm) of lawn beneath one of the brown patches that is dying back, to a spade depth, and check the soil for curl-grub numbers. It’s best to dig up a few of the dying patches of lawn in different locations to get an idea of the extent of the problem.

  • If you find up to 5 curl grubs in each square foot of lawn, then you don’t need to do anything, a healthy lawn will cope with this number.
  • If you find more than 5 curl grubs in each square foot of lawn, then you need to take action to control the pests.

Another way to asses the numbers of curl grubs present in the soil is to water the lawn well, then cover the brown areas of dying lawn with a layer of newspapers, cardboard, a hessian bag, a piece of old carpet or similar material, then place something on top such as a few bricks to keep it in place and stop it being blown away by the wind. Leave in place overnight, and in the morning lift the layer to check for curl grubs.

 

Organic Curl Grub Control

If curl grub numbers are high and require control, there are various options available which are safe and allowable in organic gardens.

  1. Neem Oil – the natural insecticide neem oil is extracted from the seed of the Neem tree (Azadirachta indica), and contains the active compounds Azadirachtin A & B. It has two modes of action – it disrupts the pest insect life cycle by preventing the insect from moulting and progressing to the next stage in its life cycle, interfering with its growth and development. It’s also an effective anti-feedant which stops pest insects eating, causing them to starve to death.  Insects will stop feeding once they ingest neem oil, but will die off a few days later, depending on the type of insect and how big it is. Neem is safe for beneficial insects as they don’t eat plant leaves which neem is usually sprayed on.For curl grub control, apply neem to lawns, garden beds and potted plants as a soil drench using a watering can. The best time to apply neem for curl grub control (or any other curl grub pesticide, natural of synthetic, safe or unsafe) is from mid spring to mid summer, as this is the time when their eggs are hatching and larvae are near the surface of the soil, where the insecticide can reach them more easily.
  2. Beneficial nematodes – these tiny microscopic worms are a a biological control, they live in the soil and carry bacteria which kill curl grubs and other pests. They actively pursue the pests in the soil, and once inside it, they release the bacteria which kills the pest. These beneficial nematodes are harmless to people, pets, plants or beneficial insects. In Australia, they’re sold as Nemassist® nematodes, and can be applied to the soil with a watering can or pump sprayer. Soil temperature needs to be above 15C at the time of application for the beneficial nematodes to be active, and they can be applied as a preventative measure from spring to winter.
  3. Milky Spore – the soil-dwelling beneficial bacterium Milky Spore (Paenibacillus popilliae) is another biological control which primarily infects Japanese beetle grubs. It’s applied as a powder over the soil and watered in thoroughly. When the grubs feed close to the surface, the ingest the spores, become infected and die. The decomposing  grubs release more of the spores into the soil for the next generation of lawn grubs. The spores will remain in in the soil for 10-20 years, maintaining control of the pests. Milky Spore requires the curl grubs pests to be present in the soil in the first place so the bacteria can multiply and take effect. Since the spores need to multiply to reach sufficient numbers in the soil to work effectively, this process may take around two to four years, so it’s not an immediate control, but it’s effective over a very long period.Another advantage of Milky Spore is that it can be used together with beneficial nematodes which help disperse the bacteria throughout the soil. If you want to use the two together, sprinkle the Milky Spore on the soil and then water in well using a watering can filled water containing the beneficial nematodes.

 

Curl Grub Prevention

One of the best ways to avoid pest problems is to NOT create environments that favour pests. Curl grub beetles prefer to lay their eggs in thin, sparse grass, so it’s best to keep lawns thick and healthy, and cut fairly high, a minimum of 5cm (2”). Water when necessary and fertilise (using natural fertilisers to preserve the natural soil ecology which controls pests, and to avoid pollution of waterways!) to maintain the condition of the lawn, and water deeply to promote deeper, stronger roots.

Curl grub populations are naturally reduced by extreme weather and disease, parasites and predators. Keeping your gardening natural means keeping it safe for living things, which encourages the living organisms which normally control these pests in Nature. Do not use poisonous synthetic chemical pesticides, herbicides and fungicides in the garden!

The most useful natural enemies which control curl grub numbers are parasitic wasps and insect-eating birds. In Australia, Magpies, a member of the Corvidae (crow)family, are a major predators of curl grubs, you’ll often see these birds digging them out of lawns. They can be encouraged to stay if there are clumps of trees for them to nest in. Many flowering native plants and companion plants attract beneficial wasps into the garden, as they provide a nectar source.

Keeping the ecological balance in the garden and maintaining a healthy ecosystem, rather than creating a chemical-warfare trashed ecological wasteland is critical. If you don’t poison or kill beneficial predatory insects, and create a natural setting that give them somewhere to live, they’ll do the work for you. Both the larval stages of click beetles (family Elateridae), and the adult and larval stages of carabid beetles (predatory ground beetles) (family Carabidae) eat curl grubs.

 

Conclusion

Perspective matters, a few curl grubs in the lawn or garden are not a problem, it’s only when their numbers get too high – which is because of an ecological imbalance, often human created, that we need to take action. Natural and organic-certified controls are available to treat curl grub problems, so there’s no need to turn your lawn or garden into a toxic playground. Seeing a few big beetles buzzing around in the garden add to the experience of enjoying Nature. Happy gardening!

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Product Review – Ryset Tree Cover Formed Insect Net

ryset-formed-insect-net

 

When protecting fruit trees from birds, possums and pest insects, there are two approaches – you can cover the fruit with individual netting bags as seen in our Product Review – Ryset Fruit Protection Bags, or you can cover the whole tree with netting.

Netting whole trees requires a very wide and long piece of netting material. Consider netting a small 2m tall x 2m wide tree. The netting needs to come up 2m from the ground, span 2m across the width of the tree, then come back down another 2m to meet the ground once again, requiring a 6m length of netting. It would need to be just as wide to cover the sides, as pictured below.

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To cover a tree more easily, what is really required is a net pre-formed as an inverted cup shape with a door, as pictured below, and that’s exactly what the product we’re reviewing here is!

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Ryset Australia has a range of pest deterrent and bird netting products, including the Ryset Formed Insect Net – A formed and fitted net designed to cover a tree. It’s 2.4m wide across the top with sides 2.8m high sewn around the circumference. The sides overlap 600m to provide a door for easy placement of the net over the tree, and easy access to the tree when fitted.

This product is constructed from 2mm woven, 45gsm white UV stabilised high density polyethylene netting. It’s intended purpose is to exclude birds, possums, pets and most flying insects such as cabbage moth, fruit fly and codling moth from fruit trees, as well as provide a 20% shade factor to reduce sunburn of fruit.

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Where can you purchase this product? Ryset is a wholesaler which supplies the retail garden and professional agricultural industry, so for home gardeners the best place to purchase Ryset’s products is from your local garden nursery.

In Melbourne, Bulleen Art & Garden Nursery sells a range of Ryset netting and fruit protection products, for online purchases nationally in Australia you can also order from The Diggers Club or from Greenharvest.

 

Product testing

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Netted mulberry tree kept low with summer pruning

 

The Ryset Australia Formed Insect Net is made of fine 2mm netting which is designed to exclude insects as well as birds and animals. I’ve been fortunate enough to test the product over several seasons, and it’s proven very durable, with no issues so far.

One of the great advantages of the finer insect netting over bird netting is that leaves and branches do not poke through the holes, so you can net a tree after it’s been pruned and the cut ends won’t snag in the netting and grow through afterwards.

The net is sufficiently large for any well-managed backyard tree, it’s 2.5m (8’) wide x 2.8m (9’) high, and as an advocate of backyard orchard culture and summer tree pruning, I recommend keeping trees low for easy harvesting and management.

 

I tested the net over a mulberry tree which produces giant black mulberries – and yes, they’re real and too precious to let birds eat as they’re totally delicious, and can grow up to almost 8cm (3”) long and weigh 11g (1/3 oz)!

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The formed netting managed to protect the entire mulberry crop successfully from marauding birds, and because the net was tied around the trunk of the tree, it also caught the freshly fallen mulberries too. Some of the mulberries which were overripe did make a mess when they landed, but despite the reputation that dark mulberries have for staining, the colour washed out from the net at the end of the season without any problems.

 

The second test for this netting was to see if we could protect a highly productive Dai Dai Maru persimmon tree from impatient ringtail possums which would sample around five different fruit a nigh to check if they were ripe yet, they got through about 25 unripe fruit before I netted. Luckily this 2.5m (8’) tree had well over one hundred fruit left on it, which also raises the point – how big do your fruit trees really need to be? This one is big enough, I keep it at this height, and it fits nicely under the formed tree net.

 

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Netted Dai Dai Maru persimmon tree pruned down to 2.5m

 

I’ve heard concerns that possums might be able to get through insect or bird netting, but my tests conform that possums in Australia cannot get through this netting at all. What I did find in another area of the garden with different netting is that rats and mice can, so if you’re seeing holes in your netting, you have a rodent problem. Possums are intelligent enough to squeeze through and further open a hole chewed through previously by rats, but they can’t get through on their own.

After netting, there was no further possum damage, and all persimmons were successfully harvested, and with such a large crop, shared with friends and family.

 

Netting a tree using this formed net is a fairly easy task, with two people and a broom to lift the netting up and over the tree (easier than using a ladder) it takes about five to ten minutes, depending on the tree, access around it and the cooperation of your volunteer. It can be done by a single person, I’ve done it before, it takes about ten minutes in my garden with closely spaced fruit trees. Since it has an overlapping door, it’s best to lay the net out to figure out where the door is, determine which side you wish to access the tree from, and align the door on that side.

Removing the netting is a bit faster, use a soft broom to push the netting up from the inside to lift it off the tree to avoid tearing it if you don’t want to use a ladder, and it’s a job easily handled by one person.

 

The mesh is quite fine so it will prevent insects from getting to your fruit, including fruit flies which are common pests in the more subtropical and tropical climates. Obviously, if your trees require insect pollinators such as bees, you only net the tree after the insects have done their work pollinating the flowers. An added benefit of the fine mesh is that it provides 20% shade which reduces sun scald (sun burning) of ripening fruit).

For those concerned about indigenous ecology, as an added benefit, fruit bats cannot get tangled in the fine mesh, it’s perfectly safe to use where they may be present.

 

Product assessment

Ryset’s Formed Insect Net is a very durable formed net that is stitched together very strongly, mine is over three years old now and still going just fine. The insect exclusion mesh which the formed net is constructed from is quite strong and you definitely can’t tear the material by hand. This product retails around the thirty-five dollar mark, and can be moved from tree to tree as different fruit come into season, so you don’t really need one for every tree in your garden. All these factors combine to make it a very affordable solution for protecting fruit from pests such as birds, possums, bats and flying insects. I know that when I cover a tree with this formed net, I won;t lose any of the harvest to pests, and that’s reassuring.

This net is well designed to accommodate the size of most managed fruit trees, is easy to deploy, and easy to remove, and protects fruit to some degree from being burnt by the sun, that’s a lot of benefits to a gardener for little cost, which is why I can recommend his product!

Deep Green rating for the “Ryset Formed Insect Net” is 5 stars!

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If you are interested in submitting a product for review, please contact us via email at deep_green@optusnet.com.au , thanks!

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