Information about plants & gardens for Brisbane & Qld
 

 

Nets

plus fabrics and other pest barrier products


You have probably seen pictures of commercial orchards under a canopy of netting designed to keep birds and bats away from ripening fruit. If the farners could enclose the whole tree in an insect-proof net, the amount of spraying that would be required would be greatly reduced. This usually isn't practical on a commercial scale, but is feasible in the home garden.

A variety of netting or cloth products are available to protect plants without spraying. Some cover whole plants or whole garden beds, while bags that protect individual fruit can also be purchased. While these protects aren't that easy to find as yet, we might expect them to become more widely available as the popularity of backyard vegetables grows.

While usually used for fruit and vegetables, there's no reason you couldn't use them to protect ornamentals such as valuable shrubs or beds of annual flower seedlings.

 

Just how sustainable are "organic" sprays?

Unless completely home-made, these still require manufacture, packaging and transport, using fossil fuel and other resources. Plus, you'll be left with the plastic bottle or other packaging (which you're ultimately paying for) to throw away.

Advantages

These days, people increasingly prefer not to use chemical sprays on their food. Over the years the more toxic ones are being withdrawn from the home garden market.

Even in the case of the less toxic "natural" or "organic" sprays (even if they do work), you have the expense and hassle of applying them. You might have to reappy regularly, or after every rain, for them to be effective. On the other hand, if you don't use all of the product straight away, the amount of time you can store them before they go "off" is an additional concern.

Nets are mostly used to exclude pests, (e.g. insects and mites, birds, bats, possums), according to the size of the mesh. The more closely-spun fabrics can also protecting plants from disease-causing fungal spores and bacteria as well as the insect vectors of viruses.

Netting could aid in disease control to some extent, depending on the extent to which it excludes vectors, reduces exposure to wind and soil splash and enhances the overall health of the plant.

With care, quality commercial nets should last for many seasons, although the lighter fabrics have a more limited lifespan.

There are other potential advantages such as shading, wind reduction, hail protection or frost protection, depending on the characteristics of the material and the nature of the crop.

Disadvantages

While the aesthetics aren't generally a high priority in vege gardens, watching the crops develop is satisfying. Nicely-laid out gardens sprinked with herbs and flowers can be quite pretty and cottage-y. Unforunately, nets and bags would rather spoil that look, but if production is your priority, backets of clean and healthy fruit and veggies will be be something you can really show off!

The amount of shade could be a disadvantage with some crops or in cool and cloudy weather. You might decide to cover only during the most vulnerable stages, or use bags only to protect the fruit. Your supplier may be able to give advice on the percentage shading and suitability for your intented crops.

For maximum effectiveness, they will have to be secured around the plant down to ground level, requiring pegging, weights, burying edges etc., which will interfere with access for crop monitoring, weeding and harvest. Care will also need to be taken to avoid tears.

Trees will need to be managed to be kept small enough to net (prune appropriately, so as to not loose too much fruiting wood). Netting individual branches is an alternative. Ramblining vines will be hard to cover. Again, protection of individual fruit may be a possibility if they're valuable enough.

Potentially, nets could trap pests that emerge from eggs laid on plants or in soil before the nets are placed. Another possible downside is the exclusion of desirable insects such as pollinators or predators. You might have to time placement (waiting until after fruit-set), or hand pollinate.

Because of the various trade-offs, exclusion products won't be the answer to every pest and disease problem, but integrated with other strategies could be an important part of managing a productive garden and reducing chemical use.

Materials

The type of materal you choose will depend on where your priorities lie with respect to the type of pests you want to exclude, cost and shading/microclimate considerations.

Fleece

Horticultural fleece is a lightweight fabric, usually non-woven (spunbonded) polyester or polypropylene. In international publications you might see these called row covers or floating row covers when they are draped directly on the plants.

Besides protecting the crop from pests, it can also be used for microclimate modification. Proper horticultural fleece should be permit and rain to pass through, but the insulating properties help trap soil warmth under the cloth and protect from frost. It's insulating properties are mostly taken advantage of in cool climates, they may also be used in warm climates to deflect heat, provide light shading and reduce drying out.

If you do require your fleece to provide frost protection, check with the supplier that the thickness and density is sufficient

Fleece may last a few seasons if handles carefully, but is not as robust as good-quality nets.

Nets

Mono-filament or knitted cloth with a large mesh size may keep out larger animals, but it can also be a danger to them, due to risk of entanglemant. Bat Conservation & Rescue Qld has some advice about wild-life friendly exclusion products and how to use them on their website (see below).

As the size of holes in the nets reduces, the range of pests excluded increases. Note that some knitted products may keep out larger insects like grasshoppers and cabbage white butterflies, but not fruit flies. The "Fruit Fly and the Home Garden" website (see below) says that 1.6mm net size is suitable for fruit fly exclusion.

To be continued in future updates...

Non-specialised products

A variety of materials you might already have around the house or garden can be pressed into service for pest protection. Not being designed for this purpose, however, they have their limitations.

Regular shade cloth - too stiff and heavy to throw directly over crops without support. May be approprate for a more permanent structure, provided the shade factor is not to great for the crop being grown.

Old Curtains - a way to recycle old net curtains but they aren't designed for the purpose so will depend on size of the mesh. Durability may vary They are unlikely to be UV stablised.

Household Fly Screen - will need to be framed in some way to be effective.

Pieces of cloth or even paper bags or newspaper may be used to protect fruit, but have obvious disadvantages with repect to ease of use and ability to withstand weather.

Chicken wire, plastic trellis and similar products might be used to keep out the larger animals. Obviously, to be effective they will need to be sturdy and secure enough, including where the material meets the ground (or even below the ground if the animal is liable to dig).

Enclosures

If you have the space, money and committment, you can erect permanent or semi-permanent structures like cages, shadehouses or polytunnels. These could use a variety of materials for screening as discussed above, along with various plastics specifically designed for such structures. These should make access to the plants a lot easier as well as looking neater.

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Where to buy

Nets designed to keep pests out of your fruit and veggie garden may be available to order from here soon.

If you can't wait, get in touch and the editor may be able to direct you to an alternative vendor offering veggie garden nets for sale. See Looking for a Supplier?.

Other resources

Here are some links for some general information about the use of pest control nets and fabrics
To net or not to net Download a PDF report on netting against birds, bats and insects from this page. Qld DPI
Netting Bat Conservation & Rescue QLD Inc.
Netting of fruit trees and vegetable gardens Sydney Bats (Ku-ring-gai Bat Conservation Society (KBCS) Inc.)
Exclusion Fruit Fly and the Home Garden, Office of the Chief Plant Protection Officer, Australia
Bagging fruits Online Information Service for Non-Chemical Pest Management in the Tropics (OISAT)
Fruit Fly (a DIY solution to protecting tomato fruit) Organic Gardening From Down Under
The Use of Floating Row Covers Colorado State University Cooperative Extension
Row Cover Vegetable Production Techniques New Mexico State University
Floating Row Cover University of Wisconsin-Extension Master Gardener Program
Floating Row CoverThe Wisconsin Master Gardener Program
Row Cover Vegetable Production Techniques New Mexico State University (PDF)
Floating row covers and vegetable insects Front Range Food Gardener blog

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