Orchardists and plantation managers could reduce the need for pesticides and increase the number of pollinating insects by having flowering time as a selection criteria for windbreak trees.
A combination of windbreak trees that flower throughout the year but not at the same time as the orchard/plantation crop, will help feed beneficial nectar and pollen feeding birds and insects.
Using macadamia plantations as a model, a suite of eight windbreak tree species that flower away from the main September flower flush of the macadamias will help feed these native friends. This suite may be :-
Care in not selecting pest hosting trees such as Cadagi, which attracts Monolepta beetles and Grevilleas which attract Twig Girdling Caterpillars need also to be considered.
In modern day agriculture there are a number of new, emotional and politically correct words. We need to acknowledge, pay homage to and be seen to be doing something about these concepts. Words such as "quality assurance", "sustainable agriculture", "integrated pest control", "best practice", "biodiversity" and the best of them all "biological control". These words and images are being thrust upon us with perfectly good reason. The customer and consumer of the products we produce want products that have, or have been produced within an environment where these "best practices" are present.
IT COULD BE A PROBLEM
Yet within or at least on the perimeter of most orchards there is a line of trees that could hold the very resource which will assist in "sustainable agriculture" and yes ..... "BIOLOGICAL CONTROL OF PESTS" its the windbreak!
Most orchardists recognise the need for windbreaks to protect their investment from storm and tempest.
Yet with a little bit of thought a windbreak can be more than just something that slows the wind. It could be a habitat for a whole range of beneficial wildlife that can assist the orchardist to be green, clean, as well as profitable.
I'm not talking as a conservationist, or a lover of warm and cuddly things, I'm talking with an eye on reduced costs to the management, increased profits and a new shirt, which red necks can fit comfortably.
By making windbreaks multiple species additional benefits can be achieved.
Multiple species windbreaks can be a habitat for owls, mopokes and other predatory birds which will eat the rats, mice and other vermin that cause havoc within an orchard. By management being familiar with these birds habitat needs, such as hollows, roost branches and alternative foods, these native birds will assist in biological control of rodents. By actively placing, specially designed artificial hollows or nest boxes high in young windbreak trees then these birds can be attracted to the property.
(Reference: Garden Birds by Clifford B Frith ISBN 0.86824 243 8)
The availability of habitat for wrens and magpies, the problem of caterpillars and crickets will become a lot less. Tall trees will help the magpies and shrubs with closed canopies will help the wrens.
In twiggy orchard trees, such as macadamia wrens will nest, but orchard routine will disturb them. Small blocks of shrubbery within a windbreak can assist these delightful little birds. Magpies seem to survive in most places. Tall trees within a windbreak will help them feel at home in an orchard.
Probably the greatest benefit for biological control of pests and the assistance to crop pollination is to have a number of flowering tree species make up an orchard windbreak.
By planting a range of trees that flower throughout the year, but not at the same time the orchard crop, a food source and habitat will be produced for beneficial birds and insects.
Many nectarivorous birds are also active insect eaters. Honey eaters are known to hawk moths such as Heliothis and the moth of the flower eating caterpillar. But their first food is nectar and pollens. Give them their first course and they will eat moths for desert.
Parasitic wasps such as scelio and scoliid wasps that parasite crickets, grass hoppers and caterpillars need to eat pollen and nectar as adults before they can lay their eggs into these pests. A regular supply of pollen and nectar from a multi special flowering windbreak will assist these pin head size wasps, to be part of the orchard's defense against pests.
Common paper wasps need somewhere away from sprays and people to set up their houses. Windbreaks can offer these sanctuaries. These wasps also will predate on caterpillars, and other pests.
Tachinid flies, will also appreciate the habitat offered by windbreaks, as they forage for caterpillars.
Some crops such as apples, pears, avocado, macadamia and many berry crops need the services of pollinating insects. A constant supply of pollen and nectar from flowering windbreak trees will assist in keeping a high background level of native bees, honey bees and other pollinating insects. Flowering windbreak trees will also assist local beekeepers make a living, again allowing a good population of bees to be available for pollination services.
The windbreak also offers a sanctuary for beneficial insects when there is a need to spray pesticides on the orchard crop. If orchard management would specifically not target windbreaks when spraying then this habitat could be important for re stocking pest parasites and predators.
It is with a high degree of personal sadness that I see orchardists planting pine trees, poplar and other non flowering windbreaks. As these trees, will act as good windbreaks but a poor habitat for birds and a non habitat and alternative food source for beneficial insects such as bees and wasps. They may also be a habitat for undesirables such as scale and fungal problems.
I know, that with a little more thought and a bit of care, the windbreak could be the home for birds and insects that will put money into the pocket of the orchard management.
(Reference Clemson A. Honey and Pollen flora)
The macadamia industry is a perfect model for multiple species windbreak. Obviously, each crop and location would need to research suitable trees relevant to their needs.
Macadamias' main flowering is in August - September. By selecting windbreak trees that don't flower in September, pollinating insects will access the crop, and not be tempted away. In the past tallowood have been the main windbreak tree. This tree is very suitable as a windbreak, however, it flowers in September and no doubt presents alternative food for pollinating insects.
I certainly would not recommend future use of Tallow wood as a windbreak species. There are many others to choose from. The following suite of species would make useful windbreak and habitat trees.
Turpentine (Syncarpia glomulifera) flowers in October-November and would support desirable pollen and nectar insects after the main flowering of macadamia.
Brush box usually flower in November and makes a useful windbreak and pollen/nectar source.
White Mahogany (E. acamoidies) usually flowers November-December and would also make a useful windbreak species.
Melaleuca species, esp (M. quinquinerivia) flower readily through the summer and autumn, it is both a useful windbreak and a great habitat for birds and insects.
Blue Fig (Elaeocarpus grandis) flowers in summer. This tree grows fast, is a useful windbreak and habitat tree, as well as a valuable cabinet timber.
Flood Gum (E. grandis) and Sydney Blue Gum (E. saligna) flower in March to June and Swamp Mahogany (E. robusta) flowers in June-July. These three trees are useful for a multi special windbreak.
Bottle Brush (Callistemon viminalis) makes an ideal windbreak tree. It is strong, reasonably dense canopy and grows to 5-7 metres. It flowers throughout the year, in response to rain and can withstand lopping and shaping. Bottle Brush would make a good windbreak tree in wet or low lying areas.
By using these trees as macadamia windbreaks, a degree of biological control of pests and the maintenance of background pollinators will occur. At the same time, plantations will be protected from storm and tempest.
Trees such as Cadagii should not be used as they attract Monolepta beetles. Grevilleas, are also supposed to attract two Girdling caterpillars.
The orchard windbreak is a valuable asset for both stopping storm damage and as a habitat for valuable orchard protecting wildlife. The management of the windbreak for those purposes is a part of economic lateral thinking that agriculture needs to have as it looks beyond 2000.
Once we have the potential to have biological control of pests the moderation in the use of poisons and pesticides can be a practical alternative.
Frith C.B. (1985). Garden Birds ISBN. 0.86824 243 8.
Clemson A. (1985). Honey and Pollen Flora. ISBN 0909605 335.