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EPISODE 5: Biodiversity in a macadamia orchard

Leoni Kojetin (Australian Macadamia Society). I'm Leoni Kojetin, the industry development manager for the Australian Macadamia Society, and today I'm with Alan and Jarrah Coates of Coates Horticulture. Alan and Jarrah have worked in the industry for a long time as consultants, and they have an enormous amount of knowledge. Today, we're talking about biodiversity in a macadamia orchard and what it actually means. Thanks Alan and Jarrah for joining me today.

Can you tell us something about your background in the macadamia industry?

Alan Coates. I've been in the macadamia industry for about 35 years as a consultant and as an educator, where I teach courses and present workshops, speak at conferences, field days and research forums, as well as spending a lot of time in the field.

Jarrah Coates.  I've been a consultant since 2001, primarily in pest and disease management, as well as checking macadamia crops, soil and leaf sampling.

Leoni. And we need to congratulate you as this year’s macadamia industry's young achiever of the year. So congratulations.

Jarrah. Thank you very much.

Leoni. It's great to have you today chatting about some of the topics that you were nominated for. So what are some of the changes that you've seen in the industry, Alan and Jarrah?

Alan. When I started in the industry, we were hand harvesting, so I've seen the introduction of mechanical harvesting into our industry. I've also seen a significant increase in research and marketing in the industry, as well as a significant expansion of planting areas, particularly in Queensland, and movement down onto the coastal floodplains.

We've brought a lot more professionalism into the industry via the AMS and the processors to a large degree. We've brought in a whole range of new varieties and have put a lot more effort into looking at ground covers on orchard floors and how they benefit the industry, and that's very relevant to what we're talking about today. We've also seen the arrival of new pests and diseases in our industry over time, particularly lace bug and macadamia seed weevil, leptocorisa and husk spot.

Jarrah. My experience is really in the Northern Rivers, where I do all my work and where all my information will come from. I don't get to see many of the other growing regions.

Over my time in the macadamia industry, I've seen changing practices from when I first started. Herbicide was widely used, for example in big, wide herbicide strips. That transitioned into zero-turn mowers, people being more aware of ground cover, trying to keep ground cover and roots to minimise erosion, and changing canopy management. That's been quite a big one. Back in the old days, it was vertical hedging, whereas now there are lots of new and wonderful ways to tackle canopy management.

Echoing what Dad said a minute ago about pest issues in the industry, in my time certainly lace bug and macadamia seed weevil have arrived and caused some problems. On the other end of things, macadamia nut borer was the major pest when I first started, and it's diminished to being almost a minor pest, I would say, in our area. And that's really due to the success of biocontrol using specific parasitic wasps.

Leoni. One of the profound changes that we do talk about is a shift away from a monoculture to a move to a biodiverse orchard. Can you explain what we understand by a monoculture?

Alan. To me, monoculture is basically about the cultivation of a single crop in a given area. And in the macadamia industry, we are, to a large degree, a monoculture, particularly if we have no inter-row or very limited inter-row species.

Jarrah. There is also no variation of plants, a lack of complexity in the ecosystem.

Leoni. What does that monoculture expose growers to? Or what does it look like for a grower on a day-to-day basis?

Alan. I think it exposes growers to potentially increased pest and disease pressure and development of resistance due to management based on chemical treatment for pests and diseases where we don't utilise the ecosystem's checks and balances that exist in a normal diverse ecosystem.

It also, I think, impacts on the below-ground issues, and can lead to imbalances in nutrients, which has implications for water management. One result is that it has potentially increased risks of pollution of waterways because we take away the filtration processes in the soil system, and we can damage our soil health because of reduced microorganism diversity.

Leoni. What you're describing is above the ground and pretty much on the orchard floor, where there is either nothing or a bare, lifeless soil or a bit of grass in some settings. And then you're describing below the ground a very lifeless environment where the roots are growing.

Alan. Yes.

Leoni. And all the problems that that brings. We know very well about erosion. We know about some of the other impacts, but what about the resilience of that orchard to weather events or to drought conditions? Have you seen how that monoculture can expose growers to those types of conditions?

Jarrah. In the last season, we've just experienced some of the worst drought conditions I've ever seen since I've been in the macadamia industry. It did seem apparent that some of the orchards that fared better in those conditions were those that either added organic matter or had higher organic matter levels and were able to retain more soil and moisture, and the trees maybe didn't suffer as badly. Obviously, there were other important factors at play, like soil type.

Leoni. What are some of the benefits of biodiversity? What does a biodiverse orchard look like? And what are some of the benefits for a grower?

Alan. I think what biodiversity can do for an orchard is it provides some buffering for our ecosystem in our orchards.

Jarrah. It provides habitat for a range of different organisms. In a monoculture, if there are limited floral reserves, for example, for pollinators or parasitic wasps, the adult stages really need pollen and nectar. And if they are not there, then obviously that environment is unsuitable for them to thrive. If you can encourage diversity of plants, and particularly flowering plants, you can support a whole wide range of organisms such as insects, which potentially lead into what Alan's talking about i.e., buffering against pest incursions.

Some examples of some things like that would be parasitic wasps. If you have a habitat for them in the orchard, they can perform pest management roles for you. If the habitat is not there, then they're not going to be there and won’t therefore perform those services for you. Also pollination, obviously. Bees, flies, birds, a whole range of organisms that can benefit your orchard. And if there is no habitat for them, then they won’t visit the orchard.

Alan. And having a diversity of plant species provides a diversity of above-ground habitat and below-ground root systems that support a diverse range of microorganisms. What that does is buffer or minimise the threat of pest or disease species predominating, providing natural suppression of pathogens. Diverse ground covers provide a diverse below-ground system, which provides balance and protection for the root system as well as encouraging root growth, which is critical to performance of macadamia trees.

Leoni. A lot of growers know about parasitic wasps that you can release into the orchards, but there are other natural predators that do an amazing job if we provide the right environment so they want to live there. Can you give us some examples of those?

Jarrah. There's lots of generalist organisms that maybe aren't as specific as a parasitoid, which relies directly on an individual, but there are also things such as spiders, predatory bugs and birds that play a more general role in eating insects, and insects are food for other insects.

People think maybe all bugs are bad, and that's certainly not the case. If there's more insect life there, then the food web is more diverse and those ecological interactions are more complex and potentially can control pests to some degree.

Leoni. Alan, I'm sure you've seen a lot of that where unfortunately, with through harsher crop protection mechanisms, we've selected for specific pests in some orchards.

Alan. Definitely. When I go into orchards, if I don't see any activity, I'm really concerned because it's really about balance in the organisms we have in the orchard. And as we've said, you've got to provide a habitat and the environment that supports and encourages those organisms.

I've worked with orchards where we let inter-rows grow. We don't specifically plant species into it, which is one of the options that we have, rather we let the inter-rows grow as soon as we finish harvesting. We've got examples where we have found the presence of lace bug in those orchards every year for a period of about seven years. We have yet had to spray for lace bug because of the natural predation and parasitism that we see from the beneficial insects that the inter-row supports. We also see in that situation, we don't have thrip problems, which I really think are primarily a secondary pest issue.

Again, it shows that the broad-spectrum insecticides compromise our natural system's ability to keep what we call secondary pests under control.

Leoni. We're looking for this biodiverse orchard which takes advantage of nature's balanced control that it brings, but it's not just a philosophical goal, it is an economic one too. This means that growers are making economic decisions. Can you expand on that?

Alan. I think it's critical that it has to be an economic decision, for example the number of insecticides that we may apply a year. In a balanced, biologically based system, we look at probably between two and four insecticide sprays a year, compared to six to seven insecticide sprays under a calendar spray program. So, there are significant savings in time and costs as far as labour, machinery and chemicals are concerned. We have other issues. The less time we run machines in orchards, the less compaction we have. If we let inter-rows grow, we have less mowing and there's a significant cost saving in doing that.

We need to be practical in what we do because we are running a business. And if we monitor what's going on in the orchard, there are occasions when we do have to spray, but we need to make those decisions based on information that we collect in the orchard rather than on a calendar basis.

Jarrah. A couple of the sites that we do have employed some inter-rows into their orchards. Interestingly, while being conscious of the economics, some people have gone in, spent a lot of money, and had some really good results. But on the other end, people have placed minimal importance in some seeding, letting seed get through to flower and then seed head and then rebuilding the seed bank and managing that. And so being aware of costs and not having to renew that all the time is another aspect.

Just letting the natural seed bank come through provides some benefit in supporting beneficial insects as well. Growers don't have to be daunted by thinking it's going to cost too much. Doing something is better than doing nothing, and you can have a positive impact on your orchard without spending too much money.

I did two of the IPM case study sites, one of which is on the Northern Rivers using an inter-row. There have been some interesting results on that farm, and we see lots of beneficial insects, and a wide range of them.

The owner has done some seeding in his orchard and has seen some interesting results with lace bug. His is a site that has minimal spray inputs. I can't say that that would be the case for all farms, but his particular site, he did one indoxacarb treatment last season, and that was basically it. I cannot say there's many sites that have achieved those sorts of results, but in saying that, different farms have different pressures and that may not be achievable for everyone.

We've had the same sort of experience at the site with some little flare-ups of lace bug in the past few seasons. We've done some very small area spraying rather than whole orchard treatments. And we think that the suppression from the inter-row on the lace bug could be in the form of a predator or parasitoid. While we've seen small spiders eating lace bug and lacewing larva eating lace bug, and in the lab, we've seen that an orius bug can eat lace bug, maybe there's something else going on there that we haven't actually observed. Overall, however, suppression seems to be taking place in the orchard.

Leoni. And certainly, that Bio Resources project, an integrated pest management project which was levy-funded, has shown an enormous amount of population increase in arthropod species with any inter-row planting, whether it's managed or not managed.

Alan. I think that's fantastic. What's been good is that we've been able to document what's going on to an extent in the inter-rows. In the past, we'd seen it and relied on a lot of anecdotal experience and evidence. So, to be able to actually put some figures on it, I think it's really important to convince people that there are benefits there.

Jarrah. The Bio Resources researchers have got some good data on numbers of thrips, one of the things to come out of their case study sites. And the reduction in thrips, that's probably from predation on and suppression of thrips by beneficial insects.

Leoni. What are some of the barriers at a farm or an industry level to adoption of these more sustainable practices?

Alan. I think one of the concerns is lack of knowledge and fear of creating problems. The classic one we hear when we talk about letting inter-rows grow is the problems we will have with rats. We can monitor this easily and it isn't really an issue that we can't deal with.

I think changing growers' mindset is critical. For them to be able to see practical examples where people are getting documented benefits is really important in changing the mindset.

Leoni. In the rat management research that's been done, more rats are supported by bush outside the orchard than are supported by the inter-rows. So, even though you might see a rat in an inter-row, it's not supportive of that species as much as the bush outside the orchard is.

Alan. That's true.

Jarrah. We do a lot of orchards, and there isn't any significant increase in rat activity in the orchards that have inter-rows compared to the orchards that don't. And where there is some rat activity in those orchards, like Alan said, it's easily managed. You can mulch that section where there might be a burrow and use equipment to gas the hole. It is very manageable. Early on people said, "Oh, you can't do it because there's going to be a hub of rats." And that just wasn't the case in our experience.

Leoni. In terms of what we've spoken about today, this goal of a bio-diverse orchard, what is next for a grower or for our industry to achieve this?

Jarrah. There's a range of things that growers can potentially do, and we've touched on a few of them.

Changing mowing habits is probably the easiest thing to do, i.e., mow less. Let some of the natural inter-row grow, especially to flower and seed head if they are species that flower, so they can support a range of insects. Options are to go to mowing every second row, changing up how they're doing their mowing.

Planting an inter-row with a seeder is certainly something that people can do. And there's more opportunity in areas in the orchard with IOM where people have done row removal or drainage areas where they've opened up large sections that allow enough light to grow an inter-row. If you have done row removal, say, and you plant that with flowering plants as well as helping with erosion management, they can also supply habitat for beneficials.

Other things too, like insectivorous birds such as thornbills and silvereyes and warblers probably are underrated. We see them, and they feed on insects. If you can plant small shrubs, flowering shrubs and prickly shrubs that provide protection from predation and from other birds it is a good idea.

If you're in an area where you have rainforest, remnant rainforest or remnant bush, if you can link those up as a way of providing for movement corridors for animals. Hollows in trees, for birds obviously and for microbats as well are a good idea. Regenerating areas in your orchard and replacing exotic weeds and planting native species that support native organisms are certainly of benefit.

Alan. One of the things that I very recently heard about that looks interesting is that there's potential for biodiversity credits, a little bit like carbon credits, and there's an organisation now that's looking at doing that. I think that sounds really exciting and could be quite an incentive for farmers, particularly macadamia farmers, because I think they're well-suited to be able to do that.

Leoni. But in many ways, some of the biodiversity credits come from an increasing production. And so an increase of biodiverse below-ground setting, we know is going to be a more productive orchard.

Alan. Definitely.

Leoni. Thank you so much for your time today. It's been great to listen to you, and we appreciate all your expertise and you sharing with us.