In an effort to help us along our Soil Hugging journey, I’d like to introduce a “GUEST BLOGGER” Series to draw on the research and experience of others within a field of their interest (or angst!).
Please note that this guest blogger has no financial interest in any company mentioned below with the exception of Terra Perma Design.
Introducing (with huge gratitude for taking the time to document this) The Guru:
As long as we have been gardening in Perth, and noticeably when patches of Cape Gooseberries pop up, we have had spider mite troubling crops through summer. The hotter the summer, the worse the spider mite and the more widespread its adoption of plant hosts.
Spider mites are tiny 0.6mm insects that suck the sap out of plants and breed rapidly until the plant can be seen covered in fine mist of spider webs in worst case.
About 5 years ago, after my Indian Ginseng (Ashwangandha – Withania somnifera) was nearly killed by what I assumed were Two Spotted mites, I decided to try some Persimilis – Phytoseiulus persimilis predatory mites from Manchill IPM.
Being very busy at the time I did not give the trial the attention it deserved. The only thing I know is that the release did not control the mites in the long term as I still have a problem this year, and have had in every year since releasing the predators.
While we have many predators eating mite eggs and the mites, they can’t seem to keep up with the mite population explosion in summer.
Tiny Lady Birds – Stethorus sp. Adult and larvae.
Lace wing Larvae (with parent for reference, although the parent is not a predator in this case)
This year the sweet potato is getting hammered. The Lion’s Tail (Klip Dagga – see future blog!) has seen the highest concentration of mites. See the flower spike picture below. Cape Gooseberries, Black Berry Nightshade, Luffa, Snake Beans, LabLab and many other plants are also playing host. This time (Jan 2015) we are equipped with cameras, microscopes, time and keen interest on our backyard microbiology.
The Lion’s Tail (Klip Dagga)
Although the tell tale signs of mite damage are well known (see some symptoms below), it can be very difficult to identify which mites you have. Damage ranges from a mottled look on the leaves (below) to the full web colony (above).
Using our Nicon D90 with Macro lens and USB Microscope we got some decent images of the mites to ask on Jetto’s Patch and to send to Biological Services. Red mites can be European Mites, Tomato Mites, Bean Mites or even two spotted mites at certain times of the year. To get a definite type you need to have a clear picture of the back hair, legs and internals. Although it’s only a best guess, both Biological Services and I think we have predominantly (problem amounts) Bean Spider Mite (Tetranychus ludeni).
Chatting to the folks at Biological Services in South Australia there are few options for predatory mites, Persimilis (breed in WA by Manchill), T. occidentalis and N. californicus (bred in SA).
Given the Quarantine fees (importing living bugs) I am glad we decided to go for Persimilis (the locally grown option), although if you don’t, then its good to know that Biological services do combine WA shipments and thus you end up paying only $10 for inspection fees for a group of their products.
Phytoseiulus persimilis was chosen mainly as it breeds up the fastest to control spider mites – it is the most widely used control. Any of the three might work – common predator mites are not fussy, they eat all of the common mites and while they may prefer one type, the scarcity and hunger will sort out the priority so I don’t have to worry. So assuming the main pest at our place is Bean Spider Mite for my piece of mind at this point, the pictures of red bodied mites from now on will be called that accordingly.
It is not the cheapest experiment at $100 min order, one bottle containing 10,000 predator mites, and we got a 2 second bottle due to our keenness, questions, photographs and general interest in the topic normally confined to Commercial Greenhouses and strawberry farmers etc.
Biological Services use Lab Lab as a perennial host plant to keep ‘food’ mites breeding to feed their predators all year round. Whilst Green house growers will have mite pests even in winter, in a backyard it is common for the spider mites to die out in winter and thus the predators also die. Given we don’t have frosts I am hoping that LabLab, Sweet Potato, Klip Dagga and other perennials will host spider mite all year and thus host predators all year. We don’t want to be purchasing predators each year, nature needs to take over the breeding program and establish a predator prey equilibrium. We don’t mind having some spider mite attacking struggling crops and chosen sacrificial plants, but currently the existing predators in our ecology can’t keep up with the breeding explosion of mites.
Other common mites that you may have can be found discussed here – http://ausveg.com.au/intranet/technical-insights/cropprotection/mites.htm. I have two spotted mite also but not in concerning numbers.
Similarly other predators can be ordered if you find someone breeding them. Start here to find all the Good Bugs.
NOTE: Backyard gardeners are not commercial growers. Mites, if not controlled, can wipe out many monoculture crops, so don’t be alarmed by the heavy handed control eradication discussions on commercial grower sites like AgDept and AusVeg. While it’s nice to avoid these pests, they are summer season pests and can be moderated by keeping the plants well wet and removing infested plants before the populations build up.
We want to run fairly dry summer garden at Terra Perma (as summer watering is a luxury and might not always be possible) at least until we have a closed canopy of trees (and thus some hope of keeping a higher humidity from the limited water used) plus I prefer to leave the pests for the predators to breed up on. Anyway, the idea is to help nature get a balance faster as I have been waiting 5 years or more and am not as patient as she is. I also appreciate that I want to grow plants out of their comfort zone and thus they will be struggling for a while. Nature would kill off struggling plants as they are bad for the gene pool. So ‘work’ is needed to protect these plants from nature.
When we go against the flow (immovable force) of nature, we must put in the effort/work to allow that deviation. Spending $100, introducing a foreign predator, and helping them establish is this ‘work’. Let’s hope nature does not slap me in the face with some serious feedback for rocking the boat. I can’t help thinking about Cane Toads……
So here we have 20,000 helpers (on ice and in an esky as it’s 38 DegC today). Let’s hope that’s enough to dent the mite population and hopefully (and more importantly) create a perennial population of predators.
Persimilis are bright orange and very fast moving compared to spider mites. They are still hard to see with the naked eye and not much bigger than a bean mite, but actually harder to spot. As you can see from the pictures below they have long legs and long bodies. You should be able to identify these guys with your naked eye on your own crops with practice (or just carry a 10x Geologists Loupe – they are very handy).
There is a good write up on Persimilis, on the Good Bugs website here: http://www.goodbugs.org.au/Good%20bugs%20available/persimilis.html
This person’s video on youtube has a stronger usb microscope than we do, so have a look at her Persimilis predators if you are keen to see them on the move (leave it muted though :)) https://www.youtube.com/watch?v=ZxlqxQTPv9g
I don’t need to say much more than I have already – we want this to become a perennial predator and have very different ecosystem to most commercial growers so all commercial information needs to be read and viewed accordingly.
The 10,000 predator mites come in a 1 litre bottle of vermiculite, which with a tap to dislodge mites from the lid and a gentle mix, you remove the screen and start shaking the vermiculite and thus Persimilis out. The idea is to apply the most predator to the worse effected areas, but you also want to distribute them throughout the crops effected. My observation is that they can move very fast and thus I think they will spread fine IF they survive and thrive, so concentrate on getting them established somewhere.
Given the mites prefer some humidity I sprayed down the plants (it was midday so very dry), allowed them to dry as the mite bottles came up to room temp. I then started applying the vermiculite. This posed a bit of an issue as my sweet potatoes are mostly trellised and the vermiculite has a tendency to fall off the leaves. Ground based applications would be fine, but if applying to vines, predator mites on lab lab leaves would have been better for lodging in the foliage. The Klipp Dagga had higher concentration of Bean Mites and held the vermiculite better so let’s hope the Persimilis at least colonise these plants and move out from there.
Once out of the bottle the mites seemed to disperse rapidly – you can see the predator and bean mites on the Dagga flower head into the webbing.
To give an idea of size, I put a mite on my arm and tried to get a photo. No, I don’t have dodgy skin and enormous hairs, it’s just a very small mite!
Some mites seemed keen to stay on the bottle so I popped it down near the struggling Luffa hoping they might eventually get to work.
Part of this experiment is monitoring the populations of predators and pray on the leaves of the release sites. I have taken some photos of representative leaves – essentially you get X mites per leaf, it’s not an exact science but when I start seeing more predators than prey I think I will have my answer. The longer aim is to get the predators to stick around through winter, but as the population is low then, so it won’t be until next summer that I will know if my $100 has been well spent. We will keep you posted on the experiment.
Cheers, Charles – Guest Blogger, I couldn’t let the Soil Hugger have all the glory !
Just because I have to have my little (far too) scientific say…. (Reference)
Class – Arachnida – eight joint-legged invertebrate animals (arthropods).
Order – Mesostigmata – “an order of mites belonging to the Parasitiformes. Unlike most members of that group, many of these mites are not parasitic but free-living and predatory. They can be recognized by the single pair of spiracles (small holes that allow air to enter the trachea) positioned laterally on the body.”
Family – Phytoseiidae – mites which feed on thrips and other mite species.
Genus – Phytoseiulus – here we are.
Shhhhhhh – I was never here!