Information post - Bug control and watering

I have been asked to describe my pest control methods. I don't want to get too in-depth about all this, but I have taken several photos (not of creepy-crawlies, that would be gross!); I've no idea at the start of this post how long it'll end up by the end.

Firstly, know your enemy.......

There are three main pests that cause problems on my Orchids. The first is mealy bug which seems to really like Phalaenopsis flowers. They appear mostly on soft growth, so emerging growth, flower spikes, etc. Mealy bug are soft-bodied little grey critters that can multiply like nobody's business. They are related greenfly and blackfly. They are easy enough to crush with fingers or the point of canes, but orchids have all sorts of nooks and crannies that they like to hide in.

The second trouble causer is scale insect.  These are partial to different orchids from mealy bugs and tend to go for Cattleya and other orchids with hard pseudobulbs and leaves. They like to lurk on the rhizomes of Cattleyas and can be really hard to eradicate. They also multiply really fast, and quite a severe infestation can build up before bugs get noticed. They are harder to kill than mealy bugs because they hide under a little shield so most chemicals just bounce off. They can be crushed with a fingernail, of course.

The third pest that can cause problems is red spider mite. Usually the first sign of a problem with spider mite is that leaves start to turn silvery and fall prematurely. Sometimes you might notice webbing under the leaves. If you look really closely you can sometimes see very tiny mites moving around under the leaves, some a pale colour and some red. They go mostly for thin leafed orchids like Catasetum and its relatives. Often Eulophia can be affected, as well as Dienia (Malaxis), and sometimes they go for Coelogyne.

So, what do we do about it before we crack open the potions and poisons?

So the first line of defence is to make life difficult for the ones that do find their way onto their orchids. Air movement is important and seems to discourage all three. I have a fan running in my growroom to keep the air circulating. Many growers have theirs running 24/7 but I just have mine running while the lights are on. I have it at ceiling level as it is quite powerful and if it blows directly over the plants it will knock them over.

I looked at fans in hydroponic shops and on eBay and all the rest of it, but I bought this one off the high street in the end. It's pretty powerful. The idea is to have the fan circulating the air so the plants are always in a gentle breeze. You should be able to see the leaves moving. This seems to help to discourage pests, and it helps prevent rots because water evaporates off the plants quickly before it can cause problems.

The next thing that helps to discourage pests is humidity; this is especially true for spider mites. I'm not sure whether it makes a difference for mealy bugs and scale, but I can say that regular spraying of the plants seems to make life more difficult for them.

An important factor in stopping pests from spreading is also one that is very difficult for me, as an orchid addict, to maintain and that is spacing. If the plants don't touch each other, its hard for bugs to spread from plant to plant. Its all swings and roundabouts, of course, because if there were fewer plants further apart it would be harder to maintain the humidity. Another way in for them is through open windows, doors, etc. It would be very hard to keep them out altogether as the air needs to be fresh and that may well involve opening windows during summer. It might be that I'll hang some fine mesh (like enviromesh) across the window so they can't get through.

So what about the potions and poisons?

I have been using the aerosol Provado ultimate bug killer as a spot insecticide on my plants for quite a long time now, as it has always seemed more effective than the regular spray gun, and it is in fact a different chemical. The received knowledge is that if you use a systemic insecticide the plant will absorb it and become magically toxic to bugs. This is perfectly true on most indoor plants, but orchids being orchids, its no that simple. Having spent years using these lotions and potions on my plants I have been watching how they work, and I think they only work by contact. Without getting too technical, Orchids have adapted to their native environment by operating much like cacti do, so they have a reduced number of stomata (pathway in and out of the leaves). Not only that, but the stomata are closed during the day. Orchid leaves have a thick cuticle to keep moisture in, and it will also keep chemicals out.  The stomata open during the night when temperatures are cooler. So if the leaves have such a thick skin and closed stomata during the day when we are likely to be spraying, there seems little point in using systemic chemicals.  Admittedly we could take to spraying during the night, but then we leave ourselves open to bacterial diseases and rots caused by splashing water around during cool nights. With fewer stomata than most plants, the Orchids are never going to be able to take up enough chemical to be properly effective.

There is another issue with using systemic chemicals on orchids. If the chemicals are only partially effective at best, this gives the bugs a fighting chance to develop resistance to the chemicals and, believe me, they do. Not looking good for the chemicals, is it?

Once I'd worked this out, I realized I needed to change tactics. Contact killers such as Pyrethrin are effective as they don't rely on being absorbed into the plant, but they do still act as a poison to the pests, so they still have the chance to develop resistance.

My new tactic is to use soap. This essentially lowers the surface tension of the water and drowns the pests. All of them. As the effect is a physical one the bugs can't develop resistance. Not only this, the soap is lovely and non-toxic. For people. It seems very effective, provided the plants are sprayed thoroughly and regularly. I have been asked whether I use washing up liquid. I guess at a pinch you could use that, but it contains detergents which we don't really want on our plants. I have been using liquid soap flakes which are pure soap and unperfumed.

I get it off the internet, but I should think you could buy this in a real shop. I can tell you it is a whole lot cheaper than Provado is. The dilution rate is a bit wooly since there aren't any proper instructions for this, so I like to use some. I use two capfuls per five litres of water, give or take a bit. I use a 5 litre pressurised spraygun with a lance so I can get even coverage without moving all the plants every time I spray.

Pretty industrial, isn't it? Anything smaller and I'd be mixing until the cows came home. There is a new product on the market (at least new to me) that I'm experimenting with that seems to be soap based, although I have to say it is a little more expensive than the stuff I have been using, but I thought it was worth a try since it is meant to be a foliar feed too. Now after all I've wittered on about regarding the orchids lack of stomata and all, why would I be interested in a foliar feed? I'm not, particularly, but the little bit of feed will get into the plants once it reaches the roots, so there is a degree of use in foliar feeds provided you drench the plants with it.

Dilution rate is nice and simple, 10ml per litre of water. This stuff seriously froths up when mixed, quite a lot of fun. Coverage seems to be nice and even and the leaves seem to shine after application. At £15 a bottle, I probably wont be making a permanent switch to this, but if it works well I might well use a bottle of it every few months.

so, hopefully that has provided a bit of information about what I get up to when I'm not writing blog posts.