I apologize in advance

[fanaticactus]

I know you're all most likely tired of hearing me complain about my ongoing problems with mealies wiping out my entire collection. I'm about at my wit's end. I'm still in the process of repotting all my cacti that have too heavy and compacted a substrate. Invariably I've found that the roots, as expected, are stunted and not growing at all. I've discovered many of them loaded with root mealies; they are immediately discarded along with their pots. Other newly-potted ones are now getting scattered attacks of mealies above ground: in axils, on spines and at the base of flowers and buds. Where do they come from? Everything has been cleaned and the gravel is all sterilized, and I use only miniscule amounts now of potting soil or an organic mix for those that benefit from it. I have resorted to using a systemic treatment on everything, even though it's getting to be a pain. All this is especially annoying and discouraging in light of my new GH, which cost a bloody fortune. Would it already be necessary to disinfect all surfaces in a GH that's not even a month old yet? How do I go about that? Not all the cacti are resting directly on shelves or benches, though. The benches have a thin mat with a wicking surface over it. How do I sterilize that if I have to? Perhaps strangely--perhaps not--when my collection spent the entire summer outdoors, I hardly had any problems with mealies. But I did have to supply shelter for them during cool spells and periods of steady rain.

Also, for which genera is wide-open fresh air essential--that is, which would do better outside the GH? I have most of the common ones: Echinopsis (and their currently lumped-in relatives such as Lobivia, Chamaecereus & Tricho), Echinocereus, Eriosyce, Escobaria, Feros, Gymnos, Mamms, Parodia, Rebutia, Thelos & Turbis. I have just one or two of some others: Ortego, Tephro, Astro, Leuchenbergia, Sclero & Stenocactus. Thank you for any help you can suggest on any of these problems.

[iann]

Curious that you have both types of mealies. They are not the same species and so it cannot be due to a single contamination that has spread. In most cases, I think someone gets one plant, or just perhaps a single pregnant mealie (they're all pregnant!) and then two years later they wonder how come every plant in the greenhouse is suddenly covered in them. Still, when you say you didn't have any problems in such-and-such conditions, it may well be that you already did have problems, but not enough to make you notice. The mealie lifecycle is quite slow.

Greenhouses do encourage them, presumably warmth, shelter from the elements and many predators, all help. They generally won't survive hard freezing, although they'll ride out an occasional light frost. They're certainly not native to your area. A new greenhouse shouldn't be the source of the infection though, and an infestation that is in most of your plants has been around for a while. Certainly it didn't start this year, unless maybe you used contaminated soil and every plant got its own set of mealie eggs.

I think you need a systemic insecticide treatment of the whole collection. There are probably pests in every pot, so discarding the really bad ones is just putting off major problems until another year. If you know you have an infestation, a root drenching with a quick contact insecticide now will kill the majority of root mealies. You can similarly spot-treat any you see above ground. Then every plant gets watered with a systemic. Then do it again next year, since something will survive lurking in an egg or a corner, or a plant that didn't have enough roots to take up the poison. Maybe a little late in the season?

Above ground mealies seem to spread very quickly. The nymphs are tiny and you won't see them, but they're mobile. The adults, all female, don't move unless they're forced to. They settle down and make eggs. Root mealies seem to spread much more slowly, or perhaps hardly at all from pot to pot, but a special system for flushing water out of one pot and moving it around to every other pot seems like a great way to help them spread.

Mealies on spines are either confused or, surprise surprise, spine mealies. Spine mealies are the nurseries of breeding females. They spin a cocoon out there, lay eggs, and then die. The cocoon remains long after it is empty, an easy reminder that you have a problem. Other mealies hide, often in axils and among wool, or perhaps it is just the hiding ones that don't get picked off!

[iann]

I don't think it is essential for any cactus species to live out in fresh air, but it depends on how you keep your greenhouse. If it is frequently closed up with high humidity, stifling daytime heat, or very warm muggy nights, that won't suit some. Equally, if it is so well ventilated that it is hardly more than a roof on stilts that won't suit some cacti, although putting them outside won't be any better. Outdoors will give higher light, cooler skin, and much cooler nights. It will suit high altitude mountain species like Sulcorebutia, Cumulopuntia, or Pediocactus, although most will need protection from the rain. Hardy species like Escobaria and Echinocereus can also be grown well in the open, perhaps with some protection from rain. They don't need it but they'll grow slower and develop a more compact and spiny appearance.

Many "other" succulents do well in the open. It keeps down pests like mites, although other pests like birds and slugs could be a problem. Echeverias, leafy mesembs, Sedums, all sorts of things.

[fanaticactus]

Thank you, Ian. I can't tell how much I appreciate the time you take to give such complete, informative answers. Your knowledge about (seemingly) all aspects of cactus horticulture is truly amazing. As I've noted in several past posts, I do sterilize all the old grit and stone I use (and reuse) in potting. Good grit is hard to find! I'm tending to use much more of a mineral substrate now and hardly any commercially bagged soil. The soil I do NOT sterilize, as many here on the Forum have said it's not necessary as long as it's a well-known brand and fresh from the bag. Now, as for the GH...it is wonderfully sturdy and (God willing) weatherproof. There is perhaps insufficient venting, although it has a screen door (plus an insulated storm door for winter), a 21" square venting window at the other end and two roof vents of the same size. I have a fan at the window trying to suck out the hot air and a larger fan at the door. [I will add photos later. I just took them and can't load them until I finish this post.] The GH has one serious problem you mention: it is wa-a-a-y-y too hot. As of 11am today, it was already 96F (35/36C ?) in there. Some Aluminet 40%shade cloth has arrived and I'm figuring out the best way to mount it. I also plan to install a more efficient fan to expel air from one of the roof vents. Meanwhile, I've taken many of the cacti outside under a pergola to escape the heat. Our temperatures this week are forecast to be in the low-to-mid 80s (27-30C ?) with only a chance of a shower one or two days. With each repotting, I've been using very tiny granules of imadocloprid in the soil to be watered in. A few years ago I also had some liquid systemic (can't find it now or remember the name, but you said at the time it smelled to high heaven--like rotting meat). I'll follow this up with those photos of the GH.

[fanaticactus]

Here's the GH showing its minimal ventilation (forgot to photograph door at other end, though) and perhaps explaining why it gets so hot in there.

IMG_1632.JPG (102.34 KiB) Viewed 1878 times

IMG_1633.JPG (96.25 KiB) Viewed 1878 times

IMG_1634.JPG (36.05 KiB) Viewed 1878 times

IMG_1635.JPG (108.72 KiB) Viewed 1878 times

IMG_1636.JPG (80.36 KiB) Viewed 1878 times

[oldcat61]

I'm in New Jersey & my GH was way too hot earlier in the summer. I didn't have the side vent, just a roof one & the door. Bought an exhaust fan from the below link & my husband cut a hole in the end wall as near to the roof as possible. http://www.greenhousemegastore.com/prod ... haust-fans" onclick="window.open(this.href);return false;. Very quiet, good price & the GH is much, much cooler. I know you spent big$$, but you many need a bit more. Sue

[fanaticactus]

Hi, Sue, and thanks for thinking of me and the GH situation. I did go to that website and saw what they had available. Has your fan gone through a winter yet? I was wondering how well it withstood the cold and wind with the louvered shutters on it. Is there some way to secure them shut during the winter? I was looking for a type of fan that can be mounted on a beam next to one of the roof vents, but that might not create enough of a draft to be effective. I was just hesitant about compromising the integrity of the solid polycarb panels. Any thoughts?

[oldcat61]

The fan hasn't seen winter yet but the louvers appear to seal well. And a Jersey winter is nothing like New England ( I used to live in Maine ). You could put it in place of the side vent & if you didn't like it, put the side window back. I tried the fan tied to the beam trick - didn't do s--t. Sue

[iann]

They really like to cut corners on the vents, don't they I always open the door on sunny days, and that is probably more than all the other vents combined. I also run a large oscillating fan and remove some of the glazing when we have a period of cloudless weather.

Shade is a last resort, because most of my plants don't want shade, but occasionally I'll throw a sheet over some or all of the greenhouse on crazy hot days. Spring is a tricky time when they sun is strong but the plants aren't used to it.

[fanaticactus]

Here's the door I forgot to snap and include this morning. Normal sized door but only the bottom half is screened. I've been leaving the inside solid door open during the nights, when the temps have been in the comfortable 50s. Sometimes I leave the screen door entirely open during the days to allow the maximum amount of airflow.

IMG_1590.JPG (83.75 KiB) Viewed 1853 times

[majcka]

Oooooo. I love your GH. I want! I want!

[fanaticactus]

Thanks, Maja. During these summer days it's actually too hot! I'm looking into getting an exhaust fan to reduce the daytime temperature inside. I've already got some shade cloth and will install it when I figure out the best way. I'm keeping my fingers crossed that it'll be perfect for keeping my collection there during the winter.

[Ivan C]

... I've already got some shade cloth and will install it when I figure out the best way...

I use "earth magnets" to hold shade cloth. They are incredibly strong and makes the cloth easily removed if necessary.

[fanaticactus]

Thank you, Ivan. I haven't heard of "earth magnets". How do they work? If, like regular magnets, they need metal--be aware that I have no exposed interior metal in the GH. Problem?

[Ivan C]

Thank you, Ivan. I haven't heard of "earth magnets". How do they work? If, like regular magnets, they need metal--be aware that I have no exposed interior metal in the GH. Problem?

Yes they are very powerful magnets. I hook the cloth over rods or clothesline and attach with the magnets. Or you can screw in metal washers and attach cloth with magnets that way. You can also attach cloths of different lengths if need be. I get mine from Princess Auto here and when you attach two together it is all you can do to separate them. The cloth is put on the inside of the GH. I don't think they would take heavy winds.

There are two magnets attached. One on each side.

Earth magnets.jpg (62.95 KiB) Viewed 1796 times