Spider Mites. Fireblight. Spider Mites. Fireblight. Try saying that rapidly three times. These are two widespread pests of a wide variety of edible and ornamental plants this time of year. How do you identify them? How do you control them? We go in search of answers with America’s Favorite Retired College Horticulture Professor, Debbie Flower.
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Fireblight Damage on a Pear Tree (photo: UCANR)
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GB 211 TRANSCRIPT Spider Mites. Fireblight.
mites , miticide , plants , spider mites , garden , pots , leaves , garden basics , fred , pruning , nursery , insects , spray , insecticide , apples , flower , predatory , fireblight , branches
Farmer Fred 0:00
Garden Basics with Farmer Fred is brought to you by Smart Pots, the original lightweight, long lasting fabric plant container. it's made in the USA. Visit SmartPots.com slash Fred for more information and a special discount, that's SmartPots.com/Fred. Welcome to the Garden Basics with Farmer Fred podcast. If you're just a beginning gardener or you want good gardening information, you've come to the right spot.
Farmer Fred 0:20
Spider mites. Fireblight. Spider mites. Fireblight. Try saying that rapidly three times! Spider mites and Fireblight. They are two very widespread pests on a lot of edible and ornamental plants every spring and summer. How do you identify them? How do you control them? We go in search of answers with America's favorite retired college horticultural Professor Debbie Flower. We're podcasting from Barking Dogs Studios here in the beautiful abutilon jungle in suburban purgatory. It's the Garden Basics with Farmer Fred podcast. And we're brought to you today by Smart Pots and Dave Wilson Nursery. And we'll do it all in under 30 minutes. Let's go!
SPIDER MITE CONTROL TIPS
Farmer Fred 1:14
We like to answer your garden questions here on the Garden Basics podcast. A lot of ways to get in your questions. You can leave a message at speakpipe.com/garden basics. You can call us or text us with a question. Maybe you have pictures to send. 916-292-8964. Email? Sure. Fred at farmerfred.com or fill out the contact box at Garden Basics dot net. Do tell us where you live, because all gardening is local. And we want to be able to pinpoint the correct solution for whatever is ailing you in your garden. We bring in America's favorite college horticultural Professor, retired. Debbie Flower is here. And Debbie, we have a question from Carmichael, California, which is in Sacramento County. From Laurie. Who writes in to say, “They're everywhere.” And she's referring to spider mites. “Their webbing is in the Creeping fig, all the succulents, the rosemary, the Agapanthus, the Black Eyed Susan, the Mahonia, the lavender, if it grows, they like it. I pulled my gorgeous Flashback and Zeolite calendulas this morning because, while they were blooming they were ok, but the foliage was just gross, yellow, gray and awful. It's like powdery mildew without the fuzzy mildew part. I left them in as long as I could, to act as a trap crop, but I couldn't take it any more. I spray the webs with a hose whenever I have one in hand, but I just can't seem to get ahead of them. It seems the same every year. But now they're on the veggies, on the chard. It's a war. What do you know about predatory mites to go after them? And what about neem oil or insecticidal soap?” Laurie, good questions.
Debbie Flower 2:52
But the first question is exactly what is causing these webs. It's obviously an arachnid, because that's what spins webs. Arachnid being a spider or spider relative, but the fact that it's everywhere now in her garden makes me wonder why. And it makes me wonder is it really spider mites? They're very, very tiny, their webs are not that big. And if it is spider mites, what happened to cause them to be so invasive? Spider mites are notorious for liking dusty places.
but not hot places.
Well, they not the hottest, but yes, they are more active in warm weather than cold right? But not hot, hot. Yes. So I'm in my house, which is very near Carmichael. I have lots and lots of just regular spiders, all different kinds, they're inside and they're outside. And so I would want her to identify the pest first before treating. And we should always do that. There were cases when I worked at Cooperative Extension and a nursery sprayed their plants in their nursery with malathion, which is an insecticide. Insecticides in general do not work on spiders or spider mites. But that killed all the predators of spiders and spider mites and all of a sudden they had a big outbreak of spider mites. So that was a problem. Was an insecticide used that killed some of the predators of the spider mites and allowed the spider mites to flourish? Is it very dusty? She talks about washing the webs with water so that indicates to me maybe it's not dusty, or it is not spider mites
Farmer Fred 4:28
and if you're watering just the tops of the leaves, you're probably not going to get the spider mites. You probably need to get underneath the leaves with some sort of hose and sprayer that has a 90 degree bend to it, so you can get under the leaves.
Debbie Flower 4:42
Yes, spider mites are very tiny. You need it in general, especially if you've never seen them before, you need at least a 10 power lens to see them. If they're plant feeders, they're kind of just sitting there. They have little fat little bodies and eight legs but there can be a stage in some of them where they only have six legs, that's part of their maturation process. And they are sort of rasping sucking insects. And so the plants that they're attacking have the symptom of what’s called stippling. It's little yellow dots all over the leaves. And so that would be an indication that you have a mite that is making a web. And only some spider mites make webs not just a regular spider, and the webs aren't going to be huge. if you have a huge population that can extend long distances, but the silks are closer together than they are in a regular spider's web.
Farmer Fred 5:31
They reproduce rather rapidly, too, when the weather is conducive to it. Probably 70-80 degree weather, and spider mites can develop into adults within 10 days. And at that point, they're ready to reproduce. A female spider mite can lay 60 eggs, which will produce 10 male and 50 Female mites. those 50 Female mites will then lay 60 eggs each, which means that the next generation will comprise 2500 females, each of which will lay 60 eggs in under two weeks. So that brings the population to 150,000. Just like that, right?
Debbie Flower 6:07
So you can see why using an insecticide that kills other predators of theirs, besides the predatory spider mites, that we haven't talked about yet, right?
Farmer Fred 6:17
Yes, exactly. And there are some predatory spider mites available. As long as you can identify exactly which variety which species of spider mite you have that's causing the problem, right. And so for that, you need a good reference with a lot of great pictures of different spider mites. And you probably need a pretty good hand lens to see them.
Debbie Flower 6:38
Yeah, or you take a leaf with the mites on it in a plastic bag, take the whole leaf, maybe even take the stem with several leaves on it. A friend of ours used to say to take a sample the size of a piece of letter paper, put it in a plastic bags, Ziploc bag, something that's closed, so they can't get out and go to your Cooperative Extension office and ask for somebody to look at it. They should have a dissecting scope, which is really cool instrument, it magnifies much bigger than a hand lens does. But hand lenses will do it too if they know what they're looking for.
Farmer Fred 7:15
I'm thinking about high school biology, frogs now. We're looking at onions, we looked at onions, cross sections of onions underneath those microscopes.
Debbie Flower 7:25
I love looking at insects under them, especially the small ones. You see things you just don't see otherwise.
Farmer Fred 7:31
How do you know if it is a spider mite problem? You could take a piece of white letter paper and hold it under the plant, shake the plant, and look carefully at the black dots, if there are any, on the white piece of paper, hold it horizontally. And if they start to move, it’s probably spider mites.
Debbie Flower 7:49
You could already have predators, although with the population you have, you may want to accelerate that process. But in all cases, and “all” is a bad word to use in horticulture, but when we're using predatory insects to control plant eating insects, the plant eating insects sit still, because they're eating the plant. The predatory insects run around. So if you look at the back of a leaf and you see a whole bunch of spots and they're sitting there then that may be the plant eating insect. If there's somebody running around, then that may be the predatory insect.
Farmer Fred 8:25
Predatory mites go after spider mites, gall midges go after spider mites, green Lacewings and other predatory bugs go after spider mites.
Debbie Flower 8:33
Right. So you can see why use of an insecticide would increase the population of spider mites that eat plants, because you've gotten rid of all of those other insects.
Farmer Fred 8:43
Which brings us back to, don't assume anything about a insecticide label. Make sure the pest you're trying to control is listed on that chemical control product label to control spider mites. It needs to be a miticide.
Debbie Flower 9:01
Miticide, right. She asked about neem oil or insecticidal soap, and those aren't specifically miticides, but they work by harming the insects’ ability to live.
Farmer Fred 9:13
But that's true of any insect that comes in contact with neem oil, right?
Debbie Flower 9:16
Right, that's more of a blanket control. It's not a specific insecticides. There are insecticides and there are miticides. And that's the other word you need to look for. If you're trying to kill mites and a neem oil can do it. But you have to touch them. That goes back to getting to the bottom of the leaf, the back of the leaf so to speak, because that's where they hang out and the insecticidal soap would be the same.
Farmer Fred 9:40
It's a probably a good idea and I used to do this, is to buy a hand sprayer that you pump up. It has a wand that has a 90 degree bend in it. And maybe if you have a regular problem with spider mites, you basically put just plain water in there, and go around your garden. And turning it so that that 90 degree bend of the nozzle is facing upwards, get underneath the leaves, and wash off the leaves thoroughly.
Debbie Flower 10:08
For those of you who don't have the big problem, but maybe growing a melon or cucumber, pumpkin, something like that the end of the season, look at the back of those leaves, you're likely to find it's great for teaching pest ID, you're likely to find a mite on the back there. It can be a whole science lesson. Use a 10 power lens and look at the back of those leaves.
Farmer Fred 10:30
something fun for the kids at home before you throw out that old vegetable plant, shake off the leaves and see what you find.
Debbie Flower 10:37
Yeah, see what moves at the end of the season. And it's because the plant is stressed, it's pretty much done. It's nothing to worry about. It's nothing to treat at that point. But it sure is a good way to look at insects and mites. The other is to prune so that the plant is open and the predatory insects that do exist naturally can get in to find the mites and consume them.
Farmer Fred 11:12
So again, when you want to plant, don't construct a jungle, go by the recommended spacing instructions for whatever you're planting. Don't try to bunch of a lot of plants together because you're cutting down the air circulation, which could lead to a lot of other problems as well. Yep, one thing we didn't say overtly and we should say overtly: clean up your garden, at the end of the season, get rid of it. But I don't even think you put it in the compost.
Debbie Flower 11:38
If it's a hot compost, yes. Meaning that you turn it regularly, check the moisture, it gets to 140 degrees in the center, then that will kill these things, their eggs and everything. But if it's not, if you just throw it in a pile and walk away, then no, you don't want to put the diseased things in there or insect infested things in there.
Farmer Fred 11:55
And there are places online where you can find predatory mites that again are very specific and only go after certain mites. So you need to know who the problem child is before you bring in some other kids do a deal with them. And we'll have links online to some places where you can find predatory mites.
Debbie Flower 12:13
I have used them in a greenhouse and they work great. But you got to know, you got to follow the directions, there will be temperature issues. You can only release during certain temperatures, certain humidities and when the population of the bad mites is at a certain level. And you have to do it regularly. So it's not like you put it out there and walk away. You have to dedicate some time and effort to it.
Farmer Fred 12:36
Debbie Downer again.
Debbie Flower 12:39
Making work. That stuff's fun!
Farmer Fred 12:41
All right, Debbie Flower. Thanks for looking at the spider mites with us.
Debbie Flower 12:45
Oh my pleasure, Fred.
Farmer Fred 12:51
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Farmer Fred 14:44
We like to answer your garden questions here on the Garden Basics podcast. Debbie Flower, America's favorite retired college horticultural professor, is here. And we got an email sent to Fred at farmerfred.com from Robert in Lodi. And I must commend Robert for formatting his email to look just like a letter should look, the way you were taught in sixth grade, decades ago. It’s perfect Robert, thank you. He says, “Hello farmer Fred. I live in Lodi, which is in California. By the way. Six years ago we planted two apple trees, one is a Fuji, one is a Pink Lady. The trunk of the Fuji is about five inches in diameter and is about 12 feet tall. The trunk of the Pink Lady is about four inches diameter and about 12 feet tall as well. Every year, new growth extends from the tips of the branches, then that new growth dies back a foot or so. The Pink Lady had more of these died back branches than the Fuji, perhaps 20 Die backs to the Fujis eight. Do you know what causes this problem? I can attach a photograph if you like.” Robert, we may not need a photograph if your answer to this question is: does it look like somebody took a blowtorch to those tips? If so, Debbie? What blowtorch would that be?
Debbie Flower 15:56
A blowtorch, except one that didn't burn the leaves? Fireblight.
Farmer Fred 16:00
Yeah, that is what we suspect. And that's a bacteria isn't it?
Debbie Flower 16:06
It is. it's carried by the pollinator, the bee, from an already infected plant to other susceptible hosts which include apples and pears. Loquat and cotoneaster. Yes, some ornamentals as well , photinia. It's called pomacious members of the rose family. They are the susceptible hosts and a pome, P-O- M-E, has that internal structure of the seed cavities, it's multiple seed cavities. My mother used to always ask me if I wanted my apples cut in stars, because if you cut across an apple, you expose those five cavities that have seeds, and it looks like a star in the middle of the apple. It isn't always five. But that's the pome, it has that structure in the center with each seed and in a little space of its own. So the plants we mentioned are pomes, and those are the only plants susceptible to fireblight. It's been tried and tried and tried again to transmit Fireblight through pruning wounds or injecting the plant with the bacterium. And it has never taken. So it is brought just by the pollinator from an already infected tree to your tree. And so you see the flowers and then they die back, and the leaves remain attached because the disease attacks so quickly, that they don't have time to fall off. And the easiest cure is to go through and cut the dead tips out plus six inches, at least six inches, of the healthy wood. That's because the bacterium is no longer in the dead part. It can't eat anything there, it's dead. It's moving into the green part. And you want to go six inches into the still-healthy green stem and remove it, so that you are for sure getting all of the bacteria out of the plant and then dispose of those cuts.
Farmer Fred 17:57
This is another good reason why we like to promote backyard orchard culture of your fruit trees on this program. Are you keeping the tree at a maximum height of six or seven feet? Because in the case of apples, you get Fireblight. Do you really want to get on a ladder and climb up 12 feet or so? No, you want to stand on the ground. So if your tree is only six or seven feet, you can control that Fireblight much easier and much more safely from ground level. And again, you want to make that cut well below where you see the dieback, six inches or 12 inches. The old recommendations used to include after each cut of an infected branch, dip your shears into bleach.
Debbie Flower 18:39
It did, but then I can't remember his name at Berkeley, who did these experiments. And other people did as well, trying to infect the plant with pruning shears or with a hypodermic needle even in some cases and they could not get the plant to get the disease so it appears it cannot be transmitted that way.
Farmer Fred 19:00
And by the way, don't ever dip your pruners into bleach because all it does is promotes rust. Yes, really. So no, you can clean them off with a rag if you want. But basically, if you make that cut six to 12 inches below where you see the damaged portions, and then what's important ,too, is cleanup getting rid of all the fallen parts that are infected . And probably ,Robert, you've seen around the tree, those parts on the ground. Just get them up, put them in the trash whenever you see them, and keep the area clean. this may involve replacing mulch that you may have underneath the tree as well. Because the winter rains can splash those spores or bacteria back up into the new growth.
Debbie Flower 19:43
Yeah, there is some talk that there are other things that can cause Fireblight to spread. That includes anything that causes fast growth in the plant.
Farmer Fred 19:53
like nitrogen fertilizer.
Debbie Flower 19:56
yes, yes. It sounds to me like they had the disease last year, Correct? Every year, the new growth extends from the tips that new growth dies back a foot or so.
Farmer Fred 20:06
Every year for the last six years.
Debbie Flower 20:11
okay, so it is in the system of the plant and you may see what are called cankers on stems and other places. Cankers look wet, maybe there are sunken parts on the branch. Those are probably due to Fireblight as well. So you would want to cut those out and make sure you're doing your copper sprays or Bordeaux spray, it is recommended that you make sure it gets all of its other pest control treatments.
Farmer Fred 20:40
Would an oil spray be effective in the wintertime?
Debbie Flower 20:43
No. It wouldn't hurt for other reasons. Yeah. When there's no leaves on the plant, you know, aphid control, that kind of thing.
Farmer Fred 20:50
But again, that would be a winter time. Application. Not in the summer. No,
Debbie Flower 20:55
these are not summer sprays. These are winter sprays.
Farmer Fred 20:56
Exactly. And I would suspect, Robert , that either you or one of your neighbors has some plants, too, that are getting infected by Fireblight
Debbie Flower 21:05
It came from somewhere. Bees can fly quite a distance. My neighbor has it in a Loquat. And I gave her the advice and she has done nothing about it. And I have apples so I'm making sure my apple stays very short. And I go out as soon as the bloom is there, and then go out daily or every second day to watch to see if those flowers die back and you get this scorching look of a black stem with a brown leaf still attached. I have not seen it, but boy, you can be sure if I see it, I will take it out immediately because that's the easiest way to control the disease in the long run.
Farmer Fred 21:39
It is most noticeable in the summertime when those branches stand out. That's burnt branches, but the actual process begins in the spring. Yes, so young. It's Fireblight. Be on the lookout for it, Robert. Debbie Flower, thanks so much.
Debbie Flower 21:53
You're welcome Fred.
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Farmer Fred 22:03
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BEYOND THE GARDEN BASICS NEWSLETTER
Farmer Fred 23:11
On Friday’s Beyond The Garden Basics Newsletter and podcast, we get your nose twitching. Garden shows for the nose. Plants with enticing aromas. It could be the flowers, it could be the leaves. There are plenty to choose from. Plus, we explain why familiar scents immediately transport us back in time to recall hopefully fond memories from years ago. It’s the way the nose is wired to the brain, which takes a different pathway than our other senses. It’s in the next Beyond the Garden Basics newsletter. It’s out Friday, July 15th. Find a link to it in today’s show notes, or visit our website, Garden Basics dot net, where you can sign up to have the free Beyond the Garden Basics newsletter delivered to your inbox each Friday. Also at Garden Basics dot net, you can listen to any of our previous editions of the podcast, as well as read a transcript of the podcast episode you are listening to now. That’s at Garden Basics dot net. For current subscribers, look for the Beyond the Garden Basics newsletter on Friday, July 15th in your email. Take a deeper dive into gardening, with the Beyond the Garden Basics newsletter. And it’s free. Find the link at garden basics dot net.
Farmer Fred 24:23
Garden Basics With Farmer Fred comes out every Tuesday and Friday and is brought to you by Smart Pots and Dave Wilson Nursery. Garden Basics is available wherever podcasts are handed out. For more information about the podcast, visit our website, GardenBasics dot net. That’s where you can find out about the free, Garden Basics newsletter, Beyond the Basics. And thank you so much for listening.