Brian Hudelson, Extension Plant Disease Specialist
Director of the Plant Disease Diagnostic Clinic
Department of Plant Pathology
UW-Madison College of Agricultural and Life Sciences
Total Time: 5:04
0:16 — What should we be concerned about?
1:22 — Any lasting effects from the cold snap?
1:49 — Diseases of the season, Insects
3:28 — Healthy plant practices
4:21 — What is Brian planting?
4:50 — Lead out
Adam Wigger: “Keeping your plants healthy”. We’re talking today with Brian Hudelson, Extension Plant Disease Specialist and Director of the Plant Disease Diagnostic Clinic, University of Wisconsin-Madison, Department of Plant Pathology, Division of Extension and the College of Agricultural and Life Sciences and I’m Adam Wigger. Brian, after this last season’s cold snap, and the extremely cold winter we had, what should we be concerned about with our plants?
Brian Hudelson: Yeah, one of the things that I’ve been seeing quite a bit of, particularly on evergreens, is a lot of die back from the winter temperatures. So some of it is just physical cold injury from that cold period we had in late January. Some of it could be dehydration if the plants did not have enough water stored internally. Going into the wintertime, plants can actually dry out. We tend to see that a lot on ewes and boxwood shrubs, those sorts of things. But a lot of different types of conifers are showing a browning of their needles and that’s probably a result of some of the really bad winter weather we experience. And in some of our deciduous trees and shrubs, the ones that leaf out in the spring, we did see some death and destruction from that cold-snap we had at the end of April, so things started to leaf out, we got cold temperatures, and unfortunately it got cold enough to kill off the leaves that came out. The fortunate part is that most trees and shrubs have a second set of buds, so they will re-leaf, and by the middle of the growing season, we won’t notice that there’s been this cold injury in April.
Adam Wigger: So will we see any lasting effects from that or will it really just be early on in the season.
Brian Hudelson: Typically it’s fairly innocuous. What can happen, if its relatively severe, it does take energy from the tree to produce that second set of leaves, so it may stunt the trees a little bit but it probably won’t be particularly noticeable. If we had several years where the same thing happened over and over again, then you might see some real severe effects on the trees but I expect it to be pretty transient if it only happens this year.
Adam Wigger: Are there any diseases or concerns that we should be worried about now that it’s getting warmer, now that we’re seeing more insects?
Brian Hudelson: Yeah one of the things I’ve been seeing and got some samples from are what are called gymnosporangium rust, that sounds like a big word, but there are three common ones that we see here in Wisconsin. There’s what’s called cedar apple rust, cedar hawthorn rust, and cedar quince rust. And they’re all very visual diseases. If you grow junipers at all, particularly red cedar, which is a type of juniper, you may start to see these large, gelatinous orange blobs that will form on the branches, that’s actually a fungal reproductive structure. So those orange blobs are producing spores, and they don’t reinfect the junipers where they’re produced, they actually infect another host. It’s rosaceous types of plants – woody trees and shrubs like crabapples, apples, and hawthorn. So what you will see later on in the growing season on the hosts, are discrete yellow or orange spots on the leaves, or if you have certain types of hawthorn, and you have cedar quince rust that’s causing the problem, you’ll see kind of spiny, kind of salmon colored fruit, that are again, very visual, and then there are spores produced on those hosts that will reinfect the juniper so the fungus bounces back between the hosts to complete its life cycle. But the really visual stuff is right now, where you see the orange, marmalade-like masses on the branches. From a disease standpoint, where we do see insects involved in moving disease causing organisms around, a lot of the virus pathogens on plants can be insect transmitted. So things like aphids, or in greenhouse settings there’s a little insect called thrips that will move these viruses from plant to plant and as they feed they drop the virus off and then the plant becomes infected.
Adam Wigger: What can we do to keep our plants healthy?
Brian Hudelson: Basically, good watering, good fertility, starting off with healthy plants that you bring home from the garden center. So make sure you’re inspecting those plants for any symptoms. If you take a look at the leaves and you see any kind of fuzzy growth on the leaf surface, particularly on the undersurface of the leaves, that can be an indication of certain types of diseases – you don’t want to buy those. And then other things when you get them home, definitely good plant spacing is important, if you crowd things too much, the plants tend to get wet and stay wet for a long period of time and that tends to be favorable for a lot of diseases to get established. That also, if you space things out farther apart, also decreases humidity around the plants. One of the more visual diseases that owners clue in on are powdery mildews. Those tend to like really humid conditions, so when we get into the middle of the summer, when its really muggy, that’s when we see a lot of this kind of whitish powdery growth on the leaves, and that’s an example of a powdery mildew.
Adam Wigger: What are you planting this season?
Brian Hudelson: I don’t plant a lot – I do what’s called “Darwinian Gardening,” so I pick plants, I stick them in my yard, and I give them benign neglect and if they survive they were meant to be in my yard. Actually, my yard has been described as the cesspool of pestilence, because I have a lot of diseases and plants in my garden – I use them for teaches classes. If you need certain viruses, I can supply those for you. For me, that’s great because I need materials to teach my students and I can just go into my yard and collect some materials and bring them in for class.
Adam Wigger: Thank you, Brian! We’ve been visiting today with Brian Hudelson, Extension Plant Disease Specialist and Director of the Plant Disease Diagnostic Clinic, University of Wisconsin-Madison, Department of Plant Pathology, Division of Extension and the College of Agricultural and Life Sciences and I’m Adam Wigger.