Effectiveness of Low-Risk Pesticides on Powdery Mildew and Leaf Spot Disease and Cranberry Leaf Mulch for Weed Suppression

Please click on the link below to see to the pdf version of the research trial results.

2011-13 CFGW powdery mildew factsheet

2013 UW-WMARS Annual Flower Evaluations

The 2013 season is over and the results of our annual flower trials have been compiled. This year we conducted evaluations on 182 flower cultivars in our general trial and an additional 85 cultivars within our CFGW (Commercial Flower Growers of Wisconsin) trial. Starting in July we conducted evaluations a total of three times, approximately one month apart.  This data is used by seed companies, commercial greenhouse growers, and the public to better select varieties that will succeed in our region of the world. We thank all participants including student evaluators Deanna Delfosse and Rachel Peters.

2013 UW-WMARS Flower Trial

2013 CFGW Flower Trial

Fungal Friends or Fungal Foes III: Fungal Pathogens that Produce Sclerotia

What is a Sclerotium?

While many fungi create spores sexually or asexually that may persist and overwinter in the soil, some fungi ensure their survival further by making specialized structures such as a sclerotium. In general, a sclerotium is composed of a hardened mass of mycelium covered by a “rind”. As denoted above, a sclerotium is used a means for the fungus to survive for a long period of time during harsh environmental conditions. Its contents provide food reserves that allow the sclerotium to germinate and release spores when conditions are favorable.

Sclerotia-Creating Fungal Families Found at WMARS:

Sclerotinia sp. of the Sclerotiniaceae:

This fungal pathogen was found by one of the interns who specializes in ornamental horticulture while she was evaluating our petunia bed. Responsible for a condition called Crown Rot of Petunias, a brittle necrotic stem was the initial symptom that gave away this pathogen’s residence. When cut open, the stem revealed a couple of tiny sclerotia.

This disease starts when either a spore germinates on the foliage of the plant or hyphael strands enter the plant through its roots. At some point, during the time of the fungal infestation, the fungus produces its sclerotia (this logically is more likely to happen closer to the end of the season when survival is less guaranteed). Unless the infected tissue is removed, the sclerotia, at this point, are opportunistically positioned to germinate during the following season (or later seasons if the immediate one is non-conducive) and will either create active hyphae or give rise to apothecial fruiting bodies that release ascospores.  Because our plants were well established, the fungus failed to take down the whole petunia plant, yet for petunia victims that are young and lack lateral branches, this disease could be devastating.

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Want to learn more information about the effects that Crown Rot has on petunias? Click the link below to watch a video that goes into further detail about this fungus, its life cycle, how to control it, etc.:

Petunias vs. Sclerotinia

Claviceps sp. of the Claviceptaceae:

I happened to come upon this fungus while observing plants in our Native Pollinator bed on the west end of the display garden. It was exciting to find these perfect specimens “blooming” from the panicle or head of the plant where seeds normally would be present. When diagnosed, this disease is referred to as “Ergot”. While the condition produced by this fungus should not be a worry to most home gardeners, species of claviceps are important to note because of the effect they have on cereal crops and the pathological conditions its sclerotia may have on human health if left unmonitored. When contaminated flour (usually rye) is produced from infected grains and a hazardous amount is consumed by a person, that person could take on a disease commonly known as Ergotism or St. Anthoney’s Fire. Essentially, the mycotoxins released from the sclerotia induce a halucinogenic state of madness in the victim. In addition to its psychological effects, it may induce muscular convulsions and gangrene which could lead to vasoconstrictions that ultimately could call for the amputation of digits or worse, limbs of the body. Because ergot is an agricultural disease and does not present itself as a big issue to the common horticulturalist, I will not go into much further detail about how to control it. Hopefully, this additional example of a sclerotia creating fungus has added some interesting trivia to your day!

Alas, I apologize, but I cannot resist telling you more about this pathogen! It is so fascinating! Below is a picture of sclerotia of Claviceps sp. that initially infected the ovaries of these grasses. It uses the plants vascular system to receive sugars so it can continue to develop until the sclerotium is fully mature. At this point, like the Sclerotiniaceae, the sclerotium may stay dormant for a long period of time until conditions become conducive to germination. When Claviceps sp. germinates, it produces a structure called a stroma, bearing ascospores that will continue its disease cycle.

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Madeline Wimmer WMARS Intern

Insect of the Week

This week we’ll be talking about one of this author’s favorite pests of the gardens, the Tomato Hornworm (Manduca quinquemaculata). The image below shows a particularly large specimen that showed up in our gardens this week.

IMG_0411Named “Hornworm” for the horn-shaped feature on its posterior, the Tomato Hornworm appears in most gardens in mid to late summer, feeding voraciously on tomato foliage. As the size of the worm suggests, a single Tomato Hornworm is capable of consuming a sizable amount of foliage in its larval stage – up to four times its own body weight in a single day!

Adult Hornworms emerge after overwintering as pupae around late June. The adults mate and lay pale green, sphere-shaped eggs singly on the undersides of tomato foliage. After hatching, larvae feed and grow in size constantly for around a month. At this point the larvae, having reached full size, will drop from the plant and pupate in the soil. This pupae then serves as the overwintering phase of the lifecycle, emerging as an adult the following year. For this reason, there is only one  generation per year for this species.

Understandably, you might believe that the Tomato Hornworm is a serious threat to your garden based on its size – this however, is not often true. Because of their size, Hornworms are easily noticed and pulled off of plants by hand. They are also controlled very effectively by natural predators, particularly parasitic wasps. Depending on the species of parasitoid wasp, either eggs or larvae are attacked. This predation effectively keeps the populations of Hornworms in check in most situations. For this reason, the Tomato Hornworm is not typically viewed as an economical threat by most growers. To control this pest, simply scout your tomatoes regularly and remove any you may discover.

If you don’t feel like killing the ones you find, Hornworms make excellent short-term pets or science projects for children or interested adults! Simply place your captured Hornworm in a nice large glass jar with some holes in the lid and a few tomato leaves. Your kids (or you, if you love insects) will love the speed at which these beautiful caterpillars eat and grow in size. It’s a great learning opportunity, and a nice alternative for everyone (including the Hornworm).

If you feel like reading more about Tomato Hornworms, here’s a hyperlink for the UW-Madison Extension page on them! Happy reading: http://hort.uwex.edu/articles/hornworms

As always, thanks for reading! Until next week, happy Hornworm hunting!

-Dave Schreiner, WMARS Intern

Culinary Creations from the Garden

Pak Choi

Scientifically classified as Brassica rapa ssp. chinensis, Pak choi is generally grouped together with a few other B. rapa subspecies referred to as “Chinese Cabbage”. Pak choi (often spelt as Bok choy, Pak choy, or Bok choi) was transliterated from the Cantonese word for “white vegetable”. Like many other Brassica plants, pak choi, is a biennial plant (a biennial plant grows vegetatively for one season and then flowers and sets fruit the following season) that is grown as an annual from seed and cultivated during its vegetative year.Gardeners who adore pak choi for its culinary uses often prefer to harvest the plant when it is small and tender (approximately 6 inches tall or shorter), yet I used larger plants for my recipe and they were still detectably delectable!

Miso Soup with Pak Choi and Tofu

Ingredients:

1/2 Block Tofu

1 Large Head or 2 Smaller Heads Pak Choi

1/2 Cup Onion

1/2 Cup Basil

1 Medium-Sized Carrot

2 1/2- 3 Tbsp Miso Paste of Choice

2 Cloves Garlic

1 Ginger Piece Sliced Thin

1 Tbsp Grapeseed Oil

Approx. 1 Tbsp Tamari Soy Sauce

2-3 Cups Water

Note: Mushrooms would make an awesome addition to this dish. If you choose to use some sliced crimini mushrooms, toss them to the the cooking pan at the same time as the onions.

pak choi ingredients

Preparation:

Combine coarsely chopped basil with peeled garlic and ginger into one bowl and set aside. Cube tofu and place cubes on a clean kitchen towel. Press tofu with towel in order to squeeze out excess moisture (this allows the tofu to fry up quicker and take-on a crispier texture). Chop of the root and the very bottom of the pak choi in order to free the leaves. Diagonally Slice each leaf (including its stalk/petiole) of pak choi into two or three pieces. The carrot can be thinly sliced with a knife or a mandolin and combined with the pak choi into a bowl separate from the other ingredients.

Cooking Instructions:

1. Briefly fry basil, garlic, and ginger in grapeseed oil until the basil wilts.

2. Move basil to the side of the frying pan or cooking pot to make room for tofu.

pak choi basil starting

3. Add cube tofu to pan and drizzle tamari soy sauce over tofu. Cook for about one minute and allow tofu to gather up a “crust” on one side before flipping it over.

pak choi tofu starting

4. Add chopped onion to the pan and continue to fry tofu until golden brown on each side.

pak choi tofu cooking

5. Add carrots and pak choi plus two Tbsp water. Cover frying pan/ soup pot with a lid and allow the vegetables to steam for one minute.

pak choi almost final

6. Add two cups of water or enough water to almost cover ingredients in the pan.

7. Allow vegetables to simmer in the water until tender.

8. Turn off the stove top burner and mix in miso paste.

9. Keep soup covered for about one minute more.

10. Gently stir soup and serve.

Pak choi soup final

Final Dish Serves 2-3 Portions.

-Madeline Wimmer, WMARS  Intern

Insect of the Week

Hey insect fans! This week we’ll be talking about the Spotted Cucumber Beetle (Diabrotica undecimpunctata), a pest of cucurbit crops that made its first appearance in the gardens this past week. (pictured below – our apologies for the small picture, this guy was FAST)

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The Spotted Cucumber Beetle is a coleopteran pest of cucurbit crops, feeding on plants in this group during both the larval and adult stages of its life cycle. As a larvae, this insect feeds on roots and shoots of growing cucurbits. As an adult, it feeds on leaves, flowers, and fruit.

The primary damage caused by this insect is not its consumption of plant material, however. Cucumber beetles carry bacteria that cause vascular wilt, and transfer them to cucurbit crops through feeding damage and fecal contamination. Vascular wilt, once established in the plant, cannot be cured and quickly causes the infected plant to wilt and die. This bacterial disease plugs up vascular tissue inside plants, blocking the flow of water and nutrients. This  blockage is what causes the initial “wilty” appearance, and is ultimately the cause of death in the plant.

Because of the severity of the problem caused by vascular wilt, it is important to scout frequently for Spotted Cucumber Beetle if you are growing cucurbit crops. If you see wilted sections of vine, it is also wise to make sure that vascular wilt is to blame for the problem. To test for vascular wilt, slice the stem of the affected plant and hold the two ends together for a few seconds. After holding the two halves together, pull them slowly apart and look for a milky, viscous sap stretching between the two ends. If this  milky sap is present, the plant has vascular wilt.

Many chemical and cultural controls are available for the control of Spotted Cucumber Beetle, but they are very diverse and highly dependent on the situation. For this reason, we’re including the link to the UW Extension page on the cucumber beetle so that you can find more detailed information if needed. Here’s the hyperlink: http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CDAQFjAB&url=http%3A%2F%2Fadams.uwex.edu%2Ffiles%2F2013%2F05%2FCucumber-Beetles.pdf&ei=wlboUfOrKcO1rgGdr4DwCQ&usg=AFQjCNExHH0uA0QZlChftDBntDcdqZuORg&bvm=bv.49478099,d.aWM

Thanks much for reading! Tune in again next week!

-Dave Schreiner, WMARS Intern

Fungal Friends or Fungal Foes II: One Last Note About Our Peonies…

Erysiphaceae:

After cutting back our peonies a few weeks ago, we started to notice a sprinkled crystal-like pattern webbing across the leaves of our plants. It was clear that these signs were a signature of a fungal pathogen, from the family Erysiphaceae, commonly known as “powdery mildew”. Referencing the University of Minnesota’s Extension website, the most common powdery mildew species found on peonies is Erysiphe polygoni. The webbing is a part of the fungal body, made up of hyphal threads, known as a mycelium. While the mycelium could potentially interfere with photosynthesis and eventually lead to yellowing of the leaves and leaf drop, it usually does not kill a peony plant. In spite of this however, it still may be an aesthetic turn-off to peony growers.

A picture of an infected peony leaf:

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Eventually, many of our plants looked like this:

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Comparing and Contrasting Powdery Mildew from Downy Mildew:

The pathogen being discussed, powdery mildew, could easily be misheard and mistaken as a completely unrelated pathogen known as “downy mildew”. Don’t let this confuse you, as there are clear biological and habitual differences that separate the two.

Biology…

First of all, even though they are both commonly known as “mildew”, powdery mildew is a true fungal pathogen and downy mildew is a part of a clade, known as the stramenopila, under the class Oomycota and a part of the family Peronosporaceae. While many common gardeners may not be familiar with this class, most people have heard of the epic Irish Potato Famine, which was caused by the Oomycete species, Phytophthora infestans. Biologically, Oomycetes are distinguished from fungi as they are diploid organisms  that have cellulose based cell walls (cellulose is what makes up a plants cell wall) and produce mobile spores that move via two flagella (flagella are small tail-like projections that help an organism orient itself and move through liquid mediums). In contrast, fungi are generally either haploid or dikaryotic organisms, that have cells walls generally composed of chitin, and produce reproductive spores with a single flagellum if the spores have one at all.

Weather Conditions…

Both downy mildew and powdery mildew love humid environments, so planting in a well ventilated area or pruning plants in order to increase air flow throughout the vegetative canopy may help prevent such disease infestations. Where the pathogenic preferences start to diverge is the temperature of the environment. Downy mildew, along with many other Oomycetes, generally thrive in cool damp conditions with visual water present in order to aid the dispersal of its spores. Powdery mildew spores (asexual) are spread by the wind, in which a heavy rain could potentially prevent its spores from spreading.

Signs:

Early signs of powdery mildew look very different than that of down mildew.

Above: signs of downy mildew (left) and powdery mildew (right) on grape leaves.       images from: http://djsgrowers.blogspot.com/2010_11_01_archive.html

Controlling Powdery Mildew:

If you dislike the look of the powdery mildew dusted leaves or happen to notice that your plants look a little sad, you may choose to control the pathogen with a simple home-made remedy spray. There are many recipes that include a combination of  ingredients such as various vegetable oils, baking soda, compost tea, and even milk! In one of our research greenhouses at the University of Wisconsin Madison, powdery mildew if commonly found on cucumber plants grown by researchers.  The greenhouse staff often uses canola oil when signs first appear and switch to using sulfur when conditions become more severe. Whatever solution you choose to use on your plants, it is recommended to alternate between different solutions as to prevent the pathogen from becoming resistant to the treatment.

Powdery mildews create both asexual spores throughout the season and sexual spores at the end of the season.  In order to prevent future problems with powder mildew, remove clutter and fallen vegetative debris from the ground.

Note: Powdery mildew sexual fruiting bodies are a special type of fungal fruiting body known as a chasmothecium and are used to scientifically identify and distinguish different species from each other.                                                                                                                image  from: http://ncsupdicblog.blogspot.com

One final message…

Both powdery mildew and downy mildew families have a wide host range and may economically affect the viability of a grower’s crop on plants like grapes vines and cut flowers. Yet, you may be relieved to know that each separate species of powdery mildew is host specific. Meaning, if you find powdery mildew on your peonies, it will NOT move to your roses or any other plants in your garden. If you happen to find powdery mildew on two different types of plants, it is most likely that they are different species.  Finally, if we find either of these pathogens in our grape vineyard here at WMARS, we’ll be sure to post a blog about that too!

-Madeline Wimmer, WMARS Intern

Insects of the Week

Insects of the Week is back! The short work week of the 4th last week pushed us a bit behind, but we’re back up and running, and we’ve got a great spread of pests  to show off this week.

Because of the very large influx of insects over the past week or two, we’re going to show off pictures of our current array of pests and the damage they cause, so the post is going to be a bit image heavy. We’ll go back and talk about some in more detail as the summer goes on and the number of new arrivals decreases. Because of the large amount of information, we’re also attaching hyperlinks to University Extension sites on these pests for more information.

Today we’re going to show off images of Squash Vine Borer, Cabbage Looper, Squash Bug, and Grape Phylloxera. Each of these pests presents its own range of difficulties and  control strategies. As you read on, keep in mind that in order to spot these insects in your homes and gardens, it is important to regularly scout your plants. Many pests will only be discovered with dedicated and regular searching.

Up first: Squash Vine Borer (Melittia cucurbitae), shown below. Look for these flashy pests on the stems of your cucurbit crops, as this is where they lay eggs.

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Eggs pictured below (the two circular orange spots on the leaf stalk). We have had to go through our trial beds and scrape as many of these off as possible.

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Here’s the UW Extension link to Squash Vine Borer: http://adams.uwex.edu/files/2013/05/Squash-Vine-Borer.pdf

Below is an image of a Cabbage Looper larvae (Trichoplusia ni). Look for these larvae on the undersides of foliage of your cole-crops. You will typically see holes in your foliage, and often greenish pellets of frass (insect excrement).

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And the damage caused to cole-crops.

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Here’s the hyperlink to the extension page on Cabbage Looper: http://hort.uwex.edu/articles/cabbage-looper

Squash Bug (Anasa tristis), shown below. Squash Bugs often assemble in very large numbers on cucurbit crops, and can cause serious blight issues when present.

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Here’s the hyperlink to the University’s extension page on Squash Bug: http://hort.uwex.edu/articles/squash-bug

This is a grape leaf with Grape Pylloxera (Daktulosphaira vitifoliae), galls shown below.

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Here’s the hyperlink to  the University’s extension page on Grape Phylloxera: http://door.uwex.edu/files/2010/10/IPMReportweek71910.pdf

Again, we’ll go back and talk about many of these in more detail later. Thanks for reading, and keep an eye out for all of these on your plants! And please enjoy the extension material.

-Dave Schreiner, WMARS Intern

Jammin’ With Service Berries…

Although various species of this woody perennial are technically classified as under the genus Amelanchier, they seem to have as many common names as they have berries! Ok… so maybe that’s a bit of an exaggeration. However, if you find yourself confused when a person asks you to taste test between Juneberry, Saskatoon, and  Serviceberry Jam, don’t be- they might all taste the same because they are, in fact, the same berry!

Serviceberries are commonly found in our area scattered around neighborhoods as ornamental plants, or growing as low-slung shrubs in the open woods. They are often mistaken for a variety of crabapple due to the apparent similarity in the appearance of the fruit and foliage. With a little practice however, it is easy to tell these delicious fruits apart from the sour and typically unusable ornamental crabapple.

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Don’t let the multiple names or initial ID confusion intimidate you. Serviceberries are well worth your effort, as they can be cooked in a number of wonderful ways including jam, pie, sauces, and more. The serviceberries out at WMARS were in full season this past week, and we tried out our jam making capabilities with delicious results. Here’s an intern taste-test picture:

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Serviceberries are extremely common, easy to cook with, and a lot of fun to eat. Get outside in your neighborhood or woodlot this weekend and try to find some of your own! Happy picking!

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– Madeline Wimmer and Dave Schreiner, WMARS Interns

Fungal Friends or Fungal Foes?

What do you imagine when you hear the word “fungus”? Do you think of the classic red-capped mushroom with white dots on its pileus (a pileus is the scientific word for a mushroom’s cap)? Or, perhaps  you imagine opening up your fridge to enjoy some juicy sweet strawberries, only to be let down by a white “fuzz” that somehow seemed to appear overnight. Either way, it’s important to emphasize the plethora of ecological roles fungi take on, including decomposition (saprophytic fungi), plant and human parasitic and/or pathogenic lifestyles, fermentation of various food products, and the creation of symbiotic relationships with plants and algae. Here at West Madison Ag Research Station, we acknowledge some fungi as our friends, yet we are also cautious  of particular groups of fungi that could potentially threaten our fruit and vegetable crops. As these blog posts come out, we hope that they will not only help you identify different fungal diseases on your crops, but that they increase your overall appreciation of fungi and their morphological and habitual diversity.

Nidulariaceae:

This week, we’ve chosen to highlight a fungal family that is neither beneficial nor harmful to our plants. In fact, we found its fruiting body (a physical structure that produces spores as a means of reproduction) growing on the wood chips used to mulch our grape vines.

The family Nidulariaceae, commonly known as the “Bird’s Nest Fungus” are saprophytes, meaning that they consume and break down dead organic matter. When observing the basidiocarps (a specific type of fruiting body), of the Nidulariaceae, it’s easy to see how this family got its name. The small spore packets at the bottom of its “nest” (technically known as a peridium) look like tiny eggs. Rain will eventually splash the spore packets away from the fruiting body, thus dispersing the spores.

Below is a picture of the fruiting bodies of a particular genus of the Nidulariaceae family (we unprofessionally identify it as the genus Cyathus). The white poofs are immature fruiting bodies. As the structure matures, the top of the basidiocarp dehisces and pulls away, revealing a few spore packets within.

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More fruiting bodies…

IMG_0195-Madeline Wimmer, WMARS Intern