Yard & Garden Line News Volume 8 Number 11                                                               July 15, 2006

Features this issue: All Those Apples Watch Out For Grasshoppers Keeping Tomato Leaf Spots in Check Garden Calendar Editorial Notes

All Those Apples
Beth Jarvis, Yard & Garden Line

David Bedford Photo credit: Dave Hansen

In two years, the Horticulture Research Center (HRC) will celebrate its 100th anniversary. It all began when Peter Gideon planted a bag of apple seeds. He wanted apples that would grow well in Minnesota. From the resulting seedlings, he selected 'Wealthy'. That selection lead the Minnesota State Horticulture Society to ask the legislature for funds for apple research.

After several false starts, the farm that is now the HRC was purchased in 1907 or 1908. In 1920, the HRC released its first apple--'Minnehaha'. Now, 24 apples later, we have 'SnowSweet' and an upcoming release, currently known as Minnesota 1914.

Has Gideon's dream been realized? David Bedford, fruit breeder at HRC, says that about 80% of the apple cultivars grown by Minnesota orchards are U of M cultivars. Apple breeding, like all plant breeding, is a process of crossing and selecting over a course of years. Bedford says of all the seedlings planted, he discards 3,000-5,000 trees per year from the apple cross pool and identifies about 20 selections per year that will go into advanced testing which can take an additional 15 to 20 years. What takes so long? Growing conditions vary slightly from year to year and location to location so you need to grow the selections for years for inconsistencies, such as those in flavor, fruit quality and yield to become evident. Disease and insect problems are also affected by weather. Bedford takes copious notes of all trial selections in which he evaluates the apples for over 20 critical traits. He laughs when he admits to an occasional "What was I thinking?" when some of the advanced selections begin to show their less desirable traits in subsequent years.

Last March, 'Honeycrisp' was recognized by the Association for University Technology Managers in their "Better World Project" as one of the 25 innovations "That Changed the World.". (See report at: http://www.betterworldproject.net/documents/AUTM BWR.pdf )

Bedford said they were awed to be in the same company as medical and technological breakthroughs such as Google, v-chips for TVs, cochlear implants, and the anti-cancer drug, Taxol, among others.

In the award, 'Honeycrisp' was credited for saving the Midwestern apple business by providing a high demand, high quality fruit for which apple growers can get a premium price. Here, where the growing season is short, apple growers need to get a high price for their crop just to break even.

Mega-producing states such as Washington are stiff competition. Washington 'Red Delicious' has been so over-planted that it's possible to get an apple that's been in storage for over a year! A few years ago, the Washington state legislature passed a law that apples couldn't be stored over 12 months. The growers revolted and the law was changed.

'Red Delicious' starch iodine index

To get an idea how long an apple might have been stored, Bedford advises finding out where it was grown For example New Zealand apples ripen in our spring, so they will be fresh in summer salads, while northern hemisphere-grown apples are from the previous fall's harvest. (Note: Recently, I spotted a sign in my TC grocery advising customers that the "southern hemisphere" apple crop was in.)

Apples don't ripen after they're picked. They simply age. Aromatics don't develop as the starch converts to sugar. Apples that were picked green will never develop the same flavor as those that picked later. So how can you tell if your apple is ripe?? The red color will tell you nothing. Look at the ground color, the non-red part. As the apple ripens, the green turns yellow. For most varieties look for a greenish yellow ground color.

If you want to know how ripe an apple really is, cut it in half and spray it with iodine. Of course, you can't do that in the grocery store. Unripe fruit will turn black from the starch reaction with the iodine. Orchardists carry guides, by cultivar, with photos that illustrate the ripeness based on the iodine test for starch content of the flesh. The least ripe apples are the darkest.

Oddly enough, pressure, measured as pounds per square inch, is also a consideration. The internal pressure of apples is measured with 18-20 pounds per square inch being ideal for a crisp apple. Lower pressure fruit is often offered as the "sale" apples or in bagged fruit.

Honeycrisp Photo credit: Dave Hansen

You and I may buy apples based on crispness and sweetness, but produce buyers often don't. Large and red top the list for wholesale buyers. 'Red Delicious' was originally striped (and from Iowa but over the years, the redder mutation have been selected. Unfortunately, these redder apples lack flavor, as they can be picked at a high starch (unripe) stage with good color. Underdeveloped, immature apples lack juiciness and flavor.

Apple afficionados won't touch a 'Red Delicious' apple. They will sniff and say "it isn't." I admitted that I used to think 'Delicious' was a good apple, 25+ years ago. Bedford pointed out that 50-some years ago, the apple hadn't been "improved" to the point it has today and probably was flavorful.

But, red still rules. Bedford pulled a catalog from a file that offered one red apple cultivar after another and redder and redder selections of each cultivar. The hunt for redder fruit continues. Bedford noted you almost can't find an original, striped 'Gala' any more.

If some apples have been ruined by red, 'Granny Smith' apples have been ruined by green. 'Granny Smith' broke the 'Red Delicious' monopoly on grocery store apples as it was the anthesis, the anti-'Red Delicious' apple. It was green and tart. But, over the last 20 years, they too, have become widely grown and are picked too green. Once flavorful, they've declined to a dense, woody apple. Green apples are easier to ruin because they can be picked immature.

But, 'Granny Smith' did open the door for other, not-solid red apples, such as 'Gala','Braeburn' 'Fuji', and 'Honeycrisp'. Produce buyers would be happy in a red and green world. Twenty five years ago they had three color choices, red, yellow and green and that was enough. Then the striped and variably-shaped apples appeared on the scene. They're still slow to purchase new cultivars but consumer demand prompts grocers to provide more choices in the apple bins. Better stores will cater to that public demand. And, Bedford concludes, "Minnesota grocery stores are better than average."

Watch Out For Grasshoppers
Jeffrey Hahn, Assist. Extension Entomologist

Grasshopper damage on  lily. Photo credit: Jeff Hahn

Grasshoppers can be pests in home gardens. Of the different species that occur in Minnesota, there are only a few kinds that are particularly common in the home landscape. These would include the twostriped grasshopper, the redlegged grasshopper, and the differential grasshopper.

Grasshoppers spend the winter as eggs that were deposited into the ground the previous year. These eggs are banana-shaped and laid in a cluster. These eggs are usually deposited in fields, preferably in undisturbed sites. From May until mid-June, these eggs hatch into immature nymphs. These young grasshoppers look just like adults except that they are much smaller and lack wings.

Grasshoppers damage plants by chewing holes in the leaves. Eventually the whole leaf or even the entire plant can be consumed. They prefer to eat grasses and are commonly found in prairies and meadows. However, gardens are also subject to grasshopper feeding where essentially any green plant is fair game. If populations are high enough even houses aren't safe as grasshoppers can damage nylon screens and masonite siding.

Managing grasshoppers can be very challenging. Exclusion is an option, although it probably isn't practical for your entire garden. You can protect valued plants by using floating row covers made of spun fabric. Be careful with plastic row covers as grasshoppers have been known chew through them. You may also consider protecting your plants with metal screening.

Insecticides are an option, although the more numerous grasshoppers are the more difficult it is to manage them. When you treat garden plants, they will still endure some damage before grasshoppers are killed. Even if you succeed with the grasshoppers in your garden, they are very mobile and more can fly into your yard. If you are finding grasshoppers on many plants, you may need to be selective in which you plants you try to protect. There are a variety of garden insecticides available, including products containing esfenvalerate, bifenthrin, permethrin, deltamethrin, cyfluthrin, acephate, or carbaryl. Be sure that the product you wish to use is labeled for the plants you want to treat.

Get the low down on this month's insect pests at Insects
http://www.extension.umn.edu/projects/yardandgarden/EntWeb/Ent.htm

Keeping Tomato Leaf Spots in Check
Michelle Grabowski, Regional Extension Educator-Horticulture

Early Blight infections showing rings inside of leaf spots

Trellis tomatoes to keep leaves off the ground and increas air movement around plants.

Early Blight infections just starting on the lower leaves of a tomato plant. Photos: Michelle Grabowski

In Minnesota three common fungal diseases plague garden tomatoes. Early Blight, caused by the fungus Alternaria solani attacks leaves, fruit, and stems of tomato plants. This disease typically starts in the lower leaves as dark brown or black spots with dark rings in the center that make it look like a target. These spots start out small but can grow to be ½ inch in diameter. Spots can grow together to cover the leaf causing it to dry up and fall off the plant. Stem infection and fruit infections are also black often with dark growth rings inside. Fruit spots typically start where the stem connects to the fruit and can grow to cover the top half of the fruit. Early Blight has been shown to be more severe in drought stressed plants, so be sure to regularly water tomatoes during this dry spell.

Septoria leaf spot, caused by the fungus Septoria lycopersici, causes only leaf spots. Septoria leaf spots are small, 1/16th - 1/8th of an inch in diameter. They have a dark edge and tan centers. Small black dots can often be seen in the center of the leaf spot. Leaves with many spots fall off the plant. In the right weather conditions, a tomato can lose the majority of its leaves from this disease, resulting in poor quality sunburned tomatoes.

Anthracnose, caused by the fungus Colletotrichum coccodes, primarily causes spots on ripening fruit. Fruit spots from Anthracnose are sunken water soaked spots often with a dark black center that will ooze pink spores in wet weather. This fungus rots the fruit from the inside and often makes it inedible. All three of these diseases have several things in common so that when you are controlling one you are often controlling the other two as well. First all three fungi survive in the soil and on plant debris from last year's tomatoes and weeds. Second they all have spores splashed up into the lower leaves to start the disease. Third they all need moisture to cause disease.

Knowing these three things, there are several cultural practices that can significantly reduce the amount of disease from these three fungi.

1. Reduce the amount of fungi in your garden
a. Plant tomatoes where no tomatoes, potatoes, peppers, or eggplants have been for the past 3-4 years.
b. Completely remove old tomato plants from the garden at the end of the season and compost or bury the old vines.
c. If this is not possible, bury old vines in the garden so soil microorganisms can break down the plant material.

2. Keep tomato leaves as dry as possible
a. Mulch tomato plants with 3-4 inches of organic mulch like leaves, hay, or wood chips. This keeps water in the soil where roots can get it. Mulch also reduces humidity in the plant canopy.
b. Use drip irrigation, soaker hose, or direct water at the base of the plant.
c. Water early in the morning so that leaves dry quickly in the sun.
d. Stake or cage plants. Moisture is highest at the soil surface, supported tomato plants dry quicker and are less likely to have disease problems (Fig. 2).
e. Space plants far enough away from each other that air flows between plants.

3. Stop spores from splashing from soil to plant and from plant to plant
a. Mulch tomato plants with 3-4 inches of organic mulch like leaves, hay, or wood chips. This stops water drops from hitting the soil and splashing spores into the plant canopy
b. Prune heavily infected leaves off tomato plants and compost or throw them in the garbage. Never remove more than 1/3 of a plants leaves!

Even with good cultural practices, fungicides are sometimes necessary to protect tomatoes from fungal diseases. Using some basic IPM principles can reduce the number of sprays needed each year. First scout your tomato plants once a week. Look at the lower leaves (this is where infection typically starts) for leaf spots. Check them closely to make sure they are caused by a fungal disease and not something else (bacteria, insect feeding, soil particles etc.). If you are unsure visit a Master Gardener plant clinic for help (http://www.extension.umn.edu/yardandgarden/MG/mgclinics/mgclinic.html).

Do not apply any fungicide until disease is actually present. By checking on plants once a week you should catch the disease before it becomes a big problem. Leaves with leaf spots can be removed from the garden. Fungicide sprays will then prevent the fungi from moving higher in the plant.

Next think about the weather. The chance of fungal disease increases with an increase in moisture on leaf surfaces. According to TOMCAST, a disease forecasting system used by professional tomato growers, a day that is 79F or warmer must have 3 hours of continuous leaf wetness for new infections to start. That's why it is so important to keep plant leaves dry. Remember rain, dew, and irrigation all create wet leaves. If the tomato leaves are dry, fungicide applications may not be necessary at all. Professional tomato growers are able to cut the number of fungicide sprays in half by paying attention to leaf moisture.

If nature does not cooperate, and moisture and fungi prevail, several options exist to protect tomato leaves and fruit. Organic options include copper and Serenade garden defense. Serenade garden defense is a biological control bacteria that protects leaves from fungi. It is new to the market but is labeled for tomato early blight. Sulfur is another organic broad spectrum fungicide available, but use sulfur carefully with tomatoes as it can burn the leaves if applied at high temperatures or at rates above what is recommended on the label. Conventional options include products with Mancozeb or Chlorothalonil listed as the active ingredient. Whether organic or conventional, always read the label and follow the instructions before using any pest control product.

Contributors: Nancy Rose Patrick Weicherding Bob Mugaas

Clipped lilies Photo credit: Beth Jarvis

Fruit and flowers:
Water everything in the landscape. Water plants at the base to avoid getting foliage wet. Foliage that goes to bed wet, or remains damp for several hourse, is more susceptible to plant disease.

Mulch for weed control and moisture retention.

Deadhead lilies before seed pods form bu cutting back to the first leaf on the stem. (See photo.) Deadhead annuals and perennials.

You can start dividing iris. Iris ofr Northern Gardens is at: http://www.extension.umn.edu/distribution/horticulture/DG1113.html .

Brambles, such as raspberries, need water now while they are producing fruit. Otherwise, you'll get dry, crumbly fruit. Pome and stone fruits, apples thru plums and cherries, also need a lot of water as they are growing and ripening fruit.

Containers really need water or to be checked daily. Containers can also be fertilized now. Water the containers first before adding any fertilizer--liquid or dry. Dilute liquid fertilizer to half strength and to not let it dry on the foliage.

Squash vine borers are probably still out there. Scout for damage. You can cut the worm out of the vine and bury the vine (which you keep well watered). You can dust the squash vines with Sevin powder or cover with row covers. Several sourced of info:
http://www.extension.umn.edu/projects/yardandgarden/ygbriefs/e219squashvineborer.html
http://www.vegedge.umn.edu/vegpest/cucs/vinebor.htm
http://www.extension.umn.edu/yardandgarden/YGLNews/YGLN-July0199.html#squash

Keep harvesting green beans to keep them producing.

Any plants lpurchased on sale can be planted now and watered. You may also sink containers into the garden or mulch them heavily if you're waiting for fall planting.

Powdery mildew is showing up. In one on line pub we read:
"An alternative nontoxic control for mildew is baking soda combined with a lightweight horticultural oil. Researchers at the University of Rhode Island have confirmed that a combination of 1 tablespoon baking soda plus 2.5 tablespoons oil in 1 gallon of water is effective against powdery mildew on roses. Use of this combination on other crops is still experimental."
More info is at: http://www.uri.edu/ce/factsheets/sheets/powderymildew.html

Trees and shrubs:

Ash flower galls Photo credit: Beth Jarvis

Water trees and shrubs in the landscape. They need 1" of water per week.

Water stress makes insect problems more pronounced so it's important to scout for insect problems in your yard. Earlier, we noted the increase in aphid populations in woody plants. Two-lined chestnut borer is very common in bur oak and white oak this year. It attacks and kills all oaks but the red oak aren't as commonly hit here, but they are more suscpetible to oak wilt. Stresses include drought stress, construction damage and oak wilt. Dieback of the crown is commonly seen. Exit holes are D shaped with the flat side of the D on the top.

Removal of the tree is best treatment option. Chemical treatment justified only on high value ornamental trees but by the time injury is apparent, it's really too late. The US Forest Service's excellentpub on the subject is at: http://www.na.fs.fed.us/spfo/pubs/fidls/chestnutborer/chestnutborer.htm

Ash flower gall infestations are extremely heavy this year. They cause clumpy green growth on the ash trees. These galls turn dark brown later. Treatment is not advised.

Dutch elm disease seems to be on the decline after peaking two years ago. It started showing up several weeks ago.

Lawn Care:
It's too hot for anything special in lawn care. Grasses are too stressed for post-emergence weed control, so leave the weeds alone. Focus on adding water.

You don't need to apply all the of water lost. Apply 3/4 of an inch at 7 to 10 day intervals. You'll still have an living turf.

Slight drought stress isn't a bad thing. However, when the grass turns brown, soil temperatures rise and may get high enough that permanent injury occurs. If the lawn is too big to water, there's nothing you can do short of praying for rain. Hope that you have enough plants that are hardened off enough to regrow.

Don't fertilize right now. Just water. We're in a holding pattern until mid-August when the lawn repair season starts.

UMORE Park is holding an open house on Aug. 17 from 4-8 p.m. Research plots for alternative grasses for low maintenance sites and corn gluten fertilizer evaluations will be available for your perusal. Researchers will be on hand to answer questions. Non-selective organic weed control product evaluation sites will also be on view. UMore park (http://www.umorepark.umn.edu/)

Editorial Notes

Vinca flowers. Photo: Beth Jarvis

Bob Mugaas will be writing about drought lawn care in an upcoming issue. There are a few more tree legalities articles as well. Dave Hanson will hopefully find time to write about the physiological drawbacks of growing evergreens in shade vis a vis incidence of winter injury, among other things.

Please feel free to cut and paste any of the articles for use in your own newsletters. All we ask is that you give our authors credit.

Back issues Yard & Garden Line News are on the Yard & Garden Line home page at www.extension.umn.edu/yardandgarden/.

Deb Brown answers gardening questions on Minnesota Public Radio's (MPR) "Midmorning" program on the first Friday of every month at 10 a.m. The program is broadcast on KNOW 91.1 FM, and available state-wide on the MPR news radio stations. (Scroll down for map.)

For plant and insect questions, visit http://www.extension.umn.edu/askmg. Thousands of questions have been answered, so try the search option in the black bar at the top left of the board for the fastest answer.

If you would like to receive an e-mail reminder when the next issue of the Yard & Garden Line News is posted to the web, just send an e-mail to: listserv@lists.umn.edu (note: the second E in listserve is omitted), leave the subject line blank, then in the body of the message, type: sub yglnewslist or to unsubscribe, enter: unsub yglnewslist

Happy gardening!

Beth Jarvis
Yard & Garden Line Project Coordinator


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