Whether you are harvesting from a backyard apple tree or visiting a local orchard, you are likely to find apples that are less than perfect at picking. Don't be dissuaded by appearances. Many of these apples are still quite edible as well as tasty.
There are several different fungal pathogens that infect apple fruit. Diagnosing apple disease problems now can help you make management decisions to reduce disease problems in the future and will help you decide which apples to eat and which to compost.
apple fruit with black raised corky spots
Apple scab infected apple
Photo: M. Grabowski, UMN Extension

Is it apple scab?

The most common disease of apples in Minnesota is apple scab. Fruit can become infected with the apple scab fungus throughout the growing season. Infections are rough corky spots on the surface of the fruit that are tan to black in color. Scab spots may be small and round or many spots may merge together to form large rough patches on the fruit.
The apple scab fungus does not rot the fruit but if infection occurs when the fruit is young and still growing, fruit may become distorted and cracked. If this occurs, other bacteria and fungi may move in and rot the fruit. Discard severely distorted or rotten fruit. Apples that have an intact skin but have some apple scab infection are edible. They can be eaten fresh or peeled and used for cooking.
apple with a cluster tiny black dots and larger green gray spots
Flyspeck and sooty mold on apple
M. Grabowski, UMN Extension 

What are the black dots and greenish-gray smudges?

Fly speck and sooty mold are fungal diseases that develop on the waxy covering of the fruit but do not infect the fruit itself. Flyspeck looks like a cluster of small black dots. Sooty mold looks looks like a small green gray smudge. These fungi never infect the living cells of the apple fruit and will not result in rot. They are purely a cosmetic condition.
Fruit with fly speck and sooty mold are edible. Sooty mold can sometimes be washed off although fly speck is more persistent.
end of an apple fruit with a brown rotten area
Black rot on apple
Photo: Clemson University - USDA Cooperative Extension Slide Series, Bugwood.org

Spots of rotting...can I eat the apple anyway?

Black rot causes more significant damage to the apple harvest because the black rot fungus causes rot of the fruit in addition to discoloration of the apple skin. Apples infected with black rot are firm but have one to a few large brown round areas on the skin. When the apple is cut in half, brown discoloration of the fruit can be seen extending from the skin all the way to the core.
Apples that have extensive rot should be composted. If only a small area of the fruit is rotted, this area can be cut out and the remaining healthy fruit can be eaten. Apples with any signs of black rot should not be stored.
Learn more about how to manage apple diseases in the home apple orchard from the UMN Apple Pest Management guide.
Author: M. Grabowski, UMN Extension

What does it mean when squash and melons have scabs, rings, and sunken spots?

Raised corky bumps caused by a scab infection on winter squash
M. Grabowski, UMN Extension

The long awaited harvest of melons and winter squash has arrived in Minnesota. Many gardeners are surprised to find sunken spots, rings, unusual color patterns, or raised corky scabs on the fruit. What caused all of these unusual spots and can the fruit be eaten?

Fruit spots can be caused by a number of different factors including fungal and viral plant pathogens. Melons, cucumbers, winter squash, and summer squash are all in the same plant family, the Cucurbitaceae. As a result, these crops often suffer from the same plant disease problems. Although many of the vine crops share disease problems, how severe the disease problem becomes varies by crop and by variety. Below are a few common disease problems found on melons and squash at harvest in Minnesota.  

Mosaic viruses

Several different mosaic viruses can infect squash and melon in Minnesota. Viruses may be spread by insects like aphids or cucumber beetles, on sap on hands and tools, or in infected seed. Infected plants have mosaic patterns of dark and light greens on the leaves and leaves may be puckered or distorted. Fruit produced on virus infected plants often have unusual color patterns, ring spots, and may be malformed.
Zucchini with unusual raised spots due to a viral infection.
M. Grabowski, UMN Extension

Are virus infected squash and melons safe to eat?

Yes, you can eat squash and melons that are infected with mosaic virus. These viruses are not harmful to humans and do not cause the fruit to rot. Often the discoloration is only skin deep. In cases where fruit are severely distorted, the texture of the fruit may be affected and may not be desirable for eating.

Fungal fruit spots on squash and melons

There are several different fungi that cause fruit rot in squash and melon. Scab and anthracnose are common in Minnesota. Both of these diseases start as a leaf spot disease and eventually infect fruit. The type of spot that occurs on the fruit depends on which disease is present and how susceptible or resistant the plant is. Anthracnose causes sunken round spots in the fruit of cucumber, squash, and melons. If moisture is present, fluffy fungal growth and powdery salmon colored spores can be seen within the fruit spot. Scab causes sunken round spots on cucumber, summer squash, and pumpkin that may be covered with a dark green to black velvety fungal growth when humidity is high. Some types of winter squash are moderately resistant to scab and will develop a raised corky bump on the fruit instead of a sunken spot. Resistant varieties are available for scab and anthracnose in some crops. 
Cantaloupe infected with anthracnose
M. Grabowski, UMN Extension 

Are melons and squash infected with a fungal fruit spot ok to eat?

Fungal fruit spot diseases will rot the fruit of the squash or melon. This rot begins just below the sunken spot visible on the outside of the fruit. In cases where only a few fruit spots occur, rotten areas can be cut out and the remainder of the fruit can be cooked and eaten. Carefully inspect winter squash at harvest. Only fruit with no signs of a fruit spot disease should be stored as rot can progress in storage.

Sometimes so many spots are present that the majority of the fruit is rotten. In other cases a fruit spot may crack open and secondary bacteria and fungi or fruit feeding insects will move into the fruit. In both situations, this fruit should be removed from the garden and buried in a compost pile that heats up and breaks down plant material completely.

Anthracnose spots on pumpkin
M. Grabowski, UMN Extension 

Japanese beetles feeding on a grapevine leaf
near Red Wing, MN. Photo: Annie Klodd
Many gardeners reading this article have either seen or dealt with Japanese beetles this season. Their population levels were high, and they could frequently be spotted enjoying the foliage of entire trees before moving on to the next palatable plant nearby.
As I have traveled the state to talk to gardeners and farmers, Japanese beetles were one of the most common questions I received. Many gardeners had stories and innovative ideas they have tried to control this invasive insect.
In response to this, I sat down with Jeff Hahn and Dominique Ebbenga in the University of Minnesota entomology department to get the scoop on what we currently know about Japanese beetles. In this recorded interview, Jeff and Dominique laid out what researchers have found, and where future efforts are going.
Some of the questions we discussed were:
Can you plant any flowers to ward off JB?
When might growers use nematodes to control JB grubs? Is it worth it?
Why do we advise against using traps for JB control?

Listen to our interview here, on the fruit and vegetable podcast called, "What's Killing My Kale?" Click on "Episode 12" and listen to the audio file.
Author: Annie Klodd, Extension Educator - Fruit and Vegetable Production

Cool weather is a reminder that fall is not far away and soon gardeners will be preparing the landscape for winter. Many plant pathogens are able to survive winter in gardens in infected leaves, flowers, branches, and fruit. Gardeners can reduce the risk of plant disease next year by using the following steps to do a thorough fall garden clean up.


green maple leaves with black spots
Tar spot on maple
M.Grabowski, UMN Extension

Trees and shrubs

  • Examine leaves before they change color for evidence of a leaf spot disease. Leaf spots come in many colors, are randomly scattered across the leaf surface, and often are more severe on the lower and inner leaves. They will be easiest to identify when the leaves are green.
  • If a leaf spot disease is found, leaves should be raked up and removed or mulched into the lawn with a mulching lawn mower after normal leaf fall. 
  • Look for branches with wilting or dead leaves. Discolored, cracked or blistered bark on these branches could indicate the presence of a canker infection on the branch. A large tumor like growth on the branch would indicate a gall.
  • If galls or cankers are found, mark the branch with paint or flagging tape to indicate the presence of a problem. 
  • Do not prune to remove the canker or gall until winter however. Trees pruned in fall before going dormant may produce young sprouts that will not have time to harden off before winter and will be killed by the cold temperatures. The best time to prune out cankers and galls is in January or February when temperatures have been consistently below 32 .

pink flowering sedum plant with brown spots on leaves
Septoria leaf spot on sedum
M.Grabowski, UMN Extension

Flower gardens

  • Examine both annual and perennial flowering plants for spots, rot, or wilt.
  • Mark the plants that are showing symptoms of disease now.
  • After a hard frost kills the plants completely remove diseased annuals and any perennials suffering from a root or crown rot.
  • Perennials with a leaf spot disease can be cut off at the soil level. Infected leaves, stems, and flowers should be removed from the garden.
  • It is ok to leave plants that have no symptoms of disease for winter interest or to support wildlife.

Green bean leaves with brown spots with a yellow halo
A bacterial leaf spot disease of green bean
M.Grabowski, UMN Extension 

Vegetable gardens

  • In a small vegetable garden it is best to remove all plants that had symptoms of a plant disease during the growing season and place them in a compost pile.
  • For large gardens, infected plants can be cut down and buried in the garden soil. In this case, the gardener should use crop rotation, and avoid planting any plant from the same plant family as the diseased crop on the site for the next 3 to 4 years.
  • Leaves from deciduous trees can be placed on the soil of a vegetable garden to prevent soil erosion over winter and provide shelter to native pollinators. 

black compost bin next to a pink flowering bleeding heart
Backyard compost bin
J. Weisenhorn, UMN Extension

What to do with diseased plant material?

  • Do NOT put any landscape plant material into the garbage. 
  • Diseased plant material should be composted in a compost pile that heats up to 148 and results in complete breakdown of all plant material. This will kill the majority of plant pathogens commonly found in Minnesota landscapes. 
  • If your backyard compost pile does not heat up sufficiently plant waste can be brought to a municipal compost facility. Some cities offer curbside pickup of compostable items.

bright red male cardinal sitting on a branch
Northern cardinal
S. Katovich, USDA Forest Service 

Pollinators and Wildlife

Many birds, native pollinators, and other wildlife utilize the plants in our landscapes to help survive the winter. 

While it is important to remove diseased plant material from the yard and garden to reduce the survival of plant pathogens, it is also important to leave healthy flower stalks, seed heads, grasses, fallen leaves, and other plant parts in the garden to support Minnesota’s pollinators and wildlife. 
M. Grabowski, UMN Extension Educator 

Jeffrey Hahn, Extension Entomologist
Much of Minnesota has experienced consistent rains through the spring and summer this year. This has led to an increase in the numbers of springtails in and around homes and other buildings. Springtails love damp conditions and are typically found in soil, leaf litter, lichen, under bark, decaying plant matter, and other areas of high moisture. Given an opportunity, they will also inhabit your home.
A typical springtail.  Note the furcula, the appendage for
jumping on the tip of the abdomen on the left.  Photo:
Susan Ellis, Bugwood.org
What do springtails look like?
Springtails are very small, between 1/16th - 1/8th inch long. They are usually slender insects (there is a group of springtails that is round and stout that is sometimes found in gardens). Most springtails are dark-colored, brown, grey or black although some species are also white, and some are even iridescent and brightly colored
These tiny insects are wingless and cannot fly but they can jump. They use a forked appendage called a furcula (located underneath the abdomen) to propel itself. When not in use, a furcula is tucked up under the body, set like a mouse trap. When it is released, it extends down rapidly sending the springtail forward. A springtail can jump many times its body length.
Why are they found in homes?
Springtails can be found indoors for several reasons. You can find them in areas of high moisture, e.g. around plumbing leaks and damp basements. They can also move indoors in large numbers from the outside when moist conditions exit around the home. Springtails can vary in abundance indoors from just a handful to very large numbers. Fortunately, regardless of their numbers, they are harmless to people and property and are just nuisances.
How can I control springtails?
If you are finding just a small number of springtails occasionally, just ignore them or physically remove them by hand or with vacuum. However, if you are seeing persistent number of springtails they are associated with a moisture problem. The best management is to dry out these areas with a fan or dehumidifier as springtails do not tolerate dry conditions. Also make any structural changes to correct the moisture problem.

While springtails are usually found on the ground, they can
also infest other areas where high moisture exists like roofs
and gutters.  Photo:  Jeff Hahn, Univ. of MN Extension
However, people without moisture problems might still encounter springtails. If they are moving in from the outside, check around the house for damp conditions. This could include rainspouts that do not carry the water far enough away from the foundation, landscapes that slope towards buildings, or excessive irrigation.
 It could even be a moisture problem with the roof or the gutters. Correct moisture conditions to help decrease springtails. As we receive less rainfall, the number of springtails will also naturally go down.
Although it may be tempting to spray a springtail problem with an insecticide, the products available are not very effective against them. Moisture control is the most effective strategy.

For more information see Springtails.
Jeffrey Hahn, Extension Entomologist
Although you can encounter blacklegged ticks (also known as deer ticks) nearly any month of the year, June and July are the times of highest risk for becoming infected with Lyme disease. That is because summer is when the immature nymphs are active. Because of their very small size, it is easier to be bitten and not know it.
Blacklegged (deer) ticks.  Top row: adult male and female.
Bottom row: immature nymphs.  Their small size, especially the
nymphs, makes it more difficult to see them and more likely to be
exposed to Lyme disease. Photo: Jim Occi, Bug Pics, Bugwood.org
Additionally, we are in full summer mode, so we are commonly hiking, camping, and doing other outdoor activities that puts us close to where ticks live. Blacklegged ticks are most common in the underbrush of hardwood forests and in fields. Although Lyme disease can occur in many areas of Minnesota, it is most common in the east central, north central and southeast areas of the state.
If you are going to be out in a known tick habitat, take precautions to protect yourself from blacklegged ticks.
* Stay on trails and when possible avoid walking into brushy, grassy areas where ticks are more common.
* Wear long, light colored pants so ticks are easier to detect. For additional protection, tuck your pants into your socks.
* Use repellents to help keep the ticks off of you: Use Deet on clothes and skin but apply products containing permethrin just to clothing.
* Do a tick check when you return from the outdoors. They are small and can be easily overlooked so look carefully! Be sure to look in out of the way places, like behind ears or behind knees.
If you do find a tick, especially if it has been biting, get it positively identified. While blacklegged (deer) ticks can transmit Lyme and other diseases, American dog ticks are not an important disease vectors.
Remember that a blacklegged tick needs to be biting to be able to transmit disease. In fact, it needs to be attached for 24 – 48 hours before it can transmit Lyme disease (the amount time varies for other diseases). Even if you are bitten, not every tick is infected with disease.
A common symptom of Lyme disease, the bullseye rash
(technically called erythema migrans, EM).  Credit: Centers
for Disease Control and Prevention (CDC)
One of the most common symptoms of Lyme disease is a red bulls-eye rash. This occurs in 70-80% of cases. This rash is usually seen 3-30 days after a tick bite. People with Lyme disease may also initially experience fever, headache, and muscle aches.
If you believe you may have Lyme disease, see a physician. When caught early, Lyme disease can be successfully treated with antibiotics.
For more information, see Ticks and their control and Tick-borne diseases in Minnesota.

Now is the time to treat for spruce needle cast diseases. Do you know what’s wrong with your spruce and how to treat it?  

M. Grabowski, UMN Extension Educator
Spruce tree suffering from Rhizosphaera Needle Cast.
M. Grabowski, UMN Extension
Many spruce trees across Minnesota have brown or missing needles along with dead branches. This damage can be caused by a variety of problems including needle cast or needle blight diseases, branch cankers, insect pests, mites, or environmental conditions.
Although management options are available for many of these problems, each problem has its own unique solution. The first step in correcting a spruce problem is getting a correct diagnosis.

Send a sample for diagnosis now

Treatment for Rhizosphaera Needle Cast or Stigmina Needle Cast, two common diseases of spruce trees in Minnesota, need to begin at this time of year. Before you treat you MUST know which disease problem your tree has! Unfortunately it is not possible to diagnose either of these disease problems without a laboratory analysis. Both fungal pathogens cause needles to discolor or fall off. Both fungal pathogens make tiny black spore producing structures along the needle. Although these spore producing structures can be seen with a hand held magnifying glass, it is not possible to distinguish between the two pathogens with a magnifying glass alone.

Where to send a sample

You can send a plant sample to University of Minnesota Plant Disease Clinic on the St. Paul campus. Samples can be dropped off in person or sent in the mail. There is a fee for diagnosis. Check the web page for current prices.

What to send

Send a branch that has live but discolored needles. The branch needs to be long enough to include needles from the past 3 to 4 years of growth. A branch that is 1 to 2 feet long is usually sufficient. This year’s needles will be pale green, soft, and at the very tip of the branch. Previous years needles will be further down the branch with a ring of rough brown bud scales on the twig separating each year of growth. Keep the sample in a cool dry location until it can be sent.
Fill out the online sample submission form and include it with the plant sample.
Bud scales on a spruce twig.
UMN Plant Disease Clinic

A spruce branch with three years of growth.
UMN Plant Disease Clinic

How to send a sample

Wrap the branch in dry newspaper and then plastic before placing it in a box for mailing. It is best to mail the sample early in the week to avoid having the plant sample sit in a storage facility over the weekend. Samples brought directly to the clinic do not need to be packaged.

What happens to plant samples at the clinic?

The plant pathologists at the UMN Plant Disease Clinic carefully inspect every plant sample submitted. Diagnosticians use a variety of techniques to identify the pest or pathogen causing the problem including microscopy, culturing and DNA analysis.
Needle discoloration and loss caused by Stigmina Needle Cast.
M. Grabowski, UMN Extension 

How do I get the results?

The results will be sent to you via email, mail, or fax. You choose by marking a box on the submission form.

Treatment options 

The results will include the name of any pests and pathogens found on the plant sample and information about research based management options available to you. More information about how to treat common spruce diseases can be found at the UMN Extension website.
If you do not want to treat your trees yourself you can hire an arborist. Arborists are tree care professionals that can work with you to provide the best care for trees on your property. 
To find a certified arborist who works in your area, you can use the Find an Arborist tool from the International Society of Arboriculture.

Jeffrey Hahn, Extension Entomologist
Typical carpenter ant.  They are identified by having a one
segmented node and an evenly round thorax when viewed in
profile.  Photo credit: Jeff Hahn, U of MN Extension
Carpenter ants are the most important ant pests found in Minnesota. They can be a problem when they nest in homes and other structures. Because nests are in wood and other hidden areas, it is challenging to know where they are located. Finding the nest and treating it is the best control for carpenter ants.
Always verify that you have carpenter ants. While, people often think of carpenter ants as “big, black ants” (which they are, up to almost ½ inch long), some carpenter ant species are red and black and are smaller, only 3/16th inch long. Some species of field ants, a nuisance species, are black and a similar size to carpenter ants.

Finding carpenter ants in your home in the spring can mean that a nest is present, especially when persistent numbers are found. If you find a swarm of winged carpenter ants indoors, that is a sign of an indoor nest. However, if you find just a few carpenter ant queens (winged or wingless) in your home, they probably just wandered into your home accidentally and no nest is actually present.
A wingless carpenter ant queen.  Finding one or two in your
home (like the author did) is not an indication of a nest
although she is looking to start a nest.  Photo credit:  Jeff
Hahn, Univ. of  Minnesota Extension
If you are having problems with carpenter ants in your home, it is very challenging to eliminate them yourself. For control to be effective, it is necessary to deliver insecticide into the nest to kill the queen and the workers. Killing the foraging workers you see does not impact the nest.
Baits can be effective for some ant problems. However, the ant baits available to residents are not sufficiently attractive or effective to successfully eliminate a carpenter ant nest.
The best control for carpenter ants is to contact a licensed pest management service to treat the nest. An inspection is important to find the foraging trails and if possible the nest(s).
There are several options for treating the nest. Many technicians use a non-repellant residual insecticide, such as Termidor, sprayed around the building’s exterior. The carpenter ants pick up the residue and take it back it to the nest where it gets spread through colony, ultimately eliminating it.
Technicians may also set out baits to control carpenter ants. They have access to a variety of baits and have the experience to use them. It is not unusual for technicians to use more than one bait to be successful. Remember that baits take time so be patient and allow carpenter ants to take enough back to control the nest.
Carpenter ants tunnel and nest in wood.  Control them to
prevent damage to your home.  Photo credit: Jeff Hahn,
Univ. of MN Extension
If the exact location of the nest is discovered, it can be treated directly with a dust. This may require drilling into walls or injecting dust through outlets.
Once treatment has been applied, a technician needs to evaluate how successful the initial control was and whether any additional steps are needed.
However, treating the entire house multiple times on a scheduled basis is considered excessive and less effective. Treatment should be targeted and as specific as possible.
For additional information, see Carpenter ants.
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