Category Archives: Fact Sheet

Vegetable Disease Quick Reference

Septoria Leaf Spot Septoria Leaf Spot and Early Blight
Host:   Tomato
Pathogens:   Septoria lycopersicia and Alternaria solani
Signs/Symptoms:  Spotting and eventual total collapse of leaves working from the bottom of the plant up
For more information see:        UW Garden Facts D0100/D0046
Late Blight Late Blight
Hosts:   Tomato, potato
Pathogen:   Phytophthora infestans
Signs/Symptoms:  Water-soaked spots on leaves, leathery areas on tomato fruits, rapid plant death
For more information see:        UW Garden Facts D0068
Blossom End Rot Blossom End Rot
Host:   Tomato, pepper, eggplant, cucumber, squash
Cause:   Calcium deficiency
Signs/Symptoms:  Decayed areas on the bottom sides of vegetable fruits
For more information see:        UW Garden Facts D0022
Powdery Mildew Powdery Mildew
Hosts:    Any vegetable, particularly vine crops, peas
Pathogens:    Miscellaneous powdery mildew fungi
Signs/Symptoms:  Powdery white growth on leaves
For more information see:        UW Garden Facts D0086
Common Corn Smut Common Corn Smut
Hosts:   Corn
Pathogen:   Ustilago maydis
Signs/Symptoms:  Pasty white masses on corn ears eventually decomposing into a brown powder
For more information see:        UW Garden Facts D0031
Black Rot Black Rot
Hosts:   Crucifers (e.g., cabbage, broccoli, cauliflower)
Pathogen:   Xanthomonas campestris pv. campetris
Signs/Symptoms:  V-shaped yellow/dead areas on leaves progressing into plant deterioration and death
For more information see:        UW Garden Facts D0019
Potato Scab Potato Scab
Hosts:    Potato, carrot, beet, other root crops
Pathogen:  Streptomyces scabies
Signs/Symptoms:  Brown, rough, scab-like areas on tubers and roots
For more information see:        UW Garden Facts D0083
Verticillium Wilt Verticillium Wilt
Host:   Tomato, pepper, eggplant, potato, vine crops
Pathogen:  Verticillium spp.
Signs/Symptoms:  Leaf yellowing and wilting of plants followed by eventual plant death
For more information see:        UW Garden Facts D0122
Aster Yellows Aster Yellows
Hosts:    Carrot
Pathogens:    Aster yellows phytoplasma
Signs/Symptoms:  Yellow/orange/purple leaves, stunted roots with tufts of white hairy roots
For more information see:        UW Garden Facts D0007
Bacterial Wilt Bacterial Wilt
Hosts:   Vine crops
Pathogen:   Erwinia tracheiphila
Signs/Symptoms:  Sectional wilting and eventual death of plants after cucumber beetle feeding
For more information see:        UW Garden Facts D0014
Basil Downy Mildew Basil Downy Mildew
Host:   Basil
Pathogen:   Peronospora belbahrii
Signs/Symptoms:  Downward-cupped, yellow leaves with purple-gray fuzz on leaf undersurfaces
For more information see:        UW Garden Facts D0015

For more information on conifer diseases:  See https://pddc.wisc.edu/ or contact your county Extension agent.

Root Rots on Houseplants

Wilting of poinsettia associated with Pythium root rot.
Wilting of poinsettia associated with Pythium root rot.

What is root rot? Root rot is a general term that describes any disease where the pathogen (causal organism) causes the deterioration of a plant’s root system. Most plants are susceptible to root rots, including both woody and herbaceous ornamentals. Root rots can be chronic diseases or, more commonly, are acute and can lead to the death of the plant.

How do you know if your plant has a root rot? Homeowners often become aware of root rots when they note that a plant is wilted, even though the soil is wet. Plants with root rots are also often stunted, and may have leaves with a yellow or red color, symptoms that suggest a nutrient deficiency. Careful examination of the root systems of these plants reveals roots that are soft and brown. These roots may have a bad odor.

Where does root rot come from? A large number of soil-borne fungi cause root rots. Pythium spp., Phytophthora spp., Rhizoctonia solani, and Fusarium spp. are the most common root rot fungi. These fungi have wide host ranges, and thus can cause root rots on a wide variety of plants. Most root rot fungi prefer wet soil conditions and some, such as Pythium and Phytophthora produce spores that can survive for long periods in soil or plant debris.

How do I save a plant with root rot? Often the best and most cost effective way of dealing with a plant with root rot is to throw it out. If you decide to keep a plant with root rot, REDUCE SOIL MOISTURE! Provide enough water to fulfill the plant’s growth needs and prevent drought stress, but DO NOT over-water.

Throw out plastic pots if plants grown in them have suffered from a root rot.
Throw out plastic pots if plants grown in them have suffered from a root rot.

We DO NOT recommend use of chemical fungicides for control of root rots on houseplants because of the limited availability of products for use by homeowners, and because those products that are available tend to be expensive.

How do I avoid problems with root rots? First, buy plants from a reputable source and make sure they are root rot-free prior to purchase. Second, replant your houseplants properly. Use a pot with drainage holes, but DO NOT put rocks or gravel at the bottom of the pot. The presence of rocks or gravel can actually inhibit drainage. Use a pasteurized commercial potting mix, NOT soil from your garden. Garden soils often contain root rot fungi. Add organic material (e.g., peat moss) to heavy potting mixes to increase drainage. Third, minimize potential contamination of your plants with root rot fungi. DO NOT reuse potting mix from your houseplants, or water that has drained from your plants, as both potentially can contain root rot fungi. After working with plants with root rot problems, disinfest tools, working surfaces and clay pots with a 10% bleach or detergent solution, or alcohol. DO NOT reuse plastic pots as they are often difficult to disinfest adequately. Finally and most importantly, moderate plant moisture. Provide enough water to fulfill your plants’ needs for growth and prevent drought stress, but DO NOT over-water. In particular, DO NOT allow plants to sit in drainage water. REMEMBER, root rot fungi grow and reproduce best in wet soils.

For more information on root rots: Contact your county Extension agent.

Lichens

There are many types of lichens. Crustose lichens (left) are crust-like and adhere tightly to the surface upon which they grow. Foliose lichens (right) are leaf-like and composed of flat sheets of tissue that are not tightly bound.
There are many types of lichens. Crustose lichens (left) are crust-like and adhere tightly to the surface upon which they grow. Foliose lichens (right) are leaf-like and composed of flat sheets of tissue that are not tightly bound.

What are lichens? Lichens are organisms that arise from mutually beneficial interactions between certain fungi and algae. The fungi provide the physical structures of the lichens, as well as protection for the algae. The algae, in turn, produce food for the fungi via photosynthesis.

What do lichens look like? Lichens come in four basic growth forms. Crustose lichens are crust-like and adhere tightly to the surface upon which they grow. Foliose lichens are leaf-like and composed of flat sheets of tissue that are not tightly bound together. Squamulose lichens are composed of scale-like parts. Fruticose lichens are composed of free-standing branching tubes.

Where do lichens come from? Lichens are everywhere. There are an estimated 13,500 to 17,000 species of lichens, and lichens can be found growing in tropical, temperate and polar regions throughout the world. Lichens will grow on almost any surface that is stable and reasonably well-lit. In temperate regions, lichens can often be found growing on the bark of trees or old fence posts. Others lichens grow in less hospitable places, such as bare rock surfaces or old headstones in graveyards, where they aid in the breakdown of rocks and the formation of soil.

There are many types of lichens. Crustose lichens (left) are crust-like and adhere tightly to the surface upon which they grow. Foliose lichens (right) are leaf-like and composed of flat sheets of tissue that are not tightly bound.
There are many types of lichens. Crustose lichens (left) are crust-like and adhere tightly to the surface upon which they grow. Foliose lichens (right) are leaf-like and composed of flat sheets of tissue that are not tightly bound.

How do I save a tree with lichens? DO NOT PANIC! Lichens do not harm trees; they are not pathogens or parasites, and do not cause disease. Lichens are self-reliant, with the algal component of the lichen producing food for the organism via photosynthesis. Lichens absorb water and minerals from rainwater and the atmosphere, and because of this, they are extremely sensitive to air pollution. As a result, the presence or absence of certain lichen species can be used as an indicator of levels of atmospheric pollutants. Information on the abundance and species of lichens growing in an area can give a good indication of the local air quality.

For more information on lichens: Contact your county Extension agent.

Plant Diseases to Watch For in 2021

Septoria Leaf Spot Septoria Leaf Spot and Early Blight
Host:  Tomato
Pathogens:   Septoria lycopersici and Alternaria solani
Signs/Symptoms:  Spotting and eventual total collapse of leaves working from the bottom of the plant up
For more information see:       UW Plant Disease Facts D0100/46
Late Blight Late Blight
Hosts:  Tomato, potato
Pathogen:   Phytophthora infestans
Signs/Symptoms:  Water-soaked spots on leaves, leathery areas on tomato fruits, rapid plant death
For more information see:       UW Plant Disease Facts D0068
Septoria Leaf Spot of Lilac Septoria Leaf Spot of Lilac
Host:  Lilac
Pathogen:   Septoria sp.
Signs/Symptoms:  Dead spots on leaves, potentially leading to complete leaf browning
Rhizosphaera Needle Cast Rhizosphaera Needle Cast
Hosts:  Colorado blue spruce, other spruces
Pathogen:   Rhizosphaera kalkhoffii
Signs/Symptoms:  Browning/purpling of interior needles of lower branches, followed by needle drop
For more information see:       UW Plant Disease Facts D0093
Gymnosporangium Rusts
Hosts:  Juniper, apple, crabapple, hawthorn, quince
Pathogen:   Gymnosporangium spp.
Signs/Symptoms:  Brown blobs with orange gelatinous masses (juniper); yellow/orange leaf spots (other hosts)
For more information see:       UW Plant Disease Facts D0058
Elderberry Rust
Hosts:  Elderberry
Pathogen:   Puccinia sambuci
Signs/Symptoms:  Light yellow, powdery growths on branches
For more information see:       UW Plant Disease Facts D0049
Scab Scab (Apple and Pear)
Hosts:   Apple, crabapple, pear, mountain-ash
Pathogens:   Venturia inaequalis, Venturia pirina
Signs/Symptoms:  Feathery-edged spots on leaves and fruits often leading to leaf loss and tree defoliation
For more information see:       UW Plant Disease Facts D0004
Bur Oak Blight
Host:   Bur oak
Pathogen:   Tubakia iowensis
Signs/Symptoms:  Wedge-shaped dead areas on leaves leading to dead leaves that stay attached to trees
Powdery Mildew
Hosts:   Herbaceous and woody ornamentals, fruits, vegetables, turf
Pathogens:   Miscellaneous powdery mildew fungi
Signs/Symptoms:  Powdery white growth on leaves
For more information see:       UW Plant Disease Facts D0084/86/87
Diplodia Shoot Blight and Canker
Hosts:  Austrian pine, other pines
Pathogen:   Diplodia spp.
Signs/Symptoms:  Dieback of branch tips with dead needles showing uneven lengths
For more information see:       UW Plant Disease Facts D0042
Boxwood Blight
Host:  Boxwood
Pathogen:   Calonectria pseudonaviculata
Signs/Symptoms:  Circular, brown leaf spots followed by leaf drop and shrub death
For more information see:       UW Plant Disease Facts D0023

For more information on plant diseases to watch for:  See https://pddc.wisc.edu/ or contact your county Extension agent.

Ten Common Plant Diseases/Disorders You Can Diagnose by Eye

Powdery Mildew Powdery Mildew
Hosts:   Herbaceous and woody ornamentals, fruits, vegetables, turf
Pathogens:   Miscellaneous powdery mildew fungi
Signs/Symptoms:  Powdery white growth on leaves
For more information see:       UW Plant Disease Facts D0084/86/87
Tar Spot - Ten Common Plant Diseases Tar Spot
Hosts:  Maples
Pathogen:   Rhytisma spp.
Signs/Symptoms:  Tarry areas (either solid spots or clusters of small spots) on leaves
For more information see:       UW Plant Disease Facts D0110
Peach Leaf Curl Peach Leaf Curl
Hosts:  Peach
Pathogen:   Taphrina deformans
Signs/Symptoms:  Light-green, yellow or purplish-red puckered areas on leaves
For more information see:       UW Plant Disease Facts D0076
Sooty Mold Sooty Mold
Hosts:  Any plant
Pathogen:   Miscellaneous sooty mold fungi
Signs/Symptoms:  Powdery black growth on leaves or needles
For more information see:       UW Bulletin A2637
Chlorosis Chlorosis
Hosts:  Oak, red maple
Cause:   Iron or manganese deficiency, often induced by high soil pH
Signs/Symptoms:  Yellow leaves with dark green veins
For more information see:       UW Plant Disease Facts D0030
Gymnosporangium Rusts Gymnosporangium Rusts
Hosts:  Juniper, apple, crabapple, hawthorn, quince
Pathogen:   Gymnosporangium spp.
Signs/Symptoms:  Brown blobs with orange gelatinous masses (juniper); yellow/orange leaf spots (other hosts)
For more information see:       UW Plant Disease Facts D0058
Black Knot Black Knot
Hosts:  Prunus spp. (plum and cherry)
Pathogen:   Apiosporina morbosa
Signs/Symptoms:  Black poop-like growths on branches
For more information see:       UW Plant Disease Facts D0018
Elderberry Rust Elderberry Rust
Hosts:  Elderberry
Pathogen:   Puccinia sambuci
Signs/Symptoms:  Light yellow, powdery growths on branches
For more information see:       UW Plant Disease Facts D0049
Golden Canker Golden Canker
Hosts:  Pagoda dogwood
Pathogen:   Cryptodiaporthe corni
Signs/Symptoms:  Gold-colored branches with orange spots
For more information see:       UW Plant Disease Facts D0055
Dog Vomit Slime Mold Dog Vomit Slime Mold
Hosts:  Any plant and on mulch
Cause:   Fuligo septica
Signs/Symptoms:  Scrambled egg-like masses on mulch or at the base of plants
For more information see:       UW Plant Disease Facts D0102

For more information on common plant diseases:  See https://pddc.wisc.edu/ or contact your county Extension agent.

Deciduous Tree Leaf Disease Quick Reference

Anthracnose for Quick Guide Anthracnose
Hosts:  Most trees, commonly ash, maple and oak
Pathogens:  Gloeosporium spp. as well as other fungi
Signs/Symptoms:  Blotchy dead areas on leaves
For more information see:  UW Plant Disease Facts D0002
Purple-bordered leaf spot Purple-Bordered Leaf Spot
Host:  Amur, Japanese, red, silver and sugar maple
Pathogen:  Phyllosticta minima
Signs/Symptoms:  Discrete, circular leaf spots with purple borders
For more information see:  UW Plant Disease Facts D0089
 Tubakia leaf spot Tubakia (Actinopelte) Leaf Spot
Hosts:  Oak
Pathogen:  Tubakia spp. (Actinopelte spp.)
Signs/Symptoms:  Discrete circular, or irregular blotchy dead areas on leaves
For more information see:  UW Plant Disease Facts D0118
 Scab Apple Scab
Hosts:  Apple, crabapple, pear, mountain-ash
Pathogen:  Venturia inaequalis, V. pirina
Signs/Symptoms:  Circular, black leaf spots with feathery edges; eventual leaf loss
For more information see:  UW Plant Disease Facts D0004
 Cedar-Apple Rust Gymnosporangium Rusts
Hosts:  Apple, crabapple, hawthorn
Pathogens:  Gymnosporangium spp.
Signs/Symptoms:  Bright yellow-orange, circular leaf spots
For more information see:  UW Plant Disease Facts D0058
 Powdery Mildew Powdery Mildew
Hosts:  Most deciduous trees
Pathogens:  Several genera of powdery mildew fungi
Signs/Symptoms:  Uniform/blotchy powdery white areas on upper and lower leaf surfaces
For more information see:  UW Plant Disease Facts D0087
 Downy Leaf Spot Downy Leaf Spot
Hosts:  Hickory, walnut
Pathogen:  Microstroma juglandis
Signs/Symptoms:  Discrete powdery white areas on lower leaf surfaces
 Clorosis Chlorosis
Hosts:  Oak, red maple
Cause:   Iron or manganese deficiency, often induced by high soil pH
Signs/Symptoms:  Yellow leaves with dark green veins
For more information see:  UW Plant Disease Facts D0030
 Scorch Scorch
Hosts:  Most deciduous trees
Cause:   Water stress induced by drought, high soil salt content, or other water-limiting factors
Signs/Symptoms:  Dead tissue on leaf margins
 Tatters Tatters
Hosts:  Most deciduous trees, but commonly oak
Cause:  Possible early season cold injury
Signs/Symptoms:  Lacy, tattered-looking leaves
For more information see:  UW Plant Disease Facts D0111

For more information on deciduous tree leaf diseases:  See https://pddc.wisc.edu/ or contact your County Extension agent.

Conifer Disease Quick Reference

Conifer - Root and Crown Rot Root and Crown Rots
Hosts:  All conifers
Pathogens:   Assorted root rot fungi/water molds
Signs/Symptoms:  Poor growth, branch dieback, discolored and deteriorated roots
For more information see:       UW Plant Disease Facts D0094
Conifer Rhizosphaera Needle Rhizosphaera Needle Cast
Hosts:  Colorado blue spruce, other spruces
Pathogen:   Rhizosphaera kalkhoffii
Signs/Symptoms:  Browning/purpling of interior needles of lower branches, followed by needle drop
For more information see:       UW Plant Disease Facts D0093
Conifer - Cytospora Canker Cytospora Canker
Hosts:  Colorado blue spruce, other spruces
Pathogen:   Cytospora kunzei
Signs/Symptoms:  Branch dieback with milky-white patches of dried sap on affected branches
For more information see:       UW Plant Disease Facts D0037
Conifer - Spruce Needle Drop Spruce Needle Drop
Hosts:  Spruces
Pathogen:   Unknown (possibly Setomelannoma holmii)
Signs/Symptoms:  Needle loss and dieback at or near branch tips
Conifer - Cedar Apple Rust Gymnosporangium Rusts
Hosts:  Juniper, apple, crabapple, hawthorn, quince
Pathogen:   Gymnosporangium spp.
Signs/Symptoms:  Brown blobs with orange gelatinous masses (juniper); yellow/orange leaf spots (other hosts)
For more information see:       UW Plant Disease Facts D0058
Phomopsis Tip Blight Phomopsis Tip Blight
Hosts:  Junipers
Pathogen:   Phomopsis juniperovora
Signs/Symptoms:  Browning and dieback of branch tips  in spring and early summer as new growth emerges
For more information see:       UW Plant Disease Facts D0077
Conifer - Diplodia Tip Blight Diplodia Shoot Blight and Canker
Hosts:  Austrian pine, other pines
Pathogen:   Diplodia spp.
Signs/Symptoms:  Dieback of branch tips with dead needles showing uneven lengths
For more information see:       UW Plant Disease Facts D0042
Conifer - Dothistroma Needle_ Dothistroma Needle Blight
Hosts:  Austrian pine, other pines
Pathogen:   Dothistroma pini
Signs/Symptoms:  Needle tip browning and death with a distinct break between live and dead tissue
For more information see:       UW Plant Disease Facts D0043
Conifer - Drought Stress Drought Stress
Hosts:  All conifers
Cause:   Insufficient water
Signs/Symptoms:  Purpling/browning of needles near branch tips or higher up in plants during the summer
Conifer - Winter Injury Winter Injury/Winter Burn
Hosts:  All conifers, particularly yew and juniper
Cause:   Insufficient water
Signs/Symptoms:  Needle browning/bleaching over winter or in spring as plants come out of dormancy
For more information see:       UW Plant Disease Facts D0127
Conifer - Herbicide Damage Herbicide Damage
Hosts:  All conifers
Cause:   Exposure to herbicides
Signs/Symptoms:  Twisted or otherwise distorted growth, needle yellowing or browning, plant death
For more information see:       UW Plant Disease Facts D0060

For more information on conifer diseases:  See https://pddc.wisc.edu/ or contact your county Extension agent.

Odorous House Ants

Odorous house ants (Tapinoma sessile) can be found across the United States and are one of the most common ants found in and around structures in Wisconsin.  These ants are known for their fondness for sugary foods and their distinctive odor when crushed.

An odorous house ant.  Photo courtesy of April Nobile (CASENT0005329, www.antweb.org.)
An odorous house ant. Photo courtesy of April Nobile (CASENT0005329, www.antweb.org.)

Appearance:  Odorous house ant adults are dark brown to black and approximately 1/8 inch long.  Their waist (petiole) has a single flattened node, which may be difficult to see because it is obscured by other body parts.  They also have 12-segmented antennae that lack a distinct club.  Odorous house ants smell like rotten coconut or blue cheese when crushed.

Biology:  Odorous house ants forage day and night, following well-established trails.  Around buildings, they often follow the edges of siding, deck boards, and door frames.  Odorous house ants are particularly fond of sugary materials such as honeydew (the feces of aphids or soft scales), and sugary foods and beverages.  Occasionally, they will feed on insects (both dead and alive) or on other items such as pet food.

Odorous house ants prefer to nest in moist areas and often create a network of interconnected nests consisting of thousands of workers and many queens.  Outdoors, they can nest in mulch beds, beneath stones or pieces of wood, under the loose bark of trees, and beneath a variety of man-made objects.  Indoors, odorous house ants can nest in wall voids and attics, in areas with damp wood or insulation, and near plumbing fixtures or vents.  When a nest is disturbed, odorous house ants can quickly relocate to another sheltered spot.  They establish new colonies after mating flights (swarms) in late spring and early summer.  Colonies can also divide in a process known as “budding”, where a queen will leave a nest with a group of workers and establish a colony in a new location.

Control:  Make sure you properly identify ants before attempting control.  Knowing the type of ant provides clues about their biology and habits, which helps in the selection of the most appropriate management options.

During warmer months, odorous house ants foraging indoors often come from outdoor nests.  Keeping plants and dense mulch away from building foundations can reduce this indoor activity.  When you see odorous house ants indoors, watch their movement, and try to track them back to where they are entering the building.

An odorous house ant colony in a “hide-a-key” rock stored outdoors
An odorous house ant colony in a “hide-a-key” rock stored outdoors

Sealing these entry points may take care of the problem.  If you can track the ants back to an outdoor nest, you can treat the nest with an aerosol or liquid ant control product (available at a hardware store or garden center).  However, because odorous house ants can have many interconnected nests, treating a single nest may not fully eliminate the problem.  Additional monitoring and treatments may be needed.

If an odorous house ant nest is indoors in an inaccessible spot such as a wall void, baits may be the best control option.  Odorous house ants usually respond well to sugar-based baits (available at a hardware store or garden center).  The ants collect the bait and take it back to the colony where the materials in the bait can kill the queen, thus eliminating the nest.  Place the bait near the foraging trails of the ants.  DO NOT apply other insecticides (e.g., spray insecticides) near the bait, as this can reduce its effectiveness.  After setting out the bait, you may notice an increase in ant activity as additional members of the colony are recruited to collect the material.  Continue to monitor the area, setting out fresh bait as needed, until ant activity fully subsides.

If your odorous house ant problem is extensive, consider consulting a pest control professional with experience in managing ants.  These professionals have additional treatment options and techniques not generally available to homeowners.

For more information on odorous house ants:  Contact your county Extension agent.

 

Beginning Vegetable Garden Basics: Site Selection and Soil Preparation

Starting a vegetable garden may seem overwhelming to a first-time gardener.  However, learning gardening basics and being successful in gardening endeavors can be quite easy.  This fact sheet focuses on how novice gardeners can select and prepare their garden site to ensure maximum success.

Careful site selection and planning can help you maximize your gardening success.
Careful site selection and planning can help you maximize your gardening success.

Where should I plant my garden?  Most vegetables require full sun (i.e., at least six hours of direct sunlight) each day.  Watch a potential garden site throughout the growing season to make sure that trees or buildings do not shade the area from late morning through the afternoon.  A garden area should be well drained; water should not puddle or significantly flow through the area during heavy rains.   Avoid low spots where frost might settle in late spring or early fall, and steep slopes where runoff or erosion could occur.  Be sure the area has a convenient water source (e.g., access to a hose) so that you can water during dry spells.  DO NOT locate a garden within the root zone of black walnut trees.  These trees produce chemicals (juglones) that interfere with the growth of many vegetables.  See University of Wisconsin Garden Facts XHT1017, Black Walnut Toxicity, for details.  Keep in mind that the roots of a tree can grow three to five times the height of a tree away from the trunk.  Finally, make sure there are no underground utility lines where you plan to garden.

How big should my garden be?  Plan the size of your garden based on what you want to grow.  Crops like beans, beets, herbs, lettuce, onions, potatoes, radishes, squash and tomatoes are good options for first-time gardeners.  Start small with just a few crops that are easy to grow and care for.  Research (e.g., online, in seed catalogs, etc.) how large your selected vegetables will grow, and plan enough garden space so that they are not crowded.  Proper spacing promotes good air circulation and sunlight exposure.  Crowded plants will be less productive, difficult to maintain, and more susceptible to diseases.  Consider using bush varieties of vining crops like squash as these take much less space than vining varieties.  Tomato plants should not touch each other when fully mature and should be trellised to prevent crowding.  Cucumbers and smaller-fruited squash can also be trellised to improve spacing.  Space vegetables like beans, carrots and radishes that are seeded in rows according to the instructions on their seed packets.

When planning your garden, consider drawing a map to scale using graph paper to be sure you have enough space for your plants.   See Extension bulletin A1989, The Vegetable Garden, available at https://learningstore.extension.wisc.edu, to learn more on garden mapping, as well as about space requirements for many common vegetables.

Adding compost can improve the structure and fertility of most garden soils.
Adding compost can improve the structure and fertility of most garden soils.

How do I prepare my garden soil?  Ideally, start preparing your garden site the year before planting.  Remove any existing vegetation from your garden site (particularly grass).  You do not want this to grow back in your garden later.  A sod cutter (available to rent in most locations) can be useful for removing grass.  Alternatively, if the garden area is small enough, you can remove grass by hand using a shovel.  Be sure to collect any excess soil from the dug sod and return it to your garden.  After removing whatever vegetation you can, cover the area with cardboard, a tarp or black plastic to smother out any remaining vegetation that you have not been able to remove.

Once your garden area has been cleared of vegetation, add compost to improve the overall soil structure.  Compost helps sandy soils hold more moisture and nutrients, and it makes clay soils lighter and better drained.  Compost also adds trace nutrients needed by plants.  Work a two to three inch layer of compost into the soil with a rototiller or shovel at least a month prior to planting.  Smooth the surface so that you are ready to plant when the weather is appropriate.

Also, consider having the soil in your garden nutrient tested through a certified lab before planting.  A soil test will provide information on the type of soil, the soil pH, the amount of organic matter, and the levels of phosphorous and potassium.  The optimal pH for a vegetable garden is around 6.5, although most vegetables will grow very well with a pH anywhere between 6.0 and 7.2.  A good soil-testing lab will also give you specific recommendations of what to add to your soil to adjust the pH and improve nutrient levels to grow vegetables more successfully.  If you do not have time to test the soil before planting, you can submit a sample later and still make amendments.  However, amending soil after planting is more challenging.

For more information on site selection and soil preparation for vegetable gardens:  Contact your county Extension agent.

Peach Leaf Curl

What is peach leaf curl?  Peach leaf curl is a common disease of peach and nectarine trees throughout the Midwest and eastern U.S.  Where the disease is severe, tree vigor and fruit quality and yield are reduced.  Peach leaf curl often becomes more prevalent after relatively mild winters, which are more favorable for the survival of the organism that causes the disease.  A related disease, plum pockets, affects plums.

Leaf distortions and discoloration typical of peach leaf curl.
Leaf distortions and discoloration typical of peach leaf curl.

What does peach leaf curl look like?  Diseased leaves are distorted with puckered, thickened, twisted areas that can be light green, yellow, or reddish to purple in color.  Leaves later turn brown and fall from the tree.  Diseased shoots are stunted with small, yellowish leaves, or have leaves arranged in tight whorls (rosettes).  Diseased flowers may abort, leading to reduced fruit set, while diseased fruit are bumpy, reddish in color, and fall prematurely.

Where does peach leaf curl come from?  Peach leaf curl is caused by the fungus Taphrina deformans, which overwinters in bark and bud scales of peach and nectarine trees.  Fungal spores infect leaves and shoots in the spring while leaves are still in the bud and as they just begin to emerge.  Mild (50 to 70°F), wet weather during this period favors infection.  Additional spores form on the surface of diseased tissue, and these spores cause new infections if the weather remains mild and wet.

How do I save trees that have peach leaf curl?  Peach leaf curl is unlikely to kill a peach or nectarine tree on its own.  However, if significant premature leaf drop occurs, trees will be susceptible to drought stress and winter injury.  To help maintain tree vigor, apply water (approximately one inch per week) at the drip lines (i.e., the edges of where the branches extend) of peach and nectarine trees during dry periods.  Also, fertilize trees with nitrogen, but avoid fertilizing after August 1; late season fertilization will prevent trees from hardening off properly before winter, making them prone to winter injury.  Finally, thin fruit if the crop load is heavy.

How do I avoid problems with peach leaf curl in the future?  Because Taphrina deformans survives in bark and bud scales, removing diseased leaves in the fall will not reduce disease.  To prevent serious problems with peach leaf curl, plant resistant or tolerant peach varieties (e.g., ‘Frost’, ‘Indian Free’, ‘Q-1-8’, varieties derived from ‘Redhaven’).  Avoid growing susceptible varieties (e.g., those derived from ‘Redskin’).  In addition, consider applying a single fungicide spray in the fall after leaf drop or in the spring before buds begin to swell to control peach leaf curl (and also plum pockets).  Effective fungicide active ingredients include chlorothalonil, copper (e.g., Bordeaux mixture), and ferbam.  Choose a fungicide that is labeled for use on edible fruit crops, and read and follow all label instructions to ensure that you use the product in the safest and most effective manner possible.

For more information on peach leaf curl:  Contact your county Extension agent.