Sunday, December 30, 2012

Sun Scald - Preventing Southwest Injury On Deciduous Trees


Winter in the garden can be a very beautiful sight indeed, but it certainly can have many downsides, at least from a plants perspective. One of these down-sides is sun scald injury to deciduous tree trunks (commonly known as Southwest injury). What is Southwest Injury? Which trees are most susceptible? What can be done to prevent Southwest injury?

What is Southwest Injury?       
Southwest injury also known as sun scald injury is a condition where the sun or strongly reflected light warms the area just beneath the outer bark of a tree (the phloem and cambial area). As this area warms the living cells within become active, but when the temperature of this area suddenly drops (as when the sun goes behind a cloud or sets for the day) the sharp temperature drop can kill these newly activated cells. The resulting damage appears as discolouration and vertical cracks. The damage is usually located on the south or southwestern side of the trunk. As the crack enlarges insects and disease may move in to worsen the problem. If the damage is not to severe the tree may callous over the wound on its own. Care should be taken at this point to prevent further injury.

Which trees are most susceptible?
  • Young deciduous trees are highly susceptible as their bark is very thin and tender. These young trees are usually grown in a sheltered position at a nursery and need time to acclimatize to their new home and to develop mature bark that will serve to protect them from the winter sun.
  • Thin barked deciduous trees like maples, cherries, mountain-ash, apple, peach, tulip trees, ash, willows, birch and lindens are highly susceptible to sun scald. They may require wrapping for several years until their bark begins to thicken.
  • Cherry, peach and plum trees with their thin dark bark are some of the most sensitive trees. They may need to be wrapped their entire life span.

What can be done to prevent Southwest injury?
For city gardeners wrapping the tree trunk with a commercial tree wrap (available at most nurseries) is probably the most effective way to protect your sensitive trees from sunscald damage. The wrap is easy to apply, affordable, and if applied correctly, is quite effective.
Basically how the wrap works is by reflecting the light away from the trunk of the tree, thus preventing the sun from warming the tissues to the point where they can become damaged, when the temperatures suddenly drop. Tree wrap is usually applied just before hard freezes, approximately the beginning of Nov. and are removed when the chance of hard freezes has past, approximately the end of April. Removal is important as the wrap can hold in moisture and created a haven for insects and disease. Newly planted trees should be wrapped for the first couple of years until they have a chance to develop thicker bark. Similarly thin barked trees should be wrapped for several years.
To apply start at the base of the trunk and spiral the wrap up the trunk to the first main branch or just beyond. To fasten the ends use a piece of electrical tape (or other water proof tape), or pin into place (pinning tape to tape, not pinning to the tree. This can be a bit tough on the fingers but a thimble can be quite helpful).
Other tips for preventing Southwest injury include:
  • Not planting highly susceptible trees in unprotected southwestern exposures.
  • Plant susceptible trees on the eastern or northern side of buildings and tall ever greens. These structures will help to shade the trees bark and prevent large temperature fluctuations.
  • Make sure your trees are well watered prior to freeze up. Drought stressed trees tend to be more susceptible to Southwest injury.
  • Do not locate susceptible trees near large light coloured, reflective surfaces. Although sun scald typically happens on the Southwest side of a tree it can happen on other sides if the light being reflected towards the tree trunk is intense enough, as with a south or west facing white fence or building structure.
  • Sunscald can also occur during the summer months. When this occurs it is usually the result of a large branch being pruned away or broken off during a wind storm. The sudden removal of this branch exposes bark and neighbouring branches to intense sunlight for which it is not accustomed to.
‘Winter Injury on Trees” by Janna Beckerman, Associate Professor, Department: Botany and Plant Pathology, Purdue University.

‘Sunscald Injury or Southwest Winter Injury on Deciduous Trees” by Katie Wagner, Extension Assistant Professor and Michael Kuhns, Extension Forestry Specialist;

‘Sunscald – ‘Southwest Disease’’ by Curtis E. Swift, Ph.D., Colorado State University Extension

Thursday, December 27, 2012

Winter Garden Care - Protecting Your Plants From Salt Damage

The snowy season has finally come upon us here in Southern Ontario and along with the snow comes snow plows and salt trucks. Why is salt so damaging? What can you do to protect your sensitive plant material from salt damage? What can be done to treat plants that have been damaged by salt?

Why is salt so damaging?
Rock salt or Sodium Chloride (Na Cl) is commonly used to deice roads and walkways. As a de-icer it is fast, easy to use, effective and affordable. On the down side though, its corrosive nature is damaging to vehicles, roads and pathways. This same salt can also be very damaging to plant material.

There are 3 ways in which salt can damage your plant material.
1.      Damage the soil: As the salts accumulate in the soil the soils structure can actually begin to change. These changes increase compaction and reduce aeration, and water infiltration. Soil pH also increases as salinity increases and beneficial soil microbes, especially Mycorrhizal fungi, can be harmed…these fungi help plants to take up nutrients.

2.      Salt spray can burn the tissues of plants and cause them to de-hydrate: On city roadways plants up to 30’-40’ away are at risk.

3.      Excess salt in the soil can cause plants to de-hydrate: Salt is a highly absorbable compound which binds very tightly with water. As it binds with the water that water becomes unavailable to the plants and even though there may be plenty of moisture in the soil the plants may experience de-hydration. Salt even has the ability to draw water from the roots, thus de-hydrating them. If the condition persists the plant will eventually die.

What can you do to protect your sensitive plant material from salt damage?
      If you are able to avoid the use of salt then this is your best bet. For times when this is not possible, like in the case of cities salting roadways then your best defence is to plant materials that are less sensitive to road salt…like Day Lilies (Hemerocallis), English ivy (Hedera helix), Liriope sp. , Russian sage  (Perovskia atriplicifolia) Feather Reed Grass (Calamagrostis acutifloria), Switchgrass (Panicum virgatum), Bluestem (Andropogon), Sea Thrift (Armeria maritima), Fountain Grass (Pennisetum alopecuroides), Green Ash (Fraxinus Americana), Junipers (Juniperus species), Bridlewreath Spirea (Spiraea x Vanhouttei), Lilacs (Syringa species)

      Stay away from sensitive plants like: Box wood (Boxus), Daffodils, Eastern Redbud (Cercis Canadensis), Red Osier Dogwood (Cornus sericea), European Filbert (Corylus avellana), Sugar Maple (Acer saccharum), Eastern Pin Oak (Quercus palustris), Silver Maple (Acer saccharinum) and Serviceberry (Amelanchier spp.).

      Construct a physical barrier around sensitive plants: This barrier may be made of plastic, burlap, or snow fencing. Whatever it is made of install it several inches from the plant you are trying to protect, placing the barrier between the pavement (the source of salt) and the plants.

What can be done to treat plants that have been damaged by salt?
      Flush out the root zone of effected plants to at least a depth of 6”. (If the soil is badly compacted you may need to first aerate the soil in order to assist the water in infiltrating).

      Apply Gypsum to the affected area. In heavy clay soils (the ones most likely to accumulate high levels of salt) the gypsum will displace sodium ions with calcium ions. This will help to improve both aeration and drainage and allow the salts to be leached from the root zone.

'Winter Salt Injury and Salt Tolerant Landscape Plants' by Laura G. Jull, associate professor of horticulture and Life Sciences, University of Wisconsin-Madison and University of Wisconsin- Extension Cooperative Extension.

‘Salt Damage in Landscape Plants’ by Janna Beckerman, Department of Botany and Plant Pathology, Purdue University

Tuesday, November 20, 2012

Boxwoods For Ontario Landscapes

Buxus or Boxwoods are a genus of evergreen shrubs and trees. They are known worldwide for their usually compact size and small, leathery leaves. Steeped in a rich tradition and heritage these versatile shrubs have graced the homes of royalty and peasants alike.

According to the American Boxwood Society there are about 90 species of boxwood world-wide and over 365 cultivars (148 of which are currently available commercially). Most of these species are tropical or sub-tropical but there are a few species and several notable varieties and cultivars that are suitable for our Ontario climate.

Choosing a Boxwood Variety That is Right For Your Landscaping Needs

With so many cultivars to choose from how does one determine what would be a good boxwood choice for their landscape? To begin with it helps to know a little bit about the growth habit of various cultivars and their growing preferences. North American selections of boxwoods can range in height anywhere's from 10' (for American boxwood) to 2' (for some of the dwarf cultivars like Boxus microphylla 'Koreana' and Buxus microphylla 'Winter Gem'). Some cultivars are more cold torerant than others, some bronze in the winter and are thus not as good of chooses for more northerly gardens especially in exposed sites. Following are a few notable varieties and cultivars, but there are many others available.

English Boxwood: (Buxus semperviren ‘Suffruticosa’)
Often referred to as common boxwood this species is native to Europe, North Africa and Western Asia. Most notable characteristics of this dwarf cultivar include a very dense growth habit and slow growth rate (averaging only 1” of growth per year). English boxwoods have a tendency to bronze in the winter and mature shrubs are susceptible to boxwood decline, especially when grown in full sun. Performs best in part sun in well drained sites.
Height: 60-90cm (2'-3')
Width: 90-120cm (3'-4')
Zone: 5-8
Landscape uses: This boxwood makes an excellent edging plant, (perhaps outlining a formal garden or along unsalted pathways and driveways). Also a good choice for knot gardens, topiary and bosai.

American Boxwood: (Buxus semperviren ‘Arbvorescens’)
This is a faster growing cultivar with a looser growth habit. Average height 6’-10’ (but some can reach up to 20'). Growth habit is upright; conical to irregular form with evergreen leaves that are more pointed at the ends rather than rounded. They will tolerate sun or shade and a variety of soil conditions.
Height: 180-300cm (6'-10')
Width: 90-120cm (3'-4')
Zone: 5-8
Landscape uses: Use for an informal large evergreen shrub or shear into a cone, pyramid or rounded globe shape. They can be used for hedges (in areas sheltered from cold winter winds) and topiary.

Japanese Boxwood: (Buxus microphylla var. japonica 'Green Beauty")
Japanese boxwoods are typically more heat and drought tolerant than their English counterparts, making them better suited to areas with hot summers. They will retain their dark green foliage even in the hottest summers but tend to bronze in cold weather. 'Green Beauty' has a moderate growth habit with a naturally rounded shape and smaller leaves that give it a more delicate texture. Also known as Boxus harlandii
Height: 120-180cm (4'-6')
Width: 120-180cm (4'-6')
Zone: 5-9
Landscape uses: Excellent for specimen plantings, small hedges and topiary.

Boxus microphylla var. koreana 'Winter Green'
(renamed to Buxus sinica var. insularis 'Wintergreen', but still sold under both names)
Owing to its Japanese parentage this selection features smaller leaves. Growth habit is mounded, slightly wider than taller, with usually a slightly loose and open habit. Slow annual growth (to 2" in height per year).
Height: 60-120cm (2'-4')
Width: 60-120cm (2'-4)
Zone: 4-9
Landscape uses: Small hedges or for edging formal beds or unsalted pathways, specimen plant in a mixed shrub or perennial bed, bonsai and containers.

Popular Hybrids: The green series introduced in Ontario by Sheridan Nurseries are a cross between Buxus microphylla var. koreana and Buxus sempervirens. These boxwoods are more cold hardy with less winter bronzing and tolerate full sun better than many varieties. Their growth habit is compact and fairly dense and tend to require little pruning, although they can be easily sheared to desired shapes. 'Green Velvet', 'Green Mountain', 'Green Gem' and 'Green Mound' are four 4 popular cultivars from this collection and well suited for Ontario landscapes.

Boxus 'Green Velvet':
'Green Velvet' is full bodied, semi-spherical (slightly wider than taller with a flatter top) and lends itself well to pruning and shaping into globe shapes. Green Velvet is a particularly hardy variety and holds its colour well into winter.
Height: 100cm (3')
Width: 120cm (4')
Zone: 4-9
Landscape uses: Makes and excellent low hedge, edging plant or specimen plant in mixed shrub or perennial bed. Also does well in containers. Mixes well in both formal and informal landscapes.

Boxus 'Green Mountain':
Has an upright, pyramid shaped growth habit that holds its shape well with very little pruning. 'Green Mountain' is a faster growing selection that holds its colour well over the winter months making it an excellent choice for hedging. This Hybrid does well in full sun when given cool moist soil conditions, but it will also do well in part-shade.
Height: 150cm (5’)
Width: 100cm (3’)
Zone: 4b-9
Landscape uses: Perfect for cone shaped specimen plantings, as mid-sized hedging, topiary, spirals and containers.

Boxus "Green Gem®':
A slow growing, dwarf cultivar with small narrow leaves. It is naturally globe-shaped with a dense branching habit that requires very little pruning. 'Green Gem' has excellent winter hardiness and holds its colour well over the winter months (although it can bronze a bit in exposed sites). This hybrid performs best when planted in a more sheltered location which protects it from strong winds and full sun. 'Green Gem' tolerates some drought.
Height: 50 -75cm (1½' - 2 ½')
Width: 50 -75cm (1½' - 2 ½')
Zone: 4b-9
Landscape uses: An excellent specimen planting for the front of a mixed shrub or perennial bed, bonsai, containers, topiary balls and edging.

Boxus 'Green Mound':
Features medium sized leaves which are oval and grow outward to a point with tight spacing along narrowly branched stems. Green foliage holds it colour well throughout the year, protection from winter winds will help to protect against winter bronzing.
Height: 100cm (3')
Width: 100cm (3')
zone: 4b-9
Landscape uses: suitable for low hedging as well as specimen planting.

How To Care For Your Boxwood Shrubs

Light requirements: Boxwood will grow in full sun but prefer part shade. (Some cultivars tolerate more sun than others. i.e. the green series hybrids prefer more sun.)

Soil pH: Boxwood prefer a soil pH between 6.5 and 7

Moisture: Moist well drained soil is preferred. Boxwood hate wet feet and are highly susceptible to root rot when grown in standing water.

Propagation: Stem cuttings are the most common technique but layering is also an option. When selecting stems to cut choose smaller 1-year old branches, they are said to have a higher concentration of growth hormones. Non hybrids can be grown from seed, to do this scarify the seeds and plant them at a depth of about 1”. Germination will take anywhere from 30 to 190 days.

Mulching: Boxwoods are shallow rooters and benefit from a shallow layer of mulch to protect the roots. Deep mulching should be avoided as it may encourage roots to grow above the soil surface putting them at high risk of damage when dried out.

Salt spray: Most boxwood are very sensitive to the salt spray from roadways, plant them far enough away from these areas to avoid injury.

Poisonous leaves: The leaves of boxwood contain steroidal alkaloids making them mildly toxic to both humans and animals.

Pruning: Boxwood can take repeated close shearing making them a popular choice for topiary, bonsai, and formally clipped hedges and shrubs. Species and cultivars (such as Buxus sempervirens) with a dense growth habit benefit from thinning to open up their centers to better air and light circulation. This encourages growth of leaves on the interior and may help to reduce disease.

Potential Problems

Boxwood blight: a fungal disease causing rapid and severe defoliation. Caused by the pathogen, Cylindrocladium buxicola. Symptoms first appear as leaf spots that are light to dark brown, with or without a dark border, as well as stem lesions or cankers. After infection has taken place white spore masses develop on the undersides of leaves. Wounding is not required

Volutella blight: a fungal disease caused by the fungus volutella buxi. Symptoms include salmon coloured spots on lower leaf surfaces and some stems, followed by yellowing and then leaf and stem death. Black steaks are sometime visible on petioles and stems. Unlike boxwood blight wounding is required for this infection to take place. Volutella buxi requires 18 hours of wet conditions in order to germinate.

Spider mites: leaves of injured plants appear stippled.

Phytophthora root rot: Caused by the fungi, Phytophthora. Plant boxes in well drained soil to help prevent this disease. Buxus sempervirens ‘Suffruticosa’ and Buxus sempervirens ‘Arborescens’ are most susceptible.

Winter Bronzing: leaves turn a bronze colour as the result of exposure to cold, dry winter winds. Plant boxes in a sheltered spot or place physical barriers (about 18” away from the plant) on the windward side to protect them.

Nematodes: these microscopic, worm-like organisms feed on the roots. Plants appear to be in decline and appear smaller than normal.

Leaf Miner: damage appears as blotch mines between the upper and lower leaf surfaces. American boxwood tends to be the most susceptible.

Boxwood decline: older English boxwoods, particularly those grown in full sun and drier soils, show a slow progressive decline.

Psyllid: Feeding of this insect causes the outer leaves to curl and form a cup which encloses the nymphs.

In spite of these potential problems boxwood remain a popular and easy to grow shrub. Whether you are looking for an evergreen to naturalize, a small tidy tree or a highly ornate shrub, boxwood has a species or a cultivar to suit almost any landscaping need.

  • Diseases and Pests of Ornamental Plants (fifth edition); Pascal P. Pirone; The New York Botanical Garden 1978
  • Lois Hole’s Favorite trees & Shrubs; by Lois Hole with Jill Fallis; 1997 Lois Hole and Lone Pine Publishing
  • Ever Green Shrubs; Alexandria, Va.; Time Life Books 1989

  • Growing Boxwoods in the Landscape; Erv Evans, extension Associate; Richard E. Bir, Extension Specialist; Stephen Bambara, Extension Entomology Specialist; Department of horticulture Science, North Carolina Cooperative Extension Service (revised 2/99)
  • IPM Series: Boxwood; University of Maryland Extension; Mary Kay Malinoski, David L. Clement, Raymond V. Bosmans; Regional Specialists, Home and garden Information center; Rev.5/2009;
  • Major Diseases of Boxwood; Mary Ann Hansen, Extension Plant Pathologist, department of plant pathology, Physiology and Weed Science, Virginia Cooperative Extension, Virginia tech, and Virginia State University, May 2009
  • Volutella blight of boxwood; Fang (Amy) Shi and Tom Hsiang; School of Environmental Sciences, University of Guelph

Friday, August 3, 2012

Corkscrew Hazelnut Infected With Eastern Filbert Blight

Corkscrew Hazelnut (Corylus avellana 'Contorta') infected with Eastern Filbert Blight
Photo credit: Kimberley Pacholko
This ornamental corkscrew hazelnut (Corylus avellana 'Contorta') has contracted a lethal disease known as Eastern Filbert Blight. The disease is caused by the fungus - Anisogramma anomola and is native to the northeastern United States and eastern Canada (although it has appeared in British Columbia, as early as 2001). Hazelnuts native to this region (Corylus americana) have proven to be more resistant to the disease (some are even immune) than the imported European hazelnuts (Corylus avellana).

Often one of the first symptoms homeowners report are droopier than normal leaves, accompanied by the dieback of twigs and branches. Dead leaves may remain attached to the branch, this often a good indicator of the disease. Upon closer inspection elongated (football shaped), dark-brown to black fruiting bodies called stromata can be found, appearing in relatively straight rows lengthwise along the branch. The stromata erupt within cankers (dead areas on the bark or stem, often sunken or raised), approximately 12 to 18 months after the area has been infected. The cankers continue to grow, eventually girdling the branch, resulting in branch dieback. (Note: According the Plant Disease Diagnostic Clinic, at Cornell University cankers can grow in size anywhere from a few centimeters up to 1 meter annually.)

In the spring, about the time the hazelnuts are at bud-break, the stromata release fungal spores. These spores are carried by rain and splashing water droplets driven by wind, to new areas of the branch, new branches and potentially new trees of the same species. New rows of stromata are also formed along the margin of the canker each year. (Note: New growth tends to be the most susceptible to new infections.) The following season new stromata will erupt in the infected areas and if not pruned off before bud-break  they too will release their fungal spores, and the cycle continues. Once a branch has died the fungal spores within that branch also die. The fungus requires moisture in order to sporulate, thus diseased branches that have been pruned-out should be burned or shredded to help prevent new infections.

Corkscrew Hazelnut (Corylus avellana 'Contorta') infected with Eastern Filbert Blight
Photo credit: Kimberley Pacholko

Usually for the small home gardener by the time the disease is diagnosed there is not much that can be done, other than to remove and destroy the tree. For larger trees or smaller trees that have been caught early the following treatments may prove helpful in treating and controlling the disease.
  • Prune out and destroy infected wood well below the cankers (1 to 3 feet below). This must be done before bud break in the spring. The branches must be pruned back this far to ensure the complete removal of all fungal spores (which are always ahead of the visual signs of the disease). Like a cancer any remaining spores can continue to grow and kill branches.
  • Plant resistant cultivars 
  • The following fungicides are registered for Eastern Filbert Blight in Canada (The list is from the B.C. Ministry of Agriculture
    1. Copper Oxychloride 50 or Copper Spray at 3.0 to 9.0 kg/ha (1.2 to 3.6 kg/acre) in at least 1,000 L/ha (400 L/acre) of water. Use the low rate on small trees and the high rate on mature trees. Do not apply within1 day of harvest. Note: Copper is generally acceptable for organic production. Check with your certifying agency.
    2. Flint 50 WG (50% trifloxystrobin) at 140 to 280 g/ha (56 to 112 g/acre) in at least 1,000 L/ha (400 L/acre) of water. Use the higher rate when disease pressure is severe. Do not apply more than 4 times per season. Do not apply more than two consecutive applications of Flint. Do not apply within 60 days of harvest.
    3. Quadris Flowable (250 g/L azoxystrobin) at 900 mL/ha (360 mL/acre). For mature trees, use at least 1,000 L/ha (400 L/acre) of water. Do not apply more than 4 times per season. Do not apply more that two consecutive applications of Quadris. Do not apply within 45 days of harvest.
Note: For Ontario residents check the Ontario Ministry of the Environment for an up-to-date list of permitted pesticides.

Look-like Diseases:
According to Jay W. Pscheidt, Extension Plant Pathologist at the Oregon State University, Eastern Filbert Blight resembles another fungal disease caused by the fungus Eutypella cerviculata. Eutypella produces similar spore producing structures, however, they are said to be smaller in size and produced on dead wood. To properly identify this fungus, take a small knife and scrap away the surface layers of the diseased area. If the disease is the result of the fungus Eutypella cerviculata  rather than EFB  you will find black rings around the stromata.

Thursday, August 2, 2012

Striped Cucumber Beetle

Does it look as though something has been chewing on the leaves of your cucumber, squash, melon or pumpkins? Are you finding girdled stems and scaring on the fruits? Perhaps you have even noticed that the plants appear smaller this season. If this sounds like your garden then chances are the Striped Cucumber Beetle has come to dine in your garden.

Meet The Pest:

Striped Cucumber Beetle Adult - Acalymma vittatum

Adult Striped Cucumber Beetles are yellowish in color, about 1/4 inch long, with three black stripes down the length of their abdomen. The thorax is yellowish with no striping while the head and antennae are dark in colour.

Plants at Risk
Cucumbers, squashes, melons, and pumpkins are the prefered food choices of the striped cucumber beetle but they will also feed on tomatoes and other garden crops if cucurbits are unavailable or there are more beetles than the available cucurbits can support.

Life Cycle
Adult beetles overwinter in plant debris and emerge in mid-spring, when temperatures reach about 18 degrees C. (right about the time cucurbit seedlings are beginning to emerge through the soil. Planting transplants rather than seeds may help give your plants a head start and get them past this vulnerable period). According to William F. Lyon and Alan Smith of the Ohio State University Extension Entomology the beetles will soon mate and the females will deposit 225-800 eggs in small clusters or singly into soil cracks at the base of cucurbit plants. This is said to occur about 8-25 days after mating, with the eggs hatching 5-8 days later. The larvae then spend about 15 days feeding on the roots and stems of fruit that is in contact with the soil. The time from egg to adult for the first generation of beetles requires about 1 month. Southern Ontario has only one generation per year.

Hand picking, crop rotation, row covers (remove during flowering period). Natural predators include: tachinid flies, soldier beetles and braconid wasps.

Cucumber Beetle Damage
Leaf Damage of Striped Cucumber Beetle

Leaves: The adult beetles chew holes in the leaves and can reduce them to tatters.

Stem Damage of Striped Cucumber Beetle

Stems: Larvae also feed on stems causing girdling.

Fruit Damage of Striped Cucumber Beetle

Fruit: Both larvae and adults feed on the fruits causing scaring.

Roots: The larvae feed on the roots which can stunt the growth of the plant. 
Cucumber Wilt Caused by the Cucumber Beetle
This cucumber plant will have to be distroyed. It has been infected with the Bacterium - Erwinia tracheiphila, causing what is referred to as Cucumber Wilt or Bacterial Wilt. The bacterium overwinters in the bodies of hibernating cucumber beetles who then introduce the bacteria into the plants through the fecal contamination of feeding wounds.The disease appears first as patches of discoloration, followed by a sudden wilting of the plant. The beetles are also known to spread squash mosaic virus. All cucurbits, except watermelon are potentially affected by the disease.

Tomato Flea Beetles

Tomato flea beetles have been busy showing off their handy work again this season. If the leaves of  your tomatoes appear as though they have been used as target practice at a rifle range, then chances are you have flea beetles. Other plants that can be damaged include: peppers, melons, potatoes, corn, spinach, eggplants and members of the brassica family (like cabbage, cauliflower, broccoli and brussel sprouts).

Flea beetles can be hard to spot as they are quite small, between 1/16 and 1/8 of an inch and quickly jump when disturbed. They come in a variety of colors from black, bluish bronze, metallic grey, or brown.

Tiny holes peppered over the leaf. This characteristic damage is called 'shot-holing'. Young seedlings are most vulnerable and can receive enough damage to kill the plant. Mature plants can usually sustain significant leaf damage. Other damage can include blemishes or pimples to root crops like radish, daikon or turnips. Flea beetles are common vectors for bacterial and viral diseases and plants attacked by these pathogens will need to be destroyed.

Life Cycle:
Flea Beetles over winter as adults, in leaf litter and garden debris. They reemurge in mid to late spring (roughly mid-May in Ontario) and soon begin mating. The females lay their eggs either singly or in clusters in the soil around the base of host plants through-out the spring and early summer. The larvae then feed on the root hairs and roots of the plants for about 1 month then pupate in the soil. The adults emerge from the soil (about the end of July) feed and then seek hibernation sites in the fall.

There are several natural controls that help reduce flea beetle populations. Check first when in doubt what is permitted in your local.
  • Beneficial's: The braconid wasp (Microcotonus vittage Muesebeck) is a predator of flea beetles. They are attracted to anise, cilantro, dill and fennel.
  • Flea beetles lay their eggs in the soil and prefer bare soil. Using mulch can help to make it difficult for them to lay their eggs.
  • Delay your spring planting  by a couple of weeks and plant larger healthy plants. This is especially advisable if you have had a very mild winter or a large flea beetle population the year before.
  • Crop rotation is recommended when possible.
  • Clean up garden debris and fallen leaves in the fall to minimize overwintering.
  • Turning over the soil in the fall will help to expose the fleas to birds and may destroy their winter hangout.
  • Diatomaceous Earth (Silicon Dioxide) is said to work for fleas (although I have not tried it myself for this purpose). Diatomaceous Earth is the ground up fossilized remains of one celled diatoms. Their razor sharp edges are capable of piercing the outer surfaces of the insects causing them to dehydrate. It usually used for soft-bodied insects. Diatomaceous Earth comes in a powder form and is sprinkled on dry.
  • Covering your plants with row covers  or cheese cloth will help to keep beetles away (ensure the holes are small enough to prevent them from getting through).
  • Insect repellents that contain garlic, mint, or hot peppers are said to be help ward off flea beetles, these will need frequent reapplication.

Sunday, July 22, 2012

Lawns and Gardens- Tips For Surviving The Summer Heat And Drought

Drought-induced Dormancy
Soaring summer temperatures  and lack of rain fall can really take a toll on your lawn.  Many grasses will try to survive by entering a dormant stage where they drink less water and stop growing. According to Milorganite, lawns can survive without water for 3-4 weeks, at day time temperatures of up to 27 degrees C; but when those temperatures begin climbing past 33 degrees C that time frame is reduced to 2-3 weeks. If you are unable to provide the inch of irrigation that a lawn requires weekly to stay green you are best to allow it to enter this dormant stage and remain there until the end of the hot, dry season. To keep your dormant lawn alive you will need to irrigate it lightly, about ½ inch, every 3 weeks (more or less often, as mentioned above depending upon the average daily temperatures). This irrigation will not make a dormant lawn green again. Greening will start when conditions get cooler and wetter.

To keep a lawn green over the summer you will need to provide a minimum of 1 inch of water per week. This will wet the soil to a depth of 4 to 6 inches (an average lawns root zone). To determine how much water your have applied set a water gauge or container in the area you are watering and once you have filled the container an inch you can turn the water off. If you make a note of how long it takes on average to put an inch of water on your lawn you should not need to measure each time.

Other lawn care tips to help you through the hot dry season:
  • Infrequent and deeper watering prior to drought will develop deeper roots, which make plants much more sustainable.  
  • Raise the blade on the lawn mower and keep the lawn tall throughout the summer. This will keep the surface of the soil from drying out, reducing the need for watering. Cool season grasses like Kentucky bluegrass, fescue, bentgrass, and perennial ryegrass should grow 2 ½ to 3 inches tall.
  • Leave grass clippings on the lawn; clippings not only decompose and provide nutrients to your lawn but they also help to hold in moisture and shade the soil.
  • Once your lawn has gone dormant fertilizing will not bring it out of dormancy. Apply your fertilizers spring and fall. This will give you nice strong roots that are better able to cope with the hot dry season.


scorched leaves on a maple tree
This maple tree located on a center boulevard in Whitby, Ontario is exhibiting classic drought symptoms of leaf scorch. Leaf scorch appears as outer edges turning brown and curling (leaves may also brown between the veins). The damage is usually symmetrical beginning at the leaf tip and working back. The fact that the damaged occurs on the edges helps to differentiate it from a disease. On diseased leaves the damage occurs away from the edges and crosses the veins. Trees facing roadways and paved pathways are more prone to leaf scorch as the hard surfaces collect and reflect, concentrated heat. Plants on the south or west sides of buildings or fences also tend to exhibit more leaf scorch. 

Drought Damage:
  • Conifers drop old needles followed by the tips of the needles turning brown. If the drought continues the new season's growth may droop, gradually yellow, then brown; needles may also be shorter and twig size may be smaller. According to Ethel M. Dutky of the Plant Diagnostic laboratory at the University of Maryland, resinous bleeding cankers on large branches and main trunk may also develop. (Bleeding cankers are caused by a fungal disease. The cankers (the swollen areas) can expand and girdle the tree or branch).
  • Evergreens gradually turn yellowish-green, then light brown. Discoloration starts at the top and progresses downward, and from the outside in. With prolonged drought conditions leaves may be smaller than normal, drop prematurely or remain attached to the tree even though brown. 
  • Boxwood exhibits a general bronzing or an orange coloration of the foliage. They require at least 1" of water per week.
  • Drought damage may or may not reveal its-self right away. Often you see the effects of drought one to two years down the road when insects and disease move in to attack the weaken tree.
  • Soil compaction will increase drought damage by not allowing rainfall and irrigation to penetrate down to the roots. Have the soil beneath the tree aerated (if compacted), then irrigate it regularly, keeping all foot traffic and heavy machinery off for the season.
  • "99% of the root system of a tree is located in the top 3' of the soil, and a good portion of these are in the top 12"." (Dr. Sharon M. Douglas, of the department of Plant Pathology and Ecology at The Connecticut Agricultural Experiment Station). "This is especially true of feeder roots. When dry soil conditions occur, the feeder roots and root hairs shrivel and become non-functional."
*Some Drought Tolerant Trees and Shrubs Include:
Trees: larch, bur oak, Colorado blue spruce, green ash, Douglas fir, amur maple,  mountain ash, red pine, eastern red cedar.
Shrubs: Crape myrtles, lilacs, smoke trees, junipers, boxwood, yews, caragana, potentilla, spirea, and hypericum.

How To Water Your Trees:
  • Water deeply and water slowly. You want the water to soak deep down to the roots not run off. Watering for short periods of time encourages shallow rooting which may lead to further drought damage.
  • For deciduous trees water, with-in the 'dripline' (the outer edges of the tree’s branches) deeply, to a depth of 12inches below the soil surface. Coil a drip hose around the trees drip line or place your garden hose on slow to medium flow under the drip line. For smaller trees water bags and 5 gallon buckets  with holes punched in the bottom also work well.
  • For evergreens, water 3’-5’ beyond the dripline on all sides of the tree.
  • According to the CSU/Denver County Extension Master Gardeners your tree should receive approximately 10 gallons of water per inch of trunk diameter (measured at knee height) for each watering. Note: It takes approximately 5 minutes to produce 10 gallons of water when you hand water using a hose at medium pressure.
Note: It is not advisable to fertilize trees that are being stressed by drought. Encouraging your tree to put on new top growth will only increase the demands and stress on the tree also the fertilizer may potentially burn the roots due to insufficient water to dilute it.

John Kennedy Rose
Roses develop long tap roots that enable them to go in search of water and nutrients. Like other tap rooted plants they benefit most from deep, but infrequent watering. The American Rose Society advises that roses should receive 1 to 2 inches of water each week. Just how deeply the water penetrates will depend on upon the soil structure. In a sandy soil one inch of water will penetrate about 12″, in a medium loam about 7″, and in a clay soil about 5″. To help the water to get down to the long root zone try building a 4"soil basin around the drip line of your rose. Slowly fill the basin (careful not to break the sides of the basin down), let it drain then fill it again.

Other Tips For Helping Your Roses Survive The Summer Heat And Drought:
  • In drought, do not cut blooms from the bush as they start to fade. Allowing flowers to form seed heads will help postpone the new growth that normally follows each blooming period. Do, however, remove seed heads soon after they have formed because they will use water to mature.
  • Mulch (2 to 3 inches around a bush) to help retain moisture from watering and reduce future watering needs. Mulching also helps keep the soil cool and helps control weeds.
  • Fertilizer should be applied sparingly. Feed roses just enough to keep them healthy without over-stimulating growth. A light hand with fertilizer protects against fertilizer burn as well.
  • Plants under stress are more likely to attract plant pests and insects and to develop disease. Help to keep your roses stress free by nourishing them an inch or 2 of water per week.

There are no hard fast rules (that I know of) for how much to water perennials. Each plants requirements can be quite different. Some like it dry while others like to remain constantly moist. As a general guide:
  • New and less established plants will require more frequent watering. This is due to the smaller root ball and its inability to reach the moisture located deeper in the soil.
  • Tap rooted plants tend to require less frequent watering (but this watering, as mentioned must be a deep watering).
  • Native plants tend to survive heat and drought well (with little supplemental water) if heat and drought is common to your area.
  • Larger plants usually require a larger amount of water at each feeding.
  • Shade lovers tend to prefer moister soil and will require more frequent watering when grown in sunnier areas of the garden.
  • Mulch your perennial beds and add plently of organic matter to your soil. Both serve to hold moisture in, reducing future watering needs.

Heat Exhaustion:
Ligularia 'The Rocket'
Some plants like this Ligularia do not much like the heat. No matter how much you water them they tend to go limp during the heat of the day. They will usually perk up again when the cooler evening temperatures arrive. However this year's heat wave with it's hot evening temperatures have not been offering the plants much relief. Another plant that tends to droop in the heat are hydrangeas. About all the home gardener can do is to ensure they remain well watered and wait for the cooler temperatures to return. (Note: Caution not to over water. Some gardeners mistake the drooping for lack of water. Check the soil first, and only water if the soil is dry to the touch).

Leaf Scorch
Cimicifuga (black bugbane)
Leaf scorch commonly occurs on lower light loving plants like this black bugbane, hostas, astilbe, solomons seal, tuberous begonias...and more. Typically permanently relocating them to a shadier, moister location is your best solution. However during extended periods of drought and heat almost any plant can become scorched including large shade trees. During these periods keep your plants, including your trees well watered.

*Drought Tolerant Perennials:

  • Artemisias - (Artemisia species)
  • Blanket flower - (Gaillardia x grandiflora)
  • Blue fescue - (Festuca cinerea)
  • Creeping phlox - (Phlox subulata)
  • Creeping potentilla - (Potentilla neumanniana)
  • German statice - (Goniolimon tataricum)
  • Globe thistle - (Echinops ritro)
  • Hens and chicks - (Sempervivum tectorum)
  • Ice plant - (Delosperma species)
  • Lambs ear - (Stachys byzantina)
  • Lavender cotton - (Santolina chamaecyparissus)
  • Little bluestem - (Schizachyrium scoparium)
  • Oriental poppy - (Papaver orientale)
  • Ozark primrose - (Oenothera missouriensis)
  • Penstemon (Penstemon species)
  • Plumbago - (Ceratostigma plumbaginoides)
  • Poppy mallow - (Callirhoe involucrata)
  • Prairie coneflower - (Ratibida columnifera)
  • Prairie dropseed - (Sporobolus heterolepsis)
  • Purple coneflower - (Echinacea purpurea)
  • Russian sage - (Perovskia atriplicifolia)
  • Snow-in-summer - (Cerastium tomentosum)
  • Stonecrop - (Sedum species)
  • Yarrow - (Achillea species)

  • Annuals:
    Annuals tend to have smaller root balls that dry out quickly in the summer heat. As such they tend to (but not always) require more frequent watering. When the weather forcasters call for a hot dry summer is may be easier to try growing some drought tolerant annuals that year and save your water lovers for years with more plentiful rainfall.

     Fuchsia showing the effects of heat stress. The plant has entered into dormancy in order to conserve its energy. It will rebound and begin blooming again once the temperatures cool down.

    Zonal and Ivy geraniums seem to thrive under the hot, dry conditions of summer

    Classic wilt symptoms of Impatiens. These water lovers can be fairly demanding when mother nature cranks up the heat.

    *A few drought tolerant annuals to choose from include:
    • Cosmos - (Cosmos sulphureus)
    • Creeping zinnia - (Sanvitalia procumbens)
    • Blanket flower - (Gaillardia)
    • Sun flower - (Helianthus annuus)
    • Dusty miller - (Senecio cineraria)
    • Annual mallow - (Lavatera trimestris)
    • Spider flower - (Cleome hassleriana)
    • Morning glory - (Ipomoea spp.)
    • Narrow-leaf zinnia - (Zinnia angustifolia)
    • Zonal Geranium - (Pelargonium zonale)
    • Annual fountain grass - (Pennisetum setaceum)
    • Globe amaranth- (Gomphrena globosa)
    • Gazania - (Gazania rigens)
    • Lantana - (Lantana spp.)
    • Verbena - (Verbena spp.)
    *(Drought tolerant does not mean the plant can go without water it merely means it is more tolerant.)