Posts tagged resistant

The deadly juglone of black walnut trees

The following is by Linn County Master Gardener, Claire Smith:

    The seeder wagon is in place.  The lawn mower towed it out of the shed down to the water way and then with two planks and my favorite son’s strong back we pushed and pulled it to the other side of the ditch.  With the addition of an old wire garden gate staked behind a sapling, a hand pump from my parent’s former home and a rock lined pseudo fire pit filled with Petunias that were on the end-of-season sale, the area reflects the peaceful primitive atmosphere I was striving for.  This is the area I mentioned in an earlier blog that became inaccessible to mow due to last year’s flood.  Hosta, native grasses and prairie perennials will grace the space next year.  We continued our zeroscaping to include a part of the road ditch that I learned is also impossible to mow after the mower and I suffered a close encounter with the culvert.  Now that waterway is filled with large rocks and what was a sloping grassy space is mulched. 

            Hosta will ring the two Black Walnut trees in the roadway ditch.  Hosta is a plant of choice there because I have some that need transplanting and they are not sensitive to Juglone, a chemical secretion from Black Walnut Trees. 

             Discovered in the 1880s, Juglone is produced in the fruit, leaves, branches and root system of several trees with Black Walnuts exhibiting the highest concentration.  The greatest intensity in the soil exists within the tree’s drip line, on an average 50 ft. radius from the trunk of a mature tree.  Plants susceptible to Juglone display yellowing leaves, wilting and eventual death.  Plants sensitive to Juglone include Peonies, Hydrangea, Asian Lilies, and Lilacs.  There are multiple choices that will withstand close proximity to Walnut trees such as most grasses, Phlox, Sedum, Daylilies, Iris and Hosta.

            Now my challenge is to determine plants that are not only resistant to Juglone, but also to the deer population in this neighborhood.  Unfortunately, Hosta is one of the critters’ favorite choices.  They have already decimated the Hosta and Bee Balm in the ditch on the other side of the lane.  A great winter  pastime will be comparison shopping perennials and grasses that are both deer and Juglone resistant as well as low maintenance for those landscapes. 

             I actually enjoy mowing.  And I like the challenge of creating and maintaining flower beds, but the  simple clean lines of zeroscaping does appeal to me.  A few plants and shrubs easily embellish the area without overstating the purpose of low maintenance.

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Getting ready for Japanese beetles

   I’ve been keeping a careful watch for Japanese beetles in my garden and enjoying my roses before the pesky beetle begins its annual invasion. The city of Cedar Rapids sent out the following today, (June 8, 2009) which made me wonder if Japanese beetles had already emerged. City arborist Daniel Gibbons, who wrote the article, assured me that he hadn’t seen any. Yet.

Japanese beetles

Japanese beetles

But, they will arrive, worse in some areas than others. If you haven’t seen this foreign invader yet, be grateful. Whether or not you have, read the following from Daniel Gibbons to learn more:

Japanese beetle has become one of the most destructive and frustrating pests for gardeners, farmers, and green industry professionals.  A transplant from Japan during the early 1900’s, Japanese beetle (Popillia japonica Newman) populations have enjoyed explosive growth across the East and Midwest.  Damage inflicted by various stages in the beetle’s life cycle can be severe to turf grasses, agricultural crops, and over 300 ornamental trees and landscape plants.  The USDA estimated in 2007 that control measures alone cost over $460 million.

Success of the non-native Japanese beetle can be primarily attributed to a lack of natural predators and a supportive climate and food source.  Although eradication is not feasible, successful management leading to reduced populations will minimize pest damage.  Those who succeed in managing Japanese beetle do so by gaining local cooperation, using an integrated approach to natural and chemical control, and by shrewdly selecting plant material when designing a garden or landscape.

Local cooperation is critical because of Japanese beetle mobility.  Despite the best efforts of one property owner, beetles from neighboring yards are usually a significant problem.  Success will increase if adjoining neighborhoods and property owners cooperate with sound management techniques.

Integrated Pest Management (IPM) is simply the use of multiple control techniques to reduce the comprehensive use of pesticides.  When properly used, IPM creates a healthy biotic environment in which populations of undesirable pests are reduced over time by the introduction of predatory elements, resistant plants, and targeted use of pesticides when necessary. 

Natural predators of Japanese beetle include microscopic nematodes (Heterorhabditis bacteriophora), naturally occurring soil bacteria (Bacillus thuringiensis), and the spores of Bacillus popillae (referred to as “Milky Spore”).  The success of these and other products can be effective, but depends on adherence to application and storage directions, climatic and soil conditions, and the presence of other pesticides or chemicals which may be harmful to these living organisms.  Products such as Milky Spore will become more effective over the span of several years when the bacterium has had time to establish.

Application of pesticides may be used to reduce heavy infestations, but should be performed by competent and trained applicators.  Some chemicals may only be used by licensed pesticide applicators.  Considerations in choosing insecticides to control Japanese beetle will include application method, seasonal timing, location, type of plant material being protected, and the presence of sensitive environment features such as waterways.  Assistance in choosing the latest formulation of pesticide for a particular site may be obtained from local garden shops or government extension agencies.

Finally, avoiding plants and trees that are susceptible to Japanese beetle is the best method to reduce the pest’s impact on a particular landscape or garden.  Keeping landscape plants healthy will also increase resistance.  The following trees are specifically targeted by Japanese beetle: Linden, Birch, Norway and Japanese maple, pin oak, beech and horse-chestnut.  Trees that show resistance to the beetle include hickory, red maple, tulip poplar, dogwood, northern red oak, pine, spruce, arborvitae and hemlock.  Resistant herbaceous plant groups include: Columbine, ageratum, coreopsis, coral-bells, showy sedum, hosta, and forget-me-not.  Herbaceous plants to avoid in areas where beetle populations are high include: rose, hibiscus, evening primrose, clematis, sunflower, peony, zinnia, asparagus and morning-glory.

Despite recent challenges with Japanese beetle, thoughtful management can reduce the impact to community gardens and landscapes.  Education, cooperation and savvy IPM practices will also reduce the impact on our pocketbooks, while promoting a healthy and vibrant growing season.

More information on Japanese beetle may be obtained through the following online sources: “Managing the Japanese Beetle: A Homeowner’s Handbook”    http://www.aphis.usda.gov/publications/plant_health/content/printable_version/JB3-07.indd.pdf

Iowa State University – Iowa Insect Information Notes http://www.ipm.iastate.edu/ipm/iiin/node/125

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