Like Punch & Judy, Bonnie & Clyde There are Infamous Co-Hosts of the Plant World October 2020
Picture this scenario: you are buying a car as you would a landscape. You shop around and consult professionals because you would like the best product for the price. They give you technical data about the car, colorful pamphlets, all sorts of information. You like a sales person’s professionalism and purchase the product. After about six months you find out driving the car causes the paint to peel. You contact your professional and they tell you casually “that’s what happens”. You’re informed that for a fee they can paint your car three times a year to maintain the aesthetic quality. This seems insane, yet it exists in the world of horticulture quite often.
Many times there are problems in the landscape which are caused by the presence of two different plants that share a common insect or disease. This situation is called Co-Hosting. In order for certain insect or disease problems to appear in the landscape, two different plants MUST be present. The best solution is to recognize this condition and remove or refrain from planting one plant or the other. That is ‘the perfect” non-chemical control, BUT.........
We do not live in a perfect world. There are cases where the Co-Hosted plants are mature and replacement is costly. The argument should be made for projected costs. How much money and chemical will be spent over the lifetime of the plant material (or the homeowner)? Does this offset the cost of replacement? It’s something to consider. We live in a “bottom line” society. The program of spraying, year after year, to alleviate a problem that is cultural, is on the edge of ludicrous.
Plants should increase the value of real estate, which is why we work, to preserve that value. Is there no other work in the landscape that we keep treating the same problem over and over? We should honestly inform landowners of the situation on their property. An option should be given to pursue an ongoing problem or change the landscape. It then becomes their well informed decision. You become the true professional, knowledgeable and honest. You are the Certified Applicator, and must decide the best, most efficient and environmentally sound approaches to landscape problems.
Some Co-Hosted problems of the horticulture world are; Diseases such as Gymnosporangium rusts, Ash rust, Birch rust and White pine blister rust. Insect problems such as Cooley spruce gall adelgid & Pine leaf adelgid. In other words, if you have cases of Rust or Adelgid you may need to find the Co-Hosts of these problems.
‘Diseases of Trees and Shrubs’ and ‘Insects that feed on Trees and Shrubs’ are Cornell University Press books that are a must for anyone involved in the application of pesticides.
Rust diseases are described in ‘Diseases of Trees and Shrubs’, pages 238-282. Adelgids are explained in ‘Insects that feed on Trees and Shrubs’, pages 76-78 & 112 plus. A few of the Infamous Co-Hosts; Ash rust needs Ash trees and Cord grass (other grasses as well). Birch rust needs Birches and Alders or Hop Hornbeam trees and White pine blister rust needs White pine and Currant or Gooseberry trees.
Gymnosporangium Rusts need the presence of Juniper (Eastern Red Cedar) and Rosacea Families. Ex. Cedar-apple rust, Cedar- Hawthorn rust, Cedar-Quince rust. Pear trellis needs Juniperus sp.- especially esp. Juniperus chinensis ‘Robusta Green’ and Pears- esp. Bradfords ........Anyone notice a pattern here? Question: What proliferates on Long Island? Answer: The first part of each gymnosporagium rust equation: Eastern Red Cedars. On Long Island we have an inherent problem if we want to plant Apples, Hawthorns and Quince and Bradford Pears
For adelgids some Co-Hosts are: Spruce and Fir, Spruce and Larch, Spruce and Pine. There are other combinations of hosts listed on page 76 of ‘Insects that feed on Trees and Shrubs’.
Horticultural oils and soaps are very effective controls for adelgids. Harsher chemicals are needed for the rust diseases. Timing of applications using Phenology and Degree days as well as pesticide information for each stage of the pests noted are in Branching Out as well as Cornell Recommends. If you are a Certified Applicator and do not know of, or subscribe to any or all of these publications, you need to “get with the program”. Cornell Extension of Suffolk County also offers the current Degree day listing on-line to help accurately time your applications. Knowledge is necessary to avoid ‘just spraying chemicals’.
We as professionals are not alone in the landscape, we have our Famous Co-Hosts; The extremely knowledgeable and helpful folks at our County Extension Offices. We also have peers, publications, on-line resources, etc.
We can keep our world beautiful and healthy; it just takes a little teamwork.