Some people repeat Ralph W. Emerson, saying “A weed is a plant whose virtues remain undiscovered.” But although I appreciate that many weeds do have virtues, I doubt that many gardeners would accept that definition as the final word. Most of us have had extensive experience with Bindweed, Thistle, Goathead, Ragweed, Dandelion and Cheat Grass; not to mention some aggressive natives like Whiplash Daisy, Wood’s Rose and Hairy Goldenaster; and certain herbs like mints, Comfrey and Sweet Grass. So in talking about managing weeds non-toxically, the main point seems to be: How can we keep certain plants under control?
It’s a common idea that Nature, left to its own devices, comes to some kind of balance. If one organism gets too numerous, something else will increase to reduce that population. In the case of monocultures created by humans, there is an enforced imbalance that has to be propped up with lots of energy and effort. So in the pursuit of sustainability, humans are opening our eyes to the possibility of biomimicry, imitating Nature. We are coming to the realization that biodiversity is far healthier and less energy intensive than monocultures born out of the aggressive hubris to control Nature. “Let Nature take her course.” But we can stack the deck in human favor first.
Colorado is said to be the worst state in the US for fireblight, and 2018 was considered by many to be one of the worst years in Colorado. Fireblight is a serious disease affecting apples, crabapples, pears, Mountain Ash and hawthorn, and sometimes quince and pyracantha (supposedly up to 73 species of plants).
This is a bad year for fireblight which is a bacterial disease which affects mostly apple, pear, crabapple, hawthorn and Mt. Ash. It is spread in the presence of moisture and enters the trees through wounds and open blossoms. Colorado is the worst state in the US for fireblight.
Because of our moist spring and extra wounding caused by hail, there is a lot of infection. Symptoms include black, hooked twig ends, brown or blackened leaves, dried up fruits and sunken cankers that can be a dull orange or black. Fireblight is a difficult disease to manage because there is no cure. Spraying chemicals is not recommended by CSU because they are not very effective, timing is critical and spraying must be repeated.
What is it? How bad is it? What do we do about it?
Emerald Ash Borer is an invasive beetle that found its way from China or eastern Asia to the US, stowing away in shipping crates. It was first identified in 2002 and has since spread to 22 states. In September 2013, Emerald Ash Borer (EAB) was discovered in the city of Boulder, which is the first known presence in Colorado. Since then a team has been stripping the bark from samplings of ash trees in Boulder to determine the extent of its spread. It is suspected that EAB has been in Boulder for three to four years.
One of the most damaging and most perplexing diseases of the Front Range is fireblight. It is a bacterial disease affecting apples, crabapples, pears, Mt. Ashes, pyracanthas, quinces, hawthorns and occasionally cotoneasters. Fireblight does not affect cherries, plums, peaches or shade trees.
When the bacterium with the lovely name Erwinia amylovora enters the trees through an opening such as a wound, a pruning cut, the open blossom or leaf pores, the tissues quickly die causing blossoms and leaves and young twigs to suddenly wilt and turn black as if scorched by fire (hence the name “fireblight”). As the bacteria spread through the tissues, secondary infection continues through the season and bark areas die, become sunken and turn black or reddish-orange. These areas are called “cankers”. Sometimes large numbers of leaves turn black but the infection stays confined to small twigs; sometimes entire large branches die; occasionally the entire tree will die.
Japanese Beetle is one of the most damaging insect pests in the Eastern and Midwestern US, but until recently, Coloradans were spared that challenge. It entered the US in 1916, but took until 2003 before a population was established in Colorado. This first infestation was in the Palisade area on the Western Slope. Even though eradication efforts were mostly successful there, established populations have been found since 2005 in Pueblo, southern Denver, Englewood, at DU and at Denver Botanic Gardens. Smaller populations are being seen now in Boulder and Jefferson County.
Nolo Bait is not a poison. It is a parasite that only affects grasshoppers and Mormon Crickets. It will not harm people, pets, wildlife or beneficial insects. It is most effective on small grasshoppers. In 3-4 weeks up to 50% of the grasshopper population will die. In addition, their eggs will be infected for the following season, and because grasshoppers are cannibalistic, they spread the disease. Put out shallow trays of the bran bait in small quantities. Wind, rain and contact with soil organisms can reduce bait available to grasshoppers.
Ducks, chickens, turkeys and guinea fowl can significantly reduce grasshopper populations. They must be fenced and put inside a safe structure every night to protect them from predators. They will also eat some plants, like vegetables.
Corn Gluten: made from corn it functions as an organic weed-and-feed. It works by keeping all seeds from germinating. Once a plant (or weed) begins to grow the Corn Gluten will not harm it. Very effective when used twice a year, in October and February. The effect lasts 6 months. The feed part is the 9% nitrogen fertilizing effect which thickens grass and stimulates the growth of all plants.
20% Vinegar: this natural acid will burn plant tissues it is sprayed on. Best to apply in bright sunlight and hot days. Spray thoroughly. Very effective on annuals; perennials may need more than one application. Be careful not to overspray on desirable plants as it is non-selective. Repeated use can acidify soils which in our alkaline soils is not usually a problem except for alkaline-loving plants like lilac.
Overview: The Good News: 100,000 insect species; only 200 pests. We do not need neonics or any toxic pesticide to grow plants well. The solution is human attention, biodiversity, nutrient-dense soils, application of nontoxic management, and tolerance.
The Bad News: Most people and most nurseries don’t know the good news. They believe the chemical companies that we need to fear and attack insects and fungi as enemies.
More Good News: The concern of ordinary citizens who call nurseries and businesses and ask them if they are using systemic neonic poisons in their plants, is having a powerful effect. These companies now know we care and will buy plants that are neonic-free if we can. This could get them to change.
Pyrethrum is one of the best known botanical insecticides, effective against a wide variety of insect pests and generally considered safe to use. Is it really safe? To answer any question about pyrethrum it must first be explained that what is referred to as “pyrethrum” can be many different products. There is pyrethrum, the raw flowers; pyrethrins,the extracts from the flowers; and pyrethroids, synthetic pyrethrum. In addition many other insecticides and enhancers are often added to formulations which are called “pyrethrum”.
I enjoyed the article by Renee Galeano-Popp in the fall 2016 Aquilegia, but I would like to take exception to her statement that in terms of alternate hosts of gooseberries and currants that “just about any Ribes species will do.”
Currants and gooseberries have been increasing in popularity among gardeners because their fruits are high in immune-building phytochemicals, because they take up less space than a fruit tree, are easier to pick the fruit, are productive even with late freezes and recent introductions are better flavored and less resistant to diseases.