Tuesday, September 20, 2022

That Dreaded Word – Blight

A leaf with the rust-colored discoloration caused by Rose rust, a fungal disease.
Rose Rust - Phragmidium mucronatum
One of the most appalling words to a gardener is “blight”. When your garden becomes infected with
blight there is no easy solution and plant damage is inevitable. Sometimes (but by no means always) it can mean your grow is a total washout. The best action to take against blight is proaction, so here’s some general information to help you understand what you could be dealing with. 

An Anthurium plant by a window with discolored leaves from blight.
Anthurium with blight
The term “blight” refers not to one specific disease but is an umbrella term for a number of plant diseases with similar symptoms that present and spread quickly. Both outdoor and houseplants can be affected by blight. Plants suffering from a blight disease first exhibit lesions on leaf tissues, which is where the pathogen has entered the plant. The leaves will then begin yellowing, spotting, browning and withering, until finally dying off. Blights are not limited to the leaves, they can affect the flowers, fruit and stems – the entire plant, in fact. All of the blights will follow this general progression of disease, but particular blights may have specific characteristics in their symptoms. For instance, fire blight is so named because it’s said the leaves look burnt, and shothole blight (aka coryneum blight) creates lesions that look like the leaves have been shot through. 

Zucchini leaves showing the hail damage that can allow pathogens to enter the plant.
Hail-battered zucchini plants
Blights are caused by bacterial or fungal infections. There are thousands of plant pathogenic fungal diseases and are generally considered the most common plant ailments. This is not to downplay the effect of the bacterial pathogens, which is considerable. Pathogens that cause blight enter the plant through tears in the plant or leaf tissue or natural openings like stomata. Environmental and growing conditions are generally the cause of both types of diseases. Cool moist conditions that persist, changes in humidity and temperature, storms and high wind, and infected soil or seeds can all be contributing factors to blight. 

Some of the many blights caused by bacterial pathogens are:

A branch of a plum showing the reddish-brown on fire blight.
Fire blight on a plum tree
Bacterial leaf blights (caused by Xanthomonas spp), which affects many common cultivars from carrots to rice

Crown gall disease (caused by Agrobacterium tumefaciens), which affects more than 600 species of vegetables, weeds, trees and shrubs 

Early blight (caused by Alternaria spp), which affects tomatoes and potatoes

Fire blight (caused by Erwinia amylovora), which affects pome fruits and mountain ash

Halo blight ( caused by Pseudomonas savastanoi pv. Phaseolicola), which affects edible bean crops and bean seed crops

2 red strawberries and one grey one covered in botrytis.
Botrytis on strawberries
Some of the many blights caused by fungal pathogens are:

Ashy stem blight aka charcoal rot (caused by Macrophomina phaseoli), which affects over 500 plant species, including cucurbits, soybeans and corn

Botrytis aka grey mold (caused by Botrytis cinerea), which affects everything from cannabis to vine crops 

Chestnut blight spotting on the leaves of a chestnut tree.
Chestnut blight attacking a tree
Chestnut blight (Cryphonectria heterostrophus), an invasive disease which has devastated chestnut trees across the US

Rhizoctonia root rot (caused by Rhizoctonia solani), which affects a wide range of plant species from legumes to ornamentals

Southern blight aka white mold (caused by Sclerotinia sclerotiorum), which affects hundreds of crops, from sunflowers to cole crops and tomatoes

Due to the devastating effect and sheer number of varieties of blight diseases, treatment should be dealt with according to the variety of blight you’re dealing with, the type of crop of crop you’re growing, and your growing conditions. There is no one, simple solution. Nevertheless, there are some growing and treatment protocols that are beneficial across the board as follows:

Crop rotation between common host plants and non-host species of plants

A woman in Vietnam watering  her fields by hand. She has a wooden harness over her shoulders that supports the 2 buckets in her hands. Practicing strict sanitation – this means everything from cleaning tools to avoid cross-contamination to removing pathogens from the soil

Proper watering – overwatering or poor drainage is a contributor to blights as they thrive in damp

Proper air circulation – especially crucial in indoor or semi-indoor grows

Thorough weeding, including the removal of volunteers and post-harvest weeding -  care should be given to the proper handling of removed materials to avoid cross-contamination

A wheelbarrow full of weeds on a grassy lawn.
Well-balanced and consistent nutrition – many blights are associated with specific nutrient deficiencies

Pruning to eliminate infected plant parts, but do so carefully to avoid harming plants that are not sick and use sanitized tools to eliminate spreading the disease or encouraging disease progression 

Keep plants as stress-free as possible

A man caressing a huge leaf. The text says, "I just love a good leaf".
We have many excellent products that address both bacterial and fungal diseases in our Disease Control section. You may find what you need by simply scrolling through there, or you can try searching for a particular disease. You won’t find every disease possibility out there, but the most important diseases are addressed in either a dedicated page or within our products. We also have a substantial Cleaning and Sanitation section that contains a selection of excellent products to fill that need. 

Take Care 

Submitted by Pam

Thursday, September 15, 2022

5 Cool Things About Nematodes

An image from a microscope of a nematode that's been colored pink for contrast.

It’s September, and here at ARBICO, it’s Beneficial Nematode season. Every year we put our Beneficial Nematodes on sale at this time to encourage our customers to get them in their garden before winter and get a jump on any soil-dwelling pests looking for a place to overwinter. If you’ve been using them, you know how big a difference they make and if you are not familiar with what they can do, now is the time to try them out. Beneficial Nematodes really should be considered an essential garden tool. To set your thought on these tiny beings, I’ve gathered some interesting tidbits about nematodes in general. 


Antarctic soil nematodes - Scottnema lindsayae
Antarctic Soil Nematodes

According to a study done in 2019, there are 57 billion nematodes for every human on our planet and they make up four out of every five animals. The type of nematode that we sell here at ARBICO are the type that prey on insects, known as Entomopathogenic Nematodes (EPNs), but they are only one of the many varieties found in the land, water and bodies of living things on earth (for more on this, see my nematode blog from 2019). The air is the only place in our world that they do not inhabit (they have no wings). In the aforementioned article, the researchers discovered that the majority of nematodes actually live in artic and sub-artic environments and not the rainforest, as one might expect (see a fun video here). An oft-repeated anecdote about the ubiquitous nematode says that if you were to remove all but nematodes from the planet, Earth’s topography would still be recognizable in the nematode mass that remains . 


Artist's version of the Devonian Period - fish are coming onto land.
Nematodes are not just everywhere; they have been here way before us. The oldest nematode discovered thus far is the Palaeonema phyticum and it lived during the Devonian period 419-359 million years ago (many millions of years before vertebrates).This nematode was found trapped in amber inside a land plant, but it had some characteristics of aquatic nematodes. This was the long period when the land, and all its flora and fauna, was developing from the sea, so these characteristics were no doubt a reflection of its evolution from a water nematode to parasite of land animals. As far as humans go, there have been references to nematodes and how they plague people as far back as 1500 BC. 


A man(from the back) working at a computer with an image of nematodes on it. There are flowers on the desk beside the computer.
Soil nematodes naturally create healthy soil and are essential to a thriving ecosystem. They aid in maintaining a healthy soil structure by aerating it, play a huge role in decomposition, and are active participants in cycling carbon and nutrients. The artic nematode scientists I mentioned before determined that a large and healthy nematode population is directly related to soil carbon. In other words, the more nematodes there are the more carbon is kept in the soil. There are scientists out there right now hoping to find a way to address climate change by studying how nematodes use carbon and their effect on its emissions.


An image of 2  Caenorhabditis elegans nematodes.
Caenorhabditis elegans 
Nematodes have proven to be a boon for researchers when a multi-cellular subject is needed. They are amazingly similar to human biology in several important ways – they develop from a single cell, have complex development, maintain a nervous system and even seem to have the capacity to learn (more here). It seems safe to say that these characteristics are what drew scientists to the Caenorhabditis elegans nematode when looking for a study subject for DNA research. It ultimately became the first multi-cellular organism to have its DNA fully sequenced. This scientific breakthrough was a world-changing event that has led to a great many scientific and cultural changes. On another note, this particular nematode was on board the Space Shuttle Columbia when it exploded on re-entry on February 1, 2003. All seven astronauts were killed, but their test-subject nematodes survived. For more on how this happened and what scientists were able to learn from it, check out this article


A hand protruding from the dirt.
Okay, so not exactly zombies because they don’t eat brains; but they can go into a living-dead state. They do this through a process called cryptobiosis, whereby they are able to suspend all their metabolic activity. Everything just stops. This extreme hibernation is as close to death as something alive can be. Nematodes go into this state when environmental conditions are extreme and unfavorable and will stay in it until conditions improve. This can make it challenging to fight damaging nematodes, but this ability is another source of interest to scientists, especially climate scientists. We all know we are in a time of extreme climate change, so there is hope that we can learn something about how to survive from the humble nematode. There are other creatures who have the ability to hibernate in this way, this short article gives some great examples.

An image of a grey nematode swimming along.
When you add some Beneficial Nematodes to your yard or garden, you are not just helping your plants. You are also taking climate action in some small way by putting nematodes to work doing their thing.

Take Care

Submitted by Pam

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