Showing posts with label disease in the garden. Show all posts
Showing posts with label disease in the garden. Show all posts

24 August 2009

Fungal diseases in the garden

With the incredible rainfall we've had here in the east, there's been ample opportunity for fungal diseases in the garden. The late blight epidemic, affecting tomato and potato crops, is an example, although blight is not technically a fungus it responds to the same cool wet conditions. Fortunately, we have no signs of blight in our nightshade crops this year, which led me to ask the question why? What did we do right? In asking this question, I also did some research on a few new (to me) fungal diseases, and what led to their introduction into our garden.

As far as late blight is concerned, I believe the two most important measures of prevention were quality, uninfected seed, and rotation. I've saved my own tomato seed for three generations, and each year I follow the method of fermenting the seed pulp before washing the seed and properly drying it for storage. The fermentation process promotes good germination, but it also destroys potential pathogens that can be harbored by the seed. Our potato seeds are put to the test by coming through a long storage period, proving that they are disease free.

Second to quality seed in disease prevention, is rotation. It is best to maintain a 2-3 year rotation of crops, and whenever you are introduced to a new disease in your garden, it is important to research the alternate hosts of this disease. It can be surprising to find dissimilar crops can host the same disease, and often weeds will harbor and spread disease. Along with rotation, it is necessary to remove any plant residue (leaves, stems, roots) from the garden and properly compost the material before returning it to the soil.

These two important factors certainly contributed to our garden's blight free status, despite the prevalence of blighted potato fields no more than 5 miles from us. Healthy plants will be able to withstand certain thresholds of disease, borne in on the wind and rain, so part of the story is plain good fortune that our crops did not succumb. But keeping the plants from contact with the soil can also prevent or suppress blight. So perhaps the layer of mulch we applied to the crops in mid-June hampered the incubation process, necessary to the spread of the disease.

I always thought of carrots as a rather trouble free crop, once they are thinned and weeded, they generally take care of themselves. We've had some damage from Carrot Root Fly (or Carrot Rust Fly), but again, rotation and fall cultivation is usually enough to keep their numbers under control. This year I have been introduced to a fungal disease that affects the carrot leaves, Alternaria Leaf Blight. It affects older crops, later in the season after the rows have closed in, reducing air flow. Like other fungi, it thrives in cool wet conditions. But where did it come from, how was it introduced to our garden?

Going back to my original statement, about the importance of quality seed, I realized that my first carrot seed saving venture was flawed. I had selected quality storage carrots to grow for seed last summer, but I had not read enough information about preventing the spread of disease through seed. Alternaria is most often transmitted through infected seed. And there is a simple method of treating seed to halt it's spread to the next crop. Many types of seeds, including the Cole family, lettuce, spinach, eggplant and nightshades, as well as carrots, can be treated in a hot water bath, for a specific length of time (see the table on this link for details). I have also read about using a hot water and cider vinegar solution, though it looks as though the temperature and length of exposure is the most effective measure of killing potential pathogens.

The Alternaria leaf blight does not much damage the crop, especially at the later stages when most of the growth is complete. For the most part, it is a problem for mechanical harvesters, as the stems break off easily, leaving roots in the ground. The most damaging effect of this fungus is that is promotes the spread of damping-off in the soil. And I do believe that my last planting of carrots was cut back by damping-off. This could lead to potential problems for direct seeded crops and young seedlings in the future.

Alternaria Leaf Blight of Carrots

Cereal crops have their own biosphere of diseases, including fungi, bacteria and viruses. Most of these disease cycles can be broken by planting non-cereal crops in rotation, but some vegetable and legume crops can host cereal diseases as well. Developing resistant seed in cereal crops is an important and active area of agricultural research. Research labs around the world are constantly responding to new mutations of cereal diseases, breeding crops with genetic resistance, and making these resistant varieties available to many Third World countries whose farmers do not depend on fungicides for healthy crops.

We bought our Vicar Hulless Oat seed from a small independent seed producer, the seed is an heirloom variety, and granted, there are few options for purchasing small quantities of cereal seeds in Canada, so we hoped for the best. The description of the seed said nothing of disease resistance, and in the future, that will be a requirement in my seed purchases. Our Hard Red Spring Wheat is a modern, disease-resistant cultivar, proven in our climate, and it has withstood the variety of cereal diseases this year. The Hulless Oats, on the other hand, are peppered with Septoria or Speckled Leaf Blotch, a fungal disease. It can easily spread to other cereal crops, so our healthy crop of wheat, only 20 feet from the infected oats, has given me first-hand evidence of the necessity of disease resistant cultivars.

Septoria or Speckled Leaf Blotch on Hulless Oats

16 June 2009

What to do when things go wrong?

Good planning, preparation and preventative measures are the best insurance of good health and success in the garden and in the barn. But, especially in the first years when the learning curve is steep, things do go wrong and disease, pests or parasites can spread quickly and reach a critical level surprisingly fast. The ability to assess the symptoms and diagnose the problem is crucial to being able to react within time to save the crop, flock or herd.

So what elements are necessary to being able to diagnose a problem or illness, especially when encountering it for the first time? An observant and knowledgeable gardener or animal husbander is generally the most qualified to diagnose a problem because that individual knows the history of the soil or animal, and is familiar with the expected state of health in her garden or herd. The subtle first symptoms of dis-ease provide the best opportunity to address a developing issue before it gets out of hand. In the garden, these symptoms will include discoloration, spots, holes, wilt, etc, and usually accompany a period of stress, including temperature extremes, dry soil, wet soil, mineral deficiency or other soil imbalance. With animals the first symptoms include lack of appetite, listlessness, dull eyes or coat, runny nose or eyes, change in stool consistency, drop in production, etc, and again usually accompany an external stressor such as change in diet, transportation or change of location within the farm (i.e. barn to pasture), temperature extremes, exposure, lack of access to fresh, clean water, isolation from the herd/flock, or introduction of un-quarantined animal to herd/flock. As with our own health, stress decreases immunity to disease or infestation.

When I observe one of these primary symptoms, my first priority is to apply a first-aid measure where appropriate, to relieve the immediate stress. These responses can range anywhere from watering a wilting crop to giving an animal a homeopathic treatment for fever. (Remember to take notes of the treatments you give, the quantity and the time applied so that you can assess the responses to treatments, and more importantly, repeat your successes in the future.) Once I have contained the situation as best as possible, and this may include removing diseased plants from the garden or isolating an animal from the herd/flock, I then begin to investigate the originating cause of these symptoms. This is where observation, knowledge and health records are put to the test. If you are an absolute novice then you will be particularly dependent on books, forums, websites and more experienced individuals to help you diagnose the problem, but every one of these situations is an opportunity to increase your knowledge, so pay attention and keep records.

Begin by making notes, in detail, of anything you notice as "out of the ordinary", and use all of your senses. In the garden this will mean noting not only the condition of the crop/plant, but also the condition of the soil, the condition of surrounding plants (including weeds), any insects you see in close proximity to the affected crop (don't forget to look at the insects at ground level or just below the soil), even a nearby soil disturbance can be a clue. I find a digital camera useful in identifying diseases or pests in the garden. In the herd or flock, these kinds of observations can be somewhat subjective, and not nearly as obvious. But from daily interaction with domestic animals you get to know each individual's particular habits, appetites and behaviors. An animal who usually meets you at the gate, but stays in the barn that morning, is not feeling well. When an animal lays down more than usual, or doesn't eat or drink quite as much or as readily, or doesn't vocalize as much as usual, or stays a bit apart from the other animals, that animal is more than likely showing primary symptoms of illness. The more obvious symptoms will include quantifiable differences in temperature, bodily fluids, discharges, loss of hair, skin eruptions, or drop in production levels. Again, use all of your senses, listen, smell, feel and watch (well, maybe not taste!), and take notes or pictures. And be sure to look for anything out of the ordinary in the yard, pasture or barn, anything the animal may have eaten or been exposed to.

Now that you have all of this observational data, it's time to hit the books, forums, your own records, or experienced individuals who are familiar with your own bio-regional conditions. Sometimes the cause of disease or infestation is obvious, and sometimes it takes a bit of investigation. More often than not, the problem is compound, not just a simple or primary cause, so I will give a few examples of conditions we have experienced this spring, one in the garden and one in the herd.

I chose this example, of diagnosing a problem in the garden, because it begins with generic symptoms that could point to any number of causes, and shows our process of elimination to reveal the root causes of the issue. About a week ago we noticed that our bush beans were a bit discolored. There was some yellowing along the veins of the leaf, and around the edges, and a few speckles of brown that we recognized as insect damage (which would be a secondary symptom, the insects being attracted to the plants sending out chemical signals of stress). The plants had slowed their growth, but were not wilting, curling or browning. This kind of discoloring usually points to a few possibilities: mineral deficiency (perhaps as result of pH imbalance), or some kind of leaf burn (UV, chemical, acid rain, frost). We could rule out a chemical burn and frost, but suspected acid rain and/or UV burn. We are in an area that receives a lot of acid rain, and we have been noticing more frequent warnings of high UVs in the weather forecasts. Three days prior to the appearance of the discolored bean leaves, we had a sunny day that rated 8 on the UV index, followed by two days of rain. After this, the beans did not look so good. There's not much we can do to protect against UV damage, but like a frost, if the plants survived the burn, they would recover. And we already do what we can to prevent over-acidification in our soil due to acid rain by applying limestone and adding humus. Calcium is also necessary for the soil to be able to maintain a neutral pH, and to prevent the soil nutrients from becoming chemically locked up as happens in acidic soil.

It seemed clear to us that our bean crop was suffering from a mineral deficiency, but the cause was still unclear. A mineral deficiency can be a problem inherent in the soil, meaning that a mineral is actually missing. Certain crops are more susceptible to certain deficiencies, but most likely, other legume crops would show similar symptoms, and the peas were unaffected. Or it can be a result of a pH imbalance, essentially making necessary minerals inaccessible to the plants. Or it can be a problem of the plant's metabolism, not being able to absorb the minerals in the soil, due to stressors such as temperature extremes or wet/dry soil. So besides the possible causes of UV burn and acid rain, (both of which, beans are sensitive to) we had also been experiencing a cool spring with overnight temperatures remaining below 10C (50F). Tropical plants like beans do not grow/metabolize below this temperature, so it could also be possible that the plants are simply too cold. But more than likely, the true cause is a combination of these factors.

As we watched the crop over the next few days, we also watched for similar signs in nearby crops, and other legumes. None appeared, and a section of the bean crop started to recover. We had put a hay-bale wind break around our transplanted tomatoes and peppers, as it had been cool. The row of beans on the other side of this wind break were looking green and beginning to grow again, before the rest of the crop. This was a sure sign that the cool overnight temperatures had played a major role in the slowed growth and discoloration of our bush beans. And as the temperatures finally begin to warm, the rest of the crop shows signs of recovery. Had we not taken the precautions of protecting our soil from acidification, a simple stressor such as cool nights could have been compounded, possibly causing a crop failure. This is why it is so important not to spare your efforts in keeping your soil healthy and balanced, much like your own immune system, so that your crops will be able to withstand the inevitable environmental stressors that occur throughout the growing season.

Again, I will choose an example of diagnosing a problem in the herd that is difficult to diagnose because of the vague symptoms and the range of possibilities they point to. Our goat herd consists of one milking doe, one meat doe (not lactating or pregnant), and two bucklings. Each of these animals has different dietary requirements, the lactating doe requiring the highest amount and quality of proteins and minerals, the bucklings requiring moderate levels to support growth, and the meat doe requiring the least, but a sufficient amount to put on weight. Likewise, our milking doe will be the animal in the herd to show signs of illness first, the bucklings second, and the meat doe being the most resistant because of the fewer demands placed on her system.

When spring broke and the goats were out on pasture, our milker started to put on more condition and began also to increase her production of milk. The whole herd showed signs of vigor and health, frisking about in the pasture. One fine spring day, while out in the garden, I watched Juniper (the meat doe), bleat and gallop, three-legged, back to the barn. She held up one of her hind legs as if it had been injured. Of course, the rest of the herd followed her in. I followed to the barn to investigate, but could not find anything wrong with her leg or foot, and she was walking just fine. Then I heard it, the drone of a Horsefly. Juniper heard it too, and again, raced for the barn. She had apparently been bit by one of these inch-and-a-half long prehistoric nightmares (which, by the way, may have been one of the contributing factors to the extinction of the dinosaurs). They take a pretty good chunk out, and it does hurt.

Penelope, who had already been spending more time in the barn to escape the blackflies and the mosquitoes, simply went on strike. She would not graze, at least not much, and not in the daytime. I assumed that she would be grazing at night, as this is what the horse and our milk cow always did. But she began to loose some of that condition, and dropped back down in milk production. So we cut some tree branches and picked buckets of raspberry leaves and evening primrose, some of her favorites that are not available in the pasture. She wasn't picking up, but she wasn't getting poorer, for two days. Then on the morning of the third day, she looked absolutely hollow, had not eaten any of the hay or forages brought into the barn, and her milk was nearly half of normal. She was listless, lethargic, breathing faster, stools were firmer and pelleted (instead of the normal softer stool of lactating animals on pasture), she was laying down in the sun, and had no appetite for grains or her favorite treats of raspberry leaves. Her lack of appetite, and absence of chewing cud told me that a good first-aid response would be to give her a homeopathic treatment for colic (it has a blend of a few ingredients used in digestive disorders). And to make sure that she has enough liquids, as dehydration would compound the issue. She responded well to a mixture of warm water, molasses and apple cider vinegar, about a tablespoon of molasses and 2 tablespoons cider vinegar for every Quart of water. I gave her as much as she would drink.

Next I hit the books, most useful to me are my homeopathic veterinary books. They give very good clinical descriptions of the illness and help me to accurately diagnose. Her symptoms matched up well with simple indigestion. Rapid breathing, sub-normal temperature (hence laying down in the sun on a hot day, when normally she would be laying in the shade), lack of appetite, listless, and the rumen would feel doughy and be inactive. I went back to the barn, and felt her rumen. It was indeed doughy, feeling like an under-kneeded ball of dough that does not spring back. There was no accumulation of gas, or tympany, which would make the rumen distended and sound hollow like a drum. This was at least good. Simple Indigestion, untreated, can compound into Acute Indigestion with toxemia (blood poisoning), or Bloat. I now had two priorities, to get Penelope's digestion working properly again, and to figure out what caused the indigestion so as not to repeat the conditions.

I felt the rumens in the rest of the herd, each feeling slightly doughy, but still somewhat active (meaning noticeable rumbling and movement in the digestive system). We watched them closely, and noticed one of the bucklings laying down, often in the sun, the next day. At noon, he was laying with his head on the ground, not a good sign. We got him up, gave him a half dose of the Colic remedy, and as much molasses, apple cider vinegar water as he would drink. He too responded well, but we were at the tipping point. If we did not get on top of this, it could easily develop into a critical stage and as I've learned from watching a healthy cow go down with milk fever, animals can deteriorate rapidly.

Penelope's appetite had responded to the treatments we gave her as a first-aid response, so we made sure she had high quality forages in front of her, in the barn, at all times. She was still on strike as to going out in the pasture, terrified by every buzzing insect (granted, she had a huge welt on one teat where a horsefly had bitten her, nasty buggers!). We scythed pasture, brambles, comfrey and primrose, and fed her in the manger. And kept up the molasses and apple cider vinegar. But we were also cautious as to what we fed her, as to avoid compounding the indigestion into bloat. Rich pastures heavy in clover can cause bloat, so we scythed mostly grassy pasture. And we were suspicious of the tree leaves, causing the indigestion. Earlier this spring, we had given them plenty of poplar, and some maple, but brought down some birch leaves on the day the horseflies came out. Was there something in the birch leaves, or something in young spring birch leaves, that is indigestible? Or was it the fact that they ate too many of the birch leaves, prefering the convenience of eating them, over going out on pasture amongst the bugs, therefore getting a high concentration of a chemical or toxin in the birch leaves, that would otherwise be harmless in small amounts?

This seemed to us the most likely cause of indigestion. So our next trip to the Internet Access Center included a session researching the toxicity of birch leaves, and indeed, there is a concentration of phenolic compounds in winter growth. These phenolic compounds have been found to depress or inhibit digestion in ruminants. See study here.

It is important to watch for signs of recovery in sick animals, if they are not responding to treatments, do not simply wait and hope they will get better eventually. If they do not respond, then most likely, the problem is not diagnosed properly, or the treatment is not being applied at the right level and frequency. Both Penelope and the buckling showed a quick response to treatments. Every dose of molasses, and apple cider vinegar, would stimulate their appetite, readily taking mouthfuls of forages instead of nibbling and nudging at the feed. The buckling's rumen was back to normal the next day, and he was resting in a cool corner of the barn at noon, chewing his cud. Penelope took a few days to recover, but each day looked less hollow, more active, had a more active appetite and rumen, and began to recover her milk production as well. On the third day since the illness she went out for a bit of a graze on the pasture, and a strong morning breeze blew the bugs away long enough for her to get a belly full. Now, a week since, the herd is back on pasture, but we still bring buckets of pasture, primrose and raspberry when the bugs are particularly thick, to the point of harassing the herd. Penelope is back up to a normal level of milk production, and putting condition back on. And we are keeping young birch leaves out of reach from now on.

It is much easier to research an appropriate treatment for a problem in the garden or the herd/flock once you understand the cause, or at the very least, can identify the symptoms. With these clues and bits of observation you can begin to diagnose the problem. Many remedies and treatments are easy to find and easy to apply, and most conditions, if not all, can be prevented in some measure. Do not neglect to research the preventative measure to avoid repeating the conditions in the future. But if you suspect or have identified a virulent pathogen or disease in your garden or herd/flock, do not hesitate to contact a professional (farmer, vet, agronomist), and maintain good hygiene to prevent spreading the disease.