Plant Diseases

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Oak Leaf Chlorosis

Leaf chlorosis (yellowing) is a perennial problem of pin oak (Quercus palustris) and other oak trees in landscapes in many parts of the Midwest. Depending on the severity of the problem, trees typically range from bright green to bright yellow. The extent of chlorosis can vary from tree to tree and even within the tree itself, with some branches appearing normal while others are severely affected. If chlorosis is severe and not treated, trees will defoliate, weaken and may eventually die. This spring, many pin oaks in the Midwestern area are showing especially severe chlorosis and, in some cases, the color of the leaves range from yellow to slightly orange. Treatment - Chlorosis in pin oaks is usually due to a deficiency of iron in the leaves. Iron is important for chlorophyll synthesis in plants, so when it is deficient, leaves cannot make chlorophyll, resulting in a yellow appearance. Chlorosis of pin oaks is typically associated with alkaline soil pH äóñ pH greater than 7. As soil pH increases, the ability of pin oaks to take up iron decreases dramatically. The best solution for iron chlorosis is to avoid planting pin oak in alkaline soils. Some closely related species, like northern pin (Q. ellipsoidalis) and scarlet oak (Q. coccinea), have excellent fall color and usually hold up better to alkaline soils than Q. palustris.

By | 2016-01-11T00:51:24-08:00 January 11th, 2016|Plant Diseases|0 Comments
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Powdery Mildew On Tomato Foliage

This looks like powdery mildew, a common fungal disease that crops up where air circulation is limited and nights are cool and humid. Growing in shade also makes the problem worse. Spray the plants with any of the organic fungicides such as Actinovate, Green Cure or Serenade. Your local nursery may have other options. Fungus disease cannot be cured, but can be arrested so plants can continue to grow and produce. Keep the affected leaves picked off the plant and up off the ground to prevent reinfection. There are various types of powdery mildews and many of them are host specific (Powdery mildew of tomato won't spread to roses, for example), so you may have more than one type of mildew. You will likely need to make changes to the overall environment to reduce the spread, like increase air circulation in/around the plants with pruning of some stems and leaves, make sure air movement into the garden area is sufficient (not being blocked by other plants or structures), and the plants requiring full sun should be in full sun all day (at least 6-8 hours/day), especially tomatoes..
Here's more info about Tomatoes and Powdery Mildew:
http://www.ipm.ucdavis.edu/PMG/GARDEN/VEGES/tomato.html

By | 2016-01-09T14:28:34-08:00 January 9th, 2016|Plant Diseases|0 Comments
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Onion White Rot

The pathogen persists as small, dormant structures, called sclerotia, in soil. Sclerotia can survive for over 20 years, even in the absence of a host plant. Disease severity depends on sclerotia levels in the soil at planting. As few as one sclerotium per 10 kilograms of soil can initiate disease. Only one sclerotium per kilogram of soil can cause measurable disease loss, and 10 to 20 sclerotia per kilogram result in infection of essentially all plants.

Sclerotia can be spread throughout a field or from field to field by flood water, equipment, or on plant material, including wind blown scales. Sclerotia remain dormant in the absence of onion or other Allium crops. Their germination is stimulated by Allium root extracts and exudates that extend into the soil about 0.5 inch from the root.
Disease development is favored by cool, moist soil conditions. The soil temperature range for infection is 50ŒÁ to 75ŒÁF, with optimum being 60ŒÁ to 65ŒÁF. At soil temperatures above 78ŒÁF, the disease is markedly inhibited. Soil moisture conditions that are favorable for onion and garlic growth are also ideal for white rot development.

By | 2016-01-07T17:24:24-08:00 January 7th, 2016|Plant Diseases|0 Comments
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Basil Leaf Spot Or Downey Mildew

Basil is susceptible to a few different disease that cause similar looking leaf spots. Your photo most resembles bacterial leaf spot disease or a fungal disease called Downey Mildew. We can't say for certain its either one of these from a photo; We'd need to examine the underside of the leaves to confirm the mildew. In any case, you'll want to read more about these diseases in addition to removing the leaves from your plant/garden, reducing humidity and avoiding splashing water on leaves. You may end up removing the entire plant if its bacterial. First, however, we recommend you review the second link included below from VegetableMDOnline/Cornell University because this mildew disease is of major concern in agricultural production of basil in your area of the U.S. Cornell asks that all suspected downey mildew of basil be reported! You'll want to follow-up right away so you can remove the leaves or plant from your garden, but you'll be asked for more information about the issue. If it turns out to be bacterial leaf spot, the third link provides more info about that disease.
http://plantclinic.cornell.edu/factsheets/basildiseases.pdf
http://vegetablemdonline.ppath.cornell.edu/NewsArticles/BasilDowny.html
http://uconnladybug.wordpress.com/2011/06/30/black-spots-on-basil-leaves/

By | 2017-09-11T15:49:28-07:00 January 6th, 2016|Plant Diseases|0 Comments
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Powdery Mildew On Zucchini

It is probably powdery mildew. This fungus is common to squashes, especially if the foliage is wet at night. Drier weather will help, but if many leaves are affected, fungicide sprays will arrest its progress and allow you to harvest.
Trim off the damaged leaves. There are several organic fungicides that are labeled for powdery mildew including Actinovate, Serenade, sulfur, and Green Cure, or ask at your local garden center. Be sure to spray under the leaves and the stems as well.

The warm days and cool nights of late summer create an ideal climate for spore growth and dispersal.

Powdery mildew can be prevented, and it can be controlled once it appears, but it can't be cured. The key to preventing it is planting mildew-resistant or mildew- tolerant varieties. Resistant varieties get less mildew than susceptible varieties; tolerant varieties may get some mildew, but it shouldn't affect the performance of the plant. Prevention also includes siting plants where they will have good air circulation, and exposing as much leaf surface as possible to direct sunlight, which inhibits spore germination.

Other methods of coping with it: pick off affected plant parts and either compost them in a hot compost pile or bag them tightly and put them in the trash. Or create a spray of 1 part milk with 9 parts water and spray the stems and tops of leaves with the solution. Reapply after rain.

By | 2017-09-11T15:49:28-07:00 January 6th, 2016|Plant Diseases|0 Comments
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Hydrangea Powery Mildew

Yes, this is powdery mildew on hydrangeas. By retail environment do you mean that the hydreangea is growing by a retail store? Or do you mean that you're selling these plants and they have mildew? In either case you can spray it with one of the organic fungicides such as Green Cure or a copper-based fungicide. Either are the least-toxic solution. Pick off the worst looking leaves and throw them away. In a retail environment I would also do something that draws the eye away from the plant...Place a brightly colored chair to one side or in front of the plant for example. (If the space is small, use a kid's chair) Or you could put a collection of whimsical ornaments around the plant or to one side. If the plant is really looking badly, you could even make fun of it depending on what type of retail store you have...a group of garden gnomes laying down on the job with signs that say "mildew control squad" for example. If you find a way to poke fun at it, take photos and post them on your store facebook page. This has been a bad year for mildew on plants, and beyond preventing the mildew from spreading quickly by using an organic fungicide the best we all can do is to try and make light of what Mother Nature delivers in some way.

By | 2016-01-06T08:09:31-08:00 January 6th, 2016|Plant Diseases|0 Comments
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Powdery Mildew On Zucchini

There appears to be powdery mildew on the leaves. This fungus is common to squashes, especially if the foliage is wet at night. Drier weather will help, but if many leaves are affected, fungicide sprays will arrest its progress and allow you to harvest.
Trim off the damaged leaves. There are several organic fungicides that are labeled for powdery mildew including Actinovate, Serenade, sulfur, and Green Cure, or ask at your local garden center. Be sure to spray under the leaves and the stems as well.

The warm days and cool nights of late summer create an ideal climate for spore growth and dispersal.

Powdery mildew can be prevented, and it can be controlled once it appears, but it can't be cured. The key to preventing it is planting mildew-resistant or mildew- tolerant varieties. Resistant varieties get less mildew than susceptible varieties; tolerant varieties may get some mildew, but it shouldn't affect the performance of the plant. Prevention also includes siting plants where they will have good air circulation, and exposing as much leaf surface as possible to direct sunlight, which inhibits spore germination.

Other methods of coping with it: pick off affected plant parts and either compost them in a hot compost pile or bag them tightly and put them in the trash. Or create a spray of 1 part milk with 9 parts water and spray the stems and tops of leaves with the solution. Reapply after rain.

By | 2017-09-11T15:49:29-07:00 January 6th, 2016|Plant Diseases|0 Comments
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Lawn Problem

Lawn problems, especially diseases, are very hard to diagnose from a photo. You might want to take a sample of the turf to your local nursery for positive id. It may not even be a disease. How often does the area get watered? Is the problem just in one spot (I'm a little suspect that this happening right next to the hose connection and in a narrow area--water issue too much or too little) ? Are sprinklers covering the lawn evenly? Are there any signs of insects in the soil on the edge of damaged areas (sometimes you can bring them to the surface by drenching the area with soapy water) ? As you can see, there are many things that could be happening. You may have to renovate the area. add organic matter and replant but first you need to be sure of whats happening.
Keep in mind, lawn fungicides must be used repeated (often every two weeks) to be effective. Also, most lawn diseases are a result of poor cultural practices, but with a lot rain, its tough.
Sorry we aren't of more help. This may help: http://archive.agric.wa.gov.au/PC_92845.html?s=1001

By | 2016-01-06T00:46:26-08:00 January 6th, 2016|Plant Diseases|0 Comments
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Septoria Leaf Spot

This appears to be Septoria leaf spot. (It is difficult to see if those are, in fact, little black spots on the leaves???). But leaf spot flourishes in damp or humid air and frequently splashing the foliage with water will encourage this fungus to get established. We see it in many gardens this year, mostly on peppers and tomatoes. First, remove all the affected leaves and place in the trash not the compost pile. Next year rotate your tomatoes because the fungus will over winter in the garden for a season and would affect next years crop. This is specific to tomatoes not cucumber or the like. Good air circulation is very important when planting. Sterilize all your garden equipment that comes in contact with the tomatoes so it doesn't spread. Mulch your tomatoes if you haven't already. It keeps the spores from splashing on the ground and spreading the disease. If the above measures do not control the disease, you may want to use fungicidal sprays. Fungicides will not cure infected leaves, but they will protect new leaves from becoming infected. Go to your local garden center for recommendations about an organic fungicide that's labeled for septoria leaf spot. Apply at 7 to 10 day intervals throughout the season according to directions. Follow harvest restrictions listed on the pesticide label. When spraying the plants, make sure you spray the undersides of the leaf as well.

By | 2017-09-11T15:49:29-07:00 January 5th, 2016|Plant Diseases|0 Comments
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Pineapple Top Dying

Since you mentioned the center leaves were dying I think you are about to lose the whole thing. Here's what you need to do when you try another one. Your soil mix is a bit heavy and holds too much water. Remember pineapples grow in very porous volcanic soil. Try using a commercial cactus and succulent mix and even add a bit more Perlite or pumice to it. You are watering too much, especially with your heavy soil. Water really well when you do, and don't water again until the top inch or so of the soil has become dry. Don't water it in the center like other bromeliads. Your northern exposure is just about as wrong as you can be. Pineapples need full sun and lots of it. I understand by your location that it has to be inside for the winter so give it a southern or western facing window if possible until you can move it outside in spring in full sun. Doing all these things should make it (your new one) quite happy and it will grow very large pretty fast. You will need to move it into a larger container maybe a couple of times over about 2 years. With 2 years more or less, and a container about the size of a half whiskey barrel you could very well set a fruit on it!

By | 2016-01-05T09:06:35-08:00 January 5th, 2016|Plant Diseases|1 Comment
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