Plant Diseases

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Leaf Spot On Gardenia

There 2 possible causes for leaf spots on gardenias. One is Bacterial Leaf Spot which is caused by bacteria--either Pseudomonas or Xanthomonas. Bacteria causes small, round ovoid spots on young, tender leaves. As the spots enlarge, the center is at first pale yellow and later becomes reddish-brown surrounded by a yellow halo. Margins of the lesions are thickened and water-soaked in appearance. Spots may coalesce to form large, irregularly shaped spots. Severe infection may cause defoliation. To control, avoid overhead watering.
The second common problem is Leaf Spot caused by the fungi--Cercospora or Phyllosticta. These fungi cause spots of various sizes on leaves throughout the year. Spots may be small, dark-brown necrotic areas surrounded by a yellow halo. In severe cases, premature leaf drop may occur. Control is obtained by spraying with a foliar fungicide. You can cut off the affected leaves to keep the problem from spreading or you can use a fungicide on your plant to prevent the disease from spreading to new leaves.
In either case, the damage that has occurred is irreversible. You will want to remove and properly dispose of affected plant parts.

By | 2016-01-05T00:02:07-08:00 January 5th, 2016|Plant Diseases|2 Comments
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Alternaria Fruit Rot

Lemon trees are part of the citrus genus of plants, prized by many home gardeners for their bright yellow fruit. Hardy in U.S. Department of Agriculture plant hardiness zones 8 through 10, lemon trees thrive in sunshine and warmth. Like other citrus varieties, lemon trees are susceptible to several fungal infections, but blackening of new fruit and premature drop are usually symptoms of Alternaria fruit rot infection.

Alternaria fruit rot, also known as black rot, is a fungal disease affecting citrus plants. It is typically caused by the fungal pathogen, Alternaria alternata. Alternaria fungus develops on dead tissue of the fruit and leaves during wet conditions, producing spores that are carried by the wind. The fungal spores require moisture to germinate and infect the fruit. Once the spores have germinated, Alternaria fungus establishes itself in the stylar end of the fruit, also referred to as the button or blossom end. Alternaria fruit rot fungus is most likely to enter the fruit through cracks or splits, where it grows into the core of the lemon fruit and causes black decay.

By | 2017-09-11T15:49:29-07:00 January 4th, 2016|Plant Diseases|0 Comments
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Tree Branch Loss

Your tree is obviously under stress. Here are a couple of observations that may be helpful. First, it appears as through there is a mound of dirt/rocks in front of the tree. Because the majority of tree roots are near the surface, they are easily damaged or killed when additional soil or material is added to their root zone. It cuts off their water and air supply and they need both. The largest limb damage/loss is in the area where the soil level has been significantly altered. The remaining root system under the tree is covered with rock so we're assuming it's not in irrigation? The tree may not be getting enough water. Once a tree is stressed, it can easily succumb to other diseases and pests. You might consider asking your local nursery for a recommendation to a reputable arborist who can come and determine the extent of damage, if the tree can be saved, and if it can, what measures need to be taken to bring it back to health. An arborist can also prune out the dead and dying branches and make recommendations for watering, fertilizing, mulching and soil grade changes.

By | 2017-09-11T15:49:29-07:00 January 4th, 2016|Plant Diseases|0 Comments
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Japanese Maple Winter Damage

Freeze damage appears on Japanese maples as a shriveling and browning or blackening of foliage. Leaves may eventually drop from the tree and branch dieback can also occur. Major branch dieback leaves remaining branches and the trunk exposed to greater sunlight, leaving them vulnerable to sunscald and creating injured bark areas that certain pests and fungal pathogens can penetrate. Generally, a freeze-damaged Japanese maple will begin to produce new growth from surviving branches within a few weeks of spring, though this new growth is often weak and spindly. Injured portions are cut back to larger branches or the main stem so that no stubs are created. A freeze-damaged Japanese maple will generally produce excessive, weak and often upright new shoots giving the plant an unattractive, crowded appearance. All of this new growth is not trimmed off at once. During the first growing season following damage, only shoots growing completely vertically or toward the center of the tree are pruned out. The following year, about 30 percent of the remaining growth is removed. It may take three to five years to restore a freeze-damaged Japanese maple to its desired form.

By | 2017-09-11T15:49:29-07:00 January 3rd, 2016|Plant Diseases|0 Comments
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Powdery Mildew On Tomato Foliage

This does look 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 a product containing Neem. 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).
Here's more info about Tomatoes and Powdery Mildew:
http://www.ipm.ucdavis.edu/PMG/GARDEN/VEGES/tomato.html

http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7406.html

By | 2016-01-02T12:15:18-08:00 January 2nd, 2016|Plant Diseases|0 Comments
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Agave Attenuata Cutting Transplant

I know how hot it is, I'm in San Diego also. Your cutting is showing damage due to the fact that it has no real root system yet to sustain it. In the long run it will probably be okay but you will have to wait for it to grow out of the damaged foliage. I would suggest that you put up some kind of sun protection to start, and as odd as it seems, don't water it for a couple of weeks. Other than that one root you said it had, it will sprout more new roots if you deprive it of water. After a couple of weeks, give it a good deep soak and then don't water again until the soil has become nearly dry - keep the sun screen up. In the case of your other cutting, (and it would have been a good idea for the first larger one as well) pot it up in a container (with a well draining soil mix) that is not too much larger than the plant and treat it the same way leaving it dry for a week or two and then giving it a good drink. The advantage of starting it in a pot is that you can put it somewhere in filtered sun (out of direct sunlight) without having to provide sun protection. Once it gets rooted well in the pot then you can pretty much plant it anywhere you want in your landscape and not worry about the leaves burning. There will be enough of a root system for you to plant it and give it ample water to grow and flourish.

By | 2016-01-02T05:57:18-08:00 January 2nd, 2016|Plant Diseases|1 Comment
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Hops Yellowing

Kudos to you for growing hops in Colorado! They are beautiful vines. The non-uniform holes could be hail damage. Because of their large leaves, hop plants are subject to hail damage and Colorado is famous for hail! However, you might want to look closely at the back side of several leaves with the holes, preferably with some magnification, to see if there is evidence of any bugs, specifically aphids. Here's a website with images of some of the more common hop pests so you can identify them - http://freshops.com/hop-growing/hop-diseases-and-pests/

The yellow leaves can be a sign of under and over watering. However, the tips of the surrounding green hop leafs have some browning on the edges, suggesting they may have been underwatered. Closely monitoring the soil moisture and keeping the soil moist, not soaked, may help prevent further leaf yellowing. Hops plants do best with drip irrigation instead of overhead watering which can encourage leaf diseases. We recommend removing the yellowed leaves both for plant hygiene and appearance. If watering changes don't minimize the yellowing of leaves, you may want to take a few of the yellowed leaves to a local nursery or the County Extension office for examination. Here's a link to your local office - http://www.extension.colostate.edu/boulder/

By | 2017-09-11T15:49:29-07:00 January 1st, 2016|Plant Diseases|0 Comments
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Basil Problem

There's really not enough shown here for us to tell whats happening. It may be basil downy mildew, but we would need to see two photos of those browned or yellowing leaves - one from the top and one of the underside of the leaf. If it's downy mildew you'll see gray mold-like growth underneath and the tops will be yellowing turning to brown.

No matter which fungal or downy mildew condition might be causing the problem you could 1) Be sure not to water too frequently or get the foliage wet when watering 2) Use Actinovate, a bacterial fungicide labeled for both downy mildew and assorted other fungal problems, being sure to spray not only tops but the underside of stems and leaves. Mix according to directions and spray weekly. 3) Fertilize with the liquid fast-food synthetic fertilizer (no time for organics to kick in this late in the season) of your choice to stimulate new growth that you can pick and use the new growth even as the disease-infected leaves continue to decline. (No harm to humans from eating leaves infected with any of these problems.)

By | 2016-01-01T11:19:10-08:00 January 1st, 2016|Plant Diseases|0 Comments
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Rose Issues

There are a couple of things troubling the rose in this photo. First, the yellow areas on the leaf indicate that the rose is possibly suffering from a nutrient deficiency. Probably Iron deficiency due to a high pH of the soil (alkaline - salt). There may be iron in the soil but it not available to the plant because of the pH. Second, the brown edges of the leaves looks like a salt burn or underwatering. Again, that word salt...If they are planted directly in the ground, you might want to give them a good deep watering a couple of times a week until you see improvement. If they are in a pot, you would want to water them thoroughly until the water is running out the drainage holes in the bottom of the pot. You might want to start a regular fertilizer program by getting a fertilizer especially for rose plants (that includes iron) and a pH test kit for the soil. Follow all directions on the fertilizer container. Third, the white fuzz on the leaves might be Powdery Mildew (it's hard to tell for sure from this photo). You might want to take a bagged sample like this into your local garden center for a hands on diagnosis of the problem and possible solution options.

By | 2015-12-31T19:29:04-08:00 December 31st, 2015|Plant Diseases|0 Comments
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Septoria Leaf Spot

This is Septoria leaf spot. The wet weather we have had this spring has contributed to it's rise in gardens this year. 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. Apply at 7 to 10 day intervals throughout the season. Apply chlorothalonil, maneb, macozeb, or a copper-based fungicide, such as Bordeaux mixture, copper hydroxide, copper sulfate, or copper oxychloride sulfate. Follow harvest restrictions listed on the pesticide label. You can also use Serenade, an organic fungicide that I personally use. When spraying the plants, make sure you spray the undersides of the leaf as well.

By | 2017-09-11T15:49:29-07:00 December 31st, 2015|Plant Diseases|0 Comments
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