Xtremehorticulture

Black Spots on Octopus Agave Leaves

Q. Is there something we need to do for these spots on the leaves of my octopus agave? A. I think this is a fungal disease that favors a higher humidity than we normally have in the desert. The disease was caused and spread by the rain and wind that we had earlier. You don’t want any fungal disease spreading to the mainstem. To prevent that, you can apply a common landscape fungicide to the cactus after you have a repeat of the rain and wind event. Watch your weather app. If your weather app says the rain is returning, apply the landscape fungicide the day after it occurs. Broad-based landscape fungicides are meant to prevent the spread of many different types of disease. Fruit and vegetable growers use copper-based fungicides as a protectant for many different kinds of foliar diseases. To be used effectively, and like most fungicides, they must be applied before the presence of disease. Organic fungicides are the only organic option worthwhile against diseases such as late blight and downy mildew. Think tomatoes, peppers, eggplant, and potatoes. These diseases have the ability to kill plants. Copper is also an essential nutrient for plants but use it sparingly. Copper fungicides, like this one from Bonide, help prevent widespread infections of many more diseases when they are caught early enough. When used occasionally, copper is also an essential minor element for plants. In the meantime, prune out any black “spots” or lesions that you see in the stems. I think these are fungal lesions with dormant fungi waiting for the next rain event to make it active again. Sanitize between any cuts to eliminate re-infecting the plant. Use 70% ethyl alcohol to sanitize a knife or pruning shears. Using both the fungicide after wet weather and cutting out the black spots helps eliminate future problems. Make sure you’re not overwatering it and improve soil drainage around its roots. Octopus agave originates in the Sonoran Desert of Mexico therefore it doesn’t like getting watered too often. For instance, it will not survive in a lawn. Take it off the irrigation controller and hand water with a hose. Watering these plants once with a hose only gets the water 3 or 4 inches deep. Water these plants five times a year; only three or four times during the summer and once during the winter. The soil must be dry between waterings!

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Agave with Black Spots on Leaves

Q. I cut out the leaves with the large black spots and lesions on my agave.  There are a few leaves with fairly small black dots speckling all over the underside (too many to cut out), should I cut off the entire leaf? Additionally, there is another photo showing the edge of the leaf that’s kind of perforated – is this age or some kind of bug/mite/disease? Agave with black spots A. I think this is a fungal disease that favors higher humidity than we normally have in the desert. The disease was caused and spread by the rain and wind that we had earlier. You don’t want that fungal disease spreading to the mainstem. To prevent that, you can apply a common landscape fungicide to the cactus if you think there is going to be a repeat of the rain and wind. Watch your weather app. If your weather app says the rain is returning, apply the landscape fungicide. In the meantime prune out any black spots that you see in the stems.  I would sanitize between any cuts to eliminate those black spots that you make. Use 70% ethyl alcohol to sanitize a knife or pruning shears. Both the fungicide during wet weather and cutting out the black spots will help eliminate problems.  Octopus agave originates in the Sonoran Desert of Mexico and Arizona. Make sure you’re not watering too often. Get it off of the irrigation controller and hand water with a hose. If you using a hose, water these plants five times a year; three or four times during the summer. Water with a hose three or four times each time you water these plants to get the water 12 to 18 inches deep as it gets bigger. Otherwise the water will only get three or 4 inches deep if you water them only once. Once you establish how often to water, don’t deviate from that except for the seasons. The number of minutes stays the same. How many times you water each month changes…that’s all. The leaves of agave won’t totally die back to the stem when part of their leaf is cut. It will just sit there, usually edged with brown where it has been cut. If it doesn’t look “funnier” and out of balance, I would suggest removing the leaves entirely. Your call. It is up to you if cutting the leaves of agave is acceptable or not. Some people don’t mind. Others do. Remember that fungicides prevent fungal diseases from getting worse. Right now, the humidity is above 15% so I don’t expect diseases to get any worse unless the plant is in poor health. I would recommend “dusting” the leaves with a fungicide dust to prevent the spread of those black spots that you are talking about. https://edis.ifas.ufl.edu/publication/PP154 Most fungicides are liquid now and not a dust. Dusts were more popular 50 years ago. If the fungicide exists as a spray, it is a different formulation from a dust. Read the directions. An alternative to dusts is to spray over the black spots as “insurance” to keep the disease from spreading if the weather or plant health changes. If it rains again, reapply the fungicide within 24 hours after it stops raining.

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Cure Yellowing Eucalyptus Tree

Q. I have a 20 plus year old eucalyptus tree. The leaves are very yellow. What is the cause of this? Its not a simple answer when it comes to yellowing eucalyptus. Could be anything. Judging from the plants around it and recent water restrictions I am wondering if it is water related. A. Yellowing leaves can mean many things. It could be a nutritional problem, watering issues, or damage from insects or disease. I need more information as well as leaf and tree pictures. Make sure it gets an iron application to the soil in the spring. To be on the safe side, apply an iron chelate such as EDDHA. This is the iron chelate called iron EDDHA. Because of its chemistry it performs well in all soil pH if applied in the spring.             Check for a watering issue or a leak that floods the soil in that area. Eucalyptus is “mesic” in their water use so an application frequency for large trees should be used. When water is applied it should be deep and wide or large shrubs that receive water should be located under its canopy. Once a tree is chosen its increasing water use as it gets bigger has also been chosen.

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Arizona Rosewood Dying

 Q. I live in Oracle, Arizona, and my 15-year-old Arizona rosewood has some dying branches in it. Not the Arizona Rosewood mentioned in the question but it is used in Las Vegas landscapes. A. Dying branches usually indicate a water transport problem, mechanical damage, diseases, chemicals or borers. Arizona rosewood is a 12- to 20-foot-tall xeric tree native to the Sonoran deserts. It is considered a lower water use alternative to oleanders. Arizona rosewood is so new to the landscape industry (less than 30 years old) that not much is known about it. This may require some detective work on your part. It should start to flower and produce small fruit between 6 to 8 years of age so your tree should have started flowering nearly ten years ago.             It is in the rose family so check for damage from borers and fireblight. Other disease possibilities that may include single branch dieback include verticillium wilt.             Even though this is a xeric plant and can handle less frequent applications of water, make sure water is applied deeply and occasionally during the summer particularly during dry periods. Water applications should be about four times each year, particularly during the hot summer months, and to a depth of about 18 inches. The water should be applied to at least half the area under the trees canopy.             There is some discussion about its potential sensitivity to landscape weed killers. Make sure nothing was used close to this plant.

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Fireblight Causes Problems with Fruit Trees if Missed Earlier

 Q. I came back from vacation and my ‘Gala’ apple tree branch was dead.  The tree also has some black spotting under the bark. I’m hoping it’s not damage from fire blight.  Both pictures are fire blight in ‘Gala’ apple tree with an older infection. As this reader suggested, the earlier symptoms were not noticed and the bacterial disease has now invaded the trunk. Most likely the trees will either die or may serve as a host for further infection of trees.  A.  I looked at the picture you sent of your fruit tree, and it looks like older fire blight disease that escaped earlier detection and is now in the trunk of your tree. Fire blight is a serious disease that is highly contagious for many apples. It’s more damaging to some apples like ‘Pink Lady’ than others such as your ‘Gala’.  It’s particularly damaging to all Asian pears.  It can be damaging to some European pears, like ‘Bartlett’ and others, such as ‘Keiffer’, it doesn’t seem to affect much here. This is fire blight disease on a recently planted ‘Bartlett’ pear. Sometimes this disease can come in on nursery plants from “dirty” growers. It is damaging to some ornamentals like pyracantha and some cotoneasters in the rose family. The varieties of these plants may show differences. It just depends on the genetics of the plant combined with the genetics of the disease. When I saw this disease in the spring it was heavily into Asian pears, some European pears and many apples and quince. What gave it away then was the early spring growth, which was black, hooked and had the presence of sap. Fire Blight control is normally through removal of the infected limbs 10 to 12 inches below where the infection is seen. What gave it away to me now are the dark cankers (black spotting) on the trunks of your trees and also the presence of sap.  The “sap” is what is contagious and can cause it to spread.  The dark cankers are probably from earlier fireblight infestations. Once this particular disease gets into the trunk the tree usually dies. If the tree continues to look bad or worsens, I would cut these trees down and get the pruning off of the property. You cannot use this wood for wood chips or anything near plants or it can reinfest susceptible plants.

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Canary Island Date Palm Problems

Q. I have a Canary Date Palm that developed yellowing leaves last year. I planted this palm about 10 years ago in my landscape. Canary Island Date Palm A. The proper name is Canary Island Date Palm. Eliminate simple possibilities first.  Water and drainage Make sure whatever method you are using to irrigate the tree has not changed because of a broken irrigation line or malfunctioning irrigation emitters. Check the soil around the tree to make sure it’s not still wet before it is irrigated the next time. The soil at four or 5 inches deep should still be starting to dry when you water again. Watering cycles of palms is similar to other large trees on your property and not to other locations like lawns, flowerbeds that require frequent irrigation. Watering palm trees as frequently as you would these locations would be a mistake. Fertilize with a palm fertilizer Palm nutrient deficiencies such as potassium, magnesium or manganese deficiencies can cause yellowing as well. Use a palm tree fertilizer such as Arizona’s Best the next time this palm tree is fertilized. Disease Possibilities There are a couple of disease possibilities that have not yet, to my knowledge, been diagnosed in southern Nevada. Three palm diseases have been noted in Southern California on this Palm. The only disease which causes fronds to yellow on Canary Island Date Palm is Fusarium Wilt. This disease can be spread from tree to tree through pruning tools. Wiping or spraying the cutting blades of pruning tools with at least 70 – 90 % isopropyl alcohol will effectively keep the disease from being spread due to a lack of sanitation to other palms. Anyone pruning these palms should never use dirty tools. Tools should be cleaned with soap and water first and then sanitized before pruning begins.

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More “White Fuzzies” in Landscapes

Q. I live in the central Las Vegas Valley and noticed a creep of linear white deposits on the stems of plants in my raised vegetable garden that has recurred in some desert-adapted plants elsewhere in the yard. It first appeared on sunflower stems, then lacinato kale, some basil, tomatoes and their stems, and now on new growth from a Vitex tree and turpentine bush. It seems to be spreading, in other words. Can you advise what this is, and any way to remedy it? A. Those “white deposits” are probably tiny “cocoons” of tiny insects in the landscape. I reorted these on my blog in previous years, calling them “white fuzzies”. I didn’t know what they exactly were either, but I knew that they were insect related. A horticulturist in the Phoenix area guessed that they were sharpshooter (insect) pupae, and he may be right. In any regard, these insect pupae “were just passing through” the landscape where they were “incidental” and probably not damaging these plants. Generally speaking, when we see white deposits on many different kinds of plants it’s usually not disease-related but may be related to insects. If guessed that these white deposits in this case are “insect related” then look at the plant and note any damage you might see. If there is no damage, then these insects are “incidental” to your plants. If you see insect damage to the plants, then they might not be “incidental” and it’s best to use your favorite least toxic insect spray and see if that stops the problem. Soap and water is usually a good first, least toxic spray and readily available. You can always try something more toxic as your second spray if that doesn’t stop the damage.

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Grape Berries Drying Up and Shriveling in Early Summer

Q. The berries on my ‘Red Flame’ grape are shriveling and turning gray but the vine looks healthy. Do you know what the problem is? This is probably one of the bunch rot diseases, either powdery mildew or botrytis. Nothing can be done now. A. From the pictures you sent it’s one of the “bunch” diseases. The bunch diseases attack only grape bunches. At the beginning of summer is when we notice disease problems on the berries of grapes such as the so-called “bunch rots”. But that’s not the time to treat. Grape fruit (the berries) develop nicely up until that time and everything appears normal. But you can’t see the disease yet. This particular disease is either botrytis or powdery mildew of grape bunches. The cause was a fungal disease, and the grape vine needed a chemical spray for protecting the grapes in about late March or early April. There’s nothing you can do now. Fungicide sprays must be applied shortly before or right after the berries start developing.             Fungicides act differently than insecticides. Disease control using fungicides and bactericides must be applied months before the disease is seen. For homeowners, copper fungicides should be applied to these bunches (you must spray the entire vine) to protect the bunches from this disease. The exact disease name is not necessary but the fungicide is. You can apply a fungicide to your ‘Red Flame’ grapes now, but it won’t do you any good. The disease will continue and more grapes will turn “gray”.. The infection is already “inside” the berries but can’t be seen. The graying of the berries is a visual “sign” the disease is present. Using chemicals to control diseases is usually a “protective” spray. Controlling insects by applying insecticides are different. Very seldom are insecticides applied as a “protectant”; a.k.a., applied before we see the problem. Insecticides are applied usually as a “curative”; after we see they are present. How to know when to apply fungicides? Commercial growers use the weather and understand that if they don’t apply the right disease control there are risks that they could lose their fruit. If the weather is right, fungicides and bactericides may be applied to susceptible plants. Any time windy or wet weather precedes fruit development or flowering, disease control (fungicides, bactericides, viricides) are applied to highly susceptible plants.

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Sap Is Oozing from My Kumquat Limbs

Q. Unfortunately it appears our kumquat trees may have bacterial blast fungus. Our tree appears very healthy and has given us a lot of fruit, but we recently noticed sap coming from the bottom of main branches. What treatment would you recommend? Sam is oozing from the limbs of this kumquat.It sounds crazy but disease stress from management issues can cause sap oozing like this to appear. The KISS rule tells me to look at the soil and watering issues first. A. I usually follow the KISS rules for diagnosing plant problems. Unless we are in a citrus production area, or there is a history of disease on these trees, I first conclude it’s a man-made problem. Regardless, we must rule out the simplest reasons first before we jump to more exotic disease problems.             Root death because soils are kept too wet cause these symptoms on citrus. For this reason, I assume the trees watered too often or there is a water drainage problem in the soil surrounding the roots. Simple test if watering too often issues After the first year of growth, all fruit trees, including citrus, should be rooted firmly in the soil. A simple diagnostic tool helps judge whether wet soils should be a concern or not. Move the tree by its trunk, back and forth, while looking at where the tree enters the soil. The tree should be firmly anchored in the soil and not move it. If tree roots move the soil easily, then the soil has probably been kept too wet and the roots began “drowning” or rotting.              There is a tendency during hot weather to water fruit trees more often, even daily. Most fruit trees, including citrus, prefer at least one day of no watering between watering days. Unless the tree is newly planted, or planted in sand, never water trees daily. Instead, increase the minutes on the clock when you do water. Mulch can add one extra day between irrigations             Anything that shades the surface of the soil during summer helps tree roots function better. Their primary functions regarding tree health are the uptake of minerals and water. They do this better, however, if the surface of the soil is mulched. Woodchips (or even shredded cardboard, shredded newspaper or straw) lying on the soil surface gives fruit trees one extra day between waterings during the summer.             If the soil is not mulched or covered, soils dry quickly and get hot in our summer sun and heat. When soils are wet, tree roots grow where there is a good mix of air and water. Unless the soil has been amended quite a distance from the tree at the time of planting, most of the tiny roots that feed on water and nutrients grow in the top 6 inches of soil.

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Brown Spots in Lawn Probably “Frogeye” Disease

Q. I have some large dead areas in my lawn. I don’t think it’s an insect problem. Watering is at 2 AM and 7 AM. This was my first lawn problem in 16 years! Unusual pattern for dead grass. Too random for irrigation I think. This picture you start to see the “frogeye” disease pattern. Looks like it could be a chemical spill. Here is where “frogeye” starts to make an impression. But its over.  A. I looked at the pictures you sent, but the last picture was the most “telling” to me. I think your lawn had a disease problem that is now finished. Don’t do anything now! Let me tell you why I came to that conclusion.             Insect problems here are not like those “rolling back like a carpet” problems described in books and online. Those descriptions apply to Kentucky bluegrass damaged by white grubs. We have grubs, but we don’t have much bluegrass anymore. Our lawns are 95% tall fescue and tall fescue reacts differently to insect damage. It pulls out like loose hair from an old animal skin. Plus, the pattern of dying grass does not resemble insect damage. Rolls Back Like a Carpet             I first thought the brown spots were an irrigation problem, but the pattern doesn’t fit an irrigation problem. With irrigation problems, dead or damaged areas are in a pattern that relates to the location of sprinkler heads. I didn’t know where the sprinkler heads were, but the damage was irregular, so I ruled out irrigation. Irrigation problems are nearly always easy to see how they connect to the sprinklers.             The pattern does, however, resemble a chemical spill flowing downhill and damaging the grass in its path. It was a possibility, but the last picture looked like advanced stages of a disease problem. We used to call this disease Fusarium blight or “frogeye”. This disease has since been renamed Necrotic Ring Spot. I thought “frogeye” was much more descriptive. Seldom will you see it this obvious but this is frogeye. See how it got its name? In advanced stages these dead areas can become one but you still look for little patches of green grass that would still be there. Sometimes its hard to see them.             What led me in the direction toward disease were the small patches of green grass still alive but surrounded by dead grass. These small green patches of grass are how “frogeye”, now Necrotic Ring Spot, got its name.             From the pictures, it looks like the disease has run its course and the grass that’s alive is healthy. I say this because the grass surrounding the dead areas appears healthy. This is the way lawn diseases usually work. They have a window of opportunity, when the weather is right for the disease to spread, and it takes off. The weather changes and the disease stops.             You would be wasting your money to apply a fungicide now that it’s over. But, don’t disturb the brown, dead grass and leave it alone until fall. If you remove it now, it opens the soil to invasion by Bermudagrass. Bermudagrass loves sunshine, bare soil and water. It hates shade. Wait until the weather cools in late September or October, remove the dead grass and either seed or sod these areas.

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