Xtremehorticulture

Xtremehorticulture of the Desert

Tops Dying Back in Japanese Blueberry

3 Comments / borers, dead branches, disease, insect, Japanese blueberries, sunburn, top dead /

Q. I’m having a problem with my Japanese blueberry trees. Some are fine but the two on the end appear to be drying out from the top down.  Do you have any idea what’s causing this? The soil is not dry and they all get the same amount of irrigation. A. The usual problem in damage or death to the top of a tree can be found on the main trunk just below the damaged area. I am guessing something has damaged the tree at that point.             The reason for the damage could be several. Borers cause mechanical damage to the trunk and shut off the water going to the top. Diseases in this same location can do exactly the same thing.             Because Japanese blueberry is relatively thin barked, sunburn from our intense sunlight can kill the trunk in that location and shut off water to the top. Humans can cause damage to the trunk and shut off its water supply as well. Top of dead stem on readers Japanese blueberry             I think we can rule out pathological diseases in our climate. The two most likely culprits are mechanical damage to the trunk by borers or the same type of damage caused by sunburn.             Inspect the trunk at the location just above the healthy area of the canopy. Use your fingers and see if you can pull away any loose bark. Borers tunnel just under the bark usually on the side towards the most sunlight. This kills that part of the trunk and the bark peels away easily.             If you don’t see bark peeling from the trunk at this location, look for discoloration of the trunk on this side facing the sun. Sunburn to the trunk can happen in one hour of intense sunlight during the midday or late afternoon.             If it is borers there is nothing you can do to raise the dead area back to life but you can protect the tree from extensive borer damage with an insecticide soil drench once a year.             In any case, you’ll be forced to remove the dead top from the tree with a pruning shears or saw this winter. Once you do this, it may open remaining branches for sunburn as well. Give them as much protection as you can.             I would not do it now because the sunlight is too intense and will probably cause even more damage to the lower, healthier part of the tree.

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Pepper Brown Spots Could Be Irrigation or Sun

Leave a Comment / bell pepper brown spot, blossom end rot, blossomend rot, dead spot, sun burn, sunburn /

Q. I have a brown area on the bottom of my bell peppers. Any ideas? A. Brown spots on bell peppers are normally from either of two things; a disorder we frequently see on tomatoes called blossom end rot or sunburn.             If it is on the bottom of the fruit and not in a spot exposed to direct sunlight it is most likely blossom end rot of pepper. Blossom end rot, just like in tomatoes, is normally associated with irregular watering even though it is a nutrient deficiency.             An inch of mulch in the vegetable bed helps to maintain more even soil moisture and less fluctuating of the water content in the plant. A more even soil moisture content has been reported to reduce the incidence of blossom end rot. Blossom end rot bell pepper             The other possibility is sunburn. If the brown spot is on the shoulder of the fruit toward the sun and not the blossom end, then it is most likely sunburn. This is because there is not enough shade covering the fruit. You will see less sunburn on peppers that are buried deeper inside the canopy of the plant.             With bell peppers in particular we want as much leaf cover over the fruit as possible. Light shade, about 30%, over the plants, also reduces sunburn. Mulching the vegetable garden also helps.             Having the garden in a location where it is exposed to morning and early afternoon sun, with shade during the late afternoon, will also reduce the problem.

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Why Are The Leaves of My Locust Tree Turning Yellow?

Leave a Comment / black locust, borers leaf drop, Idaho locust, Robe locust, sunburn, yellowing leaves /

Q. Do you have idea why some many of the leaves on this Locust tree are turning yellow? A. The most frequent problem with locust trees, Idaho or black locust, is borers in the trunks. This will cause exactly what you’re talking about, yellowing of leaves and leaf drop, followed by branch dieback.             Borers entered the trees usually where it is sunburned and that is on the west and south facing sides of the trunk or limbs. Horizontal limbs may be damaged on the upper surfaces as well.             Check the bark on the trunk or limbs see if it is loose. It may easily pull away from the trunk particularly on the South and West sides. Large limbs may be damaged by sunburn. Sunburn on the trunk of a locust tree             Remove bark away from damage to areas and clean the damage down to fresh wood. You don’t need to paint it but if the customer wants it painted, paint it. Use a liquid insecticide soil drench to help protect the tree and give it a chance to recover.

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Poor Canopy Development in Newly Planted Large Tree Could Be Lack of Water

1 Comment / borers, lack of water, large tree, locust, newly planted, poor growth, sunburn /

Q. I think I this might be a pink locust tree. I’m seeing a lot of dead branches. The tree was planted last Fall. Should I give it some fertilizer to help it push out new growth? A. The tree looks a little skimpy on the foliage side but I don’t see anything from this distance that gives me much overall concern. Check to make sure it was not planted too deep. Some landscapers are notorious for digging a hole barely large enough for the root ball. This can also be part of the problem. I tell people now if they buy a large tree from a nursery, hire some people and dig the hole before they deliver the tree and buy good amendment for the backfill while they are at it. A thin canopy like that can also mean a lack of water. The lack of water would be on the quantity applied at each irrigation, not on the frequency of irrigation. Right now that trees should get by easily receiving water twice a week. But I would guess a tree that size would require the same amount of water as about half of the box that it came in. So if that was a 24 inch box I would guess it would need 20 to 30 gallons each time it was irrigated. Apply some good fertilizer and take a hose and soak it after you made sure it was not planted too deep. Do that about once a week for the next month and see what happens.   Sunburn on locust followed by death of that side of the tree. When the bark was pulled off, borers damage was seen. If this is an Idaho or Black locust like Purple Robe, they are very susceptible to sun damage to the trunk. Once the trunk gets damaged they frequently are attacked by borers. As a precaution it might be a good idea to give it a soil drench with Merit insecticide as a precaution. The same insecticide can be found in Ferti-lome’s tree and shrub systemic insect drench. I know Viragrow has a pretty good price on it if they still have the small containers.  If at all possible you want that tree to develop lower scaffold limbs to help shade the trunk.The canopy could use some light pruning. Remove crossed branches or branches growing on top of each other or too close together. You can do that now if you don’t remove too much or wait until this winter.

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Podocarpus Leaf Scorch Update from Previous Question

Leave a Comment / fern pine, how much water do trees use, irrigation, sunburn, sunscald, watering /

Q. Thank you so much for responding to my letter. I did want some clarity on these trees because I was surprised you determined this was a watering and not sunscald. First off, these trees are in a courtyard about 5 ft apart and they are on the same run station.  The trees on the south wall are actually shaded by the wall.  The trees on the north wall are getting more direct sun, so I figured the leaves had sunscald. If you don’t mind my asking, why do you think it’s a watering issue? I clearly diagnosed it incorrectly so I’d like to learn how to better diagnosis this issue if I come across this again. Readers Podocarpus with leaf scorch on the north side.  Podocarpus showing no signs of leaf scorch and with rock mulch, a potential problem in the future. A. I recently started a Yahoo group discussion page because I felt my blog did not give enough opportunities for discussion. It can be found in Yahoo Groups as [email protected] As long as you become a member (which is free but you have to be admitted by the Administrator) you can ask questions, post your thoughts about someone else’s comments or add with your own experiences. It is meant for sharing information. To send a question for my blog you have to send it to me in an e-mail which is [email protected]             It is always difficult to assess a situation remotely. I have to rely on what I know about a particular plant, our climate and soils and my personal experience. I have these plants myself and they are located next to my home on the east side. They get a very small amount of water but it is regularly applied.             First of all, we know they are not true desert plants so we have to add a lot of extra things to get them to grow well here. Soil improvement at planting times is one of them. They will do better with wood surface mulches as well as long as you keep them away from the trunk during the first five years. Besides that, the microclimate or their exposure to the elements can make a difference.             I also know that these plants can suffer if they get watered too often or if they don’t get enough water. The problem is, they look similar if they get watered too often or not enough. When they get watered too often, the roots begin to die. Once the roots begin to die they can’t take up enough water and they look like they are drought stressed. Drought stress will be leaf tip burn like yours or even branch dieback if it is extreme. If it is a chronic lack of water in summer months they usually have leaf tip burn.             I know that plants growing on the north side of the building, or the east side as in my case, are in a cooler location than they are on the South or West sides. High temperatures, wind and lots of sunlight drive plant water use up tremendously. So, plants on the north side and East side will not use as much water as they would on the South and West sides. (As a side note, ideally, we should be irrigating plants on the south and west sides differently than the plants on the north and east sides. This means they should be on different valves.)             You called it sunscald and in a way you are right. Usually the term sunscald has to do with burning of the limbs and trunk of a tree, not the leaves. But that is a technical issue and you would not necessarily know that as a layperson but I got what you meant. We would actually call this leaf scorch or tip burn. Leaf scorch on mockorange             Leaf scorch typically occurs around the margin of the leaf. Leaf scorch occurs because not enough water is being pulled by the roots of the plant and transported to the leaves. The margins of the leaves, or edges, are furthest from the veins and they are the first to show a lack of water, resulting in scorch.             A lack of water can occur because not enough water is applied, or there is root damage so it can’t take up enough water, or the plant is just is not suitable for a very hot and dry climate and it can’t take up enough water in enough volume. We see leaf scorch in plants here like the really big sycamores (that always get cut down when they are about 15 years old because they look so bad) and a few others. Sycamore with leaf scorch due to reflected heat from south facing wall We will also see leaf scorch from plants that are stressed in other ways. For instance, if a plant is suffering in a lack of a nutrient, like iron in iron chlorosis, it will scorch when the same plant which is healthy will not. An unhealthy plant just cannot handle the extremes like a healthy one can. Leaf scorch resulting from iron chlorosis in apricot               Your plants have leaf scorch or the leaves are dying back on the north side but they are doing well on the south side, as you said. I am assuming that the plants on the north and south sides are getting similar amounts of water. If they are good on the south side, then it appears like they can handle that very hot and bright exposure okay (at least for now).             These same plants should have no problem handling a north (less stressful) exposure … but they ARE having trouble. So I ask myself, why do they look poorly on the north side when that should be where they look the best? The reason they look bad on the north side is because of leaf scorch, judging from your picture.             Leaf scorch is a lack

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Plant Podocarpus With Leaf Scorch May Be Too Much Water

4 Comments / brown leaves, fern pine, sunburn, sunscald /

Q. I planted six Podocarpus (Fern Pine) in March, three by the north wall and three by the south wall. Now the three on the north wall have leaves that are turning brown. The three on the south wall are fine. I just didn’t realize that the trees would get this much sunscald.  Any suggestions on what I can do, besides give them macronutrients and hope for the sun to change course? Readers podocarpus with leaf scorch Podocarpus showing very little podocarpus A. Judging from the picture you sent showing the leaves turning brown, I really do not think it’s going to be a continuing problem for you on the north wall once this is corrected. The south wall will be more of a challenge. I do not think this is sunscald but it is either a lack of water, watering too often or a lack of soil improvement at the time of planting.             Since the problem you are having seems to be on the north side and not the south side, I might guess that you are keeping the soil too wet on the north side or they are not getting water.             The north side and the south side are radically different micro-environments. It is much hotter on the south side than the north side. This means plants on the north side should be watered less often than plants on the south side.             Notice that I said less often. The plants on both sides should receive the same amount of water but the difference should be in how often they are watered. To accommodate this difference in frequency of irrigation, plants on the north side should be on a different valve or circuit than plants on the south side.             In the first picture it looks like you have rock for surface mulch. That will be a mistake for these plants in the future. It will be okay for a year or two but you should consider changing this out to wood mulch instead of rock.             If you are going to have problems with this plant, it will be on the south side. These plants will tolerate a little bit of drought and infrequent watering so treat them like landscape trees and shrubs with deep but infrequent waterings.             In other words, do not water them daily. At these temperatures, as long as you have good drainage, twice a week with about 10 gallons for each plant should be adequate on the south side if they are on drip emitters.             On the north side, once a week would be adequate. If they are on drip emitters, they should have an emitter on each side of the plant. Put the emitters towards the front of the plant as far from the foundation as possible.             There is a lot of calcium sulfate or gypsum in our soils. Adding water to soils high in calcium sulfate can increase corrosion on concrete.             After mid-October you can cut your watering to once a week or longer but the same amount of water. In mid-December you can water these about every 10 days.             These are evergreen plants so the damage will not disappear until new growth covers the damage to the leaves.

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Reader Had No Luck Using Spinosad and Soap and Water on Leafhoppers on Grapes

Leave a Comment / kaolin clay, leafhoppers, sunburn, surround /

My picture of grape leaf with leafhopper poopoo (the black specks) This came in from a reader regarding his lack of luck using Spinosad or soap and water sprays for leafhopper control in grapes. I want to share my experience using the diluted spray of a wettable clay compound to prevent leaf hopper damage to our grapevines. Last year our grapevines were greatly infested with leaf-hoppers. Repeated applications of insecticidal soap and spinosad could not make a dent in the insect damage. This year, we began early, when there were about 10 leaves on each arm of the vine, trying a natural wettable clay powder called Surround, that leaves a white coating of clay on wherever sprayed. We flocked the leaves both sides as best we could in a manner reminiscent of Christmas tree flocking, and left a white residue on both sides of the leaves that was intended to make leaf hoppers unable to damage the leaves through the clay barrier. The reapplication of spray becomes more difficult as the season proceeds and requires a definite commitment of the gardener to persist. Surround application to pear, turns the foliage white from the clay We can now say that for all our efforts, leaf hopper damage is much the same as last year. But there are two positives. First, the grape skeletonizer eggs don’t have a chance as they are dead abornin’. Second, the birds who are inclined to peck every last one of our figs, do not peck the whitened figs. So at last we can have some tree-ripened fruit. -Harrison Thanks Harrison. I would like to post your observations. On the other hand I have had luck with Spinosad on leafhoppers on grapes for several years in a row. It does not totally wipe them out but it did reduce the numbers considerably over previous years. And we never really saw damage to the berries themselves with the leafhoppers they were just a nuisance. As far as Surround goes I have used it at the orchard for a couple of years to reduce sunburn on apples and never really got it to work well and it was a pain to apply so gave up with about half of a 50 lb bag left.

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