Xtremehorticulture

Imidacloprid and Bee Decline Linkage

Q. I don’t like what I’m reading about Imidacloprid and wanted to know if there is a better insecticide that won’t harms bees. A. Trade names for this chemical name include Gaucho, Admire, Merit, Advantage, Confidor, Provado and Winner.This particular pesticide has a lot of problems and will probably be eliminated in the not-too-distant future because of these problems. Unfortunately, this pesticide is extremely good at what it does and fills a pest control niche that few other pesticides, if any, currently can fill. We need other choices. The niche that it fills is a very effective borer killer that is systemic and for the most part gives you season-long control. Some of the same reasons it is so good may make it also dangerous to use. Even though the label allows for its use on fruit trees for example, I discourage people from applying it to those trees because it is systemic. I believe that any systemic insecticide has the potential to enter the food that we eat. Method of application protects bees. Methods of application have a lot to do with exposure to bees. Those pesticides which are applied as a liquid or as a foliar application to the leaves and stems of plants have a higher probability of coming in contact with bees than the same pesticide applied as a soil drench. Soil drenches are liquids applied to the soil and rarely come in contact with bees. Common products containing Imidicloprid. Be careful of plants treated. However, this particular insecticide is systemic and can be transported from the roots of plants to the flowers that bees may visit. So in the case of this particular insecticide applying it as a soil drench may still be a problem for bees that visit flowers of plants that were treated with a soil drench. The larval form of many butterflies and moths rely on the leaves of some plants as a food source. Systemic insecticides applied as a soil drench may also be a problem for these insects. Best use for this pesticide? If we are to continue to use this insecticide perhaps its best use might be as a soil drench on trees and shrubs that are nonflowering and are not used as a food source by anything that we value. Alternatives? As for alternatives, I do not know one that is this effective for borer control. If we are talking about borer control then prevention is the key. This means preventing sunburn to these plants and keeping them actively growing and healthy is a partial solution. As for other insect pests that it controls you have many alternatives. However, these alternatives will probably not be as persistent so you will have to apply them more often. Whenever your focus is on protecting bees you must consider how toxic the chemical is toward these critters, avoiding applications when plants are in flower, applying foliar pesticides at very early morning hours or at dusk when bees have gone home, using pesticides which have a very short life after they are applied and are not persistent in the environment. And even more importantly we must begin to think about the use of pesticides as a last resort, not a first choice when there is a problem.

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Pruning Japanese Blueberry to Encourage Growth

Q. I have 13 Japanese blueberry’s they have been planted for quite a few years. They have grown tall but only one filled out from the bottom to top because of some shading. This shading is now gone. What can I do and when to stimulate the growth and hopefully have them fill out all over.  Japanese blueberry picture from another reader.  A. Severe shading can cause branch or limb dieback. Reduced light to branches can also cause leaf drop and poor growth on living wood. What to do? Determine if these branches are alive or dead. If they are dead then all you can do is remove them back to the trunk or back far enough to healthy wood. Grasp these branches and bend them. Dead branches will snap like a dry or dead twig. Living branches will bend and not break as easily. If you bend a living branch back far enough of course it too will break so you have to be careful when bending them. Wait and hope.If they are dead and you have pruned them back, all you can do is wait and hope that light reaching inside the plants will “sprout” new growth and fill in over time. If they are alive then do not prune them all the way back but cut off just a few inches of the ends just far enough to cut into living wood. Dead branch of Japanese blueberry from another reader. This might be one or two inches or six or more inches depending on where living wood is located. These types of cuts are called “heading cuts” and remove the terminal buds and will stimulate the plant to fill in bare areas. When to do this? Do this in about early to mid-February next spring. Fertilize the plants at that time with a tree and shrub fertilizer or even a lawn fertilizer and give the plants a two or three deep waterings with a hose a few days apart. The water from the irrigation system will move the fertilizer into the root area. The fertilizer should be a high nitrogen fertilizer. It would be helpful to give them some iron applied to the soil as well at the same time.

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Again More Rabbit Damage!

Rabbit damage to chard. Picture courtesy of another reader. Q. We live in Sun city Summerlin the rabbits are eating our plants Star jasmine, silver spoon yuccas, and even canary island date palms lower leaves. We have tried Shake-Away Fox and Coyote Urine Granules and scaring them but nothing has worked. Any suggestions or tips would be helpful. A. These kinds of products are deterrents. Once they are hungry those will not stop them and they will eat even less desirable plants. The only real way to get a handle on them is exclusion (fencing) which can look horrible. Planting less desirable plants (Arizona fact sheet found on the link below) will help push them to more desirable plants they can find in the neighbors yards. Rabbit resistant plants Arizona http://xtremehorticulture.blogspot.com/2013/10/rabbits-problem-fencing-and-rabbit.html http://xtremehorticulture.blogspot.com/2013/07/how-tall-should-wall-be-to-keep-out.html http://xtremehorticulture.blogspot.com/2013/10/rabbits-do-not-jump-over-fences.html http://xtremehorticulture.blogspot.com/2013/11/pictures-are-classic-rabbit-damage-to.html http://xtremehorticulture.blogspot.com/2014/12/damaged-cactus-edges-probably-rabbits.html

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Care and Pruning of Pyracantha and Honeysuckle

Q. I am writing and enclosing photos of my pyracantha and honeysuckle. I cannot find info on the issue/treatment. A friend suggested I email you after reading the LVRJ column. A. Thanks for the pictures but they were not very helpful without more information. Let me tell you what I know about these plants and maybe that can help. Both of these plants grow well in our climate in a mixed, non-desert landscape. They are not desert adapted or desert plants so they will not perform well with rock mulch. Over time, they will perform better using wood mulch on the surface of the soil. They should be irrigated at the same time as other non-desert plants. They should be on an irrigation valve that provides water as frequently as other nondesert trees and shrubs. Most landscape plants require at least one fertilizer application each year in the spring or late winter. You can apply these spring fertilizers into March. Any general landscape, tree and shrub fertilizer will be good. Pyracantha occasionally develops yellowing due to iron chlorosis so an application of EDDHA iron chelate to the soil at the same time as the fertilizer would be advised. Apply both within a foot of drip emitters on top of the soil. The iron chelate needs to be covered with mulch. Pyracantha has a history of borer problems, particularly if it is planted in a southern or westerly exposure in rock mulch with lots of heat and intense sunlight. Borers can be active in the plants and the plant can still appear healthy for one or two seasons. After a season or two of borer attacks branches turn brown and begin to die back. They normally die back to where the borer damage while the rest of the undamaged plant below this remains green. Prune these dead branches out and let the plant regrow from these areas. Pictures from reader Because of the dead branches, the interior wood and trunk will receive intense sunlight. This intense sunlight increases the chance of sunburn to larger limbs and the trunk. This sunburn damage attracts boring insects (borers) to those locations. Borer damage in purple leaf plum For this reason, shade from the canopy on the interior wood of the plant is extremely important. Many woody plants in the rose family, which includes Pyracantha, are subject to damage from intense sunlight due to their thin outer bark. Most of our fruit trees are also in the rose family and are subject to sun damage and borer problems. Pruning should be pruned to maintain a moderately dense canopy. A canopy which is not so open provides filtered sunlight to the interior of the plant and reduces sun damage. You don’t want it pitch black inside the canopy but you do want filtered light, not intense sunlight, for any length of time. Honeysuckle is a good vine to use here. However, it tends to get woody at the bottom as it gets older. This woodiness at the base can be managed by pruning it correctly. Woodiness at the base is promoted when the vine is pruned only at the top. Several years of pruning the top results in an unattractive plant that is mostly wood without much foliage. When pruning this plant this winter, instead focus pruning efforts on the area close to the soil surface. Find large stems originating from this area and remove one third of this older wood close to the ground. This removes a lot of plant material from the vine but promotes new growth from the pruned stems. Limb dieback of peach due to borers These types of pruning cuts encourage new growth from the base of the plant. Next winter remove one third more at the same location and you should be back on track and reversing the aging of this plant, making it more juvenile. Focus your pruning efforts closer to the ground.

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Can We Plant in December and January?

Q. We are re-doing our whole front yard and just finishing up the drip lines. Is it too late in the season to put in new plants now?  We are planning on lantana, society garlic, red yucca, Mexican bird of paradise, and some deer grass. A. We have entered the coldest part of the winter now in Las Vegas. We can expect temperatures to reach anywhere from mid teens to mid-20’s late in the night depending on where you live. All of the plants you mention, except red yucca, could be damaged if you plant now. Larger, cold hardy trees and shrubs would still be okay to plant. Wait until after the coldest period of winter has passed to plant, about the first to the second week of February. After you plant you should consider applying mulch to the soil surface surrounding them just to give them a little bit more protection. Whenever you are planting trees and shrubs into residential soils you want to mix good quality compost in the backfill surrounding plant roots. Use an equal amount mixed with the backfill surrounding plant roots.

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Which Is the Best Pomegranate Variety?

Q. Which varieties of pomegranate are good to grow in the Las Vegas area? Wonderful pomegranate grown in  Las Vegas A. Southern Nevada is a good pomegranate climate, similar to the climates where pomegranates originated in south central Asia, Persia, Pakistan, Afghanistan and India.In areas: or than this pomegranates can freeze back. In warm but humid climates pomegranates have disease problems that we never see. In the United States we have a wide selection of pomegranates available to us that have been collected from throughout the world. Some of the newer selections may be cold sensitive in parts of our Valley. I would stay away from unknown varieties unless you want to experiment. Beautiful yellow pomegranate with red arils grown in Tajikistan For the most part, all of the pomegranates available commercially do well. Of course the flagship pomegranate variety is ‘Wonderful’ with its beautiful outer and inner ruby red color. In actuality pomegranates come in a wide range of colors from dark purple to nearly black all the way to lemon yellow and off-white. Pomegranates come in a wide range of colors on the outside but the inside of the fruit can vary from dark red to pink to white and from seeded to nearly seedless (soft seeds) You will not go wrong with varieties such as ‘Sweet’ or ‘Eversweet’. A local favorite, sometimes referred to as seedless is ‘Utah Sweet’, a selection from ‘Sweet’. A variety from the former Soviet Union receiving rave reviews is ‘Parfianka’. Other varieties I have liked include ‘Sharps Velvet’, ‘Red Silk’, ‘Pink Satin’ and ‘Grenada’. One variety I have been less than thrilled about is ‘Ambrosia’, and early producer but no flavor. I have seen no winter damage on any of the varieties I mentioned above.

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What Causes Leaf Browning in Lilac?

Q. Since late September my five foot lilac planted on the West side of the house has been showing signs of stress. The lilac made it through the summer fine and all green but has recently shown browning of the leaves despite continuing to bud.  I read that fertilizers are not recommended or necessary but I am tempted to try. A. Both common and Persian lilac grow in our climate. They will not do well in a rock landscape. They prefer soils higher in organic matter. If they are surrounded by rock, they will begin to decline in about 3 to 5 years, leaves will begin to scorch, you may see some branch die back, leaf drop and a reduction or no flowering at all. Some varieties of lilac perform better here than others such as the early bloomers. An old reliable common lilac is Lavender Lady hybrid one of the first low chill lilacs produced. This particular variety requires less chilling and blooms well here. Another variety to consider might be Excel which also have a lower chilling requirement and is a very early bloomer. I would proceed with caution on low chill, late bloomers such as Angel White, California Rose and Esther Staley unless someone has had a proven record of good blooms and color. This could be a location problem. A Western exposure is too hot for it. It likes sunlight but not combined with intense heat. It is best to have it in a location protected from late afternoon sun. But I totally disagree that lilac doesn’t require fertilizer. It not only requires fertilizer once a year applied after blooming but, under desert conditions, benefits from compost or organic amendments added to the soil. Lilac will perform well with some unamended arid soils but our desert soils in Las Vegas are just too low in organic matter. Lilac likes a richer soil than unamended desert soils can provide. It likes compost, wood chips as a surface mulch and fertilizer.

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Can I Plant My Gift Hydrangea Outside?

Q. My kids sent me a hydrangea for the holidays.  I know I have to keep it as a houseplant.  When I lived in New York, mine were huge outdoors. What do I need to do keep them alive and thriving? A. Hydrangeas are not meant for planting in our climate and soils. Hydrangeas given as gifts are like poinsettias; intended to be grown in greenhouses for a one-time gift event. But what the heck, give it a shot! There are some varieties of hydrangeas that are more suitable for growing outdoors than others. Western Sunset Garden Book has recommended varieties you can try. If you are lucky enough to have gotten one of these varieties as a gift then you may have a fighting chance of keeping it alive. They need a bright location on the north or east side with filtered light. Add compost to the soil at the time of planting. The plants need an organic surface mulch that decomposes, enriching the soil, such as wood chips. It should be fertilized with an acid fertilizer every 6 to 8 weeks. If you want to go whole hog on this plant then get some aluminum sulfate and apply it to the soil when you plant and in early spring. Aluminum sulfate does a better job acidifying the soil than sulfur. Acidifying the soil helps keep the flowers of vibrant blue color. You are fighting an uphill battle on this one but if you really want it to work you must spend time and money on this plant with soil preparation, mulch and specialized fertilizers such as aluminum sulfate. Otherwise, I would not bother and enjoy it for what it was intended; a gift on a special occasion from loved ones.

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What is Causing Citrus Leaves to Yellow?

Q. What is causing the leaves on my lemon tree to turn yellow?  This has been happening gradually all year. Readers lemon leaves A. Leaf yellowing of citrus is caused by any of these problems or in combination: high light intensity, micronutrient deficiency such as iron, irrigation and drainage problems and salinity. If the yellowing occurred during the winter and it was more of a bronze appearance then I would say it was due to winter cold. Looking at the picture you sent, some of the leaves have leaf tip burn. That could be caused by salinity or a lack of water. It is possible it could also be too much water or poor drainage but I don’t think this is the case unless you are watering it several times a week. Without more information I am guessing it is a combination of high light intensity, micronutrient deficiency and possibly salts. If the leaves were more “bronzy” looking I might also conclude it could be high light intensity if it is in a location with lots of reflected light. Yellowing of citrus leaves due to high light intensity Flush salts from the soil. Apply a large volume of water to the irrigated area under the tree to flush salts that might be causing a problem. Do this two or three times over a period of a few days then revert back to normal irrigations. Water no more than every ten days right now. Make sure the volume of water is sufficient to wet the soil 18 inches deep. When new growth resumes, resort to irrigating more often but this time of the year irrigating 10 days apart should be adequate. Unkinown nutrient deficiency of citrus but probably manganese or iron. Since iron deficiency is common in the Las Vegas Valley the KISS principle tells us to treat for iron If there is rock surrounding the tree, pull it a distance of 3 feet away from the trunk. If wood mulch surrounds the tree, you do not need to pull it back. Make sure wood mulch does not contact the trunk of young trees. Keep wood mulch 6 inches away from the trunk. Next, apply iron chelate containing EDDHA beneath the tree in January near a source of water. Cover the iron chelate with wood mulch to keep it out of the sun or make sure it is placed beneath the soil surface. Magnesium deficiency of citrus Next February or after fruit set apply a normal amount of fertilizer. Organic fertilizers are best. You should see a change in the color of the new leaves next spring during growth.

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