Q. I was reading your blog, Xtremehorticulture of the Desert, about spider mite damage on Italian cypress. You recommend a miticide spray. Which one should I get? Spider mites are a hot weather problem. They can cause browing and a dusty appearance to the foliage. A. All cypress trees have problems in desert landscapes. Spider mites are common problems with Italian cypress during the heat of the summer. If you have Italian cypress it’s best to wash the foliage off with a high-pressure hose once a month during the summer. This hosing of the green foliage gets rid of dirt that covers the foliage and increase the chance of spider mite breakouts. This reader had browing on the foliage of their Italian cypress. Spider mites are a major culprit.             If Italian cypress starts turning grey first and then brown due to feeding from spider mites you will not have much choice but to spray something. If it’s not too late, start with soapy water sprays weekly to remove dust or debris interfering with predatory mites. Predatory mites control spider mites but the dust interferes with their predation. Or use plant oils such as Neem oil or  cinnamon oil in early morning hours and retest the tree to see if it worked. Mites dont have to cause webbing but spider mites do. That’s why they are called “spider” mites. There are spider mites AND leaf miners on these plant leaves. Spider mites attack all sorts of plants.             Spraying the tree with a miticide is probably a good decision if nothing else has worked. Miticides are insecticides that are good at controlling mites. Select an insecticide from the shelf at your nursery or garden center that says it controls mites on the label. The active ingredients on the label of the insecticide might include chemicals like Azobenzene, Dicofol, Ovex, or Tetradifon among others.             Unfortunately spraying with a miticide might cause you to spray again because of other pest problems. That’s why I tell you to try other methods first.

I am pretty particular about who I recommend for pruning fruit trees in Las Vegas. I began the University Orchard in North Las Vegas in 1996 and am now consulting at the 8 acre Orchard at Ahern established five years ago. The fruit trees under my care include peach, nectarine, apricot, plum, pluot, apple, European pear, Asian pear, figs, pomegranates, jujube, sweet and sour Cherry,, wine and table grapes and a myriad of other fruit trees not on this list. A young guy but Picho shows some promise pruning fruit trees. Periodically I am asked who I would trust to prune fruit trees in this area. There aren’t that many people. Pruning fruit trees is very different from pruning ornamental shade trees and it requires a specialized knowledge and skill set. Picho shows great promise in pruning plum, peach, nectarine, apple, pear for our hot desert climate. I have been working with a young man for the last three years on pruning these fruit trees at the Orchard at Ahern and I feel like he is ready to go out on his own. If you need some help or need someone to prune your fruit trees, give him a try. Contact me for more information.

Q. I recently purchased a ‘Lila’ dwarf avocado tree. I’ve never heard of an avocado tree in southern Nevada, but with warming temperatures and a tree that is supposedly cold resistant down to 15 degrees, I’m giving it a run. Are you familiar with cold resistant avocados and do you know of any living in Southern Nevada? Avocados brought into a local fair in Zimbabwe when I was there. A. You have the right attitude about growing avocado here. Give it a go but don’t expect miracles and enjoy it while you can. If you’re thinking about avocado, think about citrus as well. Both grow in the same climate zone which is subtropical. If your neighborhood has grown citrus for several years, then you can probably grow this avocado at least for a while. Classification of Avocados             Scientists classify avocados into three types: Mexican, Guatemalan and West Indian. Some of our favorite avocados from the grocery store are Mexican types. ‘Lila’ has good fruit but a bit smaller than you would buy from the store. Cold Hardy Types             ‘Lila’ (aka Opal) is one of the cold hardy varieties of the Mexican type. So instead of getting damaged at freezing temperatures like many other avocados, Lila can handle temperatures down to near 15° F for a short time when it’s fully mature. More reasonable low-temperature estimates might be the low 20s for it and others like it. Other Mexican varieties like ‘Joey’, ‘Fantastic’, ‘Opal’, ‘Poncho”, and ‘Mexicola Grande’ can be grown in areas where there are low winter temperatures as well. Semidwarf              The next good feature of ‘Lila’ for backyards is its height. It is one of the smallest cold hardy avocados you can buy. It is considered a semi-dwarf avocado tree which can grow to a height of 20 feet, but you could keep it pruned down to around 10 feet tall. Pollination             You need a second avocado tree for good fruit production. If you plant only ‘Lila’ you will get some fruit but not as many as if you get an avocado pollinator tree.

            It rained this past week. That’s good news, right? Maybe. If you are growing Asian pears, European pears like Bartlett or apples you might see a disease pop up beginning around May. Infection starts as black dieback of new growth like it was burned by fire. Fire Blight This is an extreme case of fireblight on one of the pome fruits such as apple, pear, quince or Asian pear. It usually is seen in mid to late spring when all the growth is going gung-ho.  Its normally not as obvious as the first picture. That was unusual. This is more common. Dieback of new growth and oftentimes its black just like fire hit it. This disease is called Fire Blight and can lead to tree death if not controlled when it’s first seen in May or June. It can be common several weeks after spring rains particularly if trees were flowering during spring rainy weather.             Fire Blight is a bacterial disease, so fungicide sprays won’t work. The best thing is to  remove the infected limb by pruning generously. Sanitize the blades of any pruning tools with 70% alcohol after each cut. Then bag this diseased black growth and get it off the property ASAP. Bunch Rot        This was one of the bunch rot diseases a local pathologist identified as Apergillus. It comes in many forms but oftentimes for homeowners they will control it with sprays or dusts of a copper fungicide such as Bordeaux.       Another disease I saw pop up last year in grapes was a Bunch Rot disease but not really seen until the bunches got big. However, the disease started during spring, rainy weather like we just had. For homeowners, copper containing fungicide sprays work best to contain this disease with the first of three sprays starting now as the grape bunches first start to form.

19 March 2020 Agricultural scientists and engineers have produced the world’s first map detailing global ‘hot spots’ of soil contaminated with glyphosate, a herbicide widely known as Roundup. The map is published as the world’s eyes fall on glyphosate and concerns about its potential impact on environmental and human health. Last year in the US the owner of Roundup, Monstanto (now owned by Bayer), was ordered to pay $US2 billion to a couple who said they contracted cancer from the weedkiller, the third case the company had lost. This year, Australia is emerging as the next legal battleground over whether the herbicide causes cancer with a class action suit being prepared for the Federal Court. “The scientific jury is still out on whether the chemical glyphosate is a health risk,” said Professor Alex McBratney, director of the Sydney Institute of Agriculture at the University of Sydney. “But we should apply the precautionary principle when it comes to the health risks. “And even if no evidence emerges about these risks, it is time for the agriculture industry to diversify our herbicides away from relying on a single chemical.” The map and associated study have been published in the journal Science of the Total Environment. Lead author of the paper is Associate Professor Federico Maggi from the Sydney Institute of Agriculture and Faculty of Engineering. He said: “Glyphosate is a ubiquitous environmental contaminant. About 36 million square kilometres are treated with 600 to 750 thousand tonnes every year – and residues are found even in remote areas.” The paper identifies hotspots of glyphosate residue in Western Europe, Brazil and Argentina, as well as parts of China and Indonesia. Contamination refers to concentration levels above the background level. “Our analysis shows that Australia is not a hotspot of glyphosate contamination, but some regions are subject to some contamination hazard in NSW and QLD and, to a lesser extent, in all other mainland states,” Associate Professor Maggi said. He said that given the widespread use of the herbicide, soil contamination is unpreventable. This is because it is hard to be degraded by soil microorganisms when it reaches pristine environments, or it releases a highly persistent contaminant called aminomethyl-phosphonic acid (AMPA) when it is degraded. The researchers emphasise that contamination levels do not necessarily equate to any environmental or health risks as these are still unknown and require further study. “Our recent environmental hazard analysis considers four modes of environmental contamination by glyphosate and AMPA – biodegradation recalcitrance, residues accumulation in soil, leaching and persistence,” Associate Professor Maggi said. “We found that 1 percent of global croplands – about 385,000 square kilometres – has a mid- to high-contamination hazard.” He said that contamination is pervasive globally, but is highest in South America, Europe and East and South Asia. It is mostly correlated to the cultivation of soybean and corn, and is mainly caused by AMPA recalcitrance and accumulation rather than glyphosate itself. “While there are controversial perspectives on the safety of glyphosate use on human health, little is known about AMPA’s toxicity and potential impacts on biodiversity, soil function and environmental health. Much further study is required,” Associate Professor Maggi said. Professor McBratney said aside from the risks to human health, it is poor long-term agriculture policy to rely on glyphosate as a herbicide. “Weeds are genetically adapting and building resistance to glyphosate,” he said. “And there is growing evidence that a new generation of precision herbicide application could further improve yields.” Professor McBratney said Australia was well placed to economically benefit from the development of new herbicides. “In these times of increasing food demand, relying on a single molecule to sustain the world’s baseload crop production puts us in a very precarious position,” he said. “We urgently need to find alternatives to glyphosate to control weeds in agriculture.”

Desert soils become very unstable when they are irrigated. Insect problems like borers become obvious the day after a rain. Biological activity blooms in desert soils after a rain. Mushrooms are an indicator that would is rotting because of water and biological activity in the soil.

Newly planted citrus. If a good soil mix or compost was mixed with the soil at planting time it might be good for a couple of years. But eventually the tree will grow better if it is growing with a woodchip mulch on the soil surface. I think the wire mesh is for protection from rabbits. Q. Last year we wanted a couple of citrus trees, so I bought a lemon and lime, both dwarf trees. I put them in large pots and wheeled them into the house as the weather turned cold. They didn’t get any extra light other than light from the windows. Maybe that was a mistake. Over the last couple of months one of them lost all its leaves. Should I have given them extra light? A. Leaf drop can be caused by a lot of different things including inconsistent watering and going from cold temperatures to warm temperatures, not just a lack of light. A better place to put them would have been the garage where it’s cold even though there is less light. These trees need to be outside as much as possible for their best health. When there is a slight freeze they will drop leaves. When the temperature is lower than this or lasts for a long time then small limbs will die.             Move containers with fruit trees into non-freezing temperatures just before freezing temperatures occur and move them back outside as quickly as possible after the threat of freezing temperatures are over. At low temperatures fruit trees need less light. Inside the house the trees will need more light because it is warm.             The threshold for freezing damage to begin with true lemons and limes is at 32° F or just slightly under it. If there is wind, freezing damage is more extensive. The garage environment keeps temperatures warmer and keeps them out of the wind.             At temperatures just above freezing their need for light, water and fertilizer is quite small. As air temperatures get warmer, their need for light fertilizer and water increases. As air temperatures become colder, plants require less and less light, water and fertilizer. This is true for all plants including seedlings.  Inside the garage the temperatures will be cool to cold but usually more than freezing. If you need to you can always put a space heater inside the garage to keep it from freezing. But remember, warm temperatures speed up all the plant processes.       If you put these trees inside the garage then water them only when they need water. This is easy to judge because the containers are lighter and so they are easier to lift or push around. You can use a soil moisture meter stuck to about four inches deep also. Don’t fertilize.             Inside house temperatures are too warm for “outdoor plants”. They dropped their leaves, but they will most likely put on new leaves once they are moved outside and get some warmth

Most rain is not very effective in the desert unless it comes down slowly and for a long time. Flash floods are terrible and just run off the soil surface. Normally I disregard rainfall in the desert and pretend nothing happened…unless it was slow and long. Q. The temperatures have been going up and down in the valley, so I have not started watering. This past weekend I had .07″ of rainfall. Most of my vegetation are desert plants. Should I wait until the plant start to bud out or freezing temperatures are no more? A. Starting the first week of February I will water fruit trees once a week even though they don’t need it yet. This is to push new growth and prepare them for fruit production. It’s very important in fruit trees that they never experience a lack of water while producing fruit. This can affect fruit size and development.             Water landscape plants once a week as soon as temperatures begin to warm in February. Make sure you respect their rooting depth; small plants are irrigated to no more than 12 inches deep, medium-size trees and shrubs to 18 to 24 inches and large trees above 40 feet to 36 inches deep.             Cacti and succulents are a little different because they can experience more droughty conditions than fruit trees and woody landscape plants. Give them an irrigation in early February if they haven’t been watered much during the winter.

This is a grape spur. When new growth is nearly about to happen it can be recut even shorter to only one bud or shoot if you know what you are doing. Nearly all wine grapes are spur pruned like this or shorter. Many table grapes like Thompson produce better if this spur is cut longer to include about 8 or ten buds. This type of long spur is called a “cane”. Grapes “weep” or bleed when cut just before new growth. This is normal and nothing to worry about. This will stop when new growth starts.             Delay pruning your grapevines a little bit longer. You can cut them back now but hold off on their final pruning length until after March 1. The idea is to delay the final pruning of grapes as long as possible before new growth begins. This helps reduce disease problems from developing on the grape bunches later. If there is wet or rainy weather in the next few weeks, the grapevines may have disease develop in your bunches of grapes even though everything appears normal. That’s what happened last year.             To cut them back, identify the growth on your vines that occurred last year. This growth will be a different color than other vine growth. Sanitize and sharpen pruning shears before  cutting back any grapevine growth. If you don’t sanitize your pruners, you might spread a disease from cut to cut. Right now, cut this new growth now to about 18 inches long. But this is not the final cut.             Cutting back this long growth helps you to see where to make the final cuts around the first week of March. You will perform these final cuts after March 1. You will see buds swelling on the grapes now but don’t get nervous. These buds will show some swelling and whiteness a couple of weeks before you must prune.             The final pruning cuts on grapes depends on the kind of grape that you have. Some new growth is cut back very short for spur pruning while others are cut longer if cane pruning grapes; usually 8 to 10 inches long. Thompson Seedless for instance is normally cane pruned leaving 8 to 10 inches of new growth while the new growth of most wine grapes are spur pruned (very short).

Q. I have two grape vines, one white and one red. When and how should I fertilize these grape plants? A. All grapes whether they are red, white or black are fertilized a couple of weeks before new growth begins. Your visual key to apply fertilizer is the swelling of buds for new growth. This gets the fertilizer in place and ready to be pulled into the plant by the plant roots when the plant is ready to grow. If you haven’t already done it, fertilize it now. This is a wine grape just showing new growth in mid spring, about the first or second week of March in the Las Vegas Valley. It is not too late to apply fertilizer…if it needs it.             The fertilizer, whether you are using conventional granular, compost or organic types like fish emulsion should be in contact with wet soil after it is applied. This means if your fertilizer is “fluffy”, like compost, any surface mulch is raked back, and the compost applied to the soil surface where the soil will get wet. Then rake the woodchips back and cover the soil again. Granular or liquid fertilizers like fish emulsion may be applied to the surface of  mulch and washed through it to the irrigated area of the soil using a hose. Granular or liquid fertilizers are a little easier to apply than compost.             Granular fertilizers used for established lawns work well on young vines if the soil is covered with woodchips. Fertilizers used for tomatoes or roses work well on mature vines. If you planted your grapevine with a good quality compost mixed in the backfill you may not need any fertilizer the first two or three years. Look at the grapevine and judge for yourself. If it had strong growth last year then apply a half application of fertilizer. If the vine is weak and not growing well, apply a full amount of fertilizer. Grapes perform much better with a surface layer of woodchip mulch applied to the soil surface in the desert.             Grapes don’t grow well when surrounded by rock. Your grapes will perform better with less stress. In our desert soils, grapes prefer soil covered with woodchips. If your grapes are surrounded by rock, I would strongly encourage you to rake it back, spread an inch of compost on the soil surface and cover the soil, at least six feet in diameter around the vine, with 4 inches of woodchips. Grapes struggle enough in our hot deserts without adding the extra stress from surface rock.             Apply fertilizers about 18 inches from the trunk or main stem of established vines so they don’t do any damage.