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.

Soft and rotting trunk of young peach tree. Definitely borers. Young fruit trees like peach and apple are very susceptible to borers in the desert and oftentimes don’t survive a one time attack. Older trees can recover better. Q. I recently planted a 15-gallon peach tree that I had in a planter pit all winter. I noticed that the bark was soft and almost rotting at the joints with some sap coming out. I am afraid that this can be borers but can’t say with certainty. A. Judging from the picture you sent with all the dried sap coming from the tree and given it’s a peach, I am 100% certain this is borer damage. This damage started last year. Borer adults in southern Nevada  are beetles that fly and don’t bother a tree until it’s time for the female to lay its eggs. Sap oozing from a newly planted fruit tree after a rain from borers.             Adult beetles lay their eggs on all sorts of weakened and newly planted trees and shrubs, mostly on parts of the tree at least 1 inch in diameter and in full sun. The tiny larva from the egg tunnels inside the plant just under the bark, protected from predators and usually in the spring. Here it feeds on the rich sap it finds transported from the leaves and roots. As it continues tunneling and feeding under the bark, it gets larger as it creates more and more damage from feeding. If the borer hasn’t girdled or gone most of the way around the trunk or limb sometimes you can save it without an insecticide by removing all the damaged area with a sharp, sanitized knife.             The most susceptible plants in our hot and dry desert are the small and newly planted trees and shrubs. These borers prefer fruit trees and landscape plants in the Rose family. This includes most common fruit trees and many different landscape plants. Probably peach is the most susceptible. Plants will oftentimes produce new growth or suckers below the damage from borers or from its base.             Once these plants get large enough to produce their own shade then borer problems lessen until they get a bad pruning job. Bad pruning jobs open them up to sun damage again and it starts all over. Pyracantha dieback from borers. Don’t expose the trunk or limbs to direct sunlight in the desert on these plants.             What to do? Because they are hidden from site when tunneling inside young trees,  borer larvae are difficult to find. It’s easier to see their damage the day after a rain and the tree is sopping wet. Oozing sap from the trunk and limbs in areas exposed to intense sunlight is a pretty clear indicator of borer damage. Take a sharp, sanitized knife and surgically remove the young larva. It’s been suggested to soak the tree with a hose and water if it hasn’t rained. There he or she or it is! Sometimes when you excavate the damaged area with a sharp sanitized knife you will see them busily eating away at the soft juicky rich sapwood just under the bark.             Systemic insecticides applied to the soil around the tree will kill this larva inside the tree without using a knife. The most effective insecticide for doing this job as the insecticide “imidacloprid” listed in the ingredients. One example is the Bayer product referred to as “Tree and Shrub Insect Control”. Read the label on how to apply it as a “soil drench”, protect your hands and eyes, and follow the directions exactly for best results. Remember insecticides are a LAST resort when you have no other choices left. Apply imidacloprid as a soil drench (ingredient on the label) after the tree has flowered to protect honeybees.             I caution people to apply it after the tree or shrub has finished flowering in the spring. Because it is a systemic insecticide that can last for several months, I also caution people not to eat any fruit harvested for 12 months after its application.

Q. We have Buffalograss for a lawn which we overseed every winter with ryegrass. We applied the ryegrass late this fall and it didn’t come up, but  weeds did. Now our Buffalograss lawn is covered in weeds. Is it possible to apply a “Weed and Feed” product to kill all the weeds and not hurt the Buffalograss?  If so, what would you recommend and when should this be applied? Weeds growing in Bufflograss not overseeded. Closeup of the weeds. Many very early spring weeds are winter annuals like the mustards. They are easily killed but don’t let them go to flower and seed! A. Buffalograss, like Bermudagrass, is considered a “warm season grass”. It is native to the Great Plains of the US has a reputation for low water use. All warm season grasses are brown in the winter because they are dormant due to cold weather. As their name suggests, warm season grasses prefer growing in warm or hot climates. Besides Bermudagrass and Buffalograss, other warm season grasses include zoysia, Paspalum, and St. Augustine grass among others. These grasses are sometimes called “southern grasses” because they are used primarily in southern states.             Warm season grasses start turning brown in the cool fall months sometime in November and are totally brown here by December. Seeding a “cool season grass” like ryegrass into a “warm season grass” as its transition to dormancy is happening, creates a green winter lawn. You have two lawns in one during the winter; a green lawn actively growing in a brown lawn that is “sleeping”. The key for successful “winter overseeding” is good timing. A winter lawn of cool season grass is seeded as weather begins cooling off in the fall but you can’t wait until it’s cold.             The time for winter overseeding in this climate is between the end of September and mid-October. Your November timing was too late. If you have a warm November it’s possible to make it but that’s not what happened. Last November was a cold month with unusually freezing temperatures around midmonth. It was too cold for successful overseeding.             Estimating when to overseed a lawn is like estimating when to put out tomatoes in the spring only in reverse. Pay attention to the current weather and weather predictions for the coming two weeks. If it’s unusually warm, delay overseeding a couple weeks. If a cold front is coming in then you better get busy and overseed.             Warm season lawns like Buffalograss start to “wake up” and grow when it gets warm; March or early April here. Since the Buffalograss is dormant now (brown) any weed killer that kills green growth will not harm the dormant lawn. The usual weed killer used for this purpose is glyphosate. Mow these weeds but apply the weed killer in early March. A week or so after this weedkiller has been sprayed, mow the lawn short, fertilize and water it to encourage faster green up.

Q. I have a 5-year old Prickly Pear cactus. I brought it here from Florida in 2015 and started it by planting the pads. I’m seeing some yellowing starting to develop where the spines are located. I am familiar with cochineal scale and I don’t think it’s an insect problem. What’s causing this and how do I correct it? Damage to the cactus. Perhaps from cold temps. A. Most likely this is cold damage from low winter temperatures. Most of Florida is warmer than our Las Vegas climate. Your prickly pear cactus from Florida has never seen temperatures as cold as we get in Las Vegas. Prickly Pear, a.k.a. Opuntia cactus range in their tolerance to freezing temperatures from damage seen at 32° F down to 10° F. It depends where that cactus was originally growing. This is the type of freeze damage that I am used to seeing on prickly pear cactus. These were nopal cactus from Sonora but grown in Las Vegas where winter temps were just a bit too cold for them.             Opuntia cactus are native to Central and North America with some types growing in the warm Sonoran Desert and others in our colder Mojave Desert. Pads used for propagating this cactus coming from the Sonoran Desert will not tolerate the freezing temperatures of the Mojave Desert. But Opuntia grown from pads taken from the Mojave Desert will. Next spring growth may come at the center of the pad after winter freeze damage.             In the future don’t apply any fertilizer to tender Opuntia after July 1. Not applying late summer or fall fertilizers improves their ability to withstand freezing temperatures. For a similar reason, start withholding water from Opuntia to slow their growth in the early fall months. Not encouraging new growth by withholding fertilizer and water helps to hardened them off for the cold winter months.