Lemon Yellowing After Transplanting

Q.  I believe I have a Bears lemon tree. It was growing in the ground then transplanted to a 22” planter last fall and for a variety of reasons finally  transplanted it to my raised bed a few weeks ago and used the rejuvenate soil mix from Viragrow. I cut off one third of the top when moving it, but the leaves are still yellow, I don’t see any new growth. I don’t believe tree is dying but it’s not healthy. Is it the soil?

A. First, not that it makes any difference but if you have Bears, it may be a lime, not a lemon. That might affect when it’s harvested. The Rejuvenate soil mix drains easily provided the hole drains water. If the hole drained water in 6 to 8 hours, everything is fine. Just don’t water the tree every day.

Yellow Leaves

            The yellowing and poor growth is most likely due to recovery from the damage during transplanting. Yellow older leaves stay yellow even if everything is wonderful. Watch the new growth coming out. That’s the key. If the new growth is green and not yellow then that indicates the tree is doing well. The yellow leaves will be replaced visually by dark green leaves later.

Water and Drainage

            Make sure you are not watering too often. I am watering established fruit trees with woodchips on top of the soil once a week all during February. This irrigation frequency is to push new growth and fruit production.

            If trees were just planted (or transplanted), I water twice immediately after planting and then about twice a week, every three to four days, until new growth appears. Once strong new growth appears, once a week should be often enough until about mid-April if the soil is covered in wood chips.

Stake After Moving

            Make sure the tree is staked solidly in the ground to keep the roots from moving during  establishment. I use a three or four-foot-long 3/16 rebar pounded in the ground right next to a new five or 15-gallon tree, and the tree tied to it only for the first growing season. I  tie the tree to the rebar tightly with stretchable green nursery tape. 

Saquaro Wobbling

Q. After I spoke with you yesterday, I went outside and took some pictures of my saguaro. Upon closer inspection, I found some of those dreaded black spots you mentioned at the base of the plant. I also attempted to move it and it wobbled back and forth. I'll be taking it out this spring if you think that is what should be done.

A.
Sagaro Shouldnt Wobble

That “wobbling” you mentioned is bothersome to me. These plants need to be firmly anchored into the soil if they are to remain upright. In nature the roots of the saguaro may spread out eight times its height. This provides firm anchorage in the soil. To get this kind of anchorage, water needs to be applied deep and infrequently and at large distances from, and including, the plant.

Plant Neighboring Desert Plants

            This can be done in several ways. One method is to grow other plants coming from the same climate zone at different distances from the saguaro. Irrigation supplied to these plants will be enough to encourage the roots from the saguaro to spread out. Enough water should be applied the first couple of years about a foot deep. As the saguaro gets taller, this water should be applied so it percolates 2 to 3 feet deep.

Water Once in Awhile

            Another method, and one that I really prefer, is to take a hose on a mechanical timer and inexpensive sprinkler and turn the water on for one hour. I would do this on both sides of the saguaro about 6 feet from the trunk with the water reaching the saguaro. Do this three times; in early spring, once in the summer, and again in the fall. This timing encourages root growth of desert plants but avoids the growth of Bermudagrass. If you see some Bermuda growing, whack the top off with a hoe or shovel as soon as you see it. Do this once a week until it’s gone.

Look for Black Spots

            The “wobbling” and appearance of black spots on the outside of the saguaro tell me that it’s probably getting watered too often and the water applied is too close to the trunk. Those black spots or “cankers” indicate an internal rotting of the tree.

            You can find out more about this and what to do by “Googling” the words “University of Arizona” and “problems and pests of cacti”. Scroll down and a link should appear that will take it to their publication on how to control diseases of agave,cacti, and yucca and what to do about it. Make sure you use a sharp and sanitized knife.

            Your call on whether to remove it or try to rescue it.

What Fruit Trees to Plant at a School

Q. I am working on a new project serving middle and high school age kids. The idea of fruit trees around their garden area came up and I’m wondering what trees you would suggest. They will have approximately 9 trees spaced on a grid.

A. Make sure the trees are spaced a minimum of ten feet apart and are semi dwarf.

Dwarfing or Semidwarfing Rootstocks

All fruit trees should be grafted onto dwarfing or semi dwarfing rootstocks (Citation for stone fruit, M111 for apples, OHxF333 for pears). If you don’t know the rootstock then the plant label should say “semi dwarf” or “dwarf”, not “standard”.

Many fruit and ornamental trees are grafted. The :dogleg" appearing on the trunk of a young tree is because its grafted.

Early Producers

            Since these are kids and they are normally not is school from June – September, I would think you would avoid trees that produce fruit then. That still leaves you with early producers like May Pride peach, Early Grande Peach, FlordaKing or FlordaPrince peach, Earlitreat peach, Flavorosa pluot. Royal Rosa, Flavor Giant, Katy, or Gold Kist apricots. These should produce fruit from late May until maybe early June.

There are some very early peaches like Earlitreat and FlordaKing or FlordaPrince which will probably produce peaches before June graduation.

Late Producers

For late producing fruit trees I would pick Pink Lady or Sundowner (red) or Mutsu (green) apples, Bartlett or red Bartlett pear, or Bosc pear, your favorite pomegranate, Flavor Grenade or Flavor Finale pluots, Emerald Beaut plum, Giant Fuyu persimmon or any Fuyu or Chocolate persimmon. I would suggest avoiding late producing peach. I would avoid any nectarines due to the scarring of fruit from insects. Nectarines are difficult to produce without spraying for insects. No late peaches because there aren’t any good ones in my opinion. The best peaches are in late June, July and August.

Enerald Beaut plum produces good but late fruit in Las Vegas.

Non Desert Recommendations

Be careful of planting fruit trees based upon recommendations from people not living in desert regions. The tree will most likely grow but it’s more of a question about the quality of the fruit it produces. It’s different. An interesting exploration for these children would be to compare the quality of the fruit produced by their trees with the quality of fruit purchased at the grocery store.

Flavor Finale pluot is a good fruit tree for late production in the fall.

            Dave Wilson Nursery online has a harvest calendar that you can download to your computer for your reference. The harvest schedule is for central California but is very close to harvest times in southern Nevada with a few exceptions. Be careful of fruit recommendations from non-desert climates.

Delay Pruning Grapes as Long as Possible

            I finished pruning the 300+ desert and juice grapes at The Orchard at Ahern located in downtown Las Vegas on March 8. New growth was just starting on a few of the vines. 

Grape Disease Control

I delay pruning grapes as long as possible in the spring to reduce disease possibilities and avoid any late spring frost damage after pruning. Immediately after pruning grapes, consider applying a fungicide to the vines if there were problems with grape bunches diseases last year. Repeat the fungicide application if it rains. For homeowners I would consider using Bordeaux fungicide.

 Effective fungicide sprays include the copper fungicides such as Bordeaux for homeowners. Fungicides primarily protect new growth from getting infections primarily through the pruning cuts.

            Unlike insecticides like Sevin or even organic soap and water sprays which kill insects, fungicides primarily “contain” diseases and help keep these diseases from spreading to new growth. That’s why it’s important to repeat it after a rain which can wash the fungicide from the vine.

Grapes Bleed

It’s normal for grapes to “bleed” after they have been pruned in the spring. Don’t worry. Water will stop coming from the pruning cuts when new growth appears.

           

Other Dwarf Peach Besides Bonanza

Q. I suddenly lost my favorite dwarf peach tree, Bonanza, over a year ago and I want to replace it. The local nursery said today they probably won't be carrying Bonanza peach anymore. Could you please advise me where I could purchase one as I don't know where to look?

Genetic dwarf peach trees can produce normal sized fruit.

A. I just checked online, and Bonanza genetic dwarf or miniature peach tree is available from many nurseries. Check around and see if your nursery will order it for you. If not, you can order it online in November or December from nurseries such as Bay Laurel, Grow Organic, Willis Orchards and others. They well send it to you bareroot and in good condition for immediate planting in January.

Three genetic dwarf peach trees, Eldorado, planted together. In the back is a "high bud" graft of Eldorado and the two in the front were "low bud" Eldorado peach. Genetic dwarf peach can be grafted high or low on the rootstock to give trees of different heights.

            I think you will like the fruit from any of the other genetic dwarf peach trees besides Bonanza if you find it locally. When I have tested many of the fruit coming from these genetic dwarf trees it has been good. These include Bonanza II, Garden Gold, Garden Sun, Honey Babe, Pix Zee. Eldorado and many others. Oftentimes retail nurseries don’t know what will become available later in the year so keep checking.

Why Dry Citrus Fruit?

Q. The fruit on my tangerine tree was very dry when I harvested it. My tree is about 10 feet tall when I purchased it in a 24-inch box. I had it for two years and both years the fruit has been very dry. The looks healthy and blooms good but the fruit is just not edible even when I tried to pick at different times.

A. When you plant anything from a 24-inch box make sure the soil surrounding the box was amended thoroughly with a good quality compost. Secondly, flood the entire area surrounding this plant and including this plant, with water immediately after planting. I would flood this entire area twice a few days apart before turning it over to an irrigation system.

Lack of Water

            The usual reason for dry fruit is a lack of applied irrigation water. To water this tree, use at least four drip emitters or a coil of drip tubing about 12 inches from the tree trunk. I would cover the soil with a 3 to 4-inch layer of woodchips applied to a distance at least out to the canopy of the tree.

I was going to mention another reason you could have dry fruit was harvesting late but you are harvesting at different times so I think you have that covered.

Water Deep and Cover the Soil in Woodchips

            It is very important that the tree receives water deeply and frequently enough to keep the soil moist while the fruit is getting larger. This can be deceiving as the weather is getting warmer with such a large tree. A soil moisture meter inserted into the soil under the mulch about 4 inches deep in three different locations will tell you when to irrigate again. You should irrigate when the meter has dropped about halfway, usually when it averages around “5”.

Water to 18 inches Deep

            A long thin piece of rigid steel like a piece of 4-foot-long rebar will tell you how many minutes to irrigate. For citrus trees I would apply enough water to wet the roots to a depth of about 18 inches. Pushing this rebar into the soil after an irrigation will tell you how deeply the water traveled.

Add More Emitters?

            If you are locked in to a certain number of minutes because your irrigating other plants as well, then add enough drip emitters, or increase the size of the emitters, or increase the length of the drip tubing coiled around the tree until enough water is applied with your given number of minutes.

Chemical Sprays for Mites

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.

Who to Hire to Prune Your Fruit Trees

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.

Be Realistic When Selecting a Freeze Tolerant Avocado

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.

Rain is a Good Thing in the Desert. Right?

            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.

Map of Global Hotspots of Glyphosate Contamination

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.”