58°F
weather icon Mostly Cloudy

Rainy conditions can cause diseases in plants

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. The infection starts as black dieback of new growth like it was burned by fire. 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 percent alcohol after each cut. Then bag this diseased black growth and get it off the property ASAP.

Another disease I saw pop up last year in grapes was bunch rot, but it was not really seen until the bunches got big. However, the disease started in the spring with 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 start to form.

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?

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.

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.

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 degrees 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.

The next good feature of Lila for backyards is its height. It is one of the smallest cold-hardy avocado trees you can buy. It is considered a semi-dwarf avocado tree that can grow to a height of 20 feet, but you could keep it pruned down to around 10 feet tall.

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.

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?

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 the dirt that covers the foliage and increases the chance of spider mite breakouts.

If Italian cypress starts turning gray 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 or cinnamon oil in early-morning hours and retest the tree to see if it worked.

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.

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 tree 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 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.

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.

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 with such a large tree as the weather. A soil moisture meter inserted into the soil under the mulch about 4 inches deep in three locations will tell you when to irrigate again. You should irrigate when the meter has dropped about halfway, usually when it averages around “5.”

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.

If you are locked into a certain number of minutes because you’re 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.

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?

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 will send it to you bare root and in good condition for immediate planting.

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.

Bob Morris is a horticulture expert and professor emeritus of the University of Nevada, Las Vegas. Visit his blog at xtremehorticulture.blogspot.com. Send questions to Extremehort@aol.com.

Don't miss the big stories. Like us on Facebook.
Local Videos
Cars line up for over 4 miles for food
Cars were lined up along Sahara Avenue from Palace Station to South Rainbow Boulevard for food distribution sponsored by Three Square and Central Church in Henderson.
Two large fires hit parts of the Las Vegas Valley - VIDEO
Renee Summerour wraps up the two large fire that hit part of the Las Vegas Valley Late Wednesday , early morning Thursday. RJ reporter Glenn Puit was at both scenes. (Las Vegas Review-Journal)
Las Vegas hotels light up their windows to show support during shutdown - VIDEO
Hotels on the Las Vegas Strip lit up their windows with hearts and messages to show support during the coronavirus pandemic, Wednesday night, April 1. (Le'Andre Fox and James Schaeffer/Las Vegas Review-Journal)
Isolation and quarantine center for homeless at Cashman Center - VIDEO
A new isolation and quarantine center for homeless is under construction at the Cashman Center in downtown Las Vegas, March 31. (K.M Cannon/Las Vegas Review-Journal)
Day care changes hours and takes extra steps to help guardians - VIDEO
Sarah Washington, whose children attend Discovery Gardens Childcare, shares the importance of the facility’s hour changes, and child care director Ariella Thomas discusses some other changes Discovery Gardens Childcare has made, in Las Vegas on Monday, March 30, 2020. (Elizabeth Page Brumley/Las Vegas Review-Journal) @Elipagephoto
Costco reduces hours at Las Vegas Valley stores, gasoline pumps - VIDEO
Costco announced it will reduce hours at its stores and gas pumps starting Monday. (James Schaeffer / Las Vegas Review-Journal)
Police investigate apparent murder-suicide
Las Vegas police investigate an apparent murder-suicide in the 3900 block of Chasing Heart Way on Saturday, March 28, 2020. (Ellen Schmidt/Las Vegas Review-Journal)
Homeless outreach organization feeds people in age of social distancing - VIDEO
Homeless outreach organization Food Not Bombs handed out sack lunches, hygiene kits and blankets on Foremaster Lane in Las Vegas, Thursday, March 26, 2020. Catholic Charities of Southern Nevada, which has temporarily closed its dining room and emergency night shelter, also handed out to-go lunches on Foremaster Lane. (K.M. Cannon/Las Vegas Review-Journal) @KMCannonPhoto
Nevada gets an A for social distancing
In an interactive Scoreboard by tech company Unacast, organizations can measure and understand the efficacy of social distancing. (Las Vegas Review-Journal)
Nevada construction continues as coronavirus spreads
When Gov. Steve Sisolak ordered Nevada businesses closed, he let construction workers stay on the job, deeming homebuilding and other construction “essential” lines of work.
Pedestrian struck, killed in western Las Vegas Valley crash - VIDEO
Las Vegas police are investigating after a pedestrian was struck and killed in a crash Wednesday night in the west valley. (James Schaeffer / Las Vegas Review-Journal)
Police investigate fatal crash in east Las Vegas - VIDEO
Las Vegas police said a pedestrian was killed when they were hit by a vehicle near Sloan Lane and of East Charleston Boulevard on Wednesday, March 25, 2020. (Glenn Puit/Las Vegas Review-Journal)
Seeing teachers at a distance, closed parks and lack of toilet paper - VIDEO
The neighboring towns of Logandale and Overton, northeast of Las Vegas, are experiencing the effects of coronavirus, with closed schools and playgrounds and fewer items in grocery stores. (Elizabeth Brumley/Las Vegas Review-Journal)
Las Vegas residents enjoy the snow at Lee Canyon - VIDEO
Las Vegas residents get out to enjoy the snow at Lee Canyon on Mount Charleston. (Bizuayehu Tesfaye/Las Vegas Review-Journal) @bizutesfaye
Post office stays open amidst shutdown - VIDEO
Mail delivery and services at post offices continues despite the coronavirus crisis. (Glenn Puit/Las Vegas Review-Journal)
1 person dies in east Las Vegas fire - VIDEO
One person and a dog were found dead after a fire in a detached structure adjacent to a house near East Monroe Avenue and North Betty Lane in east Las Vegas on Tuesday, March 24, 2020. (Glenn Puit/Las Vegas Review-Journal)
Albertsons, Walmart, Amazon increase pay amid coronavirus impact - VIDEO
Grocery stores and other retailers have raised employee pay as they work to meet customer demand during the coronavirus pandemic. (James Schaeffer / Las Vegas Review-Journal)
High winds move clouds across the Las Vegas Valley - Time-lapse video
Isolated showers depart when gusty winds move in probably remain through Wednesday, March 25, when another storm front is expected. (Michael Quine/Las Vegas Review-Journal)
Downtown's Pabst Blue Ribbon neon sign moving to Neon Museum - VIDEO
Yesco workers remove the Pabst Blue Ribbon neon sign at Fremont Street and Las Vegas Boulevard on Monday, March 23, 2020. The sign, which has been at the location for five years, will be displayed at the Neon Museum. A museum representative said a replacement neon sign is in the works. (K.M. Cannon/Las Vegas Review-Journal) @KMCannonPhoto
Distance Learning challenges for Clark County School District - VIDEO
Renee Summerour sits down with RJ reporter Aleksandra Appleton to discuss the challenges the Clark County School District is facing with Distance Learning, a program that was slated to begin Monday, March 23. (Renee Summerour/Las Vegas Review-Journal)
Deliver with Dignity will give 100 families meals today - VIDEO
“Deliver with Dignity” was created “to bring high-quality meals directly to the most vulnerable families in the Las Vegas Valley, keeping them and the community safe by reducing the risk of exposure to COVID-19.” (Facebook/Clark County)
CCSD board holds an emergency meeting on Distance Learning - VIDEO
The Clark County School Board held an emergency meeting on Monday morning, the day that distance learning was supposed to begin at all schools in Nevada. (Clark County School District)
Las Vegas Valley residents make medical masks for health care workers - VIDEO
Anissa Gustafson has spent most of her week sewing masks in an effort to assist health care workers in the Las Vegas Valley who are running out because of the coronavirus pandemic. (Rachel Aston/Las Vegas Review-Journal)
Coronavirus patients could inundate hospitals - VIDEO
RJ Investigations reporter Michael S. Davidson talks about how a rapid influx of coronavirus patients could soon inundate Nevada hospitals, pushing them past their capacity and threatening health care workers’ safety. (Renee Summerour/Las Vegas Review-Journal)
M Resort donates food surplus to workers - VIDEO
The M Resort donated a surplus of perishable food supplies to team members after the closure of the hotel due to a shutdown of nonessential businesses in Nevada, Friday, March 20, 2020. (Erik Verduzco/Las Vegas Review-Journal)
Costco reserved earliest hour for seniors - VIDEO
People line up outside Costco in Henderson after the store reserved earliest hour for seniors on Friday, March 20, 2020. (Bizuayehu Tesfaye/Las Vegas Review-Journal) @bizutesfaye
2 pedestrians injured after being hit by vehicle - VIDEO
Two men were injured when they were hit by a car on Warm Springs Road near Bruce Street in southeast Las Vegas on Friday, March 20, 2020. (Glenn Puit/Las Vegas Review-Journal)
Las Vegas shopping lines still long - VIDEO
Senior shoppers line up at 7 a.m. outside of Smith's Marketplace on Skye Canyon Park Drive in northwest Las Vegas, Friday, March 20, 2020. (Michael Quine/Las Vegas Review-Journal)
Dos and Dont's: Cleaning your smartphone of germs - VIDEO
Check out the dos and dont's for cleaning your phone of germs. (James Schaeffer / Las Vegas Review-Journal)
More Las Vegas Valley grocery stores offer early hours for seniors - VIDEO
A growing list of Las Vegas Valley retailers are offering special shopping hours for seniors in light of the COVID-19 pandemic. (James Schaeffer / Las Vegas Review-Journal)
Missing hiker's sister on staying hopeful - Video
Karsta Lucas, the sister of Ronnie Lucas, a hiker missing at Red Rock Canyon National Conservation Area, said Tuesday, Feb. 11, 2020, that family members remain hopeful the 33-year-old diabetic will be found safe despite spending two nights in the open without his insulin. (Glenn Puit/Las Vegas Review-Journal)
Search continues for missing hiker at Red Rock Canyon - Video
Volunteers come out to Red Rock Canyon National Conservation Area west of Las Vegas to help find a hiker, Ronnie Lucas, who went missing on Sunday, Feb. 9, 2020. (Glenn Puit/Las Vegas Review-Journal)
Search for missing hiker at Red Rock Canyon - Video
Red Rock Search & Rescue is looked for the missing hiker at Red Rock Canyon National Conservation Area on Monday, Feb. 10, 2010. The man was reported missing on Sunday. (Glenn Puit/Las Vegas Review-Journal)
Las Vegas ready to enforce homeless camping ban - VIDEO
Las Vegas police will begin enforcing a controversial camping ban on city streets on Saturday, but officials say they expect to impose the penalties available under the new ordinance only in rare instances. (James Schaeffer / Las Vegas Review-Journal)
Officials celebrate opening of Las Vegas park named for slain officer - Video
Top public officials came together Friday morning to celebrate the grand opening of Officer Alyn Beck Memorial Park in the northwest valley, named after a police officer killed in the line of duty in 2014. (Nathan Asselin/Las Vegas Review-Journal)
Wrong-way driver causes fatal crash near Las Vegas airport, authorities say - VIDEO
A suspected impaired motorist driving the wrong way on the Airport Connector caused a crash that killed another driver near McCarran International Airport early Friday morning, Jan. 17, 2020, according to law enforcement. (Glenn Puit/Las Vegas Review-Journal)
The car that Tupac was shot in is for sale - VIDEO
The vehicle that legendary rapper Tupac Shakur was riding in when he was shot after a boxing match in Las Vegas is up for auction. The black 1996 BMW 7 Series is listed by Celebrity Cars Las Vegas for $1.75 million. (Angus Kelly/Las Vegas Review-Journal)
THE LATEST
Standard-sized apple tree cannot be pruned to dwarf size

Standard-sized apple trees may grow to 35 or 40 feet in height. You might be able to keep a standard-sized tree under 20 feet tall through pruning, but the standard-sized apple tree is just too vigorous for pruning to short heights.

Delay grape pruning as long as possible

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 bunch diseases last year.

Mexican petunia needs to be contained to area

My experience with Mexican petunia is that it grows like a weed, and I consider it the broadleaf version of Bermuda grass, aka devil grass. If it’s contained in an area and prevented from spreading into the landscape, I think it will be OK.

Check for borers after rainfall

An infrequent desert rain is not a problem. But when irrigation water is applied over and over to a soil that is normally dry, these soils shift, collapse and chemically change. In urban landscapes, this can be potentially destructive.

Sanitize blades of loppers, hand shears before using

When preparing to prune plants, follow these three rules: adjusting loppers or hand shears so they don’t rip plants instead of cutting them, making sure the blade is sharp for the same reason and sanitizing the blades.

Olive tree will outgrow container so plant in ground

Desert willow can look shaggy during the winter because of the brown seedpods that hang from the tree. The seedpods provide a good supply of birdseed for various desert birds during the fall and winter months.