The damage to plants from extreme heat spikes this June and July is now obvious. Mature drought and heat-tolerant sycamores that did not receive regular deep irrigation have lost two-thirds of their leaf canopy. Crape myrtles that should be in full bloom in summer have lost nearly all of their blossoms. Lawns grasses have turned to yellow straw, rose petals look fried (they are) and fruit trees are dropping most of the immature fruit well before harvest time.

Consecutive weeks of daytime temperatures exceeding 100 degrees and nighttime temperatures remaining in the high 70s have killed many plants and trees and weakened or stunted many others. Determining whether severely heat-stressed plants and trees are dead or dying and whether they have a chance to recover vigor and good health will be a challenge during the next few months. Branch dieback, premature leaf drop, dropping of immature fruits and nuts, dead leaves, blossom drop and flower desiccation as well as yellowed or brown lawn grasses are all signs of severe heat stress as well as drought stress. 

Determining the extent of the heat damage this next month will determine whether a plant or tree is salvageable. Dead leaves don't necessarily indicate that a plant has died. Remove dead leaves on flowering annuals and summer vegetables and scratch the stems to check for green tissue underneath the top layer of bark or stem tissue. Green tissue is still alive. Check leaf nodes for swelling which indicates that new leaves are forming at the node.

Keep the soil moist and delay removing plants which show signs of life. They may well recover and begin producing again in late August.

Protection from the scorching sun this month will speed recovery when temperatures cool in fall. Try to provide full shade this month for damaged plants or plants that do not recover easily from wilting. Move container plants into full shade. Place market umbrellas and shade structures where they can provide the most shade and leave them there. 

If major structural branches on mature landscape trees and fruit and nut trees are dead, the remaining branch scaffolding may not be strong enough to hold a crop or may create a hazardous imbalance. Branches that have lost their leaves or which still hold crispy brown leaves may look dead but still be alive. Remove any dead branches that can become projectiles during fall storms, but wait until deciduous trees are dormant in mid-winter to restructure branch scaffolding. Continue to deep irrigate trees and bushes into the fall months whenever a heat spike is predicted. 

Wait to fertilize all heat-stressed plants and trees until late August when nights will be longer and a little cooler. Deep irrigate before and after fertilization. It will be tempting to feed heat-stressed plants heavily to encourage rapid new growth but feeding at half the recommended rate for the next couple of months will encourage a slow and steady recovery. Apply low-nitrogen fertilizers on landscape plants and bushes and on summer vegetables. Give fruit and nut trees one feeding of a high-nitrogen fertilizer after harvest or in September if there was no crop left to harvest. 

             

When the weather is hot outside, pests are likely to search for cool, sheltered areas – such as inside your home. But that doesn't mean it's time to spray pesticides.

Cockroaches, ants and flies are three common outdoor pests that will enter homes when they have the opportunity, said UC Cooperative Extension urban integrated pest management (IPM) advisor Andrew Sutherland.

Oriental cockroaches, usually black or dark brown, are found throughout the U.S. They live and breed in dark, damp outdoor locations. Reddish-brown Turkestan cockroaches, originally from central Asia, are now well established in California. They live outside eating decaying plant and animal matter, finding safe harbor in water meter, irrigation and electrical boxes, cracks and crevices. American cockroaches live in warm and humid underground structures, such as sewers and storm drains.

If your home isn't well-sealed, they will walk right in.

Sutherland recommends using IPM strategies to prevent cockroach infestations, starting with prevention. Reduce moisture around the home, especially within the first couple of yards of the perimeter. Remove as much food as possible from around the home.

“You never want to leave pet food outside. If you have a fruit tree, make sure the fruit is not accumulating in the yard,” he said.

Add door sweeps or door brushes to close the gap underneath doors. Garages should be sealed with a flexible threshold seal.

“Spraying cockroaches with pesticides will not fix the problem,” he said. “If you have exterior doors with a one-inch gap, it doesn't matter how many pesticides you apply to cockroaches, they are still going to come in through the door. If you want to treat cockroaches with pesticides, bait works best.”

Readily available gel and granular baits are very effective.

Ants

Argentine ants are native to South America, but they have been introduced all over the globe. The tiny black insect lives in large colonies, so their trails can resemble crowded superhighways. Researchers have discovered that they tend to enter homes two times of the year: When the first rain of the season floods their nests, and when it is hot and dry in the summer.

“Sometimes they will even move their entire brood into a protected area indoors, within a wall or cabinet void,” Sutherland said. “Argentine ants live and breed outside. If you're seeing them indoors, it's because they are foraging on a resource or they're temporarily moving their colony to avoid inhospitable conditions.”

The best control strategy is prevention. Irrigated landscape favors Argentine ants. A drought-tolerant or xeriscape landscape will be less attractive to them. Removing food sources is more difficult with ants. Sap-sucking insects like aphids, mealybugs, whiteflies and soft scale deposit a sweet, sticky residue that ants love.

“If you're able to control the sap-sucking insects, you'll control the ants. Likewise, if you control ants, you'll probably see a reduction in sap-sucking insects,” he said.

Sutherland suggests avoiding regular pesticide spray programs for pest control because of the ecological damage that results when runoff flows into storm drains, creeks and other waterways. As with cockroaches, baits can be very effective.  

“Ants are social insects. If an ant consumes a bit of insecticidal bait, it's going to share it with its nestmates. With baits you can actually kill an entire ant colony, where with sprays, at best you're going to kill the ants that cross chemical,” Sutherland said.

Sometimes, you might have an “ant emergency,” a swarm of ants that suddenly appears inside.

“There are safe steps to take,” Sutherland said. “I keep a spray bottle with a 10% soap solution. I spray it wherever I see ants and wipe them off. This works better than a contact insecticide because you also erase the pheromone trail the ants are using to find food or water. “

Flies

Many species of colorful metallic blowflies are found the world over. To control them, turn to prevention.

“Blowflies really like pet waste,” Sutherland said. “One deposit of waste can sustain a lot of flies. If you have pets, pick up and dispose of their waste.”

As a secondary control, be diligent with structural exclusion. Make sure the doors are closed, window screens are in good repair and screen doors fit well. You can buy aerosol cans of insecticide in home stores, which kills on contact as insects fly through mist. But it is cheaper and safer to kill them with a fly swatter or rolled up paper.

Learn more:

Summertime Household Pests, by Andrew Sutherland, UC IPM webinar on YouTube

UC IPM Pest Notes:
Cockroaches
Ants
Flies
Dozens of other pests

Well, you can tell it is July in Fresno! Like the song says, “The heat is on!” The only consolation is that this too shall pass (in a few months). The heat takes a toll on your roses (and you too!). I will be sounding somewhat like a broken record (is there still such a thing?) over the next couple of months. The high summer temps are less than ideal for having beautiful roses. Check your garden in the morning when it is the cooler part of the day. Look at the leaves of your plants for leaf wilt, drying or discoloring of the leaves. If they appear dull, check your plants for disease, drought or pests.

Now is not the time to fertilize. Your plants are struggling to remain hydrated. You can remove your withered petals and let hips develop for the time being. Make sure your plants have at least 3 to 4 inches of mulch around the dripline of the plant to help keep away weeds and help to maintain moisture. 

When temps get over 90° F, roses will lose moisture through their leaves. This sometimes shows up as browning along the edge of the leaf. Insufficient moisture in the root zone of your roses will cause this. It is a sign of heat stress. Make sure you give your plants adequate water on the days when we can water. If you see this, don't be tempted to remove the leaves. They will help the canes of the plant to stay shaded from the sun and not get sunburned. Sunburned canes can kill your plant.

If the edges of the leaves of your roses are crispy dry, they are sunburned. It happens here in Fresno this time of year. What causes this and do you need to cover your leaves in sunblock? No to the sunblock. Just make sure you wear it when you are in the garden. What causes sunburn on the edges of your leaves is that we have various salts in our water and in our soil. According to Curtis Smith, retired New Mexico State University Horticulture Specialist, the rose plant will take up those dissolved salts to the leaves from the roots during transpiration. As the water transpires from tiny pores in the leaves, the dissolved salts are left behind. The salts left at the leaf margin kill the plant cells in those spots when they get to toxic levels. This causes the leaves to look burned and can also cause a crusty white build up on older leaves.

So, is there a way to fix this? Make sure you water deeply (see Rosie's Corner for June 2024), to help push those salts down through the soil profile and away from the roots. Don't over fertilize with inorganic fertilizers, which are made up of salts. Use mulch to conserve moisture and it will help to keep the soil temperatures moderate. However, once a leaf is burned, it will not green back up. Best to be patient and wait for new green leaves to emerge when we deadhead again in cooler weather.

Again, check your plants for any signs of pests. Thrips and spider mites love this time of year and these temps. A strong spray of water below the leaves, followed by an overhead shower can help to keep those little critters away. Do this early in the day, on the days you can water, for at least 10 -14 days. Inspect your plants daily for any signs of infestation. A bonus is walking in the garden, a great way to reduce stress. (Did you know that in England, physicians can prescribe gardening as a treatment for reducing anxiety and stress? Scientists have found spending two hours a week in nature can lead to better health and well being.)

So, on that note, it is important for you to take care of yourself when you are in the garden. Work in the garden early in the morning and use proper, sharp and clean tools. Wear long pants, long-sleeved shirts and covered shoes. Shorts and swimsuits don't give skin protection and sandals, or bare feet won't protect your toes from dropped pruners. Use sunscreen when you are outside. A broad brimmed hat or a hat with neck protection will also help. Drink water before and after working in the garden to keep yourself hydrated. 

Dainty Bess Rose

This is one of my favorite roses. It has ruffled pink petals that surround maroon stamens. Those open blossoms allow our important pollinators to enjoy the rose as well. This is one tough rose, named in the 1920s after Bessie Archer, the wife of breeder William Edward Basil Archer of England. Archer was a furniture designer, but bred roses as a hobby. He and his daughter, Muriel G Archer, sold roses from the 1920s to the 1940s in Kent, England. As a rose breeder friend of mine said, “You don't name a bad rose after your wife if you want to stay married.” Dainty Bess is a great rose! She is a hybrid tea and comes as a climber as well.

(Photos: Wikimedia Commons)

Until next time...”It's OK to feel delicate sometimes. Real beauty is in the fragility of your petals. A rose that never wilts isn't a rose at all.” - Crystal Woods, Write Like No One is Reading