May 22, 2014 - 5:00 am
Those of you who were lucky enough to get your tomatoes planted the first part of March have already tasted your home-grown tomatoes. Quite a few of you have discovered tomatoes with black bottoms.
This problem, called blossom end rot, is seen every year here on tomatoes and sometimes peppers and eggplant. No one really knows the exact cause for this physiological disease, but scientists agree it probably comes from mineral imbalances inside the fruit. The mineral usually associated with blossom end rot is a lack of calcium.
On the East Coast, in acidic soils, the recommendation is to “lime” the soils or add calcium carbonate to the soil so the plant does not run out of calcium. But calcium sprays applied to tomatoes do not cure the problem.
This is odd because calcium sprays such as calcium chloride applied to the fruit of apple and pear trees cure their calcium deficiencies, namely bitter pit and corky spot, and work in Southern Nevada.
Until scientists understand blossom end rot better, we are stuck with the same old recommendations that I am going to repeat here and can be found elsewhere.
Don’t waste your money on calcium sprays. They don’t work. Focus your energy on mulching vegetable beds to prevent water stress in the plants. Monitor your irrigations so that plants do not become water stressed.
Q: I planted a Texas ranger shrub three weeks ago in some sandy and rocky soil. I have been watering it with about 2 gallons daily. I added 1-inch-deep bark mulch in a 1-foot circle around the plant. Now I am finding yellow, brittle leaves on the lower stems and curling leaves on top. Am I overwatering?
A: Yes, it is definitely watered too often. Overwatering can be in two forms: giving too much water or giving water too often or both at the same time. Giving too much water relates to the number of gallons you give a plant each time you water. Watering too often relates to how many times in a week you give water to a plant.
It is far more damaging if plants are watered too often rather than given too much in a single watering. Rangers do fine without wood mulch. They will benefit from it but they don’t really need it like other plants, such as roses and many fruit trees in the rose family, do.
Now, a second problem. If wood mulch is in contact with young tender stems of plants, it can contribute to a disease called collar rot. Collar rot basically rots the trunk of the plant in contact with continuously wet mulch just above the soil surface.
A third problem is just plain old root rot. This happens below ground and not at the soil surface. Root rot happens because the roots cannot breathe because of a lack of oxygen. The open spaces in the soil are continuously filled with water. Basically, the roots drown.
Bottom line: Pull the mulch away from the trunk about a foot or eliminate it. Make sure the plant is planted at the correct depth in the soil. Make a basin around the plant about 2 feet in diameter and fill this basin with water from a hose or bucket.
Set your drip emitters for twice a week during the summer. On the same days your drip emitters come on, fill the basin with water. This helps settle the soil around the root system.
When you see new growth, eliminate the watering in the basin. Use only the drip emitters from that point forward. Use enough emitters to deliver 1 to 2 gallons each time you water. Next year, add one more emitter but leave the number of minutes unchanged.
Fertilize once in January. Do not use hedge shears to prune unless you intend it to be a hedge. If the plant is intended to stand alone, use selective pruning and remove one or two of the largest stems near the base of the plant every two to three years.
Q: I have a pomegranate tree planted by birds about 20 years ago. I never had bug problems on this tree before 2011. In 2012, it produced about 150 pounds of pomegranates. In 2013, the tree did not produce any fruit at all.
This year the tree is loaded again but it is infested with those little red bugs that I think will turn into those ugly creatures you have been talking about. We don’t want to use poisons. Have there been any new developments for control? This tree is tall, maybe 25 feet, and I am only 5 foot 5. How do I spray the whole tree?
A: This particular bug, the leaffooted plant bug, is a growing problem for Las Vegas gardeners. The only way you will have a good crop of pomegranates, and most likely pistachios, is to spray.
The two choices you have are to spray with a conventional insecticide, which you call a poison, or spray with some sort of organic spray which I guess you might call nonpoisonous.
Conventional insecticides leave a longer residual on the plant so you do not have to spray as often. Most organic sprays must be repeated more often because they don’t have much of a residual or none at all.
One of the most effective organic sprays is soap. You can make your own soap sprays, but for most people I would highly recommend buying insecticidal soap already made. The soap used to make insecticidal soaps is less damaging to plants than grabbing scented Ivory liquid and using that.
Insecticidal soaps, to be effective, must be sprayed directly on the insect. They have no residual. When these bugs die from the soap, new ones will come in and invade their territory so you have to respray frequently.
The most effective time to spray soaps is toward dusk when bugs have settled in for the night. Soap sprays are not selective. They will kill any insect that comes in direct contact with your spray, good or bad.
Organic sprays containing pyrethrum, an insecticide derived from either Dalmatian or Persian chrysanthemums, will probably work well. However, pyrethrum is a poison. Use it carefully and wear protective clothing.
Synthetic or manufactured sprays that chemically resemble pyrethrum, which you would categorize as a poison, are probably going to be effective as well. Scientists tweaked the chemistry of pyrethrum to give it more knockdown power and last a little longer. These are called synthetic pyrethroids.
Chemical names in the ingredients will say things like “Permethrin” or “pyrethroid.” These chemicals emulate natural pyrethrins but are manufactured and as such are not organic.
If you decide to go conventional, then look for these names in the ingredients. Make sure the label permits you to apply it to fruit trees.
How do you spray a tall tree? I prefer to use backpack sprayers with attachments that allow spraying to those heights. Another option is to use a trombone sprayer. Trombone sprayers pull the insecticide mixture from a bucket and, with pumping action similar to playing a trombone, produce enough pressure to spray that high.
Make sure you spray on days when there is no wind. Spray early in the morning or at dusk. Wear protective clothing and shower after you are done and wash your clothes in a separate load of laundry from other clothes.
Q: I ran across an item called Grub Guard in the catalog. It contains beneficial nematodes. Would these be the same kind of nematodes that attacked my tomatoes last year?
A: These are entirely different nematodes. These are good guys and pose no problems to other plants. The ones that attacked your tomatoes are probably root knot nematodes, which are never good, always bad guys. You are safe to use beneficial nematodes in your landscape.
Bob Morris is a horticulture expert living in Las Vegas and professor emeritus for the University of Nevada. Visit his blog at xtremehorticulture.blogspot.com. Send questions to Extremehort@aol.com.