Climate, soil richness affect production of fruit with tomato plants

Q: We have several tomato plants that have grown well with lots of leaves but there is no fruit production.

A: Let’s keep in mind that some varieties of tomatoes are better suited for our hot, dry, desert climate than others. Good performing varieties include Early Girl, Patio, Jet Star, Champion, Roma, Big Boy, Better Boy, Sweet 100, cherry tomatoes in general, grape tomatoes to name just a few.

Heirlooms typically struggle in their production, so selecting a variety that you know should perform well and then experimenting with a few others that are unknown are probably good ideas.

The second problem regards the “richness” of the soil and how much fertilizer was applied. Extremely rich soils with a high percentage of manures promote a lot of top growth at the expense of flower production. So does applying too much fertilizer.

If your garden is productive, do not add more than 1 inch of compost to the soil and then dig it in to a depth of 8 to 10 inches. Unproductive soils might require 2 to 3 inches of compost applied the first year with a 1-inch layer applied in subsequent years.

Starter fertilizers added at the time of seeding or planting should be high in phosphorus (the second number) with moderate to low amounts of nitrogen (the first number). After using a starter fertilizer, don’t apply any nitrogen fertilizers until you begin to see small fruits setting. After fruit set, go ahead and feed the plants small amounts of fertilizer once a month.

The third problem regards air temperature. Once air temperatures climb above 95 F and nighttime temperatures are warm, tomatoes no longer set fruit. Some tomato varieties will stop setting fruit in the low 90s and others will stop when temperatures get a bit higher.

Keep your tomato plants healthy and wait for some cooler temperatures.

Q: This year I bought some praying mantis egg cases. It’s impossible to see when they hatch and leave home so I just thought they died.

Imagine my surprise to be finding baby mantis in my front and backyard, on the very same plants squash bugs are hitting. What do I do? Spray for the bugs or hope the praying mantis will feast on the squash bug buffet?

A: We should be realistic about what praying mantis can and cannot do. They are not focusing on “bad guys” to help you, they are just looking for a meal. Their meals include “good bugs” and “bad bugs.” Your squash bugs are included.

Should you spray? If you use a pesticide that targets a certain pest while not harming others, it can work well. For instance, Bt organic insecticide kills only the larva or worms of moths and butterflies and will not harm mantis. But, unfortunately, it will not kill squash bugs either.

However, if we are realistic, Bt also kills larva of butterflies, which are not plant pests. An example is the Monarch butterfly. In this particular case, there is no organic pesticide that we can spray to kill squash bugs and not kill mantis.

Another “organic” pesticide is insecticidal soap. Unfortunately, insecticidal soap is an indiscriminate killer; it kills any insect on contact, including squash bugs, leaf-footed plant bugs, aphids, honeybees as well as praying mantis.

When we use organic indiscriminate killers such as insecticidal soap but do not want to harm beneficial insects such as mantis, then we must direct the spray on insects we want to kill and avoid spraying the ones we do not want to harm.

This requires a lot of plant inspection on your part — looking for, identifying and targeting the bad bugs with this spray. Think of it as a search and destroy mission.

Focusing on the use of beneficial insects for controlling bad bugs limits your ability to use pesticides. You must either not use pesticides, select pesticides that will not harm the beneficial insects or direct any pesticide sprays so that they come in contact only with bad bugs.

Another approach is to use these indiscriminate killers, such as insecticidal soaps and realize you will have collateral damage. The collateral damage that occurs is the killing of good bugs and bad bugs with the hope that the good bugs will recover after the spraying is over.

If you go this route, select organic pesticides that do as little damage to the general insect population as possible. This type of spray program limits the use of beneficial insects for any long-term control. It is really a spray and pray program.

Enjoy your praying mantis. They will migrate to other parts of your landscape as well as your neighbors. Visit and inspect your garden and fruit trees often. Use plants sprays when bad bugs are getting out of control and target sprays on these bugs.

Q: I planted a tree in small container in October. The tree is 5 feet high, growing well but needs water daily. Can it be moved to a larger container or placed in the ground or do I wait until fall?

A: It is always a bad idea to plant from containers, either from container to container or directly in the ground, during the hottest summer months. The plant will struggle as it tries to re-establish itself, even for the best gardeners.

Wait until temperatures cool off, at least until mid-September or the first week in October. At that time you can either plant it in a larger container or put it in the ground.

Q: We are renting and we have a tree in our front yard that is not that old. We noticed the leaves are turning a brown on the ends and not sure if it’s because of a watering issue, disease or pest problem. I have enclosed pictures of the leaves and would appreciate any help so that we can correct the issue.

A: It appears to be an ornamental pear tree from the pictures. The leaves appear to be browning because of a lack of water. The canopy of the tree also does not seem to be very full.

My initial guess is the tree is not receiving enough water every time it is irrigated. What can be confusing is that we can see similar symptoms to trees that are receiving too much water as well but in this case I think it is not enough.

I am assuming the tree is on drip irrigation and I am also assuming it is in a rock landscape. We can increase the amount of water the tree is getting by increasing the number of drip emitters surrounding the tree and making sure these emitters are 12 to 18 inches from the trunk.

We also can increase the amount of water by increasing the number of minutes on the irrigation controller. The problem is that everything else that is watered on the same valve also will get an increase in water when it may not be necessary. Also, this will increase your water bill unnecessarily.

It is best to increase the number of emitters; that way only this particular tree will get the increase in water. Another possibility — and I don’t necessarily want you to do this — is to increase the number of days the tree is receiving water during the week.

This is frequently not a good solution to a lack of water. Trees need to receive deep irrigations with lots of water, then rest a couple of days during the summer with no additional water, and then watered again deeply.

You do not want to water trees daily if it is at all possible unless they are in containers.

In the meantime, take a hose and slowly give that tree a lot of water around its base. Do this once a week and I think you will see an improvement in the number of leaves produced and the overall quality of the tree.

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.