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Saturday, June 20, 2015

The Whiteflies are Coming! The Whiteflies are Coming!

Whiteflies are the proper name for those tiny little, gnat-like, delicate flies that swarm off of plants like tomatoes, eggplants, peppers, grapes when you touch the leaves. They are located on the undersides of the leaves (as most bugs are) and fly off of the leaves when they are disturbed.

They like the heat of the summer. They don't particularly like the cooler spring and fall
Whiteflies, most likely ash whitefly, on pomegranate
months. Whiteflies suck the juices out of plants in much the same way aphids, scale insects and mealybugs do. Because they suck plant juices by tapping into the plant with their mouthparts they poop out sugary excrement that attracts ants.

Yellow sticky traps can be made with bright yellow paper or paint and a sticky surface like vaseline
You can use yellow sticky cards hung in the garden area to trap some of them but if there are loads of them you all have to spray. Try insecticidal soap first and see if you can reduce their numbers with that. If that doesn't work, try pyrethrins sprays to see if you can get some control that way.

Tomato Plants With No Fruit. What's Happening?

Q. We have several tomato plants that had grown well with lots of leaves but there is no fruit production. We have a good soil blend and other greens like kale, red and green chard are doing well. I know that it has to do with pollination or lack of it and wonder what else we can do to help these tomato plants.
Tomato flowers not setting
A. Several factors come into play regarding tomatoes not setting fruit. Let's keep in mind that some varieties of tomatoes are better suited for our hot, dry desert climate than others. Good performing varieties have included Early Girl, Patio, Jet Star, Champion, Roma, Big Boy, Better Boy, Sweet 100, cherry tomatoes in general, grape tomatoes to name just a few. There are others as well. Heirlooms typically struggle in their production so selecting a variety that you know should perform well and then experimenting with others that are unknown is probably a pretty good idea.
Tomato flower on left has set but tomato flower on right did not.

The second problem is regarding how rich the soil is and the fertilizers applied. Extremely rich soils with a high percentage of manures can promote a lot of top growth at the expense of flower production. In other words, amending the soil with a lot of rich ingredients high in nitrogen will promote a lot of leafy top growth early in the season, delaying flowering. 

Be careful when amending garden soils that you don't overdo it with amendments. If you have a productive garden already, I would not add more than 1 inch of compost to the soil and digging it in to a depth of 8 to 10 inches. Soils that are not productive or have never been underproduction might require 2 to 3 inches of compost initially added to it with a 1 inch layer applied in subsequent years.

Starter fertilizers added to the soil at the time of seeding or putting in transplants should be fertilizers high in phosphorus (the second number) with moderate to low amounts of nitrogen (the first number). Once a starter fertilizer has been used, you should not fertilize tomatoes with a high nitrogen fertilizer until you begin to see flowers setting. After flowers have set fruit, then go ahead and feed the plants with small amounts of fertilizer once a month.

The third problem is regarding the air temperature. Once air temperatures climb above 95°F and nighttime temperatures are warm, tomatoes will no longer set fruit. 95°F is not an on and off switch for setting tomato fruit. Some tomato varieties will stop setting fruit in the low 90s and others will stop when temperatures get our bit higher.

Keep your tomatoes healthy during the heat of the summer and if summer temperatures cool off to the low 90s for a brief time they should set if nighttime temperatures are dropping as well. When temperatures climb back up again, they will stop setting again. If you can maintain tomatoes into the early fall, they will start setting fruit again when temperatures drop down.

How to Spray When Mantids Are in the Garden

This question was posted to the Desert Horticulture Yahoo discussion group! Come join our desert horticulture discussions  and ask to be a member.

Mantid egg casing on a tree.
Q. Well they are back and so the battle begins.  I’m just starting to see a stinkbug or 2 and a few leaves on my squash has eggs on them.  I know just how fast those hungry buggers can suck the life out of cukes, squash, melons or whatever sounds good to them. 

This year I bought some praying mantis eggs/nest.  It’s impossible to see when they hatch and leave home so I just thought they died.  Imagine my surprise to now be finding baby mantis’s in my front and back yard....on the very same plants the squash bugs are hitting. 

So here’s my question.  To spray for the bugs or hope the praying mantis’ will feast on the squash bug buffet? 

Thoughts, ideas or opinions?  All are very much appreciated!


A. Sue, that’s a really good question and it is one of the major difficulties we face when we try to manage our garden and fruit trees organically or as organically as possible. You have introduced an insect predator into your garden to help keep some of the "bad bugs" under control rather than to use pesticides. It is one of the cornerstones of integrated pest management or IPM. We should also 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".

This idea works great with some pesticides approved for organic production and it does not work well for others. For instance if we use a pesticide allowed in organic production that targets a certain pest while not harming others it can work fine. An example is using Bt that kills only the larva or worms of moths and butterflies but we want to protect the praying mantis. It is totally safe for the praying mantis since it targets only the worms or larva of moths and butterflies. However, if we are realistic, it also kills the larva of butterflies which are not plant pests for our gardens.

However, if we use insecticidal soap, which is also recommended in organic production, and apply it to our vegetables or fruit trees, we are applying it is an "indiscriminate killer"; it will kill any insect on contact, squash bugs, leaf footed plant bugs, aphids, honeybees as well as praying mantis. 

When we choose to use an "indiscriminate killers" but want to keep beneficials, like praying mantis, from getting harmed, then we must direct the spray on the 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 the spray. 

Focusing on the use of beneficial insects as your primary method of controlling "bad bugs" limits your ability to use pesticides. You must either not use pesticides or select pesticides which 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, to keep bad insects under control and realize you will have "collateral damage". The "collateral damage" which occurs is the killing of good bugs and bad bugs with the hope that the good bugs will recover after the spraying is over. 

You also 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 mantids. 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 your sprays on these "bad bugs".

Leaf Scorch and Thin Canopy of Ornamental Pear Probably Water

Q. We are renting and we have a tree in our front yard that is not that old.  We have been noticing that the leaves are turning a brown on the ends and not sure if it's due to 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. I looked at the pictures you sent to me. It looks like may be an ornamental pear tree. The leaves that I could see certain appear to be browning due to 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 also receiving too much water 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 watering by increasing the number of drip emitters surrounding the tree and making sure that these emitters are 12 to 18 inches from the trunk. 
We can also increase the amount of water by increasing the number of minutes on the irrigation controller. The problem when we do this is that everything else that is watered will also get an increase in water when it may not be necessary. 
Also, this will increase your water bill perhaps 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 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 arrest of 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 or unless they are in containers. In the meantime, take a hose and give that tree a lot of water at its base very slowly. 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.

Can I Replant a New Tree in Mid-Summer?

Q. I planted a tree in small container in October of 2014. The tree is now 5 feet high growing well but needs water daily. Can it be presently 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 reestablish 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.

Friday, June 19, 2015

Squash bugs are Wreaking Havoc in Your Garden

Squash bugs are there and they have been there for at least a month now. Please check on the undersides of older leaves of your summer squash, winter squash, melons and Pumpkins. These pictures may help you.If you are growing these plants, they are there. They are closely related to two other pasts that kind of remind you of squash bugs; leaf footed plant bug that we see commonly on pomegranate and the common stink bug which can cause dimples in fruit and buds to abort on fruit trees.

Look at these older postings on my blog:



Why Are My Hearts and Flowers Yellow?

Q. My Hearts and Flowers groundcover is yellow green, not deep green. Why?

Click here if you want to see aptenia

A. The primary reasons would be a lack of soil improvement at the time of planting, planting in extremely hot and bright locations and not applying adequate amounts of fertilizer. Plants growing in amended soils and fertilized quarterly will have fewer problems than plants growing in soils with little or no improvement.

What you are calling Hearts and Flowers is probably Aptenia, a waxy leafed succulent with small red or purplish red flowers that have flower petals that are spiky. The most common is a variety called ‘Red Apple’ with bright red flowers.

It originates from South Africa in regions with summer rains and sandy soils. This type of climate and soil is less extreme than our Mojave Desert. This is the reason our soils must be amended with a good quality compost at the time of planting if this plant is going to look good.

Good soil drainage is a must. This plant is native to the hot climate of South Africa provided there are summer rains and sandy soils. This means this plant must be planted in soils with good drainage if it will survive. Again, soil improvement is a must.

There is an iceplant also called Hearts and Flowers but Aptenia is more commonly planted here. In our climate, Aptenia takes full sun with amended soils but may look better if planted in full sun with shade or filtered light in the late afternoon under some circumstances.

Improving the soil at planting time is a must. Yes, it is a succulent and it will do well in rock gardens but remember Las Vegas soils are an anomaly. Soil improvement is critical compared to other parts of the desert Southwest and even other parts of the Mojave Desert.

Yellowing can be caused from a lack of nitrogen so make sure fertilizers are applied at least quarterly. Use a light application of Miracle Gro or similar product and apply an iron fertilizer at the time of planting just in case the yellowing is due from a lack of iron.