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Wednesday, May 15, 2013

Beautiful Moth Now, Deadly Assignment in Your Garden

I was working in the garage the other night, cleaning out some things and holding a small box. The overhead light was on so I could see the small box in front of me. Startling me, this flew in and landed on the box, attracted to the light.
Of course this is not my picture but can be found at
http://www.fs.fed.us/wildflowers/pollinators/pollinator-of-the-month/images/hawkmoths/eumorpha_typhon_lg.jpg This is the sphinx moth, hawk moth or sometimes we call them the hummingbird moth because they can pause in mid-air in front of a flower and sip up its nectar. However, my moth was gone as soon as I tried to get my camera. But the feds site will let me use their picture.

You will see them flying now, usually around dusk although they feed on the nectar of flowers and serve as very good pollinators, particularly of flowers with very long "throats". This is because their "tongue" is so long. But....there is a problem for gardeners.
This is the hornworm and it is the larva or immature (baby) of the sphinx/hawk/hummingbird moth. You will see them devouring grape leaves (one of their favorites), tomato leaves and other garden crops. They can be devastating this time of year and you might see them again in the fall.
It is your call but if  you want to control these "caterpillars" or larvae then use Bt (Dipel or Thuricide) or Spinosad for organic control. It will not harm the adult moth but will help in controlling the eating by the larvae. This will of course prevent the larvae that you kill from becoming more moths.

Monday, May 13, 2013

Watch for Grape Leaves Disappearing - Skeletonizer Flying

Q. I just sited my first grape leaf skeletonizer moth. I’ve learned that Bt will control the worms.   I’d like to try and minimize the larvae if I can by eradicating as many moths as possible. Can you recommend the best course of action, if any, to control the moth itself?

Grape leaf skeletonizer adult moth
A. Not a lot of people know what they look like. They are a dark, blue-black moth that resembles a wasp more than a moth. I will post a picture of the moth, eggs and damage on my blog for all to see. If you have grapes, everyone should start looking for these guys.

Grape leaf skeletonizer larva feeding ont he underside of grape leaf. This picture courtesy University of Arizona
and can be found at http://cals.arizona.edu/yavapai/diagnostics/Assets/Images/Insects/grapeleafskeletonizer1.jpg
            The adult only lives for about three days. Pretty much its sole purpose is to reproduce. The damage comes from the larvae eating the leaves, not the moth eating the leaves. The eggs are laid on the bottom of the leaf. The life cycle of the insect is about 60 days (two months). It takes about 7 days for the larvae to hatch from the deposited eggs.

            I know you want to control the adult in an attempt to control the young but it probably is not the best approach since the adult will be hard to kill. Soap and water or insecticidal soap will work IF the soapy water comes in direct contact with the moth. But since the adult does not eat the leaves, you would have to actually spray the adults to kill them.

            The larvae are fairly easy to kill since they eat grape leaves. You must spray it on the bottom of the leaves. Do this by pointing your applicator so it sprays up, on the bottom of the leaves. The Bt (Dipel, Thuricide) has about a one week residue on the leaves.

            Spinosad will also work and has about the same staying power but is a little harder on bees.
A word of caution: These larva are nasty critters. If a larva falls on your skin it will feel like you were burned by a matchhead.

Pruning Fruit Trees at Planting

Q. I planted some barefoot fruit trees earlier this year and unfortunately several did not survive. This was my fault since I didn't get them planted right away and the roots may have dried out.  I want to replace them with container nursery stock. The problem is that I want to prune the trees to knee to height per your ladderless orchard recommendations. All the nursery stock trees have limbs well above this height.  If purchased and planted now, can these trees be cut back to the lower height when planted and survive?

A. They can be pruned back provided the stems are not too large in diameter. Pick smaller container plants that are in good health. They will catch up or even surpass the size of larger container stock.

            I would make sure that the stem or trunk is well under an inch in diameter so you can cut them back. This should produce several new stems about 8 to ten inches below your cut.

            Some fruit trees sucker better than others. Peach and nectarine, for instance, have a harder time sending new shoots up after they have been cut if the diameter is too large. You should not kill the tree if you do this provided the diameter is small.

Insect Damage to Kiwi But Can't Find Insect

Q. I have a bit of a quandary. My male kiwi died and I did everything I could do to keep it alive. I then contacted Parks Seed and they sent me a new male free of charge, not even shipping. But then something started eating the leaves of my female kiwi. I searched every leaf and found nothing. I thought whatever it is must be eating at night and hiding during the day. I was right. It was a beetle. I found and identified the culprit; a black vine weevil. Now here is my question. If they have laid eggs in the pots (still in their one gallon originals) of my new male or the original female what do I do to stop the infestation if there are eggs or already larva feeding on the roots?

A. Kiwi is a bit cold sensitive for some parts of the valley. So be careful during the winter. However, we should be able to grow hardy kiwi here in most locations. You will have a hard time managing this plant in a 1 gallon container for any length of time. I would get it in the ground.

            Yes, it could be a black vine weevil or possibly root weevils which are more common here. It is possible the plant came to you with black vine weevil as a hitchhiker. Black vine weevil adults emerge in spring and cause plant injury by feeding upon blossoms, clusters, and small fruits.

            I would follow the same recommendations for growing it as our fruit trees; plant it in the ground with lots of compost at the time of planting, water it in thoroughly and stake the plant to keep it from moving, mulch the surface of the soil with organic mulch.

            If you collect some from the leaves at night and send it to the state entomologist through the State Department of Agriculture we can get this resolved.

            Control efforts are usually directed against the larvae living in the soil. Root weevils come out at night, as you have discovered, and chew on the edge of leaves leaving the edges of the leaves very raggedy looking. Control is difficult but they usually do not cause extensive damage that would kill the plant.

            When they feed on ornamentals we usually just ignore root weevils. If it is black vine weevil you would be looking at applying an insecticide to the soil in the container in an effort to control the larva or immature forms. You would need to look for an insecticide which lists that it controls vine weevil, can be used as a soil drench and is labeled for fruit crops.

Roses Growing Weaker After Installing Rock Mulch

Q. I have some well-established rose bushes (15 years) in our front yard. Five years ago we converted to desert landscape and the landscaper put about 3 inches of small rock in the area containing the roses. They seem to be healthy although the density and beauty of the blooms was weaker last year.

            I've been using liquid Miracle Gro. Is there a better liquid fertilizer, or should I consider pulling the rock away from the bases and fertilize through the soil. Thanks.

Not the readers rose but what can happen to roses over time growing in rock
mulch and little care.
A. Miracle Gro products are fine but I would also add a separate iron fertilizer. Go to your local nursery and get a one pound canister of iron EDDHA. Follow the label directions but I find it more effective to mix in a teaspoon of the product in a gallon of water and water it into the rootzone of each plant.
Some of the Miracle Gro specialty fertilizers. Actually any of these would interchangeable. Miracle Gro might disagree
but these labels are mostly to help novice gardeners select a fertilizer for specific plants.

            Each rose should get maybe one teaspoon January – March, a once a year feeding. Although best applied early, an application will work now. They should be all right if you keep it on this fertilizer schedule. Select a product that has a big middle number. There are several different ones to pick from and I don’t know their product line off the top of my head.
This is the correct iron chelate to use in our high pH soils.

            Feed roses about every two months lightly starting January – October. However the iron is needed just once a year. Do not neglect soil improvement as well by using composts and organic mulches that decompose into the soil. Roses will really appreciate wood mulch much more than rock mulch.

African Sumac Limbs Splitting

Q. Could you please give me some clue as to why my 10 year old African Sumac tree has started to get split limbs. They are splitting laterally along the length of the branch. I have had to cut off two branches in the last week because of this splitting.

A. This is the first I have heard of this problem with African sumac. Who is making the decision to remove the limbs and what is the reasoning behind it? I would be curious because there are unscrupulous maintenance people who will point out something to a homeowner and recommend a job to make money. Also, there are uneducated maintenance people who will point out something to a homeowner and recommend a job to make money.

            Sometimes natural furrowing of the bark can be mistaken for cracking. I have had several homeowners get concerned and send pictures and that is all it is. I have had African sumacs split due to snow loads on the branches but that is reasonable.

            Most reasons for cracking would be excessive weight on the limbs. Are you sure there are no children doing pull-ups on some limbs?

            This is a stretch but if the tree were growing very rapidly and pruned incorrectly I could possibly see that limb cracking might occur. Without a bit more information that is about all I can tell you with the information you gave me.

Has anyone else seen this? I would love to get some pictures so I can see the problem.

Pine tree limb splitting due to lack of taper along the limb. The weight of the branch on the end was too much for it
after a light snow. The tree was thinned to allow for less resistance to wind to lessen blow over. Improper pruning caused
the limb to not develop good taper resulting in splitting.