Garden Guy: Advice for those growing corn, avocados


Question: I spent a lot of time and effort to plant my corn. When the stalks were about 3 inches high, many of them were laying on the ground. They looked like they were all sawed off at the base. Please tell me what is going on.

Three culprits are possible. The two most common offenders are birds and rats. Netting will help to exclude the birds and maybe a scarecrow, too. Rats will come at night and nibble on the succulent seedlings. Bait or trap for rats is the solution.

There are also some caterpillars, like cutworms, that at night, will feed on the seedlings, cutting off the stem at ground level. Yet the plant is not consumed but damaged enough to cause the seedling to topple.

Removing old crop residue and surrounding weeds will reduce the cutworm population. Worms can be hand-picked at night from the ground. Spraying the seedlings and the ground with BT (Bacillus thuringiensis) may also help.

Question: Hi, Nick. Our mature avocado trees and others in our neighborhood (Kehena Beach) are severely losing their leaves while blossoming at the same time. Do you know the cause and/or the solution? My husband thinks he should prune, but I think that would only stress the trees more. Thanks for any suggestions. — J.

It is typical for avocado trees to drop many, if not all, of their leaves while the tree is in bloom. The energy that is required to produce the huge number of bloom comes at the expense of the leaves. Actually, as many as 1 million blooms are produced on a mature avocado tree, but less than 1 percent of those flowers ultimately produce fruit. Once the fruit has set, the tree will put forth a new flush of leaves.

To minimize the leaf drop, make sure the tree is well cared for – ample fertilizer and proper watering.

Question: Nick, You recently discussed the treatment of the yellow rust on jaboticaba. Your recommendation was a copper spray. What are some of the brand names that I can look for on the shelf? Secondly, when would be the best time to spray? My tree has also developed black mold on the branches. Now I know heavy rains with too much shade is not good for the tree. Should I thin out the branches to let in more sunlight? — Mahalo, D.

Here are a few names to look for when shopping for a copper fungicide: Monterey Liqui-Cop Copper Fungicide Garden Spray, Bonide Liquid Copper Fungicide and Ortho Disease BGone Copper fungicide.

Copper fungicides are known as protectants. They protect new tissue from being infected by preventing the germination of the fungal spore. They will not, however, eradicate existing infections. The time to apply a copper fungicide would be prior to infection, or when there is a need to protect a newly emerging leaf flush, blooms or fruit.

The black mold on the branches and, I presume, leaves, is most likely sooty mold.

Although jaboticaba trees are free from insect pests, the black mold is evidence of an insect infestation. These pests are secreting honeydew, a rich sweet substance which drips on the leaf and branches below. The sooty mold fungus, whose spores are in the air, will land, germinate and feed on the honeydew. The fungus does not infect the tree. If you get rid of the insects, the sooty mold problem will be solved.

Light pruning, such as removing damaged and crossed branches, and the removal of a number of the thin inside shoots, will be beneficial. For ease of picking and management, commercial trees are often topped to a height of 10-12 feet.

Hilo resident Nick Sakovich is a professor emeritus of the University of California. He has worked in the field of agriculture for 30 years. Email your questions to Sakovich at askthegardenguy@earthlink.net.

 

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