San Antonio Express News
Sunday, June 26, 2005
By Dr. Jerry Parsons
I want to publicly apologize for some of my media colleagues who have been recommending natural-sounding remedies which do NOTHING to solve target problems which are seasonal and feasibly uncontrollable. The only changes these so-called “remedies” make is a decrease in the gullible person’s bank account. These atrocities became paramount to me as I listened to a garden “expert” recommend garlic extract and soil activators for multiple soil drenches to cure the cause of dead leaves on Arizona Ash trees and eliminate worms hanging from webs on the same trees. The Arizona Ash trees had dead leaves because of the fungus disease, Anthracnose, which occurs several times in the early spring and eventually is eliminated by hotter, drier weather. The worms come every year, complete their life cycle and disappear—as outlined and identified at: http://www.plantanswers.com/garden_column/april04/1.htm. By the time the curative recommendations of garlic extract and soil activators were being made, the problems had cured themselves, and only the leaf damage and the memories of the worm problem remained. Money spent on these “remedies” was completely wasted unless there were some therapeutic ramifications for the caller — who was actually the victim of this useless, costly advice.
With that sorry episode fresh in our memories, I want to warn you of some other problems which you will need to avoid getting useless remedies for and wasting your family’s valuable resources on. Some horticulture pitfalls to avoid:
RED TIPPED PHOTINIA PROBLEMS
This is the most commonly sold shrub and, by far, the most problem-prone shrub in Texas. This shrub is highly susceptible to Red Tip Leaf Spot and yellowing caused by iron chlorosis. There is no practical cure for either problem. There is an impractical treatment which is a product (Fertilome Liquid Systemic Fungicide) which contains Propiconazole (Alamo – Banner) of oak wilt fame. It is labeled for Red Tip Leaf Spot. Propaconazole-Banner Maxx-has been shown to be pretty good for Entomosporium leaf spot control in red tip. And here is all you have to do. Start application early and preventatively, especially while young leaves are developing and sizing up. Reapply as frequently as label will allow, probably 10-14 days, until leaves are fully mature…then re-apply as needed to protect new flushes as they occur. Plants with chronic or historical problems with leaf spot should be aggressively treated as mentioned above. For plants that have not had a problem, check them and apply at first sign of infection, or maybe 1-2 preventative applications. Also important is to collect and destroy all infected leaf litter from below plants. Also, get a good line-of-credit from the bank before starting this treatment since every year as the plant gets larger, the treatments will be more costly. The PRACTICAL treatment is to eliminate sickly red-tipped Photinias as soon as possible and replace them with hollies. If you do not have red-tipped Photinias planted in the landscape-DON’T!!!
The most prolific, elusive insects (which are really spiders) of any garden are the spider mites. These girls coined the phrase, “strength in numbers,” and they are committed to the cause! When conditions are optimum (hot and dry), they can double their population in 4 days.
NOTHING works when populations are dense and weather is hot and dry. The best control is destruction of infested plant materials.
When the webworms begin, just stay in the house and wait for the populations to decline-which they will from year to year. Webworms have been written about and complained about for years with no apparent affect on the population. Please do not waste your money on the folly of releasing Trichogramma wasps into pecan trees as a way to slow down the rampant explosions of webworms seen in San Antonio over the past 2 to 3 years. Why is it a folly? No one denies that these wasps feed on webworm eggs, but huge numbers of the wasps would have to be simultaneously evenly distributed over a massive area to see any significant population reduction. The release would have to be timed perfectly. A few folks doing releases in their own backyards amounts to a drop in the ocean or sort of like spitting on a forest fire! Left alone, these insects, as do all insect populations, will cycle and decrease in numbers after a population explosion has occurred. I have seen this happen with the diamond-back moth on cabbage, leafminers on peppers and thrips spreading tomato spotted wilt virus. Pecan trees have been surviving population surges of webworms for hundreds of years so they will survive our most recent problems. If only our population can endure the ugliness caused by tree defoliation and webbing.
I hope you will think about the “uncontrollables” in your landscape and not fall prey to the idea that you can man-handle Nature. For goodness sake, if you want to attack some of these insurmountable problems, don’t waste your money on foolish man-made remedies. Chainsaw the red-tip Photinias down, bury the spider mites, and burn the webworms out of the trees-save the garlic and the “natural products” for your salads.
For an expanded version of this information and images of damage from these plant problems, see: http://www.plantanswers.com/unbeatable_foes.htm
Dr. Jerry Parsons is a Professor for Texas A&M University and a Texas Cooperative Extension Horticulturist for over 30 years in South Central Texas. For more information on this or other horticulture topics, go to www.plantanswers.com and our County Extension website at http://bexar-tx.tamu.edu.