Leaf cutting ants, fig beetles, can be tough to get rid of – Arizona Daily Star

Posted: August 6, 2017 at 2:46 am

Question: I live in Vail. These ants are stripping my trees and bushes of their leaves. Ive tried the ant baits, granular and sprays that I can buy, but they just keep coming back. So far they stripped a new pomegranate bush, a new Arizona ash (7 feet tall) and are now working on a mature desert willow tree. I can follow their trail of leaves to their nests and have tried to poison them. They will get my Lady Banksiae roses next. If you have any suggestions, they will be greatly appreciated.

Answer: Leaf cutting ants (Acromyrmex versicolor) are difficult to manage. They strip many different types of plants for the purpose of cultivating fungi on the plant parts they harvest. Because the fungi are their only source of food, they dont respond to ant baits formulated to attract other ant species that feed on sweets and protein. Its possible to protect individual plants with insecticides around the base of the plants but this is labor-intensive due to the short time these pesticides are effective in the environment before they break down. Should you be able to find their nests, treating them directly is another possibility. This is complicated by the potentially large size of the underground nests in that you cant kill them all and they will return. Amdro Ant Block is a product you can use to treat a colony once you find it but its only a temporary solution that may need to be reapplied every six months or so, depending on the situation. In any case, please be careful when applying pesticides and be sure to read the label to make sure you take precautions to protect yourself and any other non-target organisms in the area.

Q: This is a Texas persimmon planted about 3 years ago in back of our house. Can you advise me about the spots on the leaves?

A: Leaf spots can occur for a variety of reasons based on the plant and the circumstances. Common problems are often due to insufficient irrigation that causes plant stress and makes them susceptible to secondary problems such as salty soil. These may show up as brown leaf tips as shown in your photo and may be remedied by proper irrigation. The Texas persimmon (Diospyros texana) may be treated as a native in spite of its name since it is found in arid regions of Texas and Mexico. The recommended irrigation for these shrubby trees is once every 14 to 21 days between spring and fall to a depth of 24 to 36 inches.

Q: My home in the Catalina Foothills (built end of 1980s; frame stucco, custom home) appears to have minor termite issue. After our regular termite checks each year, there are usually a few small areas that need to be spot-treated. We have not had a barrier treatment since weve lived here (about four years) nor does there seem to have been any barrier treatmentinside or outside in the past five to six years. The exterminating company we use is pushing the product Sentricon as the best method for getting rid of termites. They say it is a lot safer than the barrier treatment in terms of harsh, toxic chemicals (I do not want such chemicals in or near my house) and that is by far the most effective way to get rid of termites permanently. Do you have an opinion as to the effectiveness of the Sentricon baiting method vs. yearly checks with chemical spot treating?

A: The first thing to do, if you havent already, is have the termites identified. We have approximately 17 species of termites in Arizona and only three types that are considered to be potential problems. Two of them, drywood and dampwood, are minor problems in some circumstances. The third type, the subterranean termites are a bigger deal. If you have subterranean termites, there are several methods to manage them and there are pros and cons to each type of subterranean termite management method. Sentricon is one of the most used bait systems. Baits are especially good for people that dislike the idea of a chemical barrier around their home for whatever reason. Bait systems are more expensive than chemical treatments, require more frequent monitoring, and may take longer to be effective, leaving the house at risk; since there is no good way to make the termites discover the bait. In some situations a combination of baits and spot-treating with insecticides is a good idea. Once discovered by the termites, these baits are reported to be as effective as chemical treatments.

Q: I have a mature pine tree in my backyard. Some people say it is an Aleppo. It is close to 50 feet high (40 for sure). It has grown for 25 years or so. My question involves watering. For the past several years I have diverted all the rainfall from my nearby patio roof to the drip line of this pine tree. This rain crock holds 200 gallons. And fills many times a year. The tree has responded to the extra water by putting on thick new growth several times. (The pollen coats everything with a thick dust!) This monsoon season has added water just as rainfall plus the added runoff water. (My backyard has received about 7 inches of rainfall this monsoon). I guess my question would be can a pine tree be watered too much? The soil drains well water soaks in very well. My concern might be that the tree becomes to big for its britches. If it becomes larger and larger with this new growth, what happens if the extra water stops? (I wont live forever). If the extra water stops or if even the rainfall totals drop, how will this larger version of this tree cope?

A: The short answer is yes; most plants that dont naturally grow in standing water can be watered too much. Mature pines need quite a bit of water so I doubt yours is at risk unless your drainage is slow and the roots end up in standing water. The risk is as you described: if the water stops, the tree may suffer from drought. This is currently happening all around us, as these mature pines dont often receive enough water, especially in the winter. The result is often that the trees become susceptible to secondary pests such as bark beetles. So you better plan to live longer to protect that tree.

Q: Our fig tree fruit is covered with green fig beetles and a nearby grape vine is being destroyed as they try to get to the residual grapes that are still there. Can you suggest a nontoxic way to get rid of these?

A: Unfortunately, there is not a good way to get rid of fig beetles (Cotinis nitida), toxic or nontoxic. Because they can fly and feed on a variety of plants, they are difficult to manage. The best method is to protect individual plants or fruit with a barrier such as fine mesh netting. Some people fasten net bags around stems with fruit to protect them. Ive also seen one person use plastic clamshell containers that you might find at a salad bar. Then you can reuse them to serve the ripe fruit.

Peter L. Warren is an entomologist and certified arborist specializing in landscape management and pest management. Questions may be emailed to tucsongardensage@gmail.com.

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Leaf cutting ants, fig beetles, can be tough to get rid of - Arizona Daily Star

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