Question: This is the first year we’ve had this much of a problem with splitting, rotting and dropping oranges from our orange tree. The tree is a semi dwarf Naval Orange tree that we planted about 10 years ago. It is now well over 10 feet tall and has been producing an abundance of oranges. I generally spray it two to three times a year for the fruit flies (with blue wings) that raise Cain eating the leaves and such. I’ve only gotten to them once this year. My problem is shown in the attached pictures. We’ve lost a good two-dozen oranges in the last month to this. Have you any ideas as to what may be causing this and what I can do to stop it?
Answer: Split fruit is generally a symptom of uneven irrigation. It’s no surprise it would happen now with the rain we have received recently. The way to mitigate the splitting problem is to provide enough irrigation during the dry parts of the year and make sure to turn down the irrigation when you receive rain. As Ben Franklin once said, “Moderation in all things — including moderation.” The recommended irrigation for citrus is once every seven to 10 days during the summer to a depth of 36 inches, once every 10 to 14 days in the spring and fall, and once every 14 to 21 days in the winter. By the way, you don’t need to spray your tree for fruit flies or any other insects for that matter. Most citrus insects are minor pests and only cause cosmetic damage to the tree and don’t affect fruit production or quality.
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Q: These caterpillars are everywhere!! Can’t walk outdoors without stepping on them. Also climbing garage doors etc. What kind of moth will they become?
A: These are the white-lined sphinx moth caterpillars (Hyles lineata). They are a well-known species because they can be found across most of the United States. The moths may be seen flying during the day and are sometimes referred to as hummingbird moths because they may be seen feeding on flowers while hovering. At this time of year the caterpillars are seen in great numbers as they feed on plants and then seek places to pupate for a couple of weeks before they emerge as adult moths. The caterpillars can be found eating a variety of plants, but they don’t do significant damage most of the time so they are not considered to be a pest worth managing.
You can help by reporting your caterpillar findings by sending photos of these caterpillars to a PhD student at the UA. Her name is Cristina Francois, and her email is cfrancois@email.arizona.edu.
Q: I had a lawn in bad shape and recently had it completely replaced with new more shade-tolerant Bermuda. However after a few days it is becoming a field of nutgrass. Apparently they did not remove enough soil. Now what? I read online that there are specific herbicides that can be applied weed by weed repeatedly, and they will eventually work. Do you have one to recommend? Will it harm the new turf? Or do we have to start over?
A: Nutgrass, aka nutsedge, is a prohibited noxious weed in Arizona. There are actually two species, yellow nutsedge (Cyperus esculentus) and purple nutsedge (Cyperus rotundus). Even though they are sometimes called nutgrasses, they are sedges rather than grasses. You can tell the difference by grabbing the stem. Grasses have round stems and sedges have triangular stems. We say, “sedges have edges” because it’s the easy way to remember. These are tough perennial weeds that reproduce by rhizomes and tubers that are sometimes called nuts or nutlets even though they aren’t; they only resemble nuts in size and shape. Management of nutsedge is difficult. The best method is prevention by making sure they don’t get delivered with topsoil or new plants. Once established there are some herbicides that have some effect on nutsedge populations. According to UA turf specialist, Dave Kopec, when you find nutsedge in bermudagrass, you can choose from a handful of herbicides that can be used on nutsedge. They include Image (imazaquin), Sedgehammer (halosulfuron), Monument (trifloxysulfuron), Certainty (sulfusulfuron), Katana (flazosulfuron), and Dismiss South (mixture).
Q: Hearty “volunteer” plants have recently emerged within our side yard. No clue as to what this plant is. We suspect the seeds might have been deposited by visiting birds. Would be ever so pleased if plant could be of use for nectar-feeding hummingbirds. Would appreciate your assistance with plant identification and/or description of place within the great environmental scheme of things! Do hope the plant has positive place, as we have grown quite attached to its presence!
A: That is Nicotiana glauca, aka tree tobacco. It is native to South America and was introduced to the United States in the early 1800s as a landscape ornamental. It is moderately invasive and spread by seed that is moved around by rain mostly, although some animal ingesting could come into play. Some people like it for the flowers and others think it’s a weed. Like some other members of the Solanaceae plant family, tree tobacco is poisonous so be careful. Hummingbirds are the main pollinators of this plant due to the tubular flowers so you should see that benefit. You may find bees robbing nectar by chewing a hole in the side of the flowers.
Peter Warren is the urban horticulture agent for the Pima County Cooperative Extension and the UA. Questions may be emailed to tucsongardensage@gmail.com
