Rushville Republican

September 27, 2013

In the Grow

By B. Rosie Lerner Purdue News Service
Rushville Republican

---- — Q. Enclosed is a picture of what is left of my late husband’s Norfolk Island pine tree. It would go outside in the summer and then be brought back inside for the winter. Last week I had a huge tree out back taken down. My plants, including “Subo,” the pine, were sitting at the edge of the wooded area well away from the tree to be dropped. As you would expect, one huge limb fell and bounced over on top of my tree. I am sick, as is the tree. It is 35 years old. I know it looks totally pitiful now and most people would probably get rid of it, but I would like to save it, if possible. Is there a chance for this poor tree to survive the trauma it has endured?

A. I am so sorry for the loss of your husband. I wish I could offer a bright prognosis for “Subo,” but, unfortunately, Norfolk Island pine is not able to form a new central leader once the terminal stem is lost. So, the plant will continue to look as it does now, or worse. While you might be able to root a cutting from a lateral branch, it too will not be able to form a new central leader; cuttings can only be taken from the top of the central leader stem in this particular species.

Q. I am just sick about my red raspberries. They’re just beautiful and full of large berries. But they are infested with tiny, tiny white worms. I noticed a little wet spot in the bottom of almost every berry, so upon closer investigation, I spotted the problem. What are they, and what should I do? I just watch the raspberries go to waste. I’ve had red raspberries for several years and never had such a problem. Will I have the same problem in the spring?

A. The tiny, white worms are most likely the Spotted Wing Drosophila (fruit fly), a new pest that has recently appeared in Indiana. This insect is a serious pest of soft fruits such as blackberries, raspberries, blueberries, grapes, strawberries, cherries and peaches. It can also infest apples, apricots and tomatoes, as well as weeds such as pokeweed, autumn olive, crabapple, nightshade, honeysuckle and wild grape. This aggressive, invasive pest is new to Indiana and is likely to be with us for the foreseeable future.

To determine if this is the culprit, tease open or crush the raspberry fruit carefully and look for larvae. They can initially be difficult to discern from the seeds in the pulp, but the larvae will be showing some motion while the numerous seeds will immobile. There can be several larvae in each berry. Any overripe or soft fruit is likely to be infested. If you find any evidence of infestation, Purdue entomologists suggest you spray immediately to try to knock down the population. You will probably need to make a second application a few days later to kill new adults that emerge after the initial application. Depending on how long your fruit harvest continues, you may need to reapply weekly. There are a number of insecticide products labeled for use on raspberries, including spinosad, pyrethroids and malathion, to combat this pest. Only use products that are labeled for use on raspberries, and be sure to follow the days-to-harvest limits listed on the label (likely 1-3 days). Do NOT apply any insecticides while the plants are in bloom. Controlling weeds around the raspberry planting can also help. For more information on the Spotted Wing Drosophila, see “Spotted Wing Drosophila Detected in Grapes and Berry Crops in Indiana,” http://www.ppdl.purdue.edu/ppdl/hot13/8-15.html.

Q. I’ve grown fantastic hollyhocks in the past. This spring, healthy, vigorous plants came up but then soon developed small yellow nodules all over the leaves. Although the plants bloomed, the leaves turned brown and dropped off. My hollyhocks were not as tall as usual and the blossoms are small, dull and faded. Is there a remedy?

A. Most likely it is a disease called Hollyhock Rust. Hollyhocks are susceptible to a number of different leaf-spot diseases, but, by far, the most common and destructive is rust. This fungus begins by causing tiny pinhead-sized brown spots on the undersides of the leaves. At the same time, the top of the leaf shows a larger yellow-to-orange-to-tan spot. Eventually, the spots enlarge and join together as the disease spreads to the stems and even to the green parts of flowers. The leaves then shrivel and turn brown, giving the plants a blighted appearance.

The disease especially favors damp and/or humid weather, which we certainly had plenty of earlier this summer. Gardens that have been watered regularly during dry weather provide ideal conditions as well, but morning dew and/or high humidity can also provide enough moisture for infection. Removing infected leaves promptly and cleaning up all plant residue at the end of the growing season is critical to reducing the spread of the disease.

Some fungicides that contain chlorothalonil, mancozeb or sulfur are labeled for use in controlling hollyhock rust. However, keep in mind that fungicides are preventative, not curative. They can only protect healthy foliage from becoming infected. If the plant is heavily diseased, it is too late to apply fungicides. Always consult the label for recommended rates and safety information before applying.

See also the Purdue Plant & Pest Diagnostic Lab article, “Hollyhock Rust - NOT the same fungus as Soybean Rust!”

http://www.ppdl.purdue.edu/PPDL/weeklypics/4-11-05.html#hollyhock