FEBRUARY
2006

 

 

 

By
B. Rosie Lerner
 
Purdue
Extension
Consumer Horticulturist

 

 

 

 

 

02-02-06

Question and Answer

Greetings readers! I'd like to introduce myself to you as your new "In the Grow" columnist. I've been answering Indiana gardening questions since 1984, when I joined the Purdue University Cooperative Extension Service. I grew up in Chicago, Ill., and was an urban gardener for most of my life but now live on five partly wooded acres heavily populated with critters and insects. I've never seen such a diverse array of wildlife all in one place! And I'm quite familiar with the "In the Grow column, as I was Bev Shaw's horticultural editor. Many thanks to Bev for nearly 18 years of keeping us In The Grow!

Q. I have a burning bush hedge that is about 20-25 years old. Until (4) years ago, they were always healthy/attractive and had no pest problems. In late spring/early summer of 2002, at the onset of prolonged hot weather, almost overnight, I noticed their foliage had an abnormal copper cast and the foliage started dropping -- the slightest touch resulted in the drop of many leaves. The shrubs were saturated with a fine, silky web, and there were a lot of pinhead-sized insects on the shrubs. I presumed the things were some type of mite.

The following year, 2003, I sprayed the shrubs with Malathion 2-3 times, starting in very early spring. I had no problems with pests at any time that year, and the shrubs gave no appearance of harm from the pest infestation of the preceding year. Consequently, I presumed that early spraying with Malathion was the way to control the pests. I followed the same routine in 2004 and was surprised when the foliage displayed the odd copper color. The silk-like web appeared, and a lot of the foliage fell at the onset of hot weather -- not as severe as the initial occurrence in 2002 when all the foliage dropped, but I estimate 50 percent came off.

Last year, I sprayed several times in early spring with Malathion and again had poor results as the same thing occurred as in '02 and '04. I did inspect the shrubs closely during the spring of last year and detected a lot of recently emerged leaves that were "rolled." When the leaves were unrolled, on the undersides of the leaves were what appeared to be either eggs or larvae that were black. Whatever these black things were, it appears they were not controlled by the spray, which had already been administered prior to their appearance and which was again administered after their appearance. My presumption was that these things were the beginning of the pests that sap the foliage and produce the silk-like web.

Based on what I've described, can you tell me what the pests are and what can be done to control/eliminate them, since it's apparent the Malathion spray is not getting the job done . -- Jim B., Hope, Ind.

A. The copper cast and leaf drop most likely were the result of spider mite injury. Spider mites suck plant sap with early symptoms appearing as tiny dots (called stippling), later a bronze cast to the leaves and eventually leaf drop. Though they don't really cause damage overnight, it might appear so, as we often don't notice the damage until the populations reach large numbers. Damage from warm-season spider mites can be particularly serious in hot, dry weather when plants are already suffering from drought.

The leaf-rolling insect is not likely to be related to the other symptoms, although spraying Malathion may have allowed other insect species to flourish by killing off their natural enemies, as well as the natural enemies of the mites. And, if the particular mite involved is the two-spotted spider mite (a common summer pest), spraying early in spring likely missed it altogether as it does not overwinter on the plant.

Preventing mite damage requires routine inspection of plants, so that mites can be detected early enough to intervene. Consider irrigation of plants during times of drought. Inspect your plants every other week by placing an 8.5 x 11 inch sheet of paper under a branch and tapping the plant sharply. Light infestations may be resolved by applying a strong spray of plain water from the hose twice weekly. There are numerous natural enemies of spider mites and avoiding the use of pesticides will favor their ability to do the job. Consider applying a pesticide only if you find more than two dozen mites per branch after having tried the water hose method. Insecticidal soaps and summer oils can provide effective control, if mites are actually present, but must be contacted by the spray directly. So good spray coverage of the mites is critical. Cool season mites can be successfully controlled with dormant oil.

For more information on identification and control of spider mites on ornamentals, see Purdue Entomology bulletin E-42, available online at http://www.entm.purdue.edu/entomology/ext/targets/e-series/EseriesPDF/E-42.pdf.

Q. Do you where I could get a start and/or seeds for Chinese Lanterns? In the fall, the plant is full of orange jack-o-lantern seed pods. I have tried seeds from one company and have had no luck. It must be that I am doing something wrong. Any help would be appreciated! -- Marcia B., Steuben County, Ind.

A. Known botanically as Physalis alkekengi , Chinese Lanterns are so named for the orange-red, papery outer layer of the flower (called the calyx) that resembles an oriental lampshade. The plant is a perennial and can be easily propagated by dividing. Seeds can be purchased from many mail-order catalogs, such as Parks, Johnny's, Burpees, etc. Plants and/or seed can often be found at local garden centers. But beware; this plant can quickly take over the garden as it spreads by underground stems. Because of its invasive tendencies, gardeners should only plant where growth can be curtailed, such as in containers.

Q. I have several peonies that are 80-plus years old located in an old farmstead. I would like to transplant them to a more suitable area. What would be the best way to transplant them? What do I need to do as far as fertilizer and water needs after the plants are moved? -- Rich U., Terre Haute, Ind.

A. Late summer or early autumn has long been the recommended time for transplanting or dividing peonies. This allows the plants the opportunity to establish new root growth during the cooler, more moist conditions often found in autumn. However, many gardeners are successful with early spring transplanting, when there is enough foliage showing to make them easy to find.

Planting depth is critical for good garden performance. The buds of the tuber should be set no deeper than two inches below the soil surface. Peonies that are planted too deep will produce foliage each year but may never bloom. Peonies can adapt to a wide range of soils but grow best in well-drained, sunny locations. Mix in plenty of organic matter, such as compost or well-rotted manure, into the new planting bed. A light application of low analysis, balanced fertilizer, such as ¼ cup of 12-12-12, mixed into the planting bed should be plenty. For more information on growing peonies, see Purdue Horticulture Extension bulletin HO-76, available online at http://www.hort.purdue.edu/ext/HO-76.pdf.

Q. I just took ownership of a 20-year-old prickly pear cactus, 4 foot tall. I want to repot it to a larger pot, as it has been in the same soil/pot for years, though it appears healthy. What type soil should I use and is this time of year OK to do so? – Roger

A. The old adage "if its not broke, don't fix it" applies here! A plant that has performed so well for that long is not necessarily helped by repotting. In fact, many roots will likely be broken in trying to transplant this large a specimen, not to mention the logistics of handling a 4-foot spiny cactus during such a move! There are sandy-type potting soils formulated for cacti, but my advice is to let it be. The only reason I would repot is if the plant is unstable and in need of a larger, heavier pot to avoid tipping over.

 

Writer: B. Rosie Lerner
Editor: Olivia Maddox,