JULY
2011

 

 

 

By
B. Rosie Lerner
 
Purdue
Extension
Consumer Horticulturist

 

 

 

 

 

07-07-11

Question and Answer


Q. I lost every one of my rhubarb plants late last summer and fall. The plants started dying at one end of the row and just worked on down the row to the opposite end. Someone told me it was due to grubs; another told me that it was moles eating the grubs. Since this is a plant I intend to eat, whatever I use needs to be food safe.

A. It is unlikely that moles killed your rhubarb. It is true that moles will eat grubs, but their main diet is earthworms. And while they might inadvertently disrupt the root system of some of the plants, it is unlikely that mole activity would kill an entire row. Rhubarb is susceptible to a disease called crown rot, which is problematic in wet, poorly drained soils. Also, the frequent rains that we've had this year would really aggravate this situation.

Rhubarb curculio and stalk borer are insect pests that both feed in the stem of the plant. While these pests generally cause minor damage rather than plant death, the holes they make provide entry for disease such as crown rot. Keeping the area around the plants weed free will help remove overwintering sites for these pests.

Q. We have 2 acres of woods full of honeysuckle. We have tried pulling it up but it is still coming back.

A. You have a lot of good company; most woodland homeowners are faced with the same battle. Young plants up to 2-3 years old may respond well to repeated cutting and or digging, but they often grow back. It is an ongoing battle, but it does help reduce new populations by cutting the plants before they get old enough to produce fruit. The Asian honeysuckles that invade wooded areas are the earliest to green up in spring and the last to drop leaves in the fall, so this can be an opportunity to target the honeysuckle with a very careful application of herbicide to just the honeysuckle foliage. For more established plants, cutting the trunks and carefully painting the stump with herbicide may provide some control. The Illinois Natural History Survey has an excellent discussion regarding identification and strategies for controlling this frustrating pest at www.inhs.uiuc.edu/research/VMG/bhnysckl.html.

Q. The property I moved to a year ago has a full-grown peach tree in the front yard. It is full of little baby peaches, but they are mostly all emitting a little hardened clear gel-like material. I can see from some branches that at one time there were diseased darkened spots where the limbs meet the trunk. Do you have any idea what it needs so I can salvage it and get healthy fruit?

A. This sounds like Oriental fruit moth, a primary pest of peach that will also infest plum, apricot, nectarine, cherry, apple and pear. This pest has two or more generations of young during the growing season. The early generation larvae enter young twigs and may also feed on and enter the side of the fruit. If the fruit remains on the tree, a clear, gummy exudate will ooze from the wound, eventually turning black. Additional generations of larvae are more likely to enter nearly ripe fruit from the stem end, tunneling and feeding down to the stony pit.

The pest overwinters in litter around the tree as well as on the bark; immediate removal of infested fruits and fall clean up of leaves and dropped fruit can reduce next year's woes. There has been some success of mating disruption with pheromone products as well as parasitic braconid wasps. Multipurpose fruit spray or an insecticide containing esfenvalerate or carbaryl labeled for home orchard use can provide effective control of this pest, but timing of the sprays is critical, beginning at petal fall (when 75 percent of the petals have dropped) and an additional 2-3 applications every 10-14 days. For more information on controlling pests in the home orchard, have a look at Purdue Extension Publication ID-146 Managing Pests in Home Fruit Plantings, http://extension.entm.purdue.edu/publications/ID-146.pdf

The darkened spots on the trunk could indicate a canker disease or possibly insect borer damage, but I am not able to diagnose just from that description. Consider taking digital images of the injury, both close up and overall tree to submit to the Purdue Plant & Pest Diagnostic Lab, www.ppdl.purdue.edu.

Q. I have raised day lilies for several years. I am having a major problem with wild onions in my beds. I have tried glyphosate on a paper towel with rubber gloves and wiping all the onions I can see. Seems to be getting worse rather than better. I also cut off the seed heads so as not to reseed each season. Any suggestions?

A. Wild onion is difficult to control in any situation; their narrow waxy leaves repel herbicide sprays such that very little chemical gets into the plant. This perennial weed is particularly troublesome when growing amongst herbaceous perennials, since there is no herbicide that can be applied that would control the onion without also damaging the daylilies. In fact, it would do much more harm to the daylilies than the onions! Hand pulling the onions does little good, as the underground bulbs will sprout new foliage. Hand digging the bulbs is likely the only solution but may also damage the daylily roots. Cutting the onion foliage just before spot applying glyphosate may improve control. If the bed is badly infested, it might be wise to dig up and relocate the daylilies either permanently or temporarily until the onions can be removed/controlled. Be sure to clean the daylily roots and soil from onion bulbs before replanting in the new location.

Q. How do you grow peppers (yellow, orange, red or green) like you see in grocery stores? I have tried, but they never look like the ones in the store. Is it the variety or type of fertilizers they use?

A. Growing colorful peppers requires selecting appropriate cultivars and then, in most cases, allowing the fruit to ripen on the plant. The young, immature pepper of any cultivar is usually green; the mature fruit ripens to red, yellow, orange or purple, depending on the particular cultivar. There are numerous cultivars to choose from if you raise your own transplants from seed, and most require a relatively long growing season to fully color up. There are a few cultivars that have colorful skin during their immature stage, but at this young stage the color is only in the outer skin while the inner flesh is green. Color can be lost in cooking. For more information on raising colorful peppers, see my article at http://www.hort.purdue.edu/ext/ppep.html.

 

Writer: B. Rosie Lerner
Editor: Olivia Maddox,