JUNE
2011

 

 

 

By
B. Rosie Lerner
 
Purdue
Extension
Consumer Horticulturist

 

 

 

 

 

06-02-11

Question and Answer


Q. We have an older Bartlett pear tree. It bears a lot of fruit almost every year. The pears rot around the core on the tree. I understand there was a problem last year with a lot of fruit trees, especially apple trees. But our pears rot each year and seem to be getting worse. The pears are big but rotten around the core first, and then the whole pear rots. What can I try, or what kind of spray can I try to use?

A. This sounds like a disorder known as core breakdown - aka internal breakdown, core rot and brown heart - and is characterized by softening and browning of tissues surrounding the core. In the early stage, the affected tissues are soft and watery, later becoming brown or black. Affected fruits usually have a rather disagreeable odor. Core breakdown is thought to be associated with cool growing conditions and particularly with fruits that remain on the tree too long. However, the exact cause is unknown. Some pear varieties are more susceptible than others, and unfortunately Bartlett is one that is susceptible.

Unlike other fruits, pears will reach their best quality when ripened off the tree. Pick pears when their color changes from a dark to light green or yellowish-green, but before they are fully yellow. The fruit should be relatively firm. The small dots on the skin, called lenticels, should turn from whitish to corky brown. Mature, harvested pears will ripen within a few days, if stored at 60-70 F and high relative humidity (80-85 percent).

Q. We have had problems with squash vine borer for years and recently bought some 10 percent permethrin. The instructions on the bottle only describe how to apply it to animals, not plants. Can you give me suggestions on how and when to apply it to squash and zucchini?

A. Unfortunately, it sounds like you have purchased the wrong product. You should only use products that are specifically labeled for application on vegetable crops such as squash and zucchini. In addition to being too concentrated for application on plants as is, the product may be formulated with other active or inactive ingredients that are not labeled for use on vegetable crops. It is important to read and follow all label directions BEFORE purchasing a product to be certain that product is labeled for the intended use.

Q. We have a beautiful 50-foot gingko tree that was supposed to be a male but turned out to be a female. It drops thousands of smelly apricot-like fruit and is becoming a big problem for us to keep cleaned up. Have tried fruit inhibitors but, because the tree does not really flower, we can only guess when to spray; consequently, we have had almost no success with it. Is there anything we can do to prevent the fruit? We are about ready to chop down this tree because of the work involved.

A. The fruits of the ginkgo tree are notoriously malodorous! The species has separate male and female trees, as you've noted; the goal is to plant the male to avoid fruit production. The tree has to flower in order to produce a fruit but, because this is a primitive species, the flowers are quite inconspicuous. The female trees produce petal-less, green stick-like structures and are very easy to miss. There is an excellent photo at www.wcisel.com/plants/ginkgobiloba/ginkgo_flower2.htm. Timing of fruit prevention sprays is critical and thorough coverage is not easy with such a large tree. You would not be the first to have cut down an otherwise fine specimen due to this fruiting problem.

Q. I planted a Stanley plum tree in the spring of 2005. I chose this tree because it is considered a self-pollinator. The tree is well established and flowers bountifully. Then when the fruit is about the size of a large grape, it drops every single plum off the tree. There is no sign of a pest problem. I have seen other readers ask about their trees dropping some fruit, but my tree drops every single fruit, not even leaving me one plum to enjoy. Do you have any thoughts on what would make the tree drop off every fruit for the last 3 or 4 years? Any suggestions would be greatly appreciated.

A. This certainly sounds like inadequate pollination (or, more correctly termed, fertilization of the ovules). Stanley is supposed to be self-fruitful, but even those cultivars benefit from cross-pollination. It would not hurt to plant another compatible cultivar, such as Damson or Green Gage.

Q. My roses are growing a thick red clump instead of branches and buds. I had one climber with this last year. Now this year I have 2 additional rose bushes infected.

A. While this is not enough information to draw a conclusive diagnosis, I would suspect either herbicide injury or - in worst case - a disease called rose rosette. The latter is a serious, non-curable disease of roses thought to be a virus or virus-like organism and spread by mites. Pruning out a single infected branch may stall the disease a bit, but generally, plants infected with rose rosette should be removed completely to prevent further spread to other roses. There are several websites with additional information on this disease, including the American Rose Society http://www.ars.org/?page_id=2265 and Virginia Extension http://pubs.ext.vt.edu/450/450-620/450-620.html. You might consider submitting a sample to the Purdue Plant and Pest Diagnostic Lab http://www.ppdl.purdue.edu for confirmation before taking drastic action.

 

Writer: B. Rosie Lerner
Editor: Olivia Maddox,