AUGUST
2006

 

 

 

By
B. Rosie Lerner
 
Purdue
Extension
Consumer Horticulturist

 

 

 

 

 

08-03-06

Question and Answer

Q. We have a yellow peach tree and a white peach tree. Both have had great fruit in the past. The yellow one was loaded this year, and usually the fruit ripens around the first week in July. Toward the end of June, the fruit started rotting before it was ripe! The white peach tree has several peaches on it, but they don't seem to mature. The fruit is the size of a small walnut and very hard. I have a friend who also says her peaches are not maturing. I have not been good about spraying the trees. I guess I need to start, but I'm not sure where to start. Thanks for any help you can suggest.

A. The extreme high temperatures during much of July have likely caused fruit to mature more quickly. And the humid, rainy, warm weather has been just perfect for development of the brown rot fungal disease on the fruit. Brown rot can quickly enlarge to completely cover the fruit in a couple of days! It's too late now to do much about it. Remove and discard infected fruit both on the tree and those that have fallen. Preventative fungicides can be applied to protect developing fruit but need to be applied earlier, beginning pre-bloom to prevent infection. More information on controlling pests in home fruit plantings can be found in Purdue Extension Bulletin ID-146 available online.

Not all peaches are created equal. Some varieties take longer to mature than others; however, in general, the white cultivars are not particularly late in maturing. But there are some peach cultivars that normally ripen in early to mid June, while others ripen in late August to mid September! And really heavy fruit loads result in much smaller fruit. It's hard to say without seeing a sample, but if the fruit are still only the size of walnuts, I would guess that the fruit have failed to develop due to inadequate pollination, most likely related to weather during flowering time. Small consolation, but at least the Japanese beetles, raccoons and other varmints won't get any either!

Q. I have a good-sized peach tree in my yard. It looks healthy and produces fruit. The problem is that the peaches get heavy and fall off the tree before they are ripe. What can we do to help this?

A. Many Indiana peach trees are experiencing a bumper load of fruit this year, so much so that branches are bending and breaking, and the tree is not able to support the excess fruit. Thinning the fruit to optimal spacing early after fruit set makes better-sized fruit, less risk of limb breakage and less fruit drop. Peaches should be thinned to about 6 to 8 inches apart, either by hand for small trees or by using a pole to knock off young fruit for larger trees.

Q. I am new to Indiana and need information on the growing and care of the mandevilla plant. I was under the impression upon purchasing this plant that it would grow outside year in and year out. Now I'm told that I have to take the plant in during the winter months. PLEASE help me...

A. Mandevilla is a woody vine that is only winter hardy to the tropics, but it can be overwintered indoors as a houseplant. Mandevilla should be brought in before temperatures drop below 50 F. You may need to trim the plant back to make it more manageable indoors. Place in bright, indirect sunlight and water as needed when the top inch of the soil begins to dry.

After danger of frost is past in spring, mandevilla can be moved back outside. Plant them in shade by sinking the pots to make them easier to lift in autumn. Or, grow them as container plants on the patio. Since they are vines, they will need a trellis for support. You may want to prune them back hard before moving them back outdoors to make room for new spring growth.

Q. We went to the garden last night and found these black bugs eating our tomato plants. We have never seen them before, and they are really tearing up our patch. Can you tell me what they are and what to use to get rid of them?

A. I need more of a description to be able to identify the culprit for sure. If the bugs were eating the fruit rather than the plants, I suspect the four-spotted sap beetle. They are particularly attracted to ripe fruits that have cracked or are otherwise wounded. So keeping the plants harvested frequently can help, as can a strong spray of plain water from the garden hose.

But, if the little black bugs are primarily eating the foliage, I suspect them to be flea beetles, which can walk or fly, but frequently jump when disturbed. Flea beetles are usually more problematic on potatoes and eggplant but also attack tomatoes and green peppers. Several insecticides are labeled for use on tomatoes against flea beetles, including carbaryl, permethrin, esfenvalerate and cyfluthrin . Check the label for the required number of days between application and harvest. Always read and follow ALL label directions and precautions BEFORE you apply!

Q. We have several trees in our yard (mostly near our pond) that have a light greenish-blue fungus-like appearance on the bark. It may have been there for a couple of years but has gotten worse just recently and is very noticeable. On some of the trees, the bark is splitting. Do you know what this is and if there's anything we can do to cure it? Or are we going to lose the trees?

A. You are describing what is likely to be lichens, harmless symbiotic organisms composed of a combination of fungi and either algae or cyanobacteria. Together, they live as one organism and are only using the bark of your tree for anchorage; lichens are not parasites. More information on lichens can be found at http://www.ppdl.purdue.edu/ppdl/weeklypics/1-12-04.html.

Q. My dad has a grape arbor, and a few years ago he put mulch around the base of the vines. Ever since, it seems to have a fungus. He has sprayed it, but it is not working. The grapes turn black before they ever get ripe. I don't know where to go for more info. I know this is not very much info, but it is all I know.

A. Grapes are quite susceptible to a fungal disease called "black rot," which attacks canes, tendrils, leaves and fruit. The disease is most destructive in warm, humid weather. There's not much that can be done this late in the season. However, it is possible to control the disease in the future with a combination of sound cultural practices, fungicides and resistant varieties. For more information on preventing and controlling black rot of grapes, see http://www.extension.purdue.edu/extmedia/BP/BP-36.html and http://www.hort.purdue.edu/ext/HO-45.pdf.

Q. Just wondering if you can prune tomato plants back so that they will put forth more effort on the tomatoes themselves, instead of so many leaves?

A. Ah, but it takes a lot of foliage to produce a great crop of tomatoes! First, the foliage is making carbohydrates through photosynthesis, much of which is stored in those luscious ripening fruit! Second, good coverage of foliage over the fruit provides protection from excessive sunlight, which would otherwise cause blistering and or cracking of the fruit's skin.

On the other hand, over-fertilizing with nitrogen can lead to excessive production of leaves at the expense of flowers and fruit. But, as long as the plants are also producing lots of flowers and fruits in addition to lots of foliage, be thankful.

 

Writer: B. Rosie Lerner
Editor: Olivia Maddox,