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Q. After many years of growing pumpkins successfully (I do rotate the
growing site), the past four years have been disastrous. Just before the
buds begin to truly form, the plants collapse. There seems to be no sign
of a squash borer. I would appreciate your advice. -- Nancy M.
A. It is difficult to say for sure without more specific symptoms, such
as leaf or fruit spots, discoloration, etc. Squash vine borer is a common
culprit of sudden stem collapse in pumpkins. Adults lay eggs on stems
and the undersides of leaves, but especially near the stem bottoms. The
larvae that hatch out of the eggs eat their way into the stem and continue
to tunnel around inside for a month or so. Plants sometimes start out
with temporary wilting during the heat of the day, but progressing to
eventual collapse. A close examination of the stems should reveal the
entry point, as well as some frass.
Borers can be avoided with floating row covers, which prevent adults from
laying eggs. Of course, covers will have to be removed when plants are
flowering to allow bees to pollinate flowers. Some covers may also be
too warm during hot weather.
There are several diseases that could cause what appears to be sudden
collapse of the stems, though, likely, the earlier symptoms were just
unnoticed, much like the borer.
Phytophthora Blight not only causes collapse of the stems but is also
characterized by white cottony mold growing atop a soft rot on fruit.
The disease is most likely to spread quickly in cool, wet late summer
weather. All cucurbits are susceptible, as are most tomatoes, peppers
and eggplant. Fusarium Crown Rot causes relatively sudden collapse of
stems and may also result in lesions on the fruit. This disease is very
common in Indiana and is likely to occur to some extent every year.
Both of these diseases over winter in the soil and will continue to be
a problem once soil is contaminated. There are few or no chemical controls
available to the home gardener. The best solution is to completely rotate
the garden out of pumpkins for at least a couple of years, preferably
4-5 years.
For more information on diseases of pumpkins, see Purdue Plant Pathology
Bulletin BP-17, "Identification and Management of Pumpkin Diseases,"
available online at http://www.ces.purdue.edu/extmedia/BP/BP-17/BP-17.pdf.
Q. I have four large Christmas cactus, and starts were given to me from
plants that were flowering profusely. This summer, I put them outdoors
under a large pine tree, and they grew very nicely. Then, about August,
I brought them into the basement and around November brought them up,
but they never ever bloomed. My sister has several, and they all bloom.
What am I doing wrong or not doing right? Also, I have an aloe plant and
wonder if it requires sun or shade. -- Betty K.
A. There appears to be much confusion about these unique tropical cacti
regarding care, maintenance and, especially, on how to get them to re-bloom.
So much so, that it's the most frequently visited section of our Web site.
Christmas cactus is a tropical type plant, not quite as drought tolerant
as its desert relatives and, in fact, may drop flower buds if the soil
gets too dry. The plants will wilt when under drought stress. Water thoroughly
when the top inch or so of soil feels dry to the touch.
While the Christmas cactus can adapt to low light, more abundant blooms
are produced on plants that have been exposed to more light intensity.
Moving it to a shady location outdoors for the summer is fine, but it
should be gradually accustomed to lower light when brought indoors. It
could be that your plants suffered too drastic a change when brought directly
to the basement.
Christmas cactus will bloom following a 6-8 week period of uninterrupted
long nights of about 12 hours daily, (such as between 8 p.m. and 8 a.m.).
Cool temperatures of about 50 to 55 deg. F will also induce blooming,
eliminating the need for the dark treatments.
For more information on Christmas and other holiday cacti, see http://www.hort.purdue.edu/ext/cactusFAQs.html
and http://www.hort.purdue.edu/ext/christmas_cactus.html.
3-2-06
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