Jacob Knecht
Mon, 02 Aug 2010 12:04:42 PDT
Ants have never been neutral in any horticultural setting I've ever worked
in.  As Lou mentioned, perhaps the worst thing they do is transport
mealybugs from one root mass to another.  This happens VERY quickly in
Hawai'i.  It dry leeward areas especially, but also in very wet ones,
absence of root mealies is exceptional.  There, the longer a plant lives in
a pot and the more pot bound it is, the more mealies it is bound to have.
It is my impression that at least outdoors in California, root mealies are
generally not too big of a problem with most plants, except for cacti,
succulent and bulb collectors!  I have seen many a rare amaryllid looking
sick and stunted.

Also on O'ahu there are some non-native ants that remove media so fast from
potted plants that it causes serious problems and death of plants (as
mentioned by Roy).  I have had potted houseplants collapse within three days
of the ants' excavating media out through the drainage holes!  I solved this
by applying a line of boric acid chalk to the perimeter of a terracotta
drainage saucer.  If kept dry thee ants will not cross the line.

There is one species in particular that is very efficient at farming
mealybugs on a plant, from soil level upwards.  These ants move soil
particles up the stems of plants, caking loosely but effectively around the
most vulnerable parts of the plant: growth nodes on dicots and the tender
meristem region of monocots.  Underneath these coverings the mealies are
brought in and go to work faster than if exposed to the elements.  They can
seriously weaken or kill some monocots within a very short time frame.  I
found that I must be diligent and check all plants at least once a week for
this.  The ants have killed seedling amaryllids and understorey Dypsis palms
this way.  Spraying the plant with high pressure water only temporarily
removes these structures, and I have seen the ants rebuild completely them
in 24 hours!

Like humans, (many) ant species are super successful organisms.  They are
tenacious and will pretty much always get what they want.  They can easily
spell the end of a collection (at least in Hawai'i) if left unchecked.  Also
root mealies can spread virus.


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