Ansellia africana – Failing to Thrive, Spots on Leaves
I purchased this Ansellia africana in the fall. It hasn’t produced any new growth. Now it has started to have some spots on the leaves. Do you have any recommendations?
Diagnosis: This appears to be a primary mite infection which has left the plant open to secondary bacterial infection.
Recommendations: There were a number of recommendations. Neem oil as well as Mite-X by Bonide. Since Mite-X is specific for this problem it would probably be best to start with this. Some members said that a couple of applications of Mite-X are all that is required. All the plants in the collection should be treated, these pests are very good at spreading and you will likely find them everywhere.
The bacterial brown spot (Acidovorax) can be treated with Physan or a copper based fungicide (Kocide, CuPro, Liquid Copper, Phyton), however, copper based fungicides should never be used on Dendrobiums.
Cattleya percivaliana – Underpotted
This Cattlyea percivalaiana has outgrown its pot. What is the best time of the year to repot it? What is the best media to use for repotting it into?
Recommendations: This plant seems ‘happy’ however it needs to be put into a slightly larger pot. It can be slipped out of the pot that it is in and some of the existing media gently removed. However, since it is not in active growth it is best not to damage the lead roots. It is best to repot orchids when they are active growing. In this case possibly wait till it is active growing and you have new leads. Remove it from its pot as suggested, divide the plant so it doesn’t end up being overpotted and carefully pot it so as not to damage the growing tips of the new roots.
Odontoglossums – Weeds In Pots
I have weeds growing in some of my pots, what is the best way of getting rid of them?
Diagnosis: You have both wood sorrel and ferns. These are very common weeds in orchids, especially when growing in humid environments such as a greenhouse or a grow tent.
Recommendations: There are no herbicides which work at eliminating weeds in orchid pots so these have to be eliminated manually. Wood sorrels have to be pulled by hand, they have rhizomes which can burry themselves in pots so you have to work hard at removing them. Ferns can be particularly aggressive pests in orchid pots, stealing both the nutrients and water from your plants. One of the easiest ways to kill these plants is to heat a pair of forceps red hot and stick it into the crown of the fern. This will generally kill it completely.
Phalaenopsis – Underpotted
This Phalaenopsis hasn’t been repotted in six years. It is currently growing in sphagnum moss. What is the best way for me to repot it and not break all of the aerial roots? What is the best media for me to use when I repot it?
Recommendations: This plant can be repotted at any time. It needs to be removed from the old pot and the old media gently removed from its roots. Because there are so many aerial roots the plant should be allowed to soak in room temperature water for a few hours to allow those roots to become pliable before trying to coax them into a new pot. It also might be necessary to remove some of the lower section of the plant in order to pot it lower into the pot. Potting it into a coarse media such as bark or a bark, large sponge rock, horticultural charcoal was also recommended.
Stanhopea warscewiczii – Spotting on Leaves
Is this going to get worse, and can I slow it down? I think it is a bacterial infection and I usually don’t worry too much but this seems to have gotten quite a bit worse over the winter. The pictures are of my Stanhopea warscewiczii but it is also on my Stan. occulata. Both are grown under lights in the winter and then taken outside about mid-June.
Diagnosis: This was diagnosed as bacterial brown spot (Acidovorax), it is spread by water droplets splashing on the leaves of plants and spreading from plant to plant. It can happen at times of stress, high humidity or warm temperatures.
Recommendations: The bacterial brown spot (Acidovorax) can be treated with Physan or a copper based fungicide (Kocide, CuPro, Liquid Copper, Phyton), however, copper based fungicides should never be used on Dendrobiums.