Carnivorous Plants/Disease and or bugs on nepenthes
QUESTION: I grow several species of nepenthes and hybrids. I have been getting what looks like scale and a black fungus and would like to know what to use to stop this. This year has been great growing my pitchers outdoors but it's also my first time with diseases and bugs. I am in Central Florida and I grow mostly lowlanders and intermediates. I have built a special arbor. My plants are not in full sun. They have a screen cover. We have gotten lots of rain and it has been very humid. You'd think the pitchers would love that. I have a short 2 minute video on youtube showing my problem. Hope to hear from you soon.
ANSWER: Hi Des,
Thank-you for the video. That's the way to ask and Allexperts question.
Well, I've got good news and bad news. The good news is that all of your plants look very healthy, and one of your problems really isn't a problem at all. The other one could be a bit more serious.
First the not so serious one. The black mold you're seeing on the pitchers is called sooty mildew or Fumago. It's not a pathogenic fungus since it doesn't hurt the plants. It simply feeds on the nectar the plants produce. Sarracenia get it too. Spray watering your plants more, or having them out in the rain helps since if rinses off excess nectar, but if you're having long dry spells you will eventually get older pitchers with this. It's unsightly, but doesn't harm anything. You could spray preventively, with a sulfur or Neem fungicide but there really isn't a need. This just comes with the territory.
The scale is a more serious matter. The red spotting could be somewhat related to those, but some Nepenthes just get that on older leaves, so don't be to concerned about the spotting by itself. The scale your are going to need to treat for. It looks like you have Hibiscus scale, which is the pest Leilani deals with the most, and it sounds like you got some plants from them. Spray your plants with insecticidal soap. Do this in the late evening when the plants are not in the sun, and be sure to follow label directions. Also, use a commercial product made for plants; don't do a "homemade" solution. Homemade soaps are more likely to damage plants. You'll probably need to do a follow-up spray in a few days, but just follow the label directions on that. You will need to spray all your plants, since you may have the crawlers active before you actually see the scale adults. Be sure to spray all parts of your plants, and if you have pitchers that are heavily covered, you may need to just remove those. Also, look around your yard to see if any other plants have them and treat, or remove the plants.
In the past we've not recommend insecticidal soap, but we've found it safe on Nepenthes, and is more effective for scale insect. Scales build resistance quickly to chemical insecticides. We've already had them become immune to imidacloprid which is what is in the Bayer products. Insecticidal soap is also very low tox, so it will be less harmful to beneficial insects around. It kills insects by breaking down the waxy cuticle on their exoskeletons.
Let me know how it goes.
[an error occurred while processing this directive]---------- FOLLOW-UP ----------
QUESTION: Thank you very much Jeff. Yes I did purchase some plants from Leilani. I got a special type of alata and the Mixta hybrid. I'm glad to hear that over all my pitchers are healthy and that the black stuff is normal though unslightly. I have a Lowe's close to my house. Do they carry the insecticidal soap and is there any specific one you recommend? If they don't have it I will have to order it online. Thank you so much for your help and I will definitely keep you informed and post a follow up.
Pretty much all garden centers carry insecticidal soap. I'm not sure what brand Lowe's carries, but just look at the ingredient labels. If you see Potassium salts of fatty acids, you have the right stuff. Some products are mixed with Pyrethrins, but that really isn't needed, and you are more likely to kill non-target insects with that.