I’ve been growing Sesbania grandiflora from ECHO seeds in a greenhouse at the University of Tennessee since June. It’s recently gotten what looks like a fungal growth. Can anyone help identify what it is and recommend management practices? No other plants in the greenhouse have been affected - only this plant.
Hi Gracie!
This actually isn’t a fungal issue. These are mealybugs! And a pretty aggressive amount of them. They are soft-bodied, piercing-sucking insects. They extract sugars from the plant phloem after piercing into the vascular tissue of the plant. There are lots of different natural remedies you can try. OISAT is one of my favorite resources for pest control. Their list of control options (preventative and suppressive but right now you’d select suppressive measures) for mealybugs is here: control methods overview
Personally, I use soap and oil spray on most soft-bellied insects like mealybugs once a week until the pest population is significantly reduced. You can purchase horticulture oil at most any store (even Home Depot or Lowes) or you can make your own version at home (see note from Dr. Motis on this method below):
Add 2 teaspoons (10 ml) of dish soap and 1 teaspoon (5 ml) of vegetable oil to a gallon (3.8 l) of water, in a one-gallon sprayer. After shaking the sprayer to mix the ingredients, spray the affected area, making sure to coat it well (most piercing-sucking insects prefer soft tissue like that at nodes or the underside of leaves). This simple recipe, used in conjunction with a hand-operated sprayer, is very doable for a few number of plants
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Yikes - I see that now! Thanks for the advice!
@Gracie_Pekarcik I affirm what @Stacy_Swartz said. Definitely mealy bugs.
At ECHO North America if we only have one or two plants with a bad infestation it can feel like a lot to mix up a whole gallon of mixture. We will often use several other methods of control in our green house.
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Physical Control - Either remove and destroy the plant or, if it is the only specimen or important, then simply wipe down the leaves and stems with your hands or a cloth wet with soap and/or oil. Mealy bugs are pretty easy to crush and destroy.
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Small Batch Spray - Use a small hand sprayer with neem oil soap mixture. 1TBS neem oil + 1tsp dish soap + 128oz (1g) water. You can do the calculations based on how many oz your hand sprayer is. We often use a simple 32oz sprayer from Home Depot. It does not need to be extremely precise.
Hope this helps!
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