Leaf problem on Amaryllis
I have amaryllis bulbs that I plant outside in the late spring/ early summer, once they are done flowering in the house.
Last year (2019), after the bulbs were planted outside, something was apparently chewing on the leaves. Web resources suggested that caterpillars, grasshoppers, spider mites or mealybugs attack amaryllis leaves. However, I was never able to find anything on the leaves. Spraying spinosad seemed to help somewhat, but it remained a mystery what was doing this.
Also last year the amaryllis leaves were unusually susceptible to a fungus problem. Web resources suggested red blotch, also called leaf scorch, caused by the Stagonospora curtisii fungus attacking the amaryllis. I did spray daconyl, but the fungus remained a problem the entire season.
I've attached three pictures taken last September that show typical leaf damage.
I will plant the bulbs outside soon, and I may experience these two problems again this year (2020.)
Any ideas what might have been eating the leaves? Also do you agree with the red blotch diagnosis and how best to deal with the fungus problems? I would be most appreciative for your help.
Sussex County Delaware
Chemical controls for insect pests are only recommended for severe cases of infestation. It's difficult to fully assess the extent of the damage from the photos you've posted.
The hole damage in your photos does not appear to be done by mealybugs, spider mites, or aphids. It is better to check your plants in the evening, late at night, or very early morning with a flashlight for chewing pests under the leaves and hand pick them (possibly caterpillars, grasshoppers, or slugs) off of your amaryllis (Hippeastrum) and fling them into a can of soapy water.
Chemical controls (such as general-purpose fungicides like Daconil [Chlorothalonil]) for fungus attacks only work as a preventative measure. Once the fungus is there, it is extremely difficult (if not inpossible) to get rid of it. It's difficult to assess the extent of the damage as there are no photos of the entire plant and the planting conditions it was in when the damage first occurred.
It is often recommended that (for fungal attacks on bulbs) if the damage is substantial (more than 25 percent of the plant), it is better to discard the plant (bulb and all) and start with a new plant in a new location with new, uninfected soil.
It is not known if you have planted your amaryllis (Hippeastrum) in the right conditions as you did not share that information. Hippeastrum tends not do well growing in an area that is damp, cool (below 65 degrees Fahrenheit), too shady (less than 6 hours of sunlight per day), and poor drainage (clayey soil or soil that doesn't not dry sufficiently daily). Without the ideal warmer, drier conditions, amaryllis (Hippeastrum) tends to get stressed and become prone to pests and disease.
In some states, the local Cooperative Extension office often provides plant clinics or assistance in submitting samples of an ailing plant to a plant pathology lab for a more accurate diagnosis and recommendation for treatment. As I don't know from location in the United States your question comes, I don't know which Cooperative Extension office to refer you.
Here is a site that you can use to select your area for your local Cooperative Extension office : https://nifa.usda.gov/land-grant-colleges-and-universities-partner-website-directory
Here is a publication on Amaryllis (Hippeastrum) care. It is published by the University of Florida Extension Service: https://edis.ifas.ufl.edu/pdffiles/EP/EP06000.pdf