A recent eGRO alert on "How to Deal with Diagnosis" stressed the importance of looking for symptom patterns and getting an accurate diagnosis for a plant problem.
Recently, images of a plant problem were submitted for a possible diagnosis. The affected plants were Hydrangea macrophylla. A large number of plants growing within the same
production area were affected. Mostly, the new growth showed symptoms of leaf distortion, leaf discoloration, and poor budding and flowering (Figure 1). Older leaves in the images
seemed OK. The uniformity in symptom pattern and the number of plants affected tends to suggest an abiotic or possibly an insect cause.
Initially, thrips feeding damage to developing buds was suspected. Chili thrips have been
a problem in some production facilities. The second thought was that a chemical may
have been applied that affected the new growth. However, no herbicides, growth
regulators, or other chemicals had been applied to the crop. It is extremely difficult to
make a diagnosis from submitted images; therefore, a physical sample was submitted for
evaluation. When the sample was received, there were no signs of thrips or other insects
or mites present on the plants. It was also evident that older leaves were also showing
some symptoms, just not as much as the younger leaves.
Click here to read the complete e-Gro Alert (PDF)