Nursery growers need to know the exact pathogen that causes problems in their plants before they can find a solution to it. If they cannot recognize the pathogen based on its symptoms, they have to send proper plant samples to the plant clinic for a diagnosis, and this is what most growers do. Sometimes, a grower comes to the extension office first for suggestions; the agent could provide potential solutions for the problem if the agent can identify the problem based on the symptom or refer the grower to the plant clinic for a diagnosis. In the meantime, the agent has the opportunity to ask the grower for a visit to the nursery to check on the real situation of the problem. This is what I did when a grower sent plant samples to our extension office for advice.
I was lucky that day as there was a lady working in the nursery at the address the grower left me but the palm plants with the problem were grown in a different location! The lady led me to the nursery where the problem was found on Christmas palms, which were the dominant plants in that nursery. The grower arranges the plants in blocks according to the time they were transplanted; however, the grower does not leave much space between blocks, possibly due to the relatively small size of the nursery. I wonder how the grower manages to spray to manage pests and diseases, as there is not enough space for equipment to get through. Actually, this phenomenon is not uncommon, you can even see this same issue from the front cover of the GrowerTalks magazine!
Inside the nursery, I also saw the following things (shown in the featured picture) and made suggestions to address the related issues: (1) the grower uses sprinklers for irrigation, and overall the plants appeared yellowish even though the lady said they had applied fertilizer to the plants; (2) bigger plants have fronds with advanced disease symptom while smaller plants just showed the symptom. The grower placed the young seedlings under the big plants that have many infected fronds showing advanced symptoms. This is not a good practice. Though the seedlings looked healthy, they may have been infected as the disease showed up on plants that had been transplanted a month ago! I suggested the lady place the seedlings in an isolated area and remove the fronds showing the symptom to get rid of the pathogen; (3) On some palm plants, I saw damage from insects, likely mealybugs, based on the white stuff on the fronds. I did find a few mealybugs under the microscope in my office and the pest has been found on Christmas palms in Miami-Dade County. The lady said the palm trees could die eventually because of the mealybug damage. I suggested the lady spray for mealybugs with oil-based products, such as Neem oil or Ultra fine oil, following the labels and paying particular attention to the trunks.
In the diagnosis report, the disease was determined as a Pestalotiopsis blight (https://edis.ifas.ufl.edu/publication/PP141), a common foliar problem on palms in our area. It suggests that sprinkler irrigation in the nursery may be a critical factor for the disease to spread among plants. It also said that fungicide application provides little effect in managing the disease, but removing the diseased fronds could be more effective. One important item in the report is the soil test, which indicated that there were few nutrients in the substrate, and the grower needed to apply fertilizer to the plants. So I texted the lady after receiving a copy of the report that she could apply fertilizer as a top dresser to improve the nutritious condition of the plants.
In conclusion, besides the information from the diagnosis report, growers may be provided with a better picture of their problems from an agent’s nursery visit, sometimes with information on potential problems they have missed in the submitted samples because many growers do not have scouting programs. Therefore, growers may be able to manage multiple problems in the same application to reduce costs on sprays. In addition, the agent can schedule future visits to the nursery and check on the effectiveness in control of the problems. It would benefit the growers if they have the agent for an onsite visit when submitting plant samples for diagnosis in the future.
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