Gardeners know that for all of the items you can control, the success of a garden greatly depends on the soil it is planted in. No matter what type of soil you have, knowing the nutrient requirements for plants, and what must be done to achieve that goal, will contribute greatly to success. One of the best kept gardening secrets of the University of Hawaii at Manoa, College of Tropical Agriculture and Human Resources is the Agricultural Diagnostic Service Center. The ADSC conducts analyses and diagnostic tests for UH researchers, government agencies, businesses, farms and for the knowledgeable gardeners of Hawaii. ADSC works with plant disease identification, insect identification, feed and forage analysis, chemical analysis of soil, plant tissue and water and nutrient solutions.
The menu of services and the associated costs are online at ctahr.hawaii.edu/site/ADSC.aspx. Although not listed, the ADSC also tests papaya plants to determine if they contain genetic traits associated with genetic engineered characters.
The center is headquartered on the UH-Manoa campus and is staffed by a group of dedicated individuals. Brain Bushe heads the Hawaii Island facility located at the Komohana Research and Education Center in Hilo. Bushe handles disease and insect identification for the Big Island and coordinates soil and plant tissue sample delivery to Oahu for analysis.
When submitting a sample, be certain it is properly collected and representative of the surveyed item. For insect identification, collect more than one insect if possible and collect different growth stages if available. Additional information, such as host plant name, infested plant part and location on the island where the sample was collected are beneficial to identification. For plant disease analysis, submit samples that express the disease symptoms. Don’t make the mistake of submitting dead or rotting samples. Identification of the organism that caused the disease at this stage is more difficult, if not impossible, due to the exponential growth of opportunistic organisms. For diseases that cause necrosis or rot, the best place to identify the causal disease organism is the zone between healthy and disease tissue. In this intermediate zone, the disease organism can most likely be isolated without the opportunistic organisms. It is also important to submit your sample shortly after collection.
Sample size should be appropriate and proportional to the sample of the host plant being submitted. A few leaves is fine for a foliar disease, but a section of a tree trunk and roots may be more appropriate when finding out what killed your tree. It’s a good idea to place your insect or diseased sample in a bag or sealed container to prevent its spread or escape.
For a good soil test, it is important to get a representative sample for the location you wish to evaluate. Divide the plot into fairly uniform soil type or use history. Each soil or use variety will need a separate test to correctly recommend the correct amount of fertilizer and other soil amendments required to grow a specific crop. Soil samples must be two cups — half of a quart-sized storage bag. Smaller samples may not allow for a proper test. Larger samples lead to waste. Dig a section of soil, six inches deep, and place it to the side. Cut a second section about one inch thick and place the vertical middle two inches of the section into a clean bucket. Repeat collection in several locations to get a representative sample of your field site. A zigzag pattern across the field, stopping at various points to sample is a good procedure to collect a representative sample. After collecting the sample, mix it well, breaking clumps and removing large rocks. If you have more than one sample to submit, label each bag as you collect them.
To submit samples for analysis, bring them to any of the Cooperative Extension Service offices on the Big Island. Call the Hilo office at 981-5199. The office in Waimea is located in the Public Safety Complex next to the Hawaii Department of Health; call 887-6183. Submit soil samples at the Kona Cooperative Extension Service office at 79-7381 Mamalahoa Highway in Kainaliu. Payment can be made by cash or check.
For more information on this and other gardening topics, visit ctahr.hawaii.edu/Site/Info.aspx or visit any of the local Cooperative Extension Service offices. I can be reached at firstname.lastname@example.org.