LSU AgCenter Soil Disease Insect and Nematode Labs

Robert J. Souvestre  |  8/26/2011 11:56:06 PM

Example of a good plant sample. A dying Japanese Boxwood with roots wrapped in plastic to keep moist. The leaves vary from completely dead to yellow to healthy green. (Photo by Dr. Raghuwinder Singh.)

Ask yourself these questions:
  • Does my azalea have dead branches?
  • Are my citrus fruit brown rather than orange colored?
  • Is an unidentified weed invading my lawn?
  • Are my okra plants stunted and not growing?
  • Are my hydrangea leaves yellowed or have dead spots?
If you answered "yes" to any of the questions, then you need to know about laboratory services provided by the LSU AgCenter that assist homeowners and businesses with identifying plant problems and soil fertility recommendations.

The four service labs at LSU are: the Plant Diagnostic Center and the Nematode Advisory Service, both supported by the Department of Plant Pathology and Crop Physiology and the Soil Testing and Plant Analysis Laboratory, supported by the School of Plant, Environmental and Soil Sciences. The Louisiana State Arthropod Museum's identification service, supported by the Department of Entomology, can be accessed by visiting lsuinsects.org.

The LSU AgCenter Plant Diagnostic Center is a one-stop shop for all your plant health problems. The staff has the training and experience to help you solve your plant problems. Services available through the center include plant disease diagnosis for both pathogenic and environmental causes, plant-related insect and mite diagnosis and identification, soil inhabiting nematode diagnosis and identification and weed identification. The clinic provides comprehensive services in a timely fashion that will help you properly treat a plant related problem. A routine diagnosis costs $20. Make your check payable to LSU AgCenter PDC and submit your sample to LSU campus, Life Sciences Building, Room 301, at the intersection of Highland Road and South Campus Drive in Baton Rouge, La.

An accurate diagnosis requires accurate information about the problem, including a detailed description of the symptoms and how they developed. In addition, a good fresh soil sample is a must! A good sample generally consists of plant materials showing all phases of disease development and includes plant parts with both healthy and diseased tissue. Completely dead leaves, branches and plants or rotten fruit generally are not useful, but they may be included as part of the sample.

For plants showing wilting, yellowing or general decline, submit whole plants including roots, if practical. Be sure to send plants showing early stages of disease symptoms. Dig up the plant carefully -- don’t pull it up -- and tie a plastic bag around the root ball to avoid loss of moisture.

If the problem is leaf spots, collect leaves showing both early and late stages of infection. Press leaves between cardboard so they will not crumble and submit. It is usually not possible to diagnose marginal burning or other injury symptoms on leaves.

Rots associated with fleshy organs like fruit, vegetables and succulent leaves need special attention. Do not submit those in advanced stages of decay. Select fresh specimens showing early symptoms and place in a plastic bag. Do not add extra moisture. Fleshy vegetables and fruit specimens should be wrapped separately and kept cool.

For turf, take samples from areas with both healthy and diseased grass, generally at the edges of patches. Again, dig up the grass and include foliage, roots and soil in the sample. Once you collect a sample, be sure to package it so it doesn’t dry out, but don’t add water! The lab prefers you to place samples in plastic bags rather than paper bags and submit them as soon after you collect them as possible.

For plant-related insect pest and mite samples, collect the infested part of the plant and place it in a sealed plastic bag to prevent escape.

For weed identification, send in the whole plant with roots attached and soil intact. Weeds can be packed like other plant samples. Include seed heads. A live sample is much easier to identify than a dried sample so enclose in a sealed plastic bag.

Remember: the better the specimen, the more accurate the diagnosis.

Late summer and fall are the best times to take nematode samples if you suspect these microscopic worms are attacking the plant’s root system. The LSU AgCenter Nematode Advisory Service charges $10 dollars for each nematode sample. Make checks payable to LSU AgCenter Nematode Advisory Service and attach to the required form along with at least a one pint sample of soil. Protect the sample from heat and direct sunlight. It’s best to get your sample to the lab within one to two days.

To obtain the best sample possible, remove a 4- to 6-inch core or slice of soil from approximately 20 random spots. Remove soil where plant roots are actively growing. Place all the soil in a clean plastic bucket and mix thoroughly. Remove at least one pint of soil for your nematode sample. Submit your sample to LSU campus, Life Sciences Building, Room 302, at the intersection of Highland Road and South Campus Drive in Baton Rouge, La.

The LSU AgCenter Soil Testing Laboratory accepts 1-cup soil samples to test for soil pH and soil fertility. Recently introduced soil sample kits make submitting soil samples as easy as putting them in your mailbox for postal pickup. Pick up kits at garden retailers and parish extension offices. When samples arrive at the state lab, they are air-dried and then ground to a very fine powder for analytic testing. The results and recommendations are emailed -- or mailed -- with supporting information.

Each soil sample costs $10 dollars and the total mailing cost is $5 dollars, for up to three samples per soil sample kit. For a small area, 100 square feet or less, remove a 6-inch core or slice of soil from five to six spots. Mix thoroughly in a clean plastic bucket and remove enough soil to fill the plastic bag included in the kit. For larger areas, collect soil from 10 to 20 spots. If you are unsure what you might want to grow, indicate as many plant possibilities that may be realistic.

If you have a non-plant related insect that you need identified, then you will need the services of the Louisiana State Arthropod Museum, part of the LSU AgCenter Entomology Department. Household insects like carpet beetles, clothes moths, pantry pests, termites, ants, spiders and wasps are some of the insects they will identify for you. Visit their website for specific instructions and note they accept both digital pictures and actual insect samples. The $20 dollar payment can be paid online or make your check payable to the LSU AgCenter. Submit insect samples to LSU Campus, Life Sciences Building, Room 404, at the intersection of Highland Road and South Campus Drive, Baton Rouge, La.
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