The Plant and Pest Diagnostic Laboratory (P&PDL) at Purdue University is an interdisciplinary laboratory dedicated to providing accurate and rapid identification of plant diseases, insects, weeds and cultural problems. We serve as a source of unbiased information regarding pest management strategies and provide training for plant and pest related problems.

We provide diagnostic services to county extension educators, agricultural consultants, growers, dealers, distributors, landscapers, homeowners, nursery and greenhouse operators. University research faculty and staff and inspectors associated with the Office of the State Chemist and the Entomology and Plant Pathology Division of the Indiana Department of Natural Resources (IDNR) also rely on our services.

In 2009, the staff of the Plant and Pest Diagnostic Lab along with other cooperating Extension Specialists in the Departments of Botany and Plant Pathology, Agronomy, Entomology, and Horticulture diagnosed a total of 3147 problems (Table 1) on 1905 samples. We processed 400 additional nursery samples as part of the Cooperative Ag Pest Survey (CAPS ) Phytophthora ramorum (Sudden Oak Death) nursery survey in cooperation with the IDNR.

Of the 1686 routine sample submissions to the P&PDL, 1545 were submitted as physical samples, 55 were submitted as digital images accompanied by physical samples and 76 were submitted strictly as electronic submissions of digital images to the P&PDL via a standard web-based method.

The majority of routine samples were received by the P&PDL during the months of June, July and August (Figure 1). Same day service was provided for 14% of the samples received during 2009 and 57% of the samples were completed in three days or less. A total of 82% of the samples received during 2009 were diagnosed within five working days and 97% of all samples received were answered within 10 working days. An extended turn-around time of greater than 10 days (3% of samples) was documented for those samples requiring more extensive culture work and laboratory testing (Figure 2).

Infectious diseases (43%), noninfectious disorders (37%), and arthropod-related problems (13%) were the most common primary diagnoses in 2009 (Figure 3). The most common commodities submitted to the P&PDL were ornamentals (50%) and agronomic crops (24%) (Figure 4). The remaining 26% of samples were distributed among various other commodity groups including turf, vegetables, fruit, specialty crops, and insect, fungal, and aquatic weeds identification.

An infrequent ‘visitor’ to Indiana, Late Blight of tomato, was a widespread problem in 2009. The P&PDL reacted to the unusual outbreak by using National Plant Diagnostic Network (NPDN) funds to cover the cost of diagnosis of samples with suspected late blight. Late blight samples were diagnosed as they arrived with most reports going out the same day. Along with Dan Egel, the P&PDL staff posted updates to our website and worked with media outlets to disseminate pertinent information to tomato growers concerning the threat posed by this plant disease.

A total of 113 soybean rust sentinel samples were entered into the database. The predominant foliar diseases diagnosed on the soybean sentinel samples submitted were Brown Spot (Septoria glycines), Downy Mildew (Peronospora manshurica) and Bacterial Blight (Pseudomonas savastanoi pv. glycinea). Asian Soybean Rust was only detected in one field in Indiana in Posey County on September 30th, 2009.  The soybean field where rust was found was at R7 growth stage and rust was detected at a low incidence of 7%, with 1-2 pustules per leaf.

The Plant and Pest Diagnostic Laboratory (P&PDL) serves as the plant disease diagnostic facility for the Indiana Department of Natural Resources (IDNR). In 2009, P&PDL and IDNR staff worked cooperatively to complete the 2009 National Nursery Survey for Phytophthora ramorum, a disease of regulatory concern. All 400 samples collected from the 21 Indiana nurseries surveyed tested NEGATIVE for the presence of P. ramorum. Further studies on speciation of the Phytophthora spp. isolated from infected tissue are currently being conducted. The lab also participated in a CAPS survey to look for Grapevine Yellows in several Indiana vineyards in collaboration with the CAPS survey coordinator, Larry Bledsoe, and Bruce Bordelon of the Department of Horticulture and Landscape Architecture. Grapevine Yellows was not detected.

In addition, in cooperation with the IDNR and the Indiana Crop Improvement Association (ICIA), the P&PDL also provided disease diagnosis on 76 corn samples as a part of the IDNR's Phytosanitary Certification Program.