The Plant and Pest Diagnostic Laboratory (PPDL) at Purdue University is an interdisciplinary laboratory whose mission is to provide accurate and rapid identification of plant diseases, insects and weeds; to serve as a source of unbiased information regarding pest management strategies and to provide training for plant and pest related problems.

Lab clientele include county extension educators, agricultural consultants, growers, dealers, distributors, landscapers, nursery and greenhouse operators, homeowners, 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).

In 2008, 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 2928 problems (Table 1) on 2125 samples.

Of the 1711 routine sample submissions to the P&PDL, 1619 were submitted as physical samples, 32 were submitted as digital images accompanied by physical samples and 60 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 10% of the samples received during 2008 and 49% of the samples were completed in three days or less. A total of 77% of the samples received during 2008 were diagnosed within five working days and 93% of all samples received were answered within 10 working days. An extended turn-around time of greater than 10 days (7% of samples) was documented for those samples requiring more extensive culture work and laboratory testing (Figure 2).

Infectious diseases (43%), noninfectious disorders (35%), and arthropod-related problems (14%) were the most common primary diagnoses in 2008 (Figure 3). The most common commodities submitted to the P&PDL were ornamentals (51%) and agronomic crops (24%) (Figure 4). The remaining 25% of samples were distributed among various other commodity groups including turf, vegetables, fruit, specialty crops, and insect, fungal, and aquatic weeds identification. Purdue Extension Specialists and Research Associates provided commodity related summaries of prevalent problems that occurred in 2008.

A new disease, Goss’s Wilt of corn (caused by Clavibacter michiganense subsp. nebraskensis) was confirmed on popcorn and dent corn by PPDL diagnosticians in August. Training sessions, including on-site sample diagnosis, were presented to educate corn growers and offer timely management recommendations for this disease of regulatory concern for seed corn producers.

A total of 238 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), Frog-eye Leaf Spot (Cercospora sojina), Downy Mildew (Peronospora manshurica) and Bacterial Blight (Pseudomonas savastanoi pv. glycinea). Asian Soybean Rust (Phakopsora pachyrhizi) was NOT detected in Indiana in 2008. The lab also participated in an IPM-PIPE Legume survey for four virus diseases known to occur on snapbeans in the Midwest. The ten samples of legumes collected at two different times in the growing season tested negative for the presence of Alfalfa Mosaic Virus, Bean Common Mosaic Virus, Cucumber Mosaic Virus and Bean Yellow Mosaic Virus.

The Plant and Pest Diagnostic Laboratory (P&PDL) serves as the plant disease diagnostic facility for the Indiana Department of Natural Resources (IDNR). In 2008, P&PDL and IDNR staff worked cooperatively to complete the 2008 National Nursery Survey for Phytophthora ramorum, a disease of regulatory concern. All 414 samples collected from the 23 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.

In addition, in cooperation with the IDNR and the Indiana Crop Improvement Association (ICIA), the P&PDL also provided disease diagnosis on 91 corn samples as a part of the IDNR's Phytosanitary Certification Program.