Gail Ruhl, Interim P&PDL Director/Senior Plant Disease Diagnostician

The mission of Purdue's Plant and Pest Diagnostic Laboratory (P&PDL) is to provide accurate and rapid identification of plants, pests, and plant problems; especially those suspected to be of an invasive nature. The lab serves as a source of unbiased information for plant and pest related problems and provides management strategies upon request.

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 3630 problems (Table 1) on 2307 samples in 2007 (Table 2) (Table 3).

Of the 1366 routine sample submissions to the P&PDL, 1269 were submitted as physical samples, 30 were submitted as digital images accompanied by physical samples and 67 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 8% of the samples received during 2007 and 37% of the samples were completed in three days or less. A total of 62% of the samples received during 2007 were diagnosed within five working days and 91% of all samples received were answered within 10 working days. An extended turn-around time of greater than 10 days (9% of samples) was documented for those samples requiring more extensive culture work and laboratory testing (Figure 2).

Infectious diseases (38%), noninfectious disorders (37%), and arthropod-related problems (15%) were the most common primary diagnoses in 2007 (Figure 3). The most common commodities submitted to the P&PDL were ornamentals (47%) and agronomic crops (28%) (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 2007.

A total of 356 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 detected late in the season (October) on two out of a 100-leaf sentinel sample submitted from Owen county. There was no opportunity for rust to damage this year’s soybean crop in Indiana due to late season occurrence.  An additional 11 samples of legumes and soybeans were also collected and tested for the presence of 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 2007, P&PDL and IDNR staff worked cooperatively to survey nurseries for the presence of Phytophthora ramorum, a disease of regulatory concern. All 431 samples collected from the 20 Indiana nurseries surveyed tested NEGATIVE for the presence of P. ramorum.

In cooperation with the IDNR and the Indiana Crop Improvement Association (ICIA), the P&PDL also provided disease diagnosis on 125 (95 corn; 30 soybean) samples as a part of IDNR's Phytosanitary Certification Program. An additional 68 corn samples were collected and submitted for diagnosis to provide additional NAPIS data for Indiana.