Paul J Semtner, PhD
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Dr. Semtner provides statewide leadership for research and extension programs in integrated pest management on tobacco. His research deals with the biology and management of tobacco insect pests. The objectives are to investigate the biology and insecticide resistance for the tobacco-adapted form of the green peach aphid, to determine the impact of insects and the timing of insecticide applications on tobacco yield and quality, and to assess the potential of cultural and biocontrol practices for managing insect pests. Current research projects deal with the influence of host plant and temperature on the morphology of various host-adapted forms of the green peach aphid, the impact of chemical controls and cultural practices on the incidence of insect pests on tobacco, and insect pests and their management on tobacco grown for biomass to produce valuable proteins. Other duties include serving as major advisor and mentoring graduate students. The extension program for tobacco IPM educates growers and extension agents about current pest management practices including the use of economic thresholds, field scouting, cultural practices, and insecticides for managing the major insect pests of tobacco for optimum profits and minimum impact on the environment.
Professional Memberships
- CORESTA (International Tobacco Research Society)
- Entomological Society of America
- Geogia Entomological Society
- Tobacco Workers' Conference
Personnel
- Wage or Other Employees
Former Students and Faculty Associates
- Surendra K. Dara (1995) - Quality Control Officer Certis, USA 720 5th St Wasco, CA 93280 Phone: 661-758-8471 ext. 226 Cell: 661-201-0707 Fax: 661-758-9317 (email: sdara@certisusa.com )
- Martha B. Reed (1990) - Biology Instructor Southside Virginia Community College Alberta, Virginia (email: Martha.Reed@sv.vccs.edu)
- Thomas David Reed (1990) - Tobacco Extension Specialist Virginia Tech Southern Piedmont AREC Blackstone, Virginia 23824 (email: treed@vt.edu)
- Mohd N Hamid, Dr. (1987) - Research Entomologist MARDI, Maylasia (email: norowi@mardi.my)
Projects
- Impact of conservation tillage and other cultural practices on tobacco insect pests.
Research is underway in cooperation with Dr. David Reed of the Southern Piedmont AREC to investigate insect pests and their management on conservation-tilled tobacco. Results indicate that conservation-tillage reduces the incidence of aphids and flea beetles, but its impact on hornworms has been inconsistent. Findings also indicate that flue-cured tobacco grown in conservation tillage systems can produce yield and quality similar to conventional tobacco. Research is being continued to evaluate various cultivation methods, cover crops, and insecticides for managing insect pests on tobacco. This research has helped increase the use of conservation tillage in flue-cured tobacco production in Virginia.
- Impact of tobacco splitworm on burley tobacco
The tobacco splitworm, Phthorimaea operculella, is a leaf-mining caterpillar that is becoming an important pest of tobacco in the southeastern United States. In Virginia, it has been a sporadic problem on flue-cured tobacco, but not on burley tobacco. However, since there is a shortage of burley tobacco, companies are encouraging farmers to grow burley in the flue-cured region where splitworms are common. On burley tobacco, splitworm caterpillars cause moderate damage in the field and continue to feed on the leaves and stalks in the curing barn after harvest. Research will quantify splitworm damage to burley tobacco in the field and in the curing barn. The impact on leaf quality will be compared for various levels of leaf injury for each stalk position. Splitworm development on plants in the curing barn will be investigated. Pheromone traps will be used to monitor adult flight activity in the field and in the curing barn to assess their value for predicting splitworm outbreaks. Several insecticides will also be evaluated for splitworm control.
- Influence of tobacco flea beetle management on the development of black shank in tobacco
Black shank is a major soil-borne pathogen of tobacco. The objectives of this research are to determine the influence of early-season control of the tobacco flea beetle, a pest that damages young leaves and roots, on the development of black shank in tobacco. Imidacloprid for flea beetle control and metalaxyl, a fungicide commonly used for black shank management, are being assessed for their impact on the incidence of flea beetles and black shank. In a moderately-resistant cultivar, the use of imidacloprid applied as tray drench treatments provided effective early-season control of flea beetles, reduced flea beetle emergence from tobacco root systems, and reduced the number of plants with black shank symptoms by 40% to 50% compared with the untreated check and an early-season application of metalaxyl. This study may lead to improved insect management practices for reducing the incidence of black shank in problem fields.
- Insect management on transgenic tobacco produced for high-value protein.
Genetically modified tobacco for valuable proteins has excellent potential for commercial production in the tobacco growing regions of Virginia. This crop will be produced for maximum yield of specific proteins. The plants will be grown at very high densities and clipped three to five times a year. The objectives of this research are to determine the major insect problems and to develop strategies for managing these pests. Preliminary studies indicate that several insect problems on tobacco grown for protein are different from those on tobacco produced for cured leaf.
- Insecticides for tobacco
Several potential new insecticides are evaluated annually for use on tobacco. Neonicotinoids were the most promising insecticides tested in recent years. They were clothianidin applied as a transplant water treatment for aphid and flea beetle control and foliar applications of clothianidin and acetamiprid for control of aphids, flea beetles, hornworms and budworms. Acetamiprid is a reduced risk insecticide that was labeled for aphid control on tobacco in early 2005. Previous research contributed to the registration of thiamethoxam (Actara/Platinum), emamectin benzoate (Denim), and lambda-cyhalothrin (Warrior) on tobacco.
- Integrated pest management on tobacco.
This program encourages tobacco farmers to produce their crops more efficiently, while reducing pesticide use, and improving environmental quality. Growers are taught how to use field scouting and economic thresholds, the proper methods and timing of pesticide applications, and the importance of cultural controls and beneficial organisms for managing tobacco insect pests. The use of new and safer insecticides for managing pests on tobacco is emphasized. Since most tobacco transplants are now produced in greenhouses, growers are taught integrated management techniques for greenhouses. Farmers are being informed of recommended pest management practices through publications (Flue-Cured, Burley, and Dark Fire-Cured Tobacco Production Guides, the Pest Management Guide), production meetings, field days, farm tours and indirectly through farm supply dealer and Extension agent training.publications, production meetings, field days, farm tours, farm test demonstrations, and indirectly through farm supply dealer and Extension agent training. There is close cooperation and exchange of information with entomologists from other tobacco-producing states.
- Resistance management for the tobacco-adapted form of the green peach aphid on tobacco
Studies are underway to establish baseline information on the toxicity of imidacloprid and acephate and to assess biochemical and genetic differences between tolerant and susceptible colonies of the tobacco-feeding form of the green peach aphid, Myzus persicae. We are evaluating colonies of two color morphs (red and green) of the aphid from farms located across the flue-cured and burley tobacco-producing regions of Virginia and eight other tobacco-producing states. So far, there have been moderate differences in toxicity (based on LC50 values) to imidacloprid (Admire) between the most susceptible and least susceptible colonies. Color morph appears to have no effect on resistance to imidacloprid. These tests are being continued to compare levels of tolerance among clones and to establish baselines that can be used to monitor for aphid resistance in the future.
Resources
- Agricultural Experiment Station Facilities → website
Access to heavy machinery and test plots of various crops is possible at Blacksburg and other experiment stations throughout the state. Field studies are also done on land owned by cooperators not associated with the university. In all cases arrangements for use of these facilities is made through the Major Professor. Success of such arrangements depends upon good will, responsibility, and commitment of all concerned parties.
- Entomology Laboratory - Southern Piedmont AREC
The entomology laboratory is equipped with environmental chambers that are used for experiments and insect rearing. Graduate students utilize this laboratory for their research projects. Various studies on insecticide resistance, aphid biology and host range are being conducted.
- Facilities at Southern Piedmont and Southwest Virginia ARECs
Plot land, heavy equipment, and technical support for setting up and maintaining experiments and taking data are available at the Southern Piedmont and Southwest Virginia AREC's. Most field experiments are conducted at the Southern Piedmont AREC and include research on flue-cured, burley, and dark fire-cured tobaccos. One to two experiments on burley tobacco are conducted each year at the Southwest Virginia AREC. Temporary technicians are hired each summer to assist with data collection.
- Greenhouses
Glass and plastic greenhouses are available for plant production for field, laboratory and greenhouse research.
