Lindsey Thiessen

Investigator will direct establishment and conduct of trial described in protocol. Investigator will direct collection and reporting of data as outlined in protocol and handle any disposition of trial materials necessary.

The Guava root-knot nematode (GRKN), Meloidogyne enterolobii, is an invasive and highly aggressive soilborne pathogen. GRKN overcomes all known crop resistance genes that are effective in controlling other RKN species, and thus represents a significant threat to agricultural production in NC. The threat of GRKN to the NC sweetpotato industry and the communities reliant upon the industry is estimated at 95,000 harvested acres worth $342 million. Multifaceted research of chemical control and screening for cultivar resistance is needed to investigate solutions to this problem. However, a significant hindrance to such research lies in identifying suitable field locations with sufficient GRKN populations to perform the work. This project aims to establish a contained research farm infested with GRKN. The proposed farm would allow for management studies and the ability to screen sweetpotato, soybean, tobacco, and vegetable cultivars under field conditions. To reduce the risk of accidental movement of GRKN to other sites, the farm will be enclosed in fencing, with dedicated equipment and storage building, and a decontamination station.

The recent introduction of a new root knot nematode species, Meloidogyne enterolobii, to North Carolina threatens profitable soybean production in this state. Currently 8 counties have been confirmed with this nematode since 2011. This nematode is significantly more aggressive than the other root knot nematode species found in NC, and appears to regenerate population densities to damaging levels even with fumigation. Additionally, this nematode has a wide host range that affects numerous weed species and several rotational crops, including vegetable crops, sweet potatoes, and tobacco. Chemical controls for general nematode control in soybean are limited due to the costs of application and the limited economic return with their application. Identification of varietal resistance is important to continue to economically produce soybean with this pest continuing to spread in North Carolina. Previous screening of the Official Variety Test soybean varieties resulted in no resistance to M. enterolobii being found. This project will screen the national wild soybean germplasm (n=80) to assess potential mechanisms for resistance as well as identify the sensitivity of soybean lines to this new root knot nematode.

Improving fungicide timing could lead to improved yield protection by fungicide applications by limiting the ability of pathogen to establish prior to protectant fungicide applications. Because developing a disease risk model is not immediately available to evaluate, this project has several goals: 1) evaluate timing for application of fungicides in corn to protect yield potential of the crop, 2) develop an improved disease risk model for corn fungicide applications, and 3) generate improved fungicide application timing recommendations for NC corn growers.

Some North Carolina producers are starting to shift soybean planting earlier into the spring due to success with early maturing soybean varieties. Most of the fungicide seed treatment work conducted by the Soybean Extension Program has been done with soybeans planted from mid-May through mid-June. How would our results differ when considering planting soybeans earlier in the season? The proposed research seeks to answer this question. We will evaluate ~10 fungicidal soybean seed treatments entered by prominent agricultural companies across four planting dates ranging from early April through mid-May. This research will be conducted at three locations in North Carolina including a Blackland site, Coastal Plain site, and a Piedmont site. Economic analyses will occur considering both fungicidal seed treatment cost and impact on soybean yield. Results will be disseminated to various North Carolina stakeholders at grower meetings, field days, via electronic media, and through extension publications.

Over the last three years, the USB, North Central Soybean Research Program, industry partners, the Corn+Soybean Digest, and University partners have been developed an SCN Coalition, with the stated purpose to increase awareness help growers more actively manage SCN and preserve the effectiveness of the current source of SCN resistance. We will expand the SCN Coalition locally, and each individual state specialist(s) will determine the most effective way to educate growers in their state, and through local efforts, the SCN Coalition will be most successful. This may include organizing and holding field days, organizing and holding winter meetings, distribution of Extension material, SCN soil sample processing, and/or other avenues of Extension information delivery.

Poor control of peanut leaf spots, especially late leaf spot, appears to have increased in North Carolina the past few years. Poor leaf spot control has been seen in several fields across the state and sometimes has been severe enough to warrant early digging. Although some problems could be attributed to sprays delayed by rain and wet fields, and others to use of fungicides at inappropriately low rates or extended intervals, severe leaf spot also has been observed in fields where growers used solid control programs. The purpose of this research is to further document the prevalence of leaf spot control problems and to test for the for the presence of QoI (group 11) resistance in populations of leaf spot fungi in North Carolina.

This project aims to improve soybean management by providing accurate diagnosis of diseases, insects, or abiotic disorders of soybeans submitted by extension agents. This effort will help to reduce the cost of soybean production by targeting management based on accurate diagnosis of diseases and disorders of soybean.

Frogeye leaf spot, caused by Cercospore sojina, causes damages to soybean in hot, humid climates within the United States. Fungicides are a major tool for managing damages caused by C. sojina, particularly the quinone outside inhibitors (QoI) fungicides like azoxystrobin and pyraclostrobin. QoI fungicides are ����������������high risk��������������� for fungicide resistance due to the single site mode of action. Resistance to QoI fungicides in isolates of C. sojina was first detected in Tennessee soybean fields in 2010 (Zeng et al. 2014). Since then, isolates of C. sojina that are resistant to QoI fungicides have been found in several other states in the United States. It has not yet been ascertained what level of fungicide resistance is established in North Carolina. This research will provide information regarding the level fungicide resistance in C. sojina, the causal agent of frogeye leaf spot, observed in North Carolina.

Soybean Cyst Nematode (Heterodera glycines [SCN]) and Root Knot Nematode (Meloidogyne spp. [RKN]) cause damages to soybean throughout North Carolina. Resistance is available for several races of SCN; however, multiple races of SCN heavily relying on host resistance for SCN management may lead to a race shift within a field. Crop rotation is the best control method for managing nematode populations, but some regions of North Carolina lack economical options for crop rotation.Several chemical and biological products have recently been introduced to the market, but their efficacy under different environmental conditions and to different products has not yet been established. This research will provide information regarding chemical control of SCN and RKN in soybean, including seed treatments containing chemical or biological agents for control as well as applications of chemical or biological agents. The main objective of this research is to determine best chemical management practice to reduce the impact of SCN and RKN in soybean.