P. Price

Species Composition and Seasonal Abundance of Stink Bugs (Hemiptera: Pentatomidae) in Louisiana Soybean

ABSTRACT In Louisiana during the last decade, the redbanded stink bug, Piezodorus guildinii (Westwood), has become a significant and yield-limiting pest of soybean. The redbanded stink bug was previously reported in the United States in 1892, but was never considered an economically important pest until recently. Soybeans representing four maturity groups (MG) III, IV, V, and VI were sampled weekly from beginning bloom (R1) to physiological maturity (R8) during 2008–2010 at five locations across Louisiana to determine the Pentatomidae composition. In total, 13,146 stink bugs were captured and subsequently identified to species. The predominant species included the redbanded stink bug (54.2%); southern green stink bug (27.1%), Nezara viridula L.; brown stink bug (6.6%), Euschistus servus (Say); and green stink bug (5.5%), Acrosternum hilare (Say). Redbanded stink bug comprised the largest percentage of the complex collected at four of the five survey sites. Numbers exceeding action thresholds of this stink bug complex were only detected during R4 to R7 growth stages. Redbanded stink bug accounted for the largest percentage of the stink bug complex in early maturing soybean varieties (MG III [86%] and IV [60%]) and declined in later maturing soybeans (MG V [54%] and VI [50%]). The redbanded stink bug was initially identified in southern Louisiana during 2000 and had been reported in all soybean producing regions in Louisiana by 2006. This survey is the first to report the redbanded stink bug as a predominant pest of soybeans from locations within the United States.

Fungicide Resistance in Cercospora kikuchii, a Soybean Pathogen

Isolates of Cercospora kikuchii, a soybean (Glycine max) pathogen causing Cercospora leaf blight and purple seed stain, were tested to determine baseline sensitivities (n = 50) to selected quinone outside inhibitor (QoI) fungicides by conducting radial growth assays on fungicide-amended media. Baseline effective fungicide concentration to inhibit 50% of fungal radial growth (EC50) values were compared with EC50 values for isolates collected in 2011 (n = 50), 2012 (n = 50), and 2013 (n = 36) throughout soybean-producing areas in Louisiana. Median EC50 values for isolates subjected to QoI fungicides were significantly (P = 0.05) higher across all 3 years. Cross-resistance to QoI fungicides was observed in resistant isolates collected in 2011 to 2013. Discriminatory doses were developed for QoI fungicides to distinguish between sensitive and resistant isolates. On average, 89% of all isolates screened in 2011 to 2013 were resistant to QoI fungicides. At a discriminatory dose of thiophanate methyl (TM), a methyl benzimidazole carbamate (MBC) fungicide, at 5 μg/ml, resistance was detected in the 2000, 2011, 2012, and 2013 collections at 23, 38, 29, and 36%, respectively. Isolates exhibiting multiple resistance to QoI fungicides and TM also were detected in 2011, 2012, and 2013 at frequencies of 34, 26, and 31%, respectively. Based on these results, Cercospora leaf blight management strategies in Louisiana using solo applications of QoI or MBC fungicides in soybean should be reconsidered.

Oviposition and Sex Ratio of the Redbanded Stink Bug, Piezodorous guildinii, in Soybean.

Redbanded stink bug, Piezodorus guildinii (Westwood), is a significant soybean pest across the mid-south region of the United States. The objectives of these studies were to characterize: (1) redbanded stink bug oviposition in relationship to soybean maturity group (MG), plant structure, crop phenology, and vertical distribution within the plant canopy; and (2) redbanded stink bug adult sex ratios in relationship to soybean phenology. A total of 5645 redbanded stink bug eggs in 421 egg masses (clusters) were field collected from naturally-occurring populations in MG IV and V soybean over a three year period (2009 to 2011). The mean number of eggs within a cluster was 16.6 ± 0.3. Plant structures by MG interactions were highly significant with more egg masses oviposited on leaves in MG IV (79.4%) and more on pods in MG V (72.7%). The ratio of females to males was similar in all soybean growth stages except R5, where the sex ratio increased to 1.4:1, coinciding with peak oviposition. Only 29.9% of egg clusters in MG IV and 18.3% of egg clusters in MG V were oviposited in the upper 35 cm of the soybean canopy. Based on these results, sampling strategies and insecticide application placement for stink bugs may require modification.

Draft Genome Sequence of Cercospora cf. sigesbeckiae, a Causal Agent of Cercospora Leaf Blight on Soybean

ABSTRACT Cercospora cf. sigesbeckiae is an ascomycete fungal pathogen that infects various plants, including important agricultural commodities, such as soybean. Here, we report the first draft genome sequence and assembly of this pathogen.

EVALUATION OF SULFOXAFLOR (GF-2372) AGAINST TARNISHED PLANT BUGS IN COTTON, 2010

Insecticide efficacy trials were conducted during 2010 at the Northeast Research Station (NERS) near St. Joseph, LA (Tensas Parish) and the Macon Ridge Research Station (MRRS) near Winnsboro, LA (Franklin Parish). Cotton seed (DP 555 BG/RR) was planted into a Commerce silt loam on 25 May at NERS (trial 1) and a Gigger silt loam on 1 Jun at MRRS (trials 2 and 3). Plot size was four to eight rows (40-inches on row centers) X 50 ft with four replications. Insecticides were applied with a highclearance sprayer and compressed air system calibrated to deliver 12 GPA through TeeJet TX-10 hollow cone nozzles (2/row) at 48 psi at NERS and at 9.5 GPA through TeeJet TX-8 hollow cone nozzles (2/row) at 50 psi at MRRS. In trial 1, insecticides were applied on 20 and 29 Jul, and post-treatment evaluations were made on 3, 7 DAT1, and 2, 7, 12 DAT2. In trial 2, insecticides were applied on 3 Aug and post-treatment evaluations were made on 3, 8, 10, 14 DAT. In trial 3, insecticides were applied on 25 Aug and post-treatment evaluations were made on 3, 7, 10 DAT. Plots were sampled with a standard 2.5 x 2.5 ft black cloth shake sheet by taking two samples on two-four rows (10 row ft total) of each plot. Data were subjected to ANOVA and means separated according to DNMRT. Rainfall of 7.61, 1.46, and 0.4 inches occurred during trials 1, 2, and 3, respectively.

EVALUATION OF SELECTED INSECTICIDES FOR CONTROL OF SOYBEAN LOOPER AND STINK BUG, 2007

Selected insecticides were evaluated for control of SBL and a stink bug complex (SBC) in two tests at the Macon Ridge Research Station (Franklin Parish). Soybean seed (Asgrow 5501) were planted into a Gigger silt loam soil on 11 Jun in Tests 1 and 2. Plot size was four rows (40-inches on centers) x 50 ft. Treatments were placed in a RCB design with four replications in both tests. Insecticides were applied on 21 Aug in Test 1 and 27 Aug in Test 2 with a John Deere high clearance sprayer and CO2-charged system calibrated to deliver 6 gpa through Teejet TX-6 hollow cone nozzles (2/row) at 48 psi. Treatment efficacy against SBL and SBC was determined at 2, 6, and 9 DAT in Test 1 and 2, 4, and 8 DAT in Test 2 using a standard (15 inches diameter) sweep net and taking a 25 sweep sample in each plot. Data were subjected to ANOVA and means separated according to DMRT. No rainfall occurred during these tests.

EVALUATION OF FOLIAR INSECTICIDE EFFICACY AGAINST THRIPS ON SEEDLING COTTON, 2007

Selected foliar insecticides were evaluated for control of thrips on cotton seedlings at the Macon Ridge Research Station (Franklin Parish). Cotton seed were planted into a Gigger-Gilbert silt loam soil on 7 May. Plot size was four rows (40-inch centers) X 25 ft. Treatments were placed in a RCB design with four replications. Foliar insecticides were applied with a handboom and compressed air system calibrated to deliver 10 GPA through TeeJet 8001 flat fan nozzles (2/row) at 20 psi on 25 May and 4 Jun. Insecticide efficacy was measured by randomly selecting 10 plants per plot and counting the number of immatures and adults on 28 May (3 DAT1), 1 Jun (7 DAT1), and 7 Jun (3 DAT2). Plant samples were processed using whole plant washing procedures to remove thrips. Thrips were counted using a dissecting microscope. Seedling damage was estimated visually using a 0-5 rating scale with 0 as no damage and 5 representing severe damage. Seedling damage was evaluated on 4 Jun (10 DAT1) and 13 Jun (9 DAT2). Data were subjected to ANOVA and means separated according to DMRT. Total rainfall of 4.95 inches occurred during the test.

EVALUATION OF SELECTED INSECTICIDES FOR CONTROL OF RED BANDED STINKBUGS AND THREECORNERED ALFALFA HOPPERS, 2006

Selected insecticides were evaluated for control of RBSB (adults) and TCAH (adults and nymphs) in soybean at the LSU Agricultural Center’s Sweet Potato Research Station (Franklin Parish). Soybean seed were planted into a Gigger silt loam soil on May 19, 2006. Plot size consisted of eight rows centered on 40-inches and 50 ft in length. Treatments were placed in a RCB design with five replications. Insecticides were applied on 11 Aug with a John Deere high clearance sprayer and CO2-charged system calibrated to deliver 6 gpa through Teejet TX-8 hollow cone nozzles (2/row) at 60 psi. Treatment efficacy against RBSB and TCAH was determined at 3, 5, and 7 DAT using a standard (15 inches diameter) sweep net and taking a 25 sweep samples in each plot. Data were subjected to ANOVA and means separated according to DMRT. No rainfall occurred during these tests.