8Five bacterial isolates collected from dogwood leaves were evaluated for powdery mildew control in 9 shadehouse and greenhouse environments by using foliar sprays and/or root drenching. Two 10 isolates displayed superior bioactivity and suppressed powdery mildew similar to conventional 11 fungicide thiophanate methyl (Cleary's 3336F®). The two bacteria disrupted powdery mildew spore 12 germination and ruptured spore membranes causing spore lyses. Bacterial filtrates without bacterial 13 cells were also effective in suppressing powdery mildew and disrupting spore germination and 14suggested the involvement of secondary metabolites. The two biocontrol agents (BCAs) colonized 15 roots endophytically and promoted plant growth. 16 17

No abstract

Imported fire ants (Solenopsis spp.; Hymenoptera: Formicidae) occupy 54 counties (~5.4 million ha) in Tennessee. To better understand the fire ant species distribution in Tennessee, the state was divided into 16.1 × 16.1 km grids, and a single colony was sampled for cuticular hydrocarbon and venom alkaloid analyses within each grid. A total of 387 samples was processed from which 9 (2.3%), 167 (43.2%), and 211 (54.5%) were identified as red (Solenopsis invicta Buren), black (Solenopsis richteri Forel), or hybrid (S. invicta × S. richteri) imported fire ants, respectively. The S. invicta was only found near metropolitan Nashville in Davidson and Williamson counties and at one site in Decatur Co. All samples east of Franklin Co. were identified as hybrids. Tennessee counties west of Lincoln were predominantly S. richteri (86.5%) as opposed to hybrid (13.0%) and S. invicta (0.5%). The exception was Hardin Co., which was predominantly hybrid. Counties containing both hybrid and S. richteri (all in the middle and western part of the state) included Bedford, Decatur, Franklin, Giles, Hardeman, Hardin, Haywood, Lawrence, Lincoln, Marshall, Maury, McNairy, Perry, and Wayne. The S. invicta samples collected from one Williamson Co. site were determined to be polygyne and infected with the Solenopsis invicta virus (genotype SINV-1 A). This was the first detection of polygyne imported fire ant in Tennessee. The SINV-1 A virus was also a new find at the time of detection, but has been previously reported. The survey results are being used to direct current and future biological control efforts against imported fire ants in Tennessee.

No abstract

Six biological control agents (BCAs) (two bacteria, two fungi, and two yeasts) that were previously shown to be effective against powdery mildew (Erysiphe pulchra) were tested for efficacy against Macrophomina phaseolina root rot on flowering dogwood (Cornus florida) in the greenhouse. Two of the bacterial isolates, Stenotrophomonas sp. (B17A) and Serratia sp. (B17B), were effective in controlling both macrophomina root rot and powdery mildew, similar to fungicide control thiophanate methyl, when roots were drenched with the six BCAs individually. In addition, the two bacterial BCAs improved plant growth with respect to stem diameter, stem length, dry weight, and green foliage compared with fungicide-treated plants or nontreated controls grown in sterile soil. These results confirm previous results in which B17A and B17B suppressed powdery mildew and also promoted plant growth in flowering dogwood. Although macrophomina root rot has been previously reported as a potential problem in flowering dogwood, especially in field conditions, simultaneous infection with macrophomina root rot and powdery mildew has not been previously reported. This study confirmed that M. phaseolina infection was characterized by stubby roots and black root lesions, and plants infected with both powdery mildew and macrophomina root rot had smaller root mass compared with fungicide-treated plants. Neither of the two pathogens killed their host plants, but compounded infections significantly reduced the plant root system and plant growth. The efficacy of the two bacterial isolates in controlling both powdery mildew and macrophomina root rot suggests their potential utilization in controlling both diseases in dogwood nursery production and in other plants that are hosts to both powdery mildew and macrophomina root rot. Plant growth promoted by the two BCAs may be attributed to powdery mildew and macrophomina root rot control, but comparisons between fungicide-treated plants and control plants not inoculated with BCAs or root rot pathogen suggested that the two BCAs may play a role as bio-stimulants in growth enhancement. These results also suggest that the two biocontrol agents are not phytotoxic to dogwood.