Benjamin G. Mullinix

Colonization and Population Dynamics of Thrips in Peanuts in the Southern United States

Seasonal population dynamics of tobacco thrips, Frankliniella fusca and western flower thrips (WFT) were investigated in peanut, Arachis hypogaea L., planted at various times from 1 April–12 June in six different years. Populations of adult and larval thrips were sampled in whole seedling plants, vegetative terminal buds and flowers. The primary species reproducing was determined indirectly by collecting larvae from whole plants, terminals and flowers and rearing them to adult for identification. Of 875 larvae, 486 survived to become adults (484 were F. fusca and 2 WFT). Peak populations of F. fusca adults occurred in whole plants and vegetative terminal buds ≈ 10 – 20 d after planting in April. Peaks of WFT adults occurred ≈ 12–14 d after planting in May. Maximum feeding injury occurred ≈ 28–35 d after planting and coincided with peak numbers of thrips larvae rather than populations of either F. fusca or WFT in whole plants or terminal buds. Populations of brachypterous F. fusca generally increased to a peak in the flowers at 30–60 d after planting. Populations then declined to low levels during the late summer.

Weed Management in Watermelon (Citrullus lanatus) and Cantaloupe (Cucumis melo) Transplanted on Polyethylene-Covered Seedbeds'

Abstract: Studies were conducted from 1998 to 2001 in Tifton, GA, on weed management systems in transplanted cantaloupe and watermelon grown on polyethylene-covered seedbeds. Soil fumigants were metham (748 L/ha) and a nonfumigated control. All metham applications were sprayed in a 61-cm band and incorporated with a modified power tiller. Herbicide treatments were ethalfluralin (0.8 kg ai/ha) premergence (PRE), ethalfluralin plus halosulfuron (36 g ai/ha) PRE, ethalfluralin PRE followed by glyphosate (1.1 kg ai/ha) postemergence POST-SHIELDED, ethalfluralin plus halosulfuron PRE followed by glyphosate POST-SHIELDED, and a nontreated control. Premergence herbicides were directed to row middles not covered in polyethylene, without contacting the transplants. Glyphosate was applied to row middles using a hooded sprayer, just before vine running. Overall weed control was not improved with soil fumigation in either cantaloupe or watermelon, and there was no yield response in either crop. There may be minimal benefit in transplanted cantaloupe and watermelon on polyethylene-covered seedbeds from preplant soil fumigation for weed control, in the absence of other pests. Herbicide systems that included halosulfuron PRE or glyphosate applied POST-SHIELDED improved control of yellow nutsedge compared with ethalfluralin alone. Control of Texas panicum, southern crabgrass, Florida pusley, and smooth pigweed was not improved by halosulfuron or glyphosate. Polyethylene-covered seedbeds provide a mechanical barrier to weed infestation for many species. Integration of these weed control practices gives cantaloupe and watermelon growers effective options for weed management, particularly for a troublesome species such as yellow nutsedge. Nomenclature: Ethalfluralin; halosulfuron; metham; crowfootgrass, Dactyloctenium aegyptium (L.) Willd. #3 DTTAE; Florida pusley, Richardia scabra L. # RCHSC; smooth pigweed, Amaranthus hybridus L. # AMACH; southern crabgrass, Digitaria ciliaris (Retz.) Koel. # DIGSP; Texas panicum, Panicum texanum Buckl. # PANTE; yellow nutsedge, Cyperus esculentus L. # CYPES; cantaloupe, Cucumis melo L.; watermelon, Citrullus lanatus (Thunb.) Mansf. Additional index words: Alternatives to methyl bromide, fumigation, halosulfuron, metham, plasticulture. Abbreviations: POST, postemergence; PRE, premergence; PTO, power take off.

Effect of Herbicide Application Method on Weed Management and Crop Injury in Transplanted Cantaloupe Production1

Field trials were conducted at the Coastal Plain Experiment Station in Tifton, GA, from 2000 to 2003 to study the effects of herbicide placement on weed control and cantaloupe injury. Herbicides halosulfuron (0.036 kg ai/ha), sulfentrazone (0.14 and 0.28 kg ai/ha), clomazone (0.6 kg ai/ha), and a nontreated control were evaluated. Methods of herbicide application were preplant incorporated (PPI) under the polyethylene mulch before transplanting, posttransplanting over-the-top (POST-OTT), and posttransplanting-directed (POST-DIR) to the shoulders of polyethylene-covered seedbeds. Across all herbicide treatments, PPI and POST-DIR applications were the least injurious, with POST-OTT applications the most injurious. In general, sulfentrazone (0.28 kg ai/ha) was the most injurious herbicide and halosulfuron the least injurious, regardless of herbicide placement. Halosulfuron effectively controlled yellow nutsedge and provided versatility in methods of application, with minimal injury to transplanted cantaloupe. Nomenclature: Clomazone; halosulfuron; sulfentrazone; yellow nutsedge, Cyperus esculentus L. #3 CYPES; cantaloupe, Cucumis melo L. Additional index words: Clomazone, halosulfuron, plasticulture, sulfentrazone. Abbreviations: POST-DIR, posttransplanting-directed; POST-OTT, posttransplanting over-the-top; PPI, preplant incorporated.

Potential Weed Management Systems for Organic Peanut Production

Studies were conducted near Tifton, GA to develop weed management systems for organic peanut production. Trials in 2004 and 2005 evaluated row patterns (two levels), remedial weed control (four levels), and cultivation (three levels). Row patterns were wide rows (91 cm apart) and narrow rows (30 cm apart). Remedial weed control was early-season applications of clove oil, citric plus acetic acid, broadcast propane flaming, and a nontreated control. Cultivation regimes were 1X or 2X sweep cultivation and a non-cultivated control. The experimental sites had heavy natural infestations of annual grasses and broadleaf weeds. None of the treatment combinations effectively controlled weeds season-long and resulting peanut yields were poor. Annual grasses were particularly troublesome due to ineffective control from flaming and citric plus acetic acid. Clove oil was slightly more effective in controlling annual grasses than the other remedial treatments, but annual grass control was still unacceptable. Dicot weeds were not effectively controlled by mid-season, although clove oil and flaming controlled the seedling weeds early season. The lack of residual weed control by the remedial weed control treatments resulted in heavy weed infestations by mid-season. Poor control of annual grasses, no residual weed control, and high cost of remedial treatments indicates that these systems of weed management in organic peanut production are not suited to sites with heavy weed infestations.

Texas Panicum (Panicum texanum) Interference in Peanut (Arachis hypogaea) and Implications for Treatment Decisions

Abstract Trials were conducted from 2001 through 2003 in Georgia to quantify Texas panicum interference on peanut. One set of trials investigated the effect of Texas panicum densities on peanut yie...

Peanut Response to Naturally-Derived Herbicides Used in Organic Crop Production

Weed-free irrigated trials were conducted in 2004 and 2005 to quantify phytotoxic effects of herbicides with the potential to be used in organic peanut production. Clove oil and citric plus acetic acid were each applied at vegetative emergence of peanut (VE), two weeks after VE (2 wk), four weeks after VE (4 wk), sequentially VE/2 wk, sequentially VE/4 wk, sequentially VE/2 wk/ 4 wk, and a nontreated control. Clove oil was more injurious (maximum of 28% visual injury) than citric plus acetic acid (maximum of 4% visual injury), with significant injury occurring with clove oil applied at 4-wk or sequentially. Citric plus acetic acid caused minimal peanut injury. There were no consistent effects of clove oil on peanut yield, although sequential applications of clove oil tended to reduce peanut yield. Peanut yield was not affected by citric plus acetic acid.

Annual grass control in strip-tillage peanut production with delayed applications of pendimethalin.

Abstract In strip-tillage peanut production, situations occur when dinitroaniline herbicides are not applied in a timely manner. In these cases, dinitroaniline herbicides would be applied days or weeks after seeding. However, there is no information that documents the effects of delayed applications on weed control. Trials were conducted in 2004, 2005, and 2007 in Georgia to determine the weed control efficacy of delayed applications of pendimethalin in strip-tillage peanut production. Treatments included seven timings of pendimethalin application and three pendimethalin-containing herbicide combinations. Timings of application were immediately after seeding (PRE), vegetative emergence of peanut (VE), 1 wk after VE (VE+1wk), VE+2wk, VE+3wk, VE+4wk, and a nontreated control. Pendimethalin containing herbicide programs included pendimethalin plus paraquat, pendimethalin plus imazapic, and pendimethalin alone. Among the possible treatment combinations was a current producer standard timing for nonpendimethalin weed control programs in peanut, which was either imazapic or paraquat alone applied VE+3wk. Pendimethalin alone did not effectively control Texas millet regardless of time of application (69 to 77%), whereas southern crabgrass was controlled by pendimethalin alone PRE (87%). Delayed applications of pendimethalin controlled Texas millet and southern crabgrass when combined with either paraquat or imazapic, with imazapic being the preferred combination due to better efficacy on southern crabgrass than paraquat at most delayed applications. Peanut yield was improved when any of the herbicide combinations were applied PRE compared to later applications. Across all times of application, pendimethalin plus imazapic effectively maximized peanut yield with interference from annual grasses. Nomenclature:Imazapic; paraquat; pendimethalin; southern crabgrass, Digitaria ciliaris (Retz.) Koel; Texas millet, Urochloa texana (Buckl.) R. Webster; peanut, Arachis hypogaea L., ‘C99R’