There is interest in diversifying peanut production in the southeastern U. S. to certified organic production to meet the consumer demand for organic peanut butter. Previously, the majority of the organic peanut production in the United States was in western Texas and eastern New Mexico (Guerena and Adam, 2008; USDA-ERS, 2013). Peanut production in this region is at elevations >1200 m and the growing season is short. As a result, organic peanut grown in that region are primarily Valencia peanut, which have a shorter growing season and lower yield potential than runner-type peanut. Runner peanut have superior yield, roasting qualities, and flavor making them the primary component of conventional peanut butter. Furthermore, runner peanut are commonly grown in the southeastern U. S. A persistent criticism of increased demand of organic agronomic commodities in the U. S. has been that much of resulting supply has been met by imports (Gianessi and Reigner, 2005), not by increased U. S. production. In the context of consumer demand for organic peanut butter, criticism could be deflected by increases in certified organic peanut production in the southeastern U. S. using runner-type peanut.

Difficulties in weed management in certified organic crops remains a nationwide priority for growers (Organic Farming Research Foundation, 2016), including peanut. Previous research on weed management in organic peanut has shown that herbicides derived from natural products (clove oil, acetic acid plus citric acid, and corn gluten) are generally ineffective (Johnson and Mullinix, 2008; Johnson et al., 2013). Propane flaming is a weed control option in certified organic systems, but in peanut trials propane flaming did not control annual grasses and the flaming implement was persistently difficult to use (Johnson and Mullinix, 2008).

Mechanical weed control has been consistently the most effective approach in organic peanut (Johnson et al., 2012a, 2012b; Wann 2011). Cultivation is a form of mechanical weed control that uses tillage tools to remove, cut, or disrupt weed growth in a manner that does not injure the crop. Sweep cultivation is a common form of mechanical weed control that cuts or buries seedling weeds using uniquely shaped blades (sweeps) that slice just under the soil surface in the area between the crop rows. However, weeds present in the crop row are not affected by the sweeps.

The tine weeder is a cultivation implement of European origin that operates on a different principle compared to sweeps (Colquhoun and Bellinder, 1997). The tine weeder uses multiple rows of closely spaced rods of spring steel (tines). The tine weeder uses vibratory action of the tines to displace weed seedlings (Ascard and Fogelberg, 2008; Melander and Rasmussen, 2001). In laboratory studies, a single cultivation using an implement conceptually similar to a tine weeder uprooted 51% of the emerged weed seedlings in a coarse-textured soil (Kurstjens et al., 2000). Tine weeders are very effective on annual grasses (Johnson et al., 2012a, 2012b) and seedling dicot weeds, with maximum performance when weed seed have germinated, but seedlings not emerged. Gunsolus (1990) referred to this stage of weed development as 'weeds in the white', with the white portion being the rapidly developing hypocotyl from a very young weed seedling. The tine weeder has shown great potential for use in organic peanut with the crop tolerating multiple early-season cultivations at weekly intervals (Johnson et al., 2012a; Wann et al., 2011).

The tolerance of peanut to aggressive cultivation with a tine weeder may be related to the evolutionary development of the genus. Arachis spp. evolved in South America, with A. hypogaea believed to have originated in Bolivia (Hammons, 1973). In this region, naturally occurring Arachis spp. are heavily trod and grazed by cattle. Under this selection pressure, Arachis spp. developed tolerance to that type of physical abuse and plants routinely survive. Despite the innate tolerance of Arachis spp. to abuse, subterranean fruiting of peanut can be disrupted by sweep cultivation that may unintentionally sever pegs and pods. Boyle (1952, 1956, 1961) and Mixon (1963) correlated the relationship between southern stem rot (Sclerotium rolfsii Sacc.) incidence with sweep cultivation that placed soil containing fungal sclerotia onto the lateral branches of peanut. Those findings were the basis for the long-standing peanut production recommendations to adjust sweep cultivators to minimize soil movement onto the peanut plant; colloquially termed 'non-dirting' cultivation. Since a tine weeder operates on a different principle than a sweep cultivator and does not displace soil to the same degree as sweeps, the effect of tine weeding on incidence of soil-borne diseases is unknown.

In earlier weed management trials in organic peanut, plots were cultivated as many as six times at weekly intervals with the tine weeder, sweeps, or the PTO-powered brush-hoe (Johnson et al., 2012a, 2012b; Wann 2011). No insecticides were applied for thrips (Thysanoptera: Thripidae), foliage-feeding Lepidopterans, or pod-feeding insects. Similarly, no conventional fungicides were applied for foliar or soil-borne disease control. While organic peanut in these trials were occasionally infested common insect pests, damage was never severe or judged to be yield limiting. Similar observations were made with peanut diseases; peanut were infected but epidemics were not severe.

Overall, there appears to be a distinct discrepancy between the long-standing peanut production philosophy successfully used by conventional peanut growers and the surprisingly effective systems used to manage organic peanut in the previous research trials. It was hypothesized that components in the organic peanut production system could be integrated into conventional peanut production to reduce inputs. Therefore, trials were initiated in 2012 to determine the interactive relationships among systems to manage weeds, insects, and diseases in organic peanut production.

Irrigated research trials were conducted at the University of Georgia Ponder Research Farm near Ty Ty, GA (31.510884°, -83.645913°) for three seasons from 2012 through 2014. The soil was a Tifton loamy sand (fine-loamy, kaolinitic, thermic Plinthic Kandiudults) with 88% sand, 6% silt, and 6% clay and 0.2% organic matter. The soil at this location is representative of soils in the southeastern U. S. peanut producing region and naturally infested with weeds that are common to the region.

The experimental design was a 3 x 2 x 3 factorial arrangement of treatments in a randomized complete block design with four replications. Treatments were all possible combinations of three levels of weed control, two levels of insect control, and three levels of fungal disease control. Weed control treatments were cultivation six times with a tine weeder (Aerostar Tined Weeder; Einböck GmbH & CoKG; Schatzdorf 7; 4751 Dorf an der Pram; Austria) at weekly intervals beginning four days after planting, weed-free with handweeding as-needed, and a weedy control. The tine weeder used in these trials tilled a swath 1.8 m wide. Tension of tines located immediately above the crop row was adjusted by the use of mechanical hangers, each having several hooks on which tines over the row were lifted to prevent crop damage. Gauge wheels were attached to the front of the tine weeder to add lateral stability of the implement.

Insect control was spinosad (Entrust® Naturalyte® Insect Control; Dow AgroSciences, LLC; 9330 Zionsville Road; Indianapolis, IN 46268-1189) (0.11 kg ai/ha) and a nontreated control. This formulation of spinosad is approved by the Organic Materials Review Institute (OMRI) for insect control in certified organic crop production, including peanut. Spinosad was applied twice; two weeks and four weeks after peanut emergence. Fungicide regimes were four foliar sprays of a combination of OMRI approved fungicides, a commonly used conventional fungicide for peanut disease control, and a nontreated control. The fungicide regime for certified organic crop production was cuprous oxide (2.2 kg/ha) (Nordox® 75DF; NORDOX Industrier AS; c/o Monterey Ag Resources; P. O. Box 35000; Fresno, CA 93745-5000) plus sulfur (9.0 kg/ha) (Microthiol® Disperss®; United Phosphorous Inc.; 630 Freedom Business Center, Suite 402; King of Prussia, PA 19406) (abbreviated "Cu+S"). The conventional fungicide chosen was azoxystrobin (0.45 kg ai/ ha) (Abound® Flowable; Syngenta Crop Protection, LLC; P. O. Box 18300; Greensboro, NC 27419). Both spray regimes were initiated in early-June each year and applied at three week intervals.

Plots were 1.8 m wide and 6.1 m in length. Land preparation included moldboard plowing in early May and seedbed conditioning using a power-tiller and field cultivator. Non-treated 'Georgia-04S' (Branch 2005) peanut were seeded mid-May each year in rows spaced 91 cm apart using vacuum planters (Monosem Inc.; 1001 Blake St.; Edwardsville, KS 66111) that placed seeds at a density of 20 seed/m, to a depth of 6.4 cm. The GA04-S peanut cultivar was used in these trials since it has excellent seedling vigor, rapid early season growth, and resistance to spotted wilt (tomato spotted wilt Tospovirus) (Branch 2005). This cultivar performed well in previous organic peanut research trials (Johnson et al., 2012a, 2012b).

Visual estimates of weed control compared to the nontreated control were assessed in mid-season using a scale of 0 to 100 where 0 = absolutely no weed control and 100 = complete weed control. Thrips feeding damage was monitored throughout the early season. Immediately prior to harvest, incidence of early leafspot (Cercospora arachidicola Hori), southern stem rot, and spotted wilt infection was determined. Incidence of early leafspot was evaluated using the Florida 1-to-10 intensity scale, where 1 = no leafspot disease or defoliation and 10 = plants completely defoliated or dead (Chiteka et al., 1988). Stem rot and spotted wilt incidence were measured by one or more plants affected by the diseases in a 30-cm section of row. Percent incidence of either disease were determined by number of 30-cm sections of disease loci divided by total number of 30 cm sections in the plot. Peanut yields were obtained by pre-harvest mowing to cut tops of tall weeds, digging/inverting, air-curing, and combining peanut from the entire plot using commercial two-row equipment. Yield samples were mechanically cleaned to remove foreign material, particularly weed biomass, with yields reported as cleaned farmer stock peanut.

Data were analyzed using a mixed-model analysis. Degrees of freedom were partitioned to test singularly and in combination the effects of weed control, insect control, and fungal disease control on the parameters measured. Means were separated using Fisher's LSD test (P<0.05).

There were large differences in growing conditions among years that affected weed control performance with the tine weeder, with excessive rainfall during May and June (when initial cultivations were scheduled) in 2014 (Table 1). In addition, all field operations ceased for 17 days in October 2013 due to the Federal Government shut-down and which unfortunately coincided with peanut harvest and the delay reduced peanut yield potential. Therefore, all data were analyzed by year. Analysis of variance indicated no significant interactions among weed control, insect control, and fungal disease control for all parameters. Therefore, all data are presented as main effects.

While these results directly affect pest management decisions in organic peanut production, there are possible implications for conventional peanut production. It can be extrapolated that under certain conditions insect and fungal disease control inputs in conventional peanut production can be reduced without significant yield effects and provide savings to conventional peanut growers. To adequately address the topic of reduced pest control inputs in conventional peanut production, further research using structured trials is needed across an array of growing conditions, along with demonstration on large-scale peanut plantings.