A survey of weed flora and basic weed management practices was conducted in commercial strawberry [Fragaria × ananassa (Weston) Duchesne ex Rozier ssp. ananassa] fields in central Florida during the 2019 to 2020 field season. Forty-one fields on 14 farms were surveyed, which represents a total of 907 ha or 23% of the acreage planted to strawberries in Florida. All conventional fields were fumigated, and combinations of chloropicrin and 1,3-dichloropropene were used on 72% of the fumigated acreage. Preemergence or postemergence herbicides were used in row middles on 100% of the conventional acreage, but preemergence herbicides applied under the plastic mulch were only used on 12% of the acreage. A total of 47 weed species were identified during the survey. The five weed species with the highest frequency were goosegrass [Eleusine indica (L.) Gaertn.], cutleaf evening primrose (Oenothera laciniata Hill), Carolina geranium (Geranium carolinianum L.), common ragweed (Ambrosia artemisiifolia L.), and eclipta [Eclipta prostrata (L.) L.] which occurred in 83%, 63%, 58%, 58%, and 46% of all fields surveyed, respectively. The five species with the highest overall relative abundance were E. indica, O. lanciniata, G. carolinium, A. artemisiifolia, and Brazil pusley (Richardia brasiliensis Gomes). The frequency and distribution of E. indica is of particular concern, because populations in strawberry fields are thought to be resistant to paraquat, which is the primary herbicide used for crop termination. Weed density tended to be low overall, which suggests the integrated weed management (IWM) programs adopted by most growers are effective. Mean weed density tended to be similar on conventional and organic fields and unaffected by fumigant applied the year of the survey or the number of years strawberries had been grown consecutively in a field. Weed management research moving forward should focus on the development of IWM programs for E. indica, O. lanciniata, G. carolinium, and A. artemisiifolia.

Methyl bromide (MBr) has been an industry standard for soil fumigation in a multitude of crops for decades. However, it has been banned by the United Nations Environment Programme, and alternatives to MBr must be implemented to sustain productivity in many vegetable crops that depend on soil fumigation. One alternative that has been implemented in some areas is methyl iodide (MeI). Efficacy of MeI has been demonstrated on many pest species and has been generally similar to MBr. Methyl iodide is a costly material, which has likely limited its adoption. Virtually impermeable film (VIF) and totally impermeable film (TIF) provide greater fumigant retention than low-density and high-density polyethylene film, which can allow for reduced fumigant application rates while maintaining fumigant efficacy. The objectives of this research were to evaluate TIF with reduced rates of shank-applied MeI : chloropicrin (Pic) (50 : 50 w/w) for the control of yellow nutsedge in tomato. Treatments included a standard rate of MeI : Pic (93.3 L ha−1 [178 kg ha−1 broadcast]) under VIF and TIF, three reduced rates (37.3, 56, 74.6 L ha−1 [71.2, 106.8, 142.5 kg ha−1 broadcast, respectively]) under TIF, and a nontreated control under TIF. Results indicate fumigant use rates may be reduced from a standard 93.3 L ha−1 under VIF to 37.3 L ha−1 (60% reduction) under TIF while providing yellow nutsedge control and maintaining tomato yields.

Methyl bromide (MBr) was widely used as a soil fumigant to manage pests in the planting bed prior to transplanting fresh market tomato; however, it has been banned by the United Nations Environment Programme. Alternatives to MBr must be implemented to sustain productivity in fresh market tomato. Dimethyl disulfide plus chloropicrin (DMDS : Pic) is a fumigant alternative to methyl bromide for the management of yellow nutsedge and other soil-borne pests in tomato. Fumigant costs, environmental concerns, and risk mitigation measures encourage reduced fumigant application rates. Virtually impermeable film (VIF) and totally impermeable film (TIF) provide greater fumigant retention than low density and high density polyethylene film, VIF and TIF can allow for reduced fumigant application rates while maintaining fumigant efficacy. The objectives of this research were to evaluate TIF with reduced rates of shank-applied DMDS : Pic (79 : 21 w/w) for the control of yellow nutsedge in tomato. Treatments included a standard rate of DMDS : Pic (468 L ha−1) under VIF and TIF, a high rate (561 L ha−1) under VIF, three reduced rates (187 L ha−1, 281 L ha−1, and 374 L ha−1) under TIF, and a nontreated control under TIF and VIF. Results indicated rates may be reduced from a standard 468 L ha−1 under VIF to 187 L ha−1 (67% reduction) under TIF while maintaining yellow nutsedge control and tomato yields. In addition, the results indicated that nontreated TIF managed yellow nutsedge better than nontreated VIF because of decreased penetration of the mulch by yellow nutsedge.

A survey was conducted in 2000 across 38 counties in Mississippi on 192 randomly selected soybean fields to assess the most common occurring weeds. Statewide, prickly sida, which was present in 40% of the fields sampled, was the most common. Pitted and entireleaf morningglory were present in 34 and 29% of the soybean fields, respectively. Broadleaf signalgrass and barnyardgrass were the most common annual grasses, and yellow nutsedge was the most common sedge observed. Trumpetcreeper and redvine were the most common perennial vines. In the Mississippi Delta region of Mississippi, prickly sida was present in 45% of the fields sampled. The trend of occurrence of other species in the Delta mirrored statewide results. In eastern Mississippi, prickly sida and broadleaf signalgrass were found in 43% of soybean fields. Sicklepod, common cocklebur, and balloonvine were more prevalent in eastern Mississippi, when compared with the Mississippi Delta. Since 1982, there has been a sevenfold decline in the occurrence of common cocklebur and a fourfold decline in the occurrence of johnsongrass in Mississippi soybean. Also, the occurrences of redroot pigweed, common ragweed, and fall panicum have declined. Conversely, the occurrences of yellow nutsedge and broadleaf signalgrass have increased. The occurrences of barnyardgrass, prickly sida, redvine and trumpetcreeper have been relatively static over the past two decades.