The Response of Iranian Melon (<i>Cucumis melo</i> L.) Accessions to 2,4-D Drift

One of the most widely used auxinic herbicides in southern Iran’s cereal crop fields is 2,4-D; however, the concurrent growing season of off-season melons in this region potentially leads to herbicide drift from cereal fields to the melon fields. To study the response of some Iranian wild melon accessions to three simulated drift rates of 2,4-D, including 112.1, 11.2, and 3.7 g ae ha−1, a field experiment was conducted during 2019 and 2020 growing seasons. It was found that by increasing the herbicide rate from 3.7 to 112.1 g ae ha−1, the level of visual injury increased in all accessions. However, significant variation in herbicide tolerance was observed among different melon accessions. The MEL-R1 was the most tolerant accession with only 20% injury, while MEL-D8 displayed very high injury rate (ca. 90%) as assessed at 6 weeks after treatment during 2019. The accession MEL-S3 was the most tolerant to 2,4-D drift rates (20% injury) at 6 weeks after treatment during 2020. There was no significant difference between the accessions MEL-R1 and MEL-S3 in terms of their response to 2,4-D treatment during both years of the study, as these accessions fully recovered from injury over 6 weeks after herbicide treatment. In addition, only these two accessions were able to produce yield after the application of 2,4-D at the highest rate tested (112.1 g ae ha−1). Therefore, the melon accessions MEL-R1 and MEL-S3 could be recommended for cultivation and even for breeding programs in order to develop 2,4-D-tolerant commercial cultivars in regions where this herbicide is commonly used in cereal crop production adjacent to the melon fields

The Response of Iranian Melon (Cucumis melo L.) Accessions to 2,4-D Drift

One of the most widely used auxinic herbicides in southern Iran’s cereal crop fields is 2,4-D; however, the concurrent growing season of off-season melons in this region potentially leads to herbicide drift from cereal fields to the melon fields. To study the response of some Iranian wild melon accessions to three simulated drift rates of 2,4-D, including 112.1, 11.2, and 3.7 g ae ha−1, a field experiment was conducted during 2019 and 2020 growing seasons. It was found that by increasing the herbicide rate from 3.7 to 112.1 g ae ha−1, the level of visual injury increased in all accessions. However, significant variation in herbicide tolerance was observed among different melon accessions. The MEL-R1 was the most tolerant accession with only 20% injury, while MEL-D8 displayed very high injury rate (ca. 90%) as assessed at 6 weeks after treatment during 2019. The accession MEL-S3 was the most tolerant to 2,4-D drift rates (20% injury) at 6 weeks after treatment during 2020. There was no significant difference between the accessions MEL-R1 and MEL-S3 in terms of their response to 2,4-D treatment during both years of the study, as these accessions fully recovered from injury over 6 weeks after herbicide treatment. In addition, only these two accessions were able to produce yield after the application of 2,4-D at the highest rate tested (112.1 g ae ha−1). Therefore, the melon accessions MEL-R1 and MEL-S3 could be recommended for cultivation and even for breeding programs in order to develop 2,4-D-tolerant commercial cultivars in regions where this herbicide is commonly used in cereal crop production adjacent to the melon fields

Integrated Use of Herbicides and Mulching for Sustainable Control of Purple Nutsedge (<i>Cyperus rotundus</i>) in a Tomato Crop

Purple nutsedge (Cyperus rotundus L.) is a problematic weed in tomato (Lycopersicon esculentum L.) crops causing significant yield losses. Although several chemical options are available for this weed, the level of control is often unsatisfactory, and the consistent use of herbicides has a risk of resistance evolution. Therefore, we evaluated the efficacy of two herbicide options, halosulfuron and fomesafen + S-metolachlor, alone or integrated with natural and plastic mulches in controlling purple nutsedge in tomato crops in a three-year field study. The use of herbicides or mulches alone did not provide effective weed control (below 65%). However, the combination of natural mulch and fomesafen + S-metolachlor provided the most effective weed control by reducing the density and biomass of purple nutsedge by up to 83% and 81%, respectively, as compared with the season-long untreated control. The use of a natural mulch in combination with the herbicides halosulfuron or fomesafen + S-metolachlor also resulted in the highest tomato yield (ca. 3.3 kg per plant). This integrated treatment improved tomato yield by over 400% as compared with the season-long untreated control. The integrated use of a plastic mulch and two chemical options resulted in a 67–74% weed biomass reduction and a 332–368% yield increase over the season-long untreated control. These findings suggest that the combinations of herbicides and mulches are effective integrated weed management options for purple nutsedge in tomato crops

<b>The susceptibility of various watermelon (</b><b><i>Citrullus lanatus</i></b><b>) accessions to 2,4-D drift</b>

Due to the widespread application of 2,4-D in controlling the broadleaf weed species in southern cereal crop production systems of Iran, a risk of non-target drift threatens the watermelon crops in these regions. A 3-yr field experiment (2019-2021) was conducted to evaluate the susceptibility of sixteen Iranian watermelon accessions to the use of three 2,4-D drift doses. The WA-H712 was the least sensitive accession to 2,4-D doses of 3.7, 11.2, and 112.1 g ae ha-1 with the lowest herbicide injury of 15, 10, and 5%, respectively, when observed at 8 wk after treatment. Only the plants of accession WA-H712 tolerated the herbicide damage and produced economic yield after the application of 2,4-D at the drift dose of 112.1 g ae ha-1. The lower doses of 3.7 and 11.2 g ae ha-1 reduced the yield of this accession by only 10 and 20%, respectively, compared with untreated control. Therefore, based on these results, watermelon accession WA-H712 could be grown in areas prone to drift doses of 2,4-D. This accession can also serve as a genetic resource in conventional or modern breeding programs to introduce 2,4-D-tolerant cultivars of watermelon.</p