Evaluation of Sulfentrazone Alone or in Combination with Other PRE and POST Herbicides for Weed Control in Tomato (Solanum lycopersicum) and Strawberry (Fragaria ×ananassa)

Sulfentrazone was recently registered for use in tomato and strawberry in Florida. Field experiments were conducted at the Gulf Coast Research and Education Center in Wimauma, FL, to evaluate PRE sulfentrazone applications when applied on flat soil 30 days before bed formation (PRE-f), on the bed top immediately before laying plastic mulch (PRE-t), applied PRE-t as a tank mix with other PRE herbicides, or PRE-t followed by POST halosulfuron or rimusulfuron (POST). Sulfentrazone did not damage the tomato and strawberry crop and had no effect on strawberry and tomato fruit yield. It was as effective as the industry standards but none of the evaluated herbicide treatments provided adequate weed control. POST halosulfuron in tomato resulted in significantly greater nutsedge control at 11 (14%) and 13 (27%) weeks after initial treatment (WAIT) compared with other treatments in Fall 2019 and Spring 2020, respectively. However, in tomato, tank-mixing sulfentrazone with S-metolachlor or metribuzin did not enhance nutsedge control. Weed control did not improve with increased rates or with the use of PRE-f followed by (fb) PRE-t applications in tomato. PRE-t sulfentrazone fb POST halosulfuron was an efficient nutsedge management option in tomato. Sulfentrazone alone did not effectively control weeds in tomato or strawberry. Increased rates of sulfentrazone with the use of PRE-f fb PRE-t sulfentrazone applications did reduce (34%) total weed density in strawberry.

Potential pollinators of Fragaria ananassa (Rosales: Rosaceae) in the Perico valleys of Jujuy (Argentina)

The aims of this study were to identify and estimate the potential pollinators of Fragaria ananassa Duch. “strawberry”, through the analysis of pollen carried out on their bodies. The study was carried out on a commercial farm in Las Pampitas, located in the Perico valleys, Jujuy province (Argentina). Floral visitors and other arthropods were sampled and identified, and their diversity was analyzed. The samples of insects selected to obtain the pollen carried were processed following the acetolysis technique. The potential pollinators of the strawberry crop were estimated by calculating the pollination probability index. The floral visitors corresponded to representatives of Hymenoptera, Diptera, Hemiptera, Lepidoptera, Coleoptera and even Araneae. Apis mellifera L. was the most frequent floral visitor and presented more strawberry pollen than other selected insects. The pollination probability index estimated that this species had a high probability of being a pollinator. Other pollinators such as Allograpta exotica Wiedemann, Halictidae, Meliponini and even Thripidae could complement the action of the honeybee. This is the first contribution to the knowledge of the pollination of F. ananassa in the agroecosystems of Jujuy.

Impact of Nitrate and Ammonium Ratios on Flowering and Asexual Reproduction in the Everbearing Strawberry Cultivar Fragaria × ananassa Albion

Ever-bearing (EB) strawberries are long-day cultivars that show perpetual flowering behavior. Compared to June-bearing short-day cultivars, EB cultivars can initiate flowers with less dependency on light and temperature levels. This leads to a more consistent flowering and fruiting pattern, making EB cultivars favorable for areas with long growing seasons. However, this flowering pattern also brings significant challenges to open-field strawberry nurseries. Consistent flower development in EB cultivars frequently leads to increased labor cost for manual flower removal on nursery ground. The alteration of flowering behavior via fertilizer regimes could be a cost-effective tool for strawberry nurseries. However, while it is known that the source of nitrogen (N) impacts strawberry flowering, its effect on strawberry propagation rates needs further investigation. The objective of this study was to investigate the impact of nitrate (NO3−) to ammonium (NH4+) ratio on flower and daughter plant production in the EB strawberry cultivar ‘Albion’ (Fragaria × ananassa c.v. ‘Albion’). Strawberry plants were grown in a completely randomized design under greenhouse conditions (26.6 °C, 16 h photoperiod). Four treatments of NO3−:NH4+ were implemented: (1) 100%:0%; (2) 80%:20%; (3) 60%:40%; (4) 50%:50%. Strawberry plants fertilized with a 60%:40% NO3−:NH4+ ratio produced 17–31% fewer inflorescences than those fertilized with 100%:0% (8.8 ± 1.19) and 80%:20% (10.3 ± 1.85) ratios. The production of daughter plants remained similar in all four treatments. Our results show that increased ratios of ammonium in combination with decreased ratios of nitrate reduce flowering of EB strawberry cultivars, while propagation rates remain consistent. These results could potentially lead to the development of fertilizer regimes for strawberry nurseries to reduce flower production in EB cultivars.

Brown Marmorated Stink Bug (Halyomorpha halys Stål.) Attack Induces a Metabolic Response in Strawberry (Fragaria × ananassa Duch.) Fruit

The polyphagous brown marmorated stink bug (Halyomorpha halys Stål.) is an important pest in many countries. Recently it was noticed that it can feed on and cause damage to strawberries (Fragaria × ananassa Duch.). The metabolic response of strawberries to brown marmorated stink bug attacks was studied. Brown marmorated stink bugs attacked strawberry fruit which had 18% lower total sugar content compared to that of the control treatment. However, organic acid content had no significant difference among the three treatments, with the exception of shikimic acid, which had the highest content in the attacked fruit. Thirty-one phenolic compounds were identified. Results showed a strong effect on secondary metabolites due to H. halys attacks. Halyomorpha halys treatment had 27% higher total analyzed phenolic content compared to the indirect Halyomorpha halys treatment. The brown marmorated stink bug significantly increased total ellagic acid derivatives (33.1% to 37% higher), hydroxycinnamic acids (22.3% higher) and anthocyanins’ (39% higher) contents. Fruit attacked by Halyomorpha halys also had higher catechin and epicatechin content than that of the control treatments. This pest had a significant influence on the plant’s secondary metabolism, and this improved our understanding of how a strawberry plant reacts to the attacks of this very important pest. H. halys-infested fruit are not suitable for commercial production, due to the production of off-flavors.

Stable Reference Gene Selection for qRT-PCR Normalization in Strawberry (Fragaria × ananassa) Leaves under Different Stress and Light-Quality Conditions

Selecting an appropriate reference gene is of crucial importance for improving the accuracy of qRT-PCR analyses. In this study, strawberry (Fragaria ananassa) seedlings were subjected to different environmental conditions including heat, cold, drought, salt, white-light, blue-light, and red-light treatments. The expression levels of seven candidate reference genes, including Fa18S, FaGAPDH, FaPIRUV, FaDBP, FaHISTH4, FaACTIN1, and FaACTIN2, in the strawberry leaves were measured by qRT-PCR. Then, four programs (geNorm, NormFinder, BestKeeper, and RefFinder) were employed as tools to evaluate the expression stability of the candidate reference genes. The results showed that the expression stability of the reference genes varied under different conditions. For the cold stress and white-light treatments, FaACTIN2 was evaluated to be the most stable reference gene. FaGAPDH should be used as the reference gene under salt-stress condition and red-light treatment. For the data normalization under drought-stress treatment, FaDBP is the recommended reference gene with the highest expression stability. FaHISTH4 was observed to be the best reference gene for data normalization under heat stress and blue-light treatment. This work provides information on selecting reference genes for accurate gene expression analyses of target genes in strawberry leaves under various abiotic stress and light-quality conditions.