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- Author or Editor: Bielinski M. Santos x
Field trials were conducted in Constanza, Dominican Republic to determine the most effective fungicide application programs against potato late blight, and the cost component associated to those programs. Fungicide programs were: a) chlorothalonil (1.0 kg a.i./ha) every 5, 8, 11, 14 or 17 days; b) chlorothalonil rotated with metalaxyl (1.5 kg a.i./ha) every 5, 8, 11, 14 or 17 days; c) mancozeb (1.5 kg a.i./ha) every 8 days (grower standard); and d) a nontreated control. Examined data indicated that the highest `Granola' marketable tuber weights were obtained with the rotation of metalaxyl and chlorothalonil applied every 5, 8 or 11 days (14, 9 or 6 applications/season). This same rotation every 5 or 8 days (14 or 9 applications/season) was the most effective controlling late blight. There was no correlation between disease severity and marketable yield. For the cost components, the fungicide rotation applied every 11 days reduced application costs by 29%, in comparison with applications every 8 days.
Two field studies were conducted to determine whether foliar kaolin clay applications would reduce water volumes during the establishment of bare-root strawberry (Fragaria ×ananassa) transplants. Transplant establishment treatments resulted from combinations of duration of sprinkler irrigation and foliar application of kaolin clay were: a) 4 days of sprinkler irrigation, b) 4 days of sprinkler irrigation plus kaolin clay on day 5, c) 6 days of sprinkler irrigation, d) 6 days of sprinkler irrigation plus kaolin clay on day 7, e) 8 days of sprinkler irrigation, f) 8 days of sprinkler irrigation plus kaolin clay on day 9, and g) 10 days of sprinkler irrigation (control). One day of sprinkler irrigation was defined as the application of 8 hours per day of irrigation to ensure plant establishment, using ≈6000 gal/acre per hour of water. Kaolin clay treatments were applied using a rate of 25 lb/acre and on the early morning of the following day after sprinkler irrigation was suspended. Treatments influenced the number of established plants and diameter at 4 and 8 weeks after transplanting (WAT), leaf greenness at 8 WAT, and early and total fruit weight. There were no differences in the number of established plants among treatments that received 10 days of sprinkler irrigation (control), 8 days of sprinkler irrigation followed by kaolin clay on day 9, and 6 days of sprinkler irrigation followed by kaolin clay on day 7, ranged between 97% and 98% plant survival. The highest strawberry early and total fruit weights (3.6 and 15.7 tons/acre, respectively) occurred in plots transplanted with either 6 days of sprinkler irrigation plus kaolin clay on day 7, 8 days of sprinkler irrigation plus kaolin clay on day 9, or 10 days of sprinkler irrigation. These data indicated that the addition to kaolin clay after 6 or 8 days of sprinkler irrigation improved strawberry establishment, growth, and yields to the same levels as the control treatment, while saving at least 20% of the water volume needed for establishment.
Although methyl bromide (MBr) has been phased out in developed countries, limited amounts will still be available in the United States for the next few years through critical-use exemptions. Therefore, production practices reducing MBr use are desirable from the grower and environmental standpoints. Fumigation efficacy depends on the duration of fumigants in the soil and mulch permeability; thus, field trials were conducted to compare MBr retention of low- and high-density polyethylene (LDPE and HDPE respectively) mulches with seven metallized mulches and virtually impermeable films (VIF) from different manufacturers, and to assess the effect of MBr retention on nutsedge (Cyperus rotundus and C. esculentus) control with these mulches. The compared mulches were 1) white VIF; 2) black VIF; 3) white-on-black VIF; 4) cowound VIF, which has a clear nylon layer that covers the bed and is superimposed with a layer of black HDPE mulch; 5) metallized; 6) metallized heat trap with a black stripe on the bed center; 7) metallized with a black stripe on the bed center; 8) black LDPE mulch; and 9) black HDPE mulch. All treatments received 175 lb/acre of MBr + chloropicrin (Pic; 67:33 v/v). A nonfumigated control plot covered with LDPE mulch, and a treatment covered with HDPE mulch and fumigated with 350 lb/acre of MBr + Pic were also established. Nutsedge emergence through mulches increased rapidly beginning 18 days after treatment (DAT). Nutsedge populations at 28 DAT in the nonfumigated control covered with LDPE mulch had the greatest emergence (88.8 plants/ft2), followed by LDPE and HDPE mulches with 175 lb/acre of MBr + Pic (67.0 plants/ft2), HDPE mulch with 350 lb/acre of MBr + Pic (25.0 plants/ft2), and VIF and metallized mulches with 175 lb/acre of MBr + Pic (<2 plants/ft2). There were no significant differences in fumigant retention between the metallized mulches and VIF. These mulches retained 3.7 and 1.8 times more MBr than HDPE and LDPE mulches fumigated with 175 and 350 lb/acre of MBr + Pic, respectively.
Two field trials were conducted to determine the effect of reduced methyl bromide plus chloropicrin (MBr + Pic 67:33 v/v) rates applied under two types of virtually impermeable films (VIF) on nutsedges (Cyperus spp.) and stunt nematode (Tylenchorhynchus spp.) control, and bell pepper (Capsicum annuum) crop yield. A split-plot design with six replications was established, with MBr + Pic rates in the main plots and mulch types as subplots. MBr + Pic rates were 0, 88, 175, and 350 lb/acre. Mulch types were low-density polyethylene (LDPE) mulch, Hytibar VIF, and Bromostop VIF. Results showed that there were no differences on weed and nematode control, and bell pepper fruit yield between the two types of VIF. Two exponential models characterized the nutsedge responses to MBr + Pic rates with LDPE mulch and VIF, with weed densities declining as MBr + Pic rates increased. Reducing MBr + Pic rates by one-half (175 lb/acre) under VIF provided similar nutsedge control as the full-rate (350 lb/acre) with LDPE mulch. Similar results were observed with stunt nematode, where the most effective control occurred with VIF. Bell pepper yield with LDPE mulch responded linearly to increased MBr + Pic rates. However, a logarithmic model described the response of pepper yields to the fumigant rates under VIF. The application rate of this fumigant could be effectively reduced to 25% of the commercial rate (350 lb/acre) under either VIF, without causing significant bell pepper yield losses.
‘Tasti-Lee’™ (‘Fla. 8153’) is the first tomato (Solanum lycopersicum) released in Florida exclusively for the premium specialty market, with characteristic superior flavor and elevated lycopene concentration. Research was conducted to determine the appropriate nitrogen (N) fertilization and in-row distances for ‘Tasti-Lee’ tomato and thus improving the opportunities for successful adoption for this cultivar. Three N fertilization programs and two in-row distances were tested. Total N rates (204, 239, and 274 lb/acre) were the result of the combination of 50 lb/acre of N during prebedding plus each of the following drip-applied N fertilization programs: 1) 1.5 and 2.0 lb/acre per day from 1 to 4 weeks after transplanting (WAT) and 5 to 12 WAT, respectively; 2) 1.5, 2.0, and 2.5 lb/acre per day during 1 to 2 WAT, 3 to 4 WAT, and 5 to 12 WAT; and 3) 1.5, 2.5, and 3.0 lb/acre per day during 1 to 2 WAT, 3 to 4 WAT, and 5 to 12 WAT, respectively. In-row distances were 18 or 24 inches between plants, providing 5808 and 4356 plants/acre. Early and total marketable yields of ‘Tasti-Lee’ tomato were influenced by in-row distances and N fertilization programs, but not by their interaction. The highest early marketable fruit yield was found in plots treated with the highest N rate among fertilization programs (+6%), and in plots planted 18 inches apart (+7%) in comparison with the lowest N rate and the 24-inch spacing. Tomato plots treated with the highest N rate (274 lb/acre) resulted in the largest total marketable yield (+8%). Among the in-row distances, when plants were transplanted 18 inches apart, tomato total marketable yield increased by 18% compared with 24 inches between plants.
Field trials were conducted from 1999 to 2003 to determine whether chloropicrin (Pic) stimulates nutsedge (Cyperus spp.) emergence through polyethylene mulch, and to examine at which Pic rate the stimulatory effect is maximized. Shank-injected Pic rates were 0, 50, 100, 150, 200, and 250 lb/acre. Application rates between 107 and 184 lb/acre of Pic stimulated nutsedge sprouting through polyethylene mulch by 60%, 400%, 58%, and 120% more than the nontreated control during four of the seasons. Rates above 250 lb/acre eliminated the stimulatory effect on nutsedge, reducing densities to the same levels as the nontreated control. The exact physiological mechanism of this stimulation is still unknown.
Field studies were conducted to compare the performance of several methyl bromide (MBr) alternative programs on sting nematode (Belonolaimus spp.) control and marketable yield of ‘Camarosa’ strawberry (Fragaria ×ananassa). The tested fumigation programs were 1) MBr + chloropicrin (Pic; 67:33 v/v) at 350 lb/acre, 2) Pic + metam sodium (MNa) at 300 lb/acre and 37.5 gal/acre, 3) 1,3-dichloropropene (1,3-D) + Pic at 35 gal/acre, 4) 1,3-D + Pic and dazomet at 35 gal/acre and 200 lb/acre, 5) propylene oxide at 45 gal/acre, 6) furfural + allyl isothiocyanate (AITC) at 600 lb/acre, 7) furfural and MNa at 56 and 50 gal/acre, 8) furfural + AITC at 400 lb/acre followed by four furfural applications of 6 gal/acre/injection, 9) furfural and MNa at 37 and 33 gal/acre followed by four furfural applications of 6 gal/acre/injection, 10) fosthiazate and Pic at 4.5 and 150 lb/acre, and 11) a nontreated control. The fumigation programs consisting of 1,3-D + Pic and dazomet, 1,3-D + Pic, Pic and MNa, and fosthiazate and Pic proved to be as valuable as the grower-standard MBr + Pic on strawberry plant vigor, sting nematode control, and early and total marketable yields.
The effects of different populations densities of smooth pigweed and common purslane were determined in field trials conducted in organic soils. `South Bay' lettuce was planted in twin rows on 90-cm planting beds. Weed densities used were 0, 2, 4, 8, and 16 weeds per 6 m of row (5.4 m2). Phosphorus (P) was applied broadcast (1200 kg P/ha) and banded 2 inches below each lettuce row (600 kg P/ha). Lettuce fresh weights were collected 8 weeks after emergence. Data collected indicated that P regime and density had significant effects on lettuce yield and quality. For both weeds, yield decreased as density increased. In all cases, lettuce showed greater yields at a given density when grown with P banded than when P was applied broadcast. Critical density for smooth pigweed for P broadcast was between 2 and 4 plants per 5.4 m2, whereas this critical density occurred between 8 and 16 plants per 5.4 m2 when P was banded. Yield reductions of up to 24.4% and 20.1% occurred at the highest smooth pigweed density for broadcast and banded P, respectively. Two common purslane plants per 5.4 m2 were enough to reduce lettuce yields. Banding P helped lettuce to produce significantly more within each common purslane density. Yield reductions of 47.8% and 44.3% occurred at the highest common purslane density for broadcast and banded P, respectively. Apparently, banding P gives an additional advantage to the crop against smooth pigweed and common purslane.
The effects of different smooth pigweed and common purslane removal times and two phosphorus (P) fertility regimes were studied under field conditions. Head lettuce (cv. South Bay) in organic soils low in P fertility. Smooth pigweed and common purslane were grown at a density of 16 plants per 6 m of row (5.4 m2) and five removal times (0, 2, 4, 6, and 8 weeks) after lettuce emergence. Phosphorus (P) was applied broadcast (1200 kg P/ha) and banded 2 inches below each lettuce row (600 kg P/ha). Lettuce fresh weights were collected 8 weeks after emergence. When smooth pigweed was removed after 4 weeks, significant reductions (–17%) were observed for P banding. However, these reductions occurred after 2 weeks if P was broadcast. No significant differences were observed if removal was imposed later for P broadcast, whereas lettuce yields gradually decreased as removal time was delayed. These findings indicate that P banding can counteract the negative impact of smooth pigweed on lettuce and may allow farmers to delay weed control (if necessary) for another 2 weeks without significant yield reductions. Common purslane interference did not cause significant lettuce yield reductions as compared to the weed-free control for 6 weeks when P was banded, whereas this was true for P broadcast up to 4 weeks. Phosphorus fertility regime significantly influenced the period of weed interference of common purslane with lettuce, reducing its impact when P was banded.
The standard strawberry (Fragaria ×ananassa) production system in Florida uses bare-root transplants with three to five leaves; however, commercial transplants are typically variable in size. The objective of this experiment was to study the effects of transplant crown diameter on the subsequent performance of three short-day strawberry cultivars under central Florida conditions. Trials were carried out during the 2012–13 and 2013–14 growing seasons with six treatments resulting from the combination of three cultivars and two crown diameter categories. Transplants of ‘Florida Radiance’, ‘Strawberry Festival’, and WinterStar™ were sorted into two initial crown diameter size ranges: <10 mm and >10 mm. Treatments were established in a split-plot design with cultivars as the main plot and four replications. Dry plant biomass was collected at 6 weeks after transplant (WAT). Canopy diameter and crown diameter were measured at 6 and 18 WAT and fruit harvest started at 8 WAT. There were no interactions between cultivar and initial crown diameter for any of the measured variables. For early yield, larger crowns led to 46% (3.5 Mg·ha−1) and 38% (3.9 Mg·ha−1) higher early yield than smaller crowns in 2012–13 and 2013–14, respectively. Crown diameters >10 mm also resulted in 18% (23.5 Mg·ha−1) and 27% (17.4 Mg·ha−1) higher total yields in 2012–13 and 2013–14, respectively.