A study was conducted in subtropical south Texas in 1989 to determine the effects of planting method, polyethylene mulch, and rate of drip irrigation on cantaloupe growth, yield and quality. Irrigation at .25, .50, .75, 1.0, or 1.25 times pan evaporation had little effect on soil moisture or yield, with all water application levels keeping the soil close to field capacity. Transplanting vs. direct seeding enhanced early vine growth and caused earlier yield, although direct seeded plants later caught up and had final cumulative yields slightly higher than the transplants. Black polyethylene mulch also improved earliness and reduced the number of culls compared to bare soil, but at the lowest watering level total yields were reduced by the mulch due to deflection of the rainfall received. The combined practices of transplanting and polyethylene mulch caused approximately a 9 day earliness advantage over the treatment that was direct seeded on bare soil although final yield was unaffected. Soil salinity buildup may cause problems which would affect the position of the drip line and the frequency and amount of water applied.
Robert Wiedenfeld, Eden Hinojosa, and Robert Stubblefield
Milton E. McGiffen Jr., Steven A. Fennimore, W. Thomas Lanini, and Carl E. Bell
The Food Quality Protection Act may result in the withdrawal from use of many herbicides in the “minor” crops: fruits, vegetables, herbs, flowers, and ornamentals. An obvious mitigation strategy is to test and register newer, low-rate herbicides that are currently used only in large-acreage field crops. The newer herbicides have low mammalian toxicity, few off-target effects, and are often used at rates of less than 0.1 kg/ha. Many of the older herbicides are applied at rates of several kg/ha and have off-target effects that can make their use problematic. Low-rate herbicides could replace the older chemicals commonly used in horticultural crops. We have tested several promising low-rate herbicides: carfentrazone, cloransulam, dimethenamid, halosulfuron, rimsulfuron, and sulfentrazone. Broccoli, cantaloupe, carrot, lettuce, onion, spinach, and processing tomato varieties were screened for tolerance to low-rate herbicides at four locations in California that included desert, inland, and coastal environments. All of the crops tested had tolerance for one or more of the low-rate herbicides. Data on similar tests for other horticultural crops will also be presented. The potential for registering these herbicides in vegetables and other horticultural crops varies with the crop and the pesticide's manufacturer. Pesticides that may soon face removal from widespread use will be reviewed. Herbicides and other potential alternatives to currently registered herbicides will be examined to determine possible practical alternatives for specific crops and weeds.
J. Farias-Larios, M. Orozco, S. Guzman, and A. Gutiirrez
Sweetpotato whitefly (Bemisia tabaci Gennadius) is one of the serious pests on cucurbits and causes injury by sucking sap and by the transmission of virus. In Western Mexico, melon and other vegetable crops have been subjected to losses as a results of whitefly feeding and whitefly-transmitted virus infection. Traditional control is based in the Metamidophos and Endosulfan applications (more than 10 times). Recently, Imidacloprid has been reported as new alternative to whitefly control. Thus, this study was conducted to determine the effect of Imidacloprid under different applications methods on sweetpotato whitefly populations and cantaloupe yield. Ten treatments were evaluated: 1) seed + basal stem, 2) seed + soil at 8 cm, 3) seed + soil (near to seed), 4) seed + soil (seedlings emergence), 5) seed only, 6) basal stem, 7) soil (plant emerged), 8) foliage, 9) Metamidophos and Endosulfan (regional application), and 10) control, without application. These were arranged in a randomized complete-block design with four replications. Each replication had four beds 7.5 m long. Number of whitefly adults was determined weekly on 24 plants selected at random for each treatment (two leaves/plant). At 22, 39, 57, and 73 days after showing, the whitefly nymphs/cm2 were also counted. Imidacloprid applied to foliage five times showed the best whitefly control during the entire crop season, reducing injury and increasing melon yield at 1346.7 cartons/ha, while Metamidophos and Endosulfan showed an intermediate effect (1073.6 cartons/ha).
L.P. Brandenberger and R.P. Wiedenfeld
The squash leaf curl virus (SLCV), transmitted by the sweet potato whitefly (Bemesia tabaci biotype B), is widespread on fall-planted watermelon in the Rio Grande Valley and Coastal Bend areas of south Texas. The objective of the study was to evaluate colored mulches for their effects on whitefly populations, virus incidence, and watermelon yield. Eleven polyethylene films were included as treatments in both a spring and fall study and were replicated five times in a randomized block design. Plastic mulches caused substantial improvement in melon yields (40%) in the spring crop, similar to responses obtained in other studies on cantaloupes. Fall yield increases due to the use of mulches did not occur. Whitefly populations were much lower in 1996 than they have been in previous years, therefore this was not an adequate test of its effects on whitefly behavior. Even so, there were indications in the fall crop that the use of plastic mulch tended to result in lower whitefly numbers. No evidence was found of any difference between the various mulch materials regarding whitefly counts.
Gary W. Elmstrom and Donald N. Maynard
Muskmelon (Cucumis melo L. reticulatus group), commonly called cantaloupe by growers, shippers, and consumers is a relatively minor crop in the southeastern U.S. The principal restraint on increased muskmelon production in this area is the lack of varieties that consistently produce high quality fruit. Resistance to both fruit rots, especially those induced by Fusarium, and foliar diseases such as downy mildew, powdery mildew, and gummy stem blight are also important because of the high humidity and frequent rainfall common to this area. The ideal shipping variety should have the capacity to produce high yields of round to oval, sutureless, heavily netted fruit that average 1.4 kg each, and that have a deep salmon-colored flesh, a small tight seed cavity, high soluble solids, and a pleasant taste and aroma. Evaluations at Leesburg and Bradenton, Florida over a three-year period have identified several western-type muskmelons well-adapted to this area. `Explorer', `Goldmark', `Mission', and `Tasty Sweet' ranked high in most of the categories mentioned above and should be evaluated in more extensive trials, which should include a study of postharvest quality.
Penelope Perkins-Veazie, Julie Collins, Richard Hassell, Steve Olson, Donald Maynard, Jonathan Schultheis, Missy O'Hern, Toni Magby, and Shelli Magby
Mini watermelons are the size of cantaloupes and weigh 1.5 to 3 kg (4 to 8 lbs). Melons of 18 selections were grown in replicated trials in North Carolina, South Carolina, and north and south Florida. Melons were harvested when ripe, and samples of heart and locule tissue were frozen and sent to Lane, Okla. A total of 960 samples, representing 6-12 melons per selection per location, were analyzed for total lycopene content using colorimeter and spectrophotometer methods. Subsamples of `Mohican', `Hazera 6007', `Vanessa', `Petite Treat', and `Precious Petite' were analyzed by HPLC for carotenoid profiles. Total lycopene content ranged from 52 to 108 μg·g-1, depending on variety. Selections were grouped into two levels of lycopene content. The varieties Precious Petite, Petite Perfection, Betsy, Bonny, Petite Treat, Valdoria, Vanessa, Hazera 5133 and 5138, RWT 8149, 8155, 8162 had 60 to 79 μg·g-1 lycopene and the varieties Hazera 6007, 5123, 5109, 5177, Mohican, and Extazy had 80 to 100 μg·g-1. Melons harvested from the Florida locations had more total lycopene than those from North and South Carolina. `Precious Petite' had more β-carotene as a percentage of total carotenoids than other varieties tested. These results indicate that lycopene content is affected primarily by germplasm and also by environment.
Delays in transplanting vegetable seedlings are often a problem due to cold, wet spring weather. This results in the production of overgrown transplants, which are more difficult to transplant and often do not survive. The objective of this study was to find a non-chilling temperature at which to short-term-treat transplants in order to slow down vegetative growth. `Superstar' muskmelon and `Royal Jubilee' watermelon seedlings were greenhouse-grown at 20°C during Mar. 1996. Fifty-cell trays of transplants were grown to the first true leaf stage and then held in a dark cooler at 7.5 or 12.5°C for 4 to 8 days. Control plants were kept in the greenhouse. Transplants were repotted into larger pots after the treatment. Preliminary experiments revealed that 8 days of 7.5°C was too severe of a temperature for watermelon and cantaloupe transplants. Six days of 7.5°C was effective in significantly reducing stem and leaf area growth without seedling death for both types of melons. Shorter durations at 7.5°C or the same duration at 12.5°C was less effective in retarding stem elongation. Surface area of the transplant leaves, after the reduced temperature treatment and subsequent growth, was much more sensitive to a drop in temperature and the length of temperature treatment. In 1997, these treatments will be repeated in the greenhouse and also in the field.
Joseph G. Masabni
Halosulfuron (Sandea 75WG) is labeled for pre- or posttransplant use in tomato, cucumber, cantaloupe, among other vegetable crops. For pretransplant usage, the label specifies a 7-day waiting period after halosulfuron application under the plastic mulch before transplanting tomatoes. This period may be too long for growers who are busy in the spring with planting and pesticide sprays while on a race with the constantly changing climate of early spring. Experiments were conducted in the last 2 years to determine whether transplanting tomato within 7 days of halosulfuron application had any deleterious effects on tomato. In 2003, tomatoes were transplanted daily from day 0 through 7. Plant survival and height were collected. Tomato plants survived all dates of transplanting treatments. Plant height indicated that plants transplanted early were taller than those transplanted late, only because they had more time to establish and grow in the field. There was no adverse effect to tomato growth. In 2004, tomatoes were set on a 2-day interval from day 0 through 10 after halosulfuron application under the plastic mulch. Plant height, visual rating, % early blight infection, and yields were collected. A severe early blight infection confounded the results of herbicide applications. Still, it was clear that halosulfuron 0.026 or 0.051 kg a.i./ha had no effect on plant height or visual rating. Yields were not statistically different from those of the control, when the effect of early blight was factored out.
J. Farias Larios, J. G. López Aguirre, E. Rincón Cruz, and F. Radillo Juarez
Since 1980, farmers from western Mexico have cultivated melon cantaloupe; however, during the past few years, they have seen the better advantages of honeydew melon. Some of them represent a good alternative to farmers because chemical products and labor costs are reduced, and because they are tolerant to several diseases. The purpose of this experiment was to evaluate 15 new hybrids of honeydew melon in western Mexico. The hybrids evaluated were: Dey Break, Hmx 4596, Hmx 4595, Hmx 4607, Sunex 7051, Rocio, creme de menthe, Silver world, Emerald sweet, Sme 5303, Sme 5302, Santa Fé, PSR 10994, and PSR 8994, Honey Brew was test. Fifteen -day-old plants were transplanted by hand. Treatments were replicated four times in a randomized complete-block design. Beds 1.2 m wide and 7.0 m long were prepared, 1.5 m between beds, distance plant-plant 0.5 m (plant density ≈13,332 plant/ha). Results show that yield of SME 5302, SME 5303, HMX 4596, Rocío, Dey Break, PSR 8994, Sunex 7051, and HMX 4607 had a yield higher of 50 t/ha, Emerad sweet had more number fruit (59 per 10 plants), whereas SME 5303, SME 5302 and Silver world had higher fruit weight (>1.719 gr). We suggest the evaluation of these hybrids in other regions to know the adaptation to different conditions and to select the best in commercial quality and production.
L.A. Wasilwa, T.E. Morelock, and J.C. Correll
Anthracnose is a destructive foliage and fruit disease of cucurbits worldwide, particularly on cucumber, watermelon, and cantaloupe. Three fungal taxa have been implicated in the cucurbit anthracnose complex [Colletotrichum orbiculare (CO), C. magna (CM), and the putative teleomorph Glomerella cingulata var. orbiculare (GC)]. In the past 7 years we have assembled a large geographically diverse collection of cucurbit isolates that have been characterized for virulence, vegetative (heterokaryon) compatibility, and mitochondrial and nuclear DNA RFLPs. All isolates that are pathogenic on cucurbit foliage are CO, belong to one of the four VCGs, and belong to a single mtDNA RFLP haplotype. Three races of CO (1, 2, and 2B) can be distinguished by their disease reactions on cucumber (`Marketer' and `H19') and watermelon (`Black Diamond' and `Charleston Gray') differentials. Race 1 (cucumber pathogen) and race 2 (watermelon pathogen) were the most common. Examination of virulence on cucurbit fruit indicates that CM and GC are more aggressive than CO, indicating that they could primarily be fruit-rot pathogens. Race 1 and 2 have been used effectively for screening disease resistance in cucumber and watermelon. Isolates of CM, GC, and Colletotrichum spp. recovered from fruit lesions were not pathogenic or were weakly virulent on cucurbit foliage and were diverse with regard to VCGs, nuDNA, and mtDNA RFLPs. However, CM and GC were more virulent on cucurbit fruit than CO.