In the northeastern United States, vegetable crop classes and growers' meetings are often held during winter months when field demonstrations are impossible. A pot-sized demonstration was set up in the greenhouse in May and Nov. 2002 as a student laboratory to show the effects of season extension materials on the early growth of winter squash. The treatments were black plastic mulch and rowcover, alone and in combination. The treatments were also placed on either a heated [18.3 °C (65 °F)] or unheated germination mat to simulate warmer and cooler spring soils. Butternut squash (Cucurbita moschata) was sown in 10.2 × 10.2 × 11.43-cm (4 × 4 × 4.5 inches) pots in soilless medium. The plants were grown and observed for 30 days, then harvested and weighed. The plants in the greenhouse grew as expected of plants grown under similar conditions in the field. Bottom heat, mulch, and rowcover had an increasingly greater effect on the growth of subsequent leaves as shown by comparisons of leaves 1, 2, and 3. Warmer soils tended to have the greatest effect on all measured parameters, but this was not as obvious in the May experiment as it was in the November experiment. Thus, this pot demonstration can be used in a student laboratory. The pots and plants are small enough to transport to and set up at winter growers' meetings as well.
Anne K. Carter and Roseann Stevens
`Jalapeño M' pepper (Capsicum annuum L.) seeds were soaked for 40 h in solutions of 0.0, 0.5, 1.0, 2.0, or 3.0 mM GA3 (using Release, 10% GA3) and 0.0, 1.75, 3.5, 7.0, or 10.5 mM ethephon in all combinations in petri dishes at 25 °C. The seeds were rinsed, dried for 24 hours, then germinated at either 25 or 40 °C. Thermoinhibition was induced at 40 °C, as nontreated seeds failed to germinate, but 99% of the seeds germinated at 25 °C after 7 days. Pretreatment with H2O alone partially alleviated thermoinhibition at 40 °C (41% germination). Pretreatment with ethephon alone resulted in up to 50% germination and with GA3 alone up to 79% germination. The effects of the GA3 and ethephon were additive, as the highest germination percentage (91%) at 40 °C was obtained with 3.5 mM ethephon + 3.0 mM GA3. The percentage of abnormal radicles was <1% in all treatments. Chemicals used: (2-chloroethyl) phosphonic acid (ethephon); gibberellic acid (GA3).
Anne K. Carter and Roseann Stevens
`Jalapeño M' pepper (Capsicum annuum L.) seeds were soaked for 40 h in solutions of 0.0, 0.5, 1.0, 2.0, or 3.0 mm GA3 (using Release, 10% GA3) and 0.0, 1.75, 3.5, 7.0, or 10.5 mm ethephon in all combinations in petri dishes at 25 °C. The seeds were rinsed, dried for 24 hours, then germinated at either 25 or 40 °C. Thermoinhibition was induced at 40 °C, as nontreated seeds failed to germinate, but 99% of the seeds germinated at 25 °C after 7 days. Pretreatment with H2O alone partially alleviated thermoinhibition at 40 °C (41% germination). Pretreatment with ethephon alone resulted in up to 50% germination and with GA3 alone up to 79% germination. The effects of the GA3 and ethephon were additive, as the highest germination percentage (91%) at 40 °C was obtained with 3.5 mm ethephon + 3.0 mm GA3. The percentage of abnormal radicles was <1% in all treatments. Chemicals used: (2-chloroethyl) phosphonic acid (ethephon); gibberellic acid (GA3).
Anne K. Carter and Dennis Clason
Six varieties of Cupsicum annuum, L were selected for the study (Joe Parker, NuMex Sweet, NuMex R Naky, Tam VeraCruz, Sandia, and Conquistador). All seeds were primed in -.90 MPa NaCl, -1.35 MPa NaCl; -1.24 MPa CaCl2, -1.94 MPa CaCl2, -1.43 MPa K2HPO4, -2.09 MPa K2HPO4, and a nonprimed control at 23C in an incubator for 5 days. Seeds were dried for 2 days at 23C, then planted in soilless media under a 10/14 day/night cycle in incubators at either 23C or 15C. Emergence was counted daily for 21 days. Statistical analysis was performed on the rate of emergence and the maximum number of seeds emerged by day 21. There was a significant variety × treatment × temperature interaction when the rate of emergence was used as the variable. Priming improved the rate of emergence over the control among all varieties, treatments and temperatures, but the effect of seed priming on the maximum emergence varied from one variety to the other. Priming was more effective at 15C. The start of emergence averaged 3.5 days over the control at 23C and 7.3 days over the control at 15C. Seeds emerged an average of 7 days faster at 23C than at 15C. Sandia and Conquistador appear to be sensitive to priming treatments and temperature.
Anne K. Carter and Charles S. Vavrina
The germination of five commercial cultivars of jalapeño and cayenne pepper were tested to determine cultivar response of Capsicum annuum L. to supra-optimal temperatures. Two seedlots of `Cayenne, Large Red Thick', `Ole', `Jalapeño M', `Mitla', and `Tam Veracruz' were evaluated on a thermogradient table at temperatures of 20, 25, 30, 35, and 40 °C. Percent germination and time to 50% of final germination (T50) were calculated. All cultivars exhibited thermodormancy, but the degree of inhibition varied within temperature and cultivar. No cultivar had >1.0% germination at 40 °C. Generally, the T50 varied among cultivars, but not among temperatures within a cultivar (T50 at 40 °C was not measured). Cultivar selection should be considered when growing fall transplants in Florida.
Anne K. Carter and Roseann A. Stevens
Thermoinhibition has been observed in chile (Capsicum annuum L.) transplants grown in greenhouses in southern climates. Hormones have been used successfully as a treatment for thermoinhibition in other vegetable crops. This experiment examined the effects of Ethrel and Release as treatments to improve germination in chile seeds germinated at a supraoptimal temperature. Seeds of `Jalapeno M' were soaked in solutions of Ethrel at 1.75, 3.0, 7.0, or 10.5 mM concentration or Release at 0.50, 1.0, 2.0, or 3.0 mM concentration, or 16 different combinations of the two growth regulators. The seeds were soaked in the treatment solutions for 40 hours at 25°C. A H2O-soaked and a non-soaked control were also included. Afterwards, the seeds were rinsed, dried, then germinated in 25°C or 40°C incubators. At 25°C, all treatments reached 98% germination or better after 10 days, indicating that none of the treatments were detrimental to germination. At 40C, germination percentages amongtreatments ranged from 0% for the nonsoaked control to 90% for a Release–Ethrel combination. Generally, the combination treatments resulted in germination percentages higher than either Ethrel or Release used alone. Results of these tests in petri dishes indicate the possibility of growth regulators being used to overcome thermoinhibition in chile. A greenhouse study is underway.
Matthew T. Rulevich, Francis X. Mangan, and Anne K. Carter
Field studies were conducted in 1998 and 1999 in Massachusetts to assess the effects of transplants, black polyethylene mulch, and polyester spun-bonded row cover on early fruit set and total yield of two squash (Cucurbita moschata Duchesne) cultivars: `C42 × La Segunda' calabaza and `Waltham' butternut. Treatment comparisons included direct-seeded or transplanted squash, with or without black polyethylene mulch, and with or without the addition of a row cover in all combinations. The use of transplants was more effective at stimulating early fruit set and highest total yield than the use of mulch and row cover. The initiation of fruit set using transplants was advanced 9 days relative to direct-seeding. Mulch and row cover treatments significantly advanced early fruit set by 7 and 5 days, respectively, but only in 1998. Yields for both winter squash were 45% higher using transplants compared to direct seeding, 19% higher using mulch compared to bare soil, and 16% higher using row cover compared to no row cover. Total yields were higher for both cultivars in 1999 (warm, dry season) than in 1998 (cool, wet season). Use of transplants with plastic and row cover compared to the use of direct seed with neither plastic nor row cover increased yield of calabaza by 100% in both 1998 and 1999. Only the direct seeded plus plastic plus row cover treatment had yields that were similar to any of the transplanted treatments. Transplant treatments also increased number of fruit per plant and fruit size for both calabaza and butternut.
Rosalind Cook, Anne Carter, Pamela Westgate, and Ruth Hazzard
Corn oil and Bacillus thuringiensis ssp. kurstaki (Bt) applied directly into the silk channel of a corn ear has been shown to be an effective pesticide against corn earworm, Helicoverpa zea (CEW), and european corn borer, Ostrinia nubilalis (ECB). Field studies were conducted in 2000 and 2001 to determine the influence of application timing on ear quality at harvest. Two blocks of corn were planted during each year to observe treatment effects under varying populations of the two insect species. The treatment consisted of 0.5 mL (0.017 floz) of food grade corn oil containing a suspension of Bt at 0.08 g (0.003 oz) a.i. per ear applied directly into the silk channel at the husk opening. One treatment application was made on each silk day 3 through 11 from first silk; silk day 1 was the first day that 50% or more of ears had 2.5 cm (1 inch) of silk protruding from the husk. One treatment did not receive the oil + Bt suspension. All ears were harvested at milk stage, on silk day 25. The number of CEW larvae in treated ears increased with later application days in 2000, but not in 2001. Damage from larval feeding was mainly found near the tip of the ear, and damage ratings were lower compared to untreated ears for all treatment days for both plantings in 2000, and through application day 8 in the late planting of 2001. ECB larvae were reduced for all treatment days in both plantings in 2000 and the late planting of 2001. The percentage of ears rated as marketable (i.e., free of feeding damage) ranged from 71% to 100% in treated plots compared to 30% to 77% in the untreated plots. There was a linear decrease in marketability with later application days in two of the four plantings. The greatest decrease in marketability was after application day 7. Because the oil application affects kernel development at the tip, the length of ear with under-developed kernels, or cone tip, was measured. The number of ears with cone tip decreased linearly with the later application days in all plantings. There was 10% conetip or less after day 7 in 2000 and day 6 in 2001. The best combination of effective insect control resulting in the highest rates of marketable ears with the least degree of cone tip was achieved in this experiment by application of oil + Bt suspension on day 7. Year to year variation in the environment would suggest a range from day 6 to 8.
Rosalind Cook, Anne Carter, Pam Westgate, and Ruth Hazzard
Field studies were conducted in 2000 and 2001 to rate the efficacy and longevity of four pesticide treatments against corn earworm (Helicoverpa zea) larvae (CEW) in sweet corn (Zea mays). The four treatments used were 1) corn oil, 2) Bacillus thuringiensis ssp. kurstaki (Bt), 3) oil + Bt, and 4) an untreated plot. All treatments were applied on silk day 5. Silk day 1 was the first day that more than 50% of the ears had 2.5 cm (1 inch) or more silks emerging from the husk using a hand-held pump applicator. Two first-instar CEW larvae were placed directly into silk channel of selected ears on 6 different days (days 3, 6, 9, 12, 15, and 18 after first silk). The same six ears were then harvested 4 days later. Untreated ears had more live CEW and higher levels of feeding damage than the other three treatments ears for all harvest days in both years. The number of CEW found per ear was lower when Bt was included in the treatment. The use of corn oil gave the lowest damage ratings on almost all harvest days in both years. Treatments which contained oil had the highest number of marketable ears in both years, but also the highest percentage of underdeveloped kernels at the tip of the ear (6% to 9%). The oil and Bt treatments appeared to control CEW for at least 17 days, from silking through maturity. This treatment regime appears to be a promising alternative for growers to conventional pest management methods.