In each of 3 years, the average number of thrips in tomato (Lycopersicon esculentum L. cv. Mountain Pride) blooms was greater on tomatoes grown on white plastic mulch than on tomatoes grown on black plastic mulch, aluminum plastic mulch, or bare ground. Early season differences, however, diminished with time as plants grew and shaded a larger portion of plastic mulch. Weekly applications of 12 insecticide treatments failed to reduce thrips populations below that found in the control. No significant differences were found among treatments in the quantity, quality, or earliness of tomato yields. Incidence of tomato spotted wilt (vectored by some thrips species) was too low to detect statistical differences or determine the importance of thrips population in disease epidemiology. Western flower thrips (Frankliniella occidentalis) was the most common species found, followed by eastern flower thrips (F. tritici) and tobacco thrips (F. fusca). Thrips control, in the absence of tomato spotted wilt, is not justified for the thrips populations encountered in this study.
Saintpaulia ionantha `Utah' plants were grown in growth chambers at constant 15, 20, 25, and 30°C temperatures and daily photosynthetic irradiances of 1, 4, 7, and 10 mol1 m-2 day-1 delivered by 23, 92, 161, and 230 μmol m-2 s-1 for 12 hours. Models were developed describing leaf unfolding rate (LUR) and flower development rate (FDR) as a function of temperature and irradiance by recording the dates of leaf unfolding and flower opening over the course of the experiment and then calculating rates using regression. Both LUR and FDR increased as temperature increased from 15 to 25°C and then decreased. Both LUR and FDR increased as irradiance increased from 1 to 4 mol m-2 day-1. Increasing daily irradiance above 4 mol m-2 da y-1 did not significantly increase LUR or FDR. Model validation data are being collected from plants growing under 3 irradiance levels in greenhouses maintained at 15, 20, 25, and 30°C air temperatures.
Stock plant productivity is an important concern for growers of ‘Snow Angel’ coral bells (Heuchera sanguinea) because this variety produces a limited number of basal cuttings. The objective of the study was to determine the best growth substrate and container size combination to maximize productivity of stock plants. A secondary objective was to determine if the stock plant treatments influenced the rooting of vegetative cuttings. The study used three different container sizes (2.8, 11.4, and 14.6 L) and four commercial soilless substrates that were primarily composed of the following: bark, peat, and perlite (substrate 1); bark, peat, and vermiculite (substrate 2); bark, peat, and coarse perlite (substrate 3); and peat (substrate 4). Two stock plant experiments were conducted using the same 12 treatment combinations, and a subset of those stock plants was randomly selected for the rooting studies that immediately followed each stock plant experiment. Stock plants responded to substrate treatments differently depending on the batch of substrate in which they were grown. The most successful stock plants, which produced more cuttings per plant and per square foot, as well as larger cuttings, were those grown in substrate 3 (Expt. 1) and substrate 2 (Expt. 2). Regardless of the substrate, the highest number of cuttings per square foot was obtained from stock plants grown in 2.8-L containers, indicating that the smaller containers allow for the most efficient use of space when growing ‘Snow Angel’ stock plants for 6 to 8 months. The rooting of vegetative cuttings was successful (98% to 100% of cuttings rooted after 4 weeks under mist) for all treatment combinations, although higher numbers of visible roots were produced during the second study and may be due to larger fresh weights of cuttings.
The use of plastic mulch and spunbonded row covers in melon production has increased in the past decade (2, 3,5). Research has shown that muskmelon (Cucumis melo L.) and watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] can be grown successfully with black plastic mulch (BPM) and/or row covers. When row covers are used in combination with BPM, higher yields and earlier maturity of some crops are achieved than when BPM is used alone (1, 2, 5). Though numerous studies (1, 2, 4) have reported the benefits of black plastic mulch and row covers in melon production, information is limited on response of melons using these materials with different planting methods. The objective of this study was to investigate the effect of BPM and row cover on direct-seeded and transplanted muskmelon production.
Cropping systems were compared among vegetable crops which are commonly grown for profit on a 5–10 ha farm. Tomato [Lycopersicon esculentum (Mill.) ‘Jet Star’], cabbage [Brassica oleracea (L.) var. capitata ‘Sunup’], collards [Brassica oleracea (L.) var. acephala ‘Vates’], and muskmelon [Cucumis melo (L.) ‘Gold Star’] were monocropped; cabbage was intercropped with tomatoes; and collards were intercropped with muskmelon. Crop yield, production cost, and economic returns of the intercrop system were comparable to those of the crops produced alone.
Double-cropping systems were compared to the same vegetable monocropped. Snap beans [Phaseolus vulgaris (L.) ‘Bush Blue Lake’], sweet corn [Zea mays (L.) ‘Sundance’], cauliflower [Brassica oleracea (L.), Botrytis group, ‘Snow Crown’], summer squash [Cucurbita pepo (L.) ‘Zucchini Elite’], and broccoli [Brassica oleracea (L.), Italica group, ‘Green Comet’] were used. The double-crop systems used were spring snap bean and fall cauliflower, summer squash and fall broccoli, and spring sweet corn and fall snap beans. The monocrop system was used as a control for the double-crop systems. The greatest net returns were: 1) squash monocropped or squash/broccoli double-cropped, 2) squash double-cropped, 3) cauliflower or cauliflower/snap bean double-cropped, and 4) broccoli or cauliflower or snap beans monocropped. Fall snap beans provided the least economic return. The double-cropping system allows an option of crop production with a potential increase in yield and economic returns using half the amount of land per year required for either crop grown in monoculture. In addition, these systems reduce the risk of economic failure during a year of low-market demand for either crop grown alone.
Stock plant productivity is an important concern for growers of mojave sage (Salvia pachyphylla) because this species produces more woody growth as the plant ages. The objective of the study was to determine the best growth substrate and container size combination to maximize stock plant productivity. A secondary objective was to determine whether the stock plant treatments influenced the rooting of vegetative cuttings. Three different container sizes (3, 12, and 15.5 qt) and four soilless substrates composed primarily of bark, peat, and perlite (substrate 1); bark, peat, and vermiculite (substrate 2); bark, peat, and coarse perlite (substrate 3); and peat (substrate 4) were used. The stock plant experiment was conducted using 12 treatment combinations, and a subset of those stock plants was selected randomly for the rooting study that immediately followed the stock plant experiment. Stock plants responded to substrate treatments differently. The most successful stock plants, which produced more cuttings per plant and per square foot, as well as larger cuttings, were those grown in substrate 3. Regardless of substrate, the highest number of cuttings per square foot was obtained from stock plants grown in 3-qt containers, indicating that the smaller containers allow for the most efficient use of space when growing mojave sage stock plants for 4 to 6 months. The rooting of vegetative cuttings was successful (88% to 100% of cuttings rooted after 4 weeks under mist) for all treatment combinations.
A 3-year study to evaluate mulch type (reflective and black) and new virus resistant summer squash (Cucurbita pepo L.) varieties was undertaken. In the first year of the study (1996), in Shorter, Ala., under slight virus pressure, silver painted mulch suppressed virus symptoms through the final evaluation 2 months after planting. In addition, virus symptoms were significantly more prevalent on `Dixie' compared to `Supersett', `Tigress', `HMX 5727', `Jaguar', `Destiny III', and `Prelude II'. In the second year (1997), two different experiments were conducted in Savannah, Ga., where there was no virus pressure. In the first experiment at the Savannah location, `Tigress' and `HMX 6704' had significantly higher yields than `Destiny III', `Prelude II', `Puma', `Jaguar', `Meigs', `Dixie', and `Supersett'. In the second Savannah experiment, `Prelude II' and `Destiny III' had significantly higher yields than `Zucchini Elite', `Supersett', `HMX 6704', and `Jaguar'. In 1998 at Shorter, there was no difference in virus incidence based on mulch used. Although there were differences in virus incidence among varieties, the lowest incidence was 70% of plants infected for `Prelude II'. In addition to field evaluations, these varieties were evaluated for resistance to zucchini yellow mosaic virus under greenhouse conditions. Varieties HMX 7710, HMX 6704, Puma, Tigress, Prelude II, Jaguar, and Destiny III were significantly more resistant compared to varieties Zucchini Elite, Meigs, Supersett, and Dixie. In conclusion, reflective mulch was effective only under slight virus pressure.
Common bean (Phaseolus vulgaris L.) is a nutritionally complete food, but contains antinutritional compounds that reduce digestibility. One group of compounds includes the raffinose family oligosaccharides (RFOs) (raffinose, stachyose, and verbascose), which are partly responsible for flatulence after beans are eaten. RFOs stabilize cell membranes during seed desiccation and when the seed rehydrates during germination. While low levels of RFOs are desirable nutritionally, high levels may enhance germination and emergence, particularly in cold, wet soils. Eight landraces selected for high and low sucrose, raffinose, and stachyose content, were crossed in a diallel mating design to investigate genetic control of the RFOs. Derivatized soluble sugars were measured using gas-liquid chromatography. Fructose, sucrose, raffinose, and stachyose were detected. In the F1, fructose varied from 0.1 to 2.5 mg·g-1 dry weight (DW), sucrose from 17.2 to 56.5 mg·g-1 DW, raffinose from 0.1 to 4.1 mg·g-1 DW, and stachyose ranged from 7.6 to 43.7 mg·g-1 DW. Griffing's analysis estimates of general combining ability were on average, 16.5 times larger than specific combining ability for all the RFOs, indicating that additive genetic variance was most important. Significant reciprocal differences were detected in the F1 and F2, but not in the F3. RFO accumulation was partially dominant as indicated by Hayman's analysis. Narrow sense heritability averaged over F2 and F3 generations for sucrose, raffinose, stachyose, total sugar, and total oligosaccharides were 0.22, 0.54, 0.44, 0.17, and 0.27, respectively. Moderate heritabilities indicate that manipulation of RFO accumulation in this set of bean lines would probably need to be done on a progeny row basis with replication.