Thrips are the major insect pest of onions grown in South Texas. Four cultivars, `IPA-3', `TG1015Y', `1664' (glossy control), and `1900B' (waxy control), were grown in a split-plot design with insecticide sprayed or nonsprayed treatments as the main plots and cultivar as the subplots. The experiment was conducted at the Texas Agricultural Experiment Station, Weslaco, Texas, in the 1995-96 season. The objectives of the study were to compare `IPA-3' and `TG1015Y' for thrips resistance and evaluate possible resistance mechanisms that may be present in `IPA-3'. The average number of thrips per plant and leaf damage rating were significantly higher for `TG1015Y', indicating that some resistance is present in `IPA-3'. However, there were no significant differences in yield between the two cultivars. A comparison of leaf wax characteristics indicated no significant difference between `TG1015Y' and `IPA-3' using gravimetric or gas chromatography techniques. However, scanning electron micrographs of `TG1015Y' leaves appeared more similar to `1900B' and `IPA-3' appeared more similar to `1664'. The insecticide spray treatment had significantly fewer thrips, less damage, and higher yield than the nonsprayed treatment.
Brian K. Hamilton, Leonard M. Pike, Alton N. Sparks, David A. Bender and Richard W. Jones
Eric H. Simonne, John T. Owen and Joseph M. Kemble
The efficacy of garlic spray (GS; Garlic Barrier™) as an alternative to conventional chemical control of disease and insect pests was evaluated on bell pepper and lettuce. Treatments consisted of a recommended chemical spray as needed (Treat. 1), GS applied once (Treat. 2) or twice (Treat. 3) a week, and water spray applied twice a week (Treat. 4). Because of no pest pressure during the test, no chemical sprays were used in Treat. 1. Differences among bell pepper yields were not significant (P > 0.50). For lettuce, Treat. 2 resulted in significantly (P = 0.02) higher head yield. Differences among treatments were not visually detectable in the field. These results suggested that GB applied at the manufacturer's rate (Treat. 2) did not adversely affect bell pepper and lettuce growth and yield. Garlic smell was not detectable on either vegetables, even after Treat. 3. Due to a low pest pressure, this study failed to identify beneficial effects of the GS. Without more scientific reports, relying only on GS to control pests of bell pepper and lettuce may involve uncontrolled risks.
Elaine M. Grassbaugh, Mark A. Bennett and Andrew F. Evans
Successful crop production and optimum yields, regardless of the species, can be accomplished only when maximum stand establishment is achieved. Stand reduction after planting typically results in reduced yields and lower crop quality. Several classes of factors (environmental, edaphic, biotic) contribute to successful stand establishment in crop production and should be considered in growing medicinal plants. Environmental factors (e.g., temperature and moisture extremes) as well as pathogens and insect pests that attack seeds and seedlings may contribute to reduced stands. Soil related factors such as pH, nutrient availability, and crusting may also restrict seedling growth. Understanding the requirements for optimum seed germination and the environmental conditions into which the seed is sown is essential for uniform crop establishment. Vigor tests can aid growers in determining the optimum temperature range for seed germination. Many cultural practices may also influence soil related factors and contribute to successful stand establishment in the field. Seed vigor tests (SSAA, thermogradient results) along with seed treatments and enhancements can assess seed vigor, improve germination and lead to more reliable stands of medicinal species.
Daniel F. Warnock
When breeding floriculture plants, one must have a targeted phenotype and genotype in mind before the initial cross-pollination event is performed. In the case of the floriculture breeding program at the University of Illinois, our initial goal was to develop a commercially acceptable, yet novel, Impatienswallerana(bedding plant impatiens) phenotype with improved resistance to the western flower thrips, Franklinella occidentalis, a significant insect pest in production greenhouses. This study describes the process used to obtain a large impatiens phenotype (>61 cm tall and >125 cm wide) with acceptable branching, leaf color, flower size, flower number, flower display, and flower colors with improved resistance to western flower thrips. A reliable and simple evaluation technique, based on the number of leaves expressing western flower thrips feeding damage after inoculation, was developed and utilized to create more resistant impatiens genotypes based on generation means. Using a 1 to 9 scale, mean damage ratings for the original germplasm populations 1, 2, and 3 were 5.18, 6.02, and 6.11, respectively, with the trend for populations 1, 2, and 3 skewed toward susceptible plants. Germplasm with novel phenotypes were derived from crosses with plants in populations 1 and 3 with commercial cultivars. These novel phenotypes had improved levels of resistance with a mean rating of 5.06 and a normal shaped distribution. The potential for improving resistance to western flower thrips feeding exists within available germplasm and the tools necessary for proper evaluations are available.
Juan Manuel González Gonzalez, Francisco Radillo Juarez, Marcelino Bazan Tene and Juan Carlos González Ramos
Soursop (Annonamuricata L.) is reproduced by seeds from `Criollo' cultivars in Mexico. The replication of desirable agronomic traits is difficult when selected plants are from sexual reproduction. The heterogeneity of plants is observed as taller trees, irregular fresh fruit yield, variable fruit quality, different insect pests, disease susceptibilities, and lower number of plants per hectare. There is an extended time period for recovering investments and commericialization problems due to fruit quality and price. Vegetative propagation is an alternative for reducing the heterogeneity of soursop trees. Three grafting methods were evaluated for propagating soursop in the dry tropic region of Colima, Mexico: 1) splice side graft; 2) wedge graft; and 3) bud graft. The experiment was carried out on the Tecoman Campus of the Universidad de Colima. Rootstocks were from 8-month-old healthy plants, 1-m tall and 1-cm diameter, obtained from `Criollo' seedlings, and the scions were obtained from a healthy 10-year-old `Sin Fibra' donor tree. This donor tree was selected for its excellent agronomic traits and fruit yield. Vigorous and terminal scions were used, disinfected with fungicide, and used the same day of excision. The experiment was distributed under a completely randomized design. Splice side grafting had 67% success after 60 days, while wedge grafting and bud grafting had 0% success.
Thomas L. Davenport, Stanley P. Burg and Thomas L. White
U.S. regulations prevent importation of fresh horticultural commodities that have not received an approved quarantine treatment assuring 100% mortality of potentially invasive insect pests. Because imported mangoes are likely to be infested by the Caribbean fruit fly (Anastrepha suspensa Loew) and other tropical fruit flies such as A. ludens Loew, A. striata, A. distincta, A. fraterculus, A. serpentina, or A. oblique, they must be hot-water treated prior to shipment in order to satisfy quarantine requirement. Hot water treatment often damages the fruit, especially if it is not fully mature. Hypobaric (low pressure = LP) intermodal shipping containers developed by the VacuFreshSM Corp. preserve fresh commodities, such as horticulturally mature mangoes, far longer than is possible using other technologies. We tested the ability of over 70,000 Caribbean fruit fly eggs and larvae to survive a simulated optimal hypobaric condition for shipment of mangoes (15 mm Hg, 98% RH, at the lowest, safe non-chilling temperature, 13 °C). A. suspensa eggs or larvae were maintained on agar media, flushed with one air change per hour at the storage pressure, and shielded with Mylar to prevent radiant heat uptake and limit evaporative cooling. Nearly 98% of the eggs and larvae were killed within 1 week at 15 mm Hg in eight replicated experiments. All eggs were killed at that pressure by 11 days, whereas a significant number survived at ambient pressure. Shipment of fresh produce using this technology promises to provide quarantine control while preserving the freshness of fully mature tropical fruits and vegetables.
Raul Leonel Grijalva-Contreras, Rubén Macias-Duarte, Fabián Robles-Contreras and Manuel de Jesus Valenzuela-Ruiz
Mexican production of vegetables under greenhouse conditions has been increased notably during the last year to about 1500 ha. The main crop in greenhouse production is tomato, but european cucumber is a potential crop due to high yield and quality, with a good price in the marketplace and a short growing season. The objective of this trial was to evaluate eight european cucumber varieties and to choose those with high yield and fruit quality, and disease resistance. The experiment was carried out at the experimental station (INIFAP-CIRNO). Greenhouse conditions were: polyethylene (8.0 mL), without temperature control; natural ventilation; and soil with electrical conductivity of 1.22 dS·m-1 and pH 7.96. Sowing date for seed was 15 Oct. 2004. Plant density was 3.78 plants per m2. The harvest period was 26 Dec. 2004 to 11 Mar. 2005, with an average of 10 cuttings. Varieties with highest yield were `Imanaol', `Bermejo', `Dominica', and `Kalunga', with 18.9, 15.2, 14.8, and 14.3 kg·m2, respectively. Fruit quality was excellent in all varieties; however, `Imanaol' had the highest percentage of size and fruit number. The main insect pest during the year was white fly (Bemissiasp.) and the most important disease was powdery mildew (Erishipecichoracearum).
R.A. Malvar, P. Revilla, P. Velasco, M.E. Cartea and A. Ordás
The pink stem borer (PSB) (Sesamia nonagrioides Lefebvre) and the European corn borer (ECB) (Ostrinia nubilalis Hübner) are the major insect pests of corn (Zea mays L.) in Mediterranean countries, although larvae of other insects can also cause damage. The objective of this research was to evaluate the effect of sweet corn hybrids, planting time, and environment on damage by various insects. Data were recorded on the number of larvae of each of the aforementioned pests and damage produced in the ear 20 days after pollination and in the ear and stem when plants were dry. PSB was the most abundant pest, followed by ECB. Other insects, such as Mythimna unipuncta (Haworth) and Helicoverpa armigera (Hübner) were rarely found in sweet corn plants. ECB was constant over time, PSB had larger seasonal variation, and M. unipuncta and H. armigera were highly variable over time. There were significant differences among planting dates and growing cycles for damage traits in each environment. Interactions among hybrids, planting dates, and environments were significant. Dry ears were damaged more than fresh ears and stems had more larvae than ears. The economic value of the crop was seriously affected because most fresh ears had some damage, and seed production would be severely affected by PSB.
Joyce G. Latimer, Reuben B. Beverly, Carol D. Robacker, Orville M. Lindstrom, Ronald D. Oetting, Denise L. Olson, S. Kristine Braman, Paul A. Thomas, John R. Allison, Wojciech Florkowski, John M. Ruter, Jerry T. Walker, Melvin P. Garber and William G. Hudson
Pesticides have been the primary method of pest control for years, and growers depend on them to control insect and disease-causing pests effectively and economically. However, opportunities for reducing the potential pollution arising from the use of pesticides and fertilizers in environmental horticulture are excellent. Greenhouse, nursery, and sod producers are using many of the scouting and cultural practices recommended for reducing the outbreak potential and severity of disease and insect problems. Growers are receptive to alternatives to conventional pesticides, and many already use biorational insecticides. Future research should focus on increasing the effectiveness and availability of these alternatives. Optimizing growing conditions, and thereby plant health, reduces the susceptibility of plants to many disease and insect pest problems. Impediments to reducing the use of conventional pesticides and fertilizers in the environmental horticulture industry include 1) lack of easily implemented, reliable, and cost-effective alternative pest control methods; 2) inadequate funding for research to develop alternatives; 3) lack of sufficient educational or resource information for users on the availability of alternatives; 4) insufficient funding for educating users on implementing alternatives; 5) lack of economic or regulatory incentive for growers to implement alternatives; and 6) limited consumer acceptance of aesthetic damage to plants. Research and broadly defined educational efforts will help alleviate these impediments to reducing potential pollution by the environmental horticulture industry.
Juan Manuel González-González, Salvador Guzmán-González and Sergio Chavez-Luna
Starfruit (Averrhoa carambola L.) is reproduced by seeds from `Criollo' cultivars. The replication of desirable agronomic traits is difficult when selected plants are from sexual reproduction. The heterogeneity of plants is observed as higher trees, irregular fresh fruit yield, variable fruit quality, differential insect pest and disease susceptibilities, and extended period for recovering the inversion. Vegetative propagation is an alternative for reducing the heterogeneity of starfruit trees. Four grafting methods for propagating starfruit in the coast of Colima, Mexico: splice-side graft, wedge graft, whip graft, and bud graft were evaluated. The experiment was carried out on the Tecoman campus of the Universidad de Colima. The ambient conditions were dry tropic (BS1). Seven-month-old rootstocks were obtained from Criollo seedlings, and the scion was obtained from a healthy 15-year-old `Miss' donor tree. The experiment was distributed under a completely randomized design. The splice-side graft had 70% success and was the best, bud graft had 40% success, wedge graft, had 5% success and whip graft 0% success, and was the least successful.