Location:2010 Annual Report
1a. Objectives (from AD-416)
1) Develop or adapt methods and models to detect and predict interactions between irrigation and nutrient applications and pests in economically important crop systems to minimize inputs and costs; 2) determine the influence of spatial and temporal variation within and among fields in landscapes on specialty crop growth, insect responses, and overall system performance; and 3) develop production management strategies to improve water use efficiency, reduce environmental impacts and increase water conservation through reuse for economically important crops grown in sub-tropical regions.
1b. Approach (from AD-416)
Quantify and model relationships between water, soil properties, pest dynamics, and plant properties with the aim of improving crop yield, quality and economic return on sub-tropical crops. Biochemical and physical sensor technologies will be developed and evaluated as gauges of system responses to water availability and other inputs. Remote sensing technologies will be developed or adapted to evaluate effects of field- and watershed-scale spatial and temporal variabilities on water use efficiency and input management strategies. Resulting knowledge will be integrated into novel management practices that improve water use efficiency, crop productivity, environmental servicing, and profitability of sub-tropical farming enterprises.
3. Progress Report
Current work includes several aspects of the Asian citrus psyllid problem. Research on insect attraction, resistance, and other aspects of host/insect biology is progressing. New research has been started in the area of water, nutrient, and biological stresses on regional crops to improve water and nutrient use efficiency. Sugarcane insect and crop cultural practices are being studied to improve crop productivity and reduce environmental problems associated with sugarcane production. Soil amendments, crop, water, and residue management techniques are being evaluated for citrus, sugarcane, blackberries, and watermelons.
1. Weed barriers increase yield and reduce weeds in blackberries. Weed control in blackberries is a costly problem for organic producers and those who wish to reduce their reliance on herbicides. At the southern limits of blackberry production, late-season yields are reduced because of high day-time temperatures generated by solar irradiation and other environmental constraints. In a field experiment using 'Kiowa' root cuttings established in 2008, weeds were controlled mechanically by hand and with an industrial grade laminated white plastic. After the third picking, 40% shade was applied to half of the bare ground and white plastic treatments. In 2010, the second of two fruiting seasons in this study, yield was improved by either white plastic or white plastic and shading compared to conventionally bare soil-grown fruit. The percentage of reflected light through the canopy was improved by white plastic and was not influenced by shading. White plastic used alone resulted in a greater improvement in cumulative season yield when compared with shade alone. In addition, using white plastic increased average fruit weight and cut hand-weeding time by over half. Based on our findings, profits are increased with greater blackberry yields and by reduced costs of weed control by using white plastic mulch.
2. Alternative soil management techniques aid watermelon production. Current watermelon production practices reduce soil quality and require much irrigation, which increase input costs. To address these problems, watermelon studies evaluated two minimally tilled transplant methods as compared to the standard method of raised beds in a high residue field; soil temperature and water inputs were monitored. High surface residue resulted in higher soil surface temperatures, but temperatures were higher at 2- and 12-inch depth in the raised bed-grown melons. Season soil moisture tension was not affected by transplant method; nor was fruit yield or quality, but the percentage of marketable melons was lower in the conventionally bedded melons. Although water use efficiency was similar with all treatments, there were cultivar differences in yield and quality, indicating a beneficial cost effect of the alternative production method. Establishment and production costs can be reduced by growing watermelons in high residue fields with chisel and strip-tillage transplanters with no loss in yield or melon quality or alteration in other production practices.
3. Boll weevil life cycle does not include seasonal diapause in South Texas. A synthesis study was completed on adult boll weevil diapause (an important resting and survival tool in some insects). The finding of the study indicated that growers and regulators cannot rely on diapause-based control measures. Much of the newer data generated in the subtropics of South Texas indicate that boll weevils are active and breeding during the winter months. Thus the paradigm of functional diapause in this climate is incorrect and should be considered when developing control protocols.
4. Sugarcane leaf chemistry affects Mexican rice borer attraction. What makes Mexican rice borer, an important pest of sugarcane, choose a particular site to lay eggs on sugarcane leaves was determined. Site selection stimuli were identified and prioritized, whereby specific leaf characteristics (leaf folding and leaf dryness) were found to be the most important factors that favor oviposition, while physiochemical factors play important roles in making some sugarcane varieties more resistant or vulnerable to the pest. Sugarcane varieties that show pronounced leaf curling may be more susceptible to infestation. This finding will improve sugarcane breeding and cultural practices to minimize the economic damage caused by this insect.
5. Amino acids in sugarcane leaves affect aphid resistance. Sugarcane aphid causes widespread economic losses. Resistance to the aphids is of particular importance to the sugarcane industry because the insects vector yield-reducing viruses of sugarcane. Plant resistance to two species of sugarcane aphid, and the underlying mechanisms of that resistance, was found to involve a free amino acid identified by USDA-ARS that is present in susceptible varieties, but not in resistant varieties. Resistance can be predicted by a simple biochemical marker, an amino acid. This can be a tool for plant breeders to improve sugarcane variety releases that resist aphid attack.
6. Garlic partially effective on pepper insects, aids plant development. Environmentally friendly alternatives to conventional insecticides were studied in Weslaco, Texas, particularly the effects of garlic extract on sweet peppers and on cowpeas. In sweet peppers, garlic extract failed to suppress pepper weevil, Anthonomus eugenii; leafminers, and lepidopterous larvae, but it did have an effect on increasing fruit set, likely through increased budding because garlic extract has been shown to stimulate budding in another crop. On cowpeas, garlic extract protected crop quality from the cowpea weevil, Chalcodermus aenus, but it did not affect numbers of peas harvested. Our findings suggest that the usefulness of garlic may be somewhat crop-specific and targeted to certain kinds of insects. It may provide an economic alternative to expensive pesticides for some crops.
5. Significant Activities that Support Special Target Populations
1. One scientist produced sweet potato plants (in collaboration with scientists from CQFI Research Unit) and bitter melon plants for distribution to local consumers to grow in their backyard for food. While sweet potatoes provide a staple food for people, bitter melons provide edible fruits for cooking that are well known to control diabetes. Cooked fruits, fruit juice (very bitter), or dried fruit powder of bitter melons are commonly used for controlling diabetes in Asian countries. Diabetes is very common among Hispanic population in the Rio Grande Valley, and therefore, increased use of this vegetable crop will have far-reaching health benefits for local community. Thus, we are providing free services, as well as plant material, to local communities for growing food plants in their backyards as well growing plants with distinct health benefitting properties. 2. Work continues in support of the Farmer's Market initiative. One scientist is serving as an advisory consultant for soil management and crop production at the Mercado Community Gardens at Elsa, TX. An award was presented (12-09-2009) from a congressman's office recognizing the contributions of a Weslaco-based ARS scientist to the goals of the Mercado Delta Development Corporation.
Lester, G.E., Makus, D.J., Hodges, D. 2010. Relationship between fresh-packaged spinach leaves exposed to continuous light or dark and bioactive contents: Effects of cultivar, leaf size, and storage duration. Journal of Agriculture and Food Chemistry. 58(5):2980-2987.