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United States Department of Agriculture

Agricultural Research Service

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2011 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
Several tracks of research for important crops have continued. Work on the Asian citrus psyllid and greasy spot disease in grapefruit has produced promising results for control of these important diseases. Research on insect attraction, resistance, and other aspects of host/insect biology is producing valuable information for further development. New research has been started in the area of water, nutrient, and biological stresses on regional crops to improve water and nutrient use efficiency. A new research project has been proposed that centers on deficit irrigation effects on regional crops. Progress on sugarcane insect and crop cultural practices includes work to identify pest-resistant varieties and to quantify the effects of deficit irrigation on crop productivity. Other work has shown alternative crop residue practices can improve crop nutrient uptake efficiency and water relations. Soil amendments, such as composts, have been shown to be beneficial for citrus, sugarcane, blackberries, and watermelons. New knowledge of nutrient movement through commercial weed barriers has demonstrated the utility of synthetic mulches for organic vegetable fertilization.

4. Accomplishments
1. New tool for combating citrus greening disease. The Asian citrus psyllid carries a devastating citrus disease called "citrus greening" that is threatening the U.S. citrus industry. The insect is attracted only to new leaf growth, and these "flushes" naturally occur infrequently. Scientists at Weslaco, Texas, have developed techniques to cause citrus to flush when needed for studying disease infection. Stressing citrus trees by exposure to cool temperatures, or by removing some leaves, stimulates new growth and flowering. The technique promises to accelerate development of new methods to control this costly disease.

2. Sugarcane varieties found resistant to destructive insect pests. Several commercial varieties of sugarcane grown for food or biofuel were found to be resistant to the sugarcane aphid and to the yellow sugarcane aphid, which are responsible for spreading important sugarcane viruses. A scientist at Weslaco, Texas, tested important commercial varieties in field and greenhouse experiments and found which varieties show natural resistance to the aphids. If the variety resists the aphids, the virus is not likely to be transmitted. By planting only resistant varieties, growers can reduce economic losses caused by the viruses transmitted by the aphid vectors. This knowledge will benefit sugarcane grower by ensuring only resistant varieties are planted.

3. Weed barriers found valuable for organic producers. Adding fertilizer to crops grown with weed-fighting ground covers is difficult for organic producers; by rule, they must use organic fertilizers, most of which are not readily soluble. Solid organic fertilizers must first be decomposed by microorganisms in the soil to release the trapped nutrients, a very slow process if the material is not mixed into the soil. Without the ability to incorporate the solid fertilizers into the soil because of the weed barrier on the soil surface, organic growers must either forego further fertilization or use very expensive soluble organic-approved materials. A scientist at Weslaco, Texas, determined that woven ground covers offer relief from this problem. Different weed barrier materials were tested to see if they would allow nutrients to pass through with irrigation water. When woven fabric weed barriers were used, nutrients, organic carbon, and minerals were found to leach through into the soil at rates that support plant growth. This means that growers now have a better option for soil fertility management in organically produced crops, such as watermelon and tree fruits, which are commonly grown with weed barriers.

Review Publications
Showler, A., Anciso, J.R., Castro, B. 2011. Effect of garlic extraction on injury by cowpea, Curculio Chalcodermes aenus Boheman (Coleoptera: Cucurlionidae), and other pests, to cowpea, Vigna unguiculata L. Walp. Biopesticides International. 6(2):112-120.

Showler, A.T., Beuzelin, J.M., Reagan, T.E. 2011. Alternate crop and weed host plant oviposition preferences by the Mexican rice borer (Lepidoptera: Crambidae). Crop Protection. 30(7):895-901.

Akbar, W., Showler, A.T., Beuzelin, J.M., Reagan, T.E., Gravois, K.A. 2011. Evaluation of aphid resistance among sugarcane cultivars in Louisiana. Annals of the Entomological Society of America. 104(4):699-704.

Malik, N.S., Perez, J.L. 2011. The effect of high temperature interruptions during inductive period on the extent of flowering and on metabolic responses in olives (Olea europaea L.). Scientia Horticulturae. 129(2):207-212.

Malik, N.S. 2011. Feasibility of growing olives on selected sites along coastal Texas. Journal of American Pomological Society. 5:139-146.

Showler, A. 2010. Do boll weevils really diapause? American Entomologist. 56(2):100-105.

Last Modified: 2/23/2016
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