No other forage crop cultivated in the United States can be used in as many ways as alfalfa. The variety of its uses make it a most useful forage crop. The distribution of alfalfa is world wide and it plays a leading role in the production of livestock and their products. For general feeding of farm animals, alfalfa is unsurpassed. Used for pasture, it has a high capacity, which leads to large gains in grasing animals. If properly rotated and cared for, it adds nitrogen to the soil in a form that is available to plants and thereby increases crop yields. In addition to these assets, alfalfa is a valuable source of essential nutrients and vitamins for livestock.

The tarnished plant bug, Lygus lineolaris, is an economically important polyphagous pest with a broad host range. With occurrence of insecticide resistance, strategies to limit its ability to reproduce, which would curb population growth, are becoming increasingly more valuable. Strategies toward this goal include the application of insect growth regulators (IGRs) and utilization of resistant cotton lines. This thesis summarizes experiments that elucidate the physiological underpinnings of the mode of action of novaluron, an IGR, and a cotton chromosome substitution (CS) line on the reproductive physiology of L. lineolaris. Investigations reported herein indicate that novaluron inhibits oviposition by inhibiting ovarian development and decreasing the expression of a gene (LlCHS-1) encoding chitin synthase. Transcriptomic analysis of ovarian tissue of L. lineolaris fed on a resistant CS line compared to a control line revealed the downregulation of genes involved in chitin synthesis and upregulation of genes involved in chitin degradation.

The tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), is considered the most economically important pest of midsouth cotton. This study was designed to understand the impact of tarnished plant bug populations in the later weeks of flowering cotton and residual effects of novaluron with subsequent applications. Experiments evaluated dynamic threshold approaches in the later flowering period of midsouth cotton, the impacts of novaluron plus subsequent applications at the 3rd week of square, as well as residual properties in a laboratory experiment. Results suggest that a dynamic late season approach can reduce the amount of insecticide applications targeting tarnished plant bug with no penalty to yield. Populations were observed at lowest densities where applications of novaluron were tank mixed with an adulticide (acephate) at the 3rd week of square. Results of this experiment will be important in refining seasonal management recommendations for tarnished plant bug in midsouth cotton production systems.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2003. / Härtill 4 uppsatser.