Average monthly values of incoming radiation, extraterrestrial radiation, sunshine, and sky cover frorn 32 climatological stations in the United States were used as a basis to develop radiation equations. Empirical relations between incoming radiation and more commonly available climatic and geographic variables, such as percent of relative sunshine, mean daily sky cover, station elevation and extraterrestrial radiation, were established using an empirical procedure used by Christiansen (1966, 1967) to compute his evaporation and evapotranspiration formulas. The reliability of the equations developed was deternlined by comparing the computed values of incoming radiation with measured values at Davis, California and for the Republic of Venezuela (Servicio de Meteorologia, 1965). For comparison, the formulas developed in this study and formulas developed by Fitzpatrick (1965), Black (1954), Glover and McCulloch (cited by Fitzpatrick, 1965) Morton (1965), and Bennett (1965) were applied to Venezuelan incoming solar radiation stations.

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The efficacy of two different autonomous Ultraviolet-C (UV-C) units on two spotted spidermite, Tetranychus urticae Koch (Acari: Tetranychidae), and greenhouse whitefly, Trialeurodes vaporariorum. (Hemiptera: Aleyrodidae). was tested in four commercial strawberry fields in California. In 2020, California strawberry growers used 12 million pounds of active ingredients (AIs) to keep pests under economic thresholds. While pesticides are an important part of an integrated pest management program, their use poses threats to the environment and human health. To protect agricultural workers, the public and the environment, regulators in California have consistently limited or removed the use of certain pesticide AIs. For strawberry growers in the state, this trend signifies that reliance on pesticides may not be a sustainable approach. Resistant pest populations further intensify the need for more sustainable pest control measures. Tetranychus urticae populations in California strawberry production have documented resistance to at least three AIs; abamectin, bifenazate, and hexythiazox. Trialeurodes vaporariorum populations in California strawberry production have documented resistance to five AIs; imidacloprid, thiamethoxam, dinotefuran, acetamiprid, and chlorpyrifos. To address this issue, stakeholders must invest in research and development of new non-chemical control methods. One of these methods is the use of autonomous UV-C for pest control. These systems emit UV-C radiation, which affects the cellular and genetic structure of organisms, leading to detrimental effects. One unit, by Tric Robotics, emits an avg of 250 J m−2 of UV-C irradiation and was tested in three different strawberry fields. Another unit by Saga Robotics emits an avg of 200 J m−2 was tested on a single field different from the first three. In each field, a plot was treated with UV-C twice weekly at night. Untreated controls were not possible with this study, so UV-C has been tested against each grower’s standard (GS) treatment. Twenty leaflets from the middle and 20 bottom tier of the strawberry plant canopy were collected weekly to assess the presence of T. urticae and T. vaporariorum. Samples were compared using Kruskal-Wallis rank sum tests with Bonferroni adjusted Dunn tests in the R statistical environment. The data showed that UV-C may be an effective tool for the control of certain T. vaporariorum stages in strawberry. Follow-up studies with untreated controls are needed to validate the efficacy of UV-C on T. urticae and further validate the positive results observed on T. vaporariorum.

In 1908, Sackett described for the first time what appeared to be a new bacterial disease of alfalfa in Colorado. To this particular disease he applied the name “stem blight" and attributed the cause to a bacterium, Pseudomonas medicaginis. For some two decades or more Sackett's work on this disease was accepted. During this time stem blight, which was first thought to be indigenous to the western United State, was reported from nine states east of the Rocky Mountains. In 1933, Johnson and Valleau described a disease of alfalfa, characterized by stem lesions very similar in appearance to those of stem blight as described by Sackett. These authors determined the cause of this new disease to be a fungus" Phoma medicaginis Malbr. and Roum., and gave to it the name "black stem". Richards in 1934" in reporting on the resistance of certain alfalfa varieties to stem blight in Utah, states in a foot note that a species of Phoma was isolated with considerable uniformity from bacterial stem blight lesions. This author raises the question as to the possible dual etiology of stem blight in Utah. Research work by Remsberg and Hungerford in Idaho, more definitely suggested this dual etiology of' the stem blight complex. These authors determined the black stem lesions on alfalfa to be caused by Phoma medicaginis, and indicated that the darker lesions caused by this fungus were distinct from the lighter colored lesions characteristic of the bacterial stem blight described by Sackett. Because of the similarity of the late stage of bacterial stem blight to the insipient stage of black stem, much confusion has arisen as to their identity and etiology It has been the policy in Utah during recent years to refer to this wide range of stem lesions as stem blight, recognizing that the exact nature and etiology is not known. This disease complex presents a problem in Utah of major economic importance. It is the purpose of this thesis to bring together the known facts regarding stem blight; to determine the specific etiology of the stem blight lesions on alfalfa as they occur in Utah, and if possible to establish definite criteria by which the components of the stem blight complex might be separated.

It has been advocated by many sheep raisers and individuals interested in the wool industry of utah, that wool manufacturing should become a leading industry of this state. Factors which seemingly corroborate such contentions are readily apparent. Utah's annual wool clip ranges between eighteen and twenty-five million pounds of wool (1)*. The state is located in the center of the Western range states where the bulk of the higher quality wool of this country is grown. A part of the marketing costs of freight, commission charges to a limited extent, and high storage costs could be decreased. These savings would result in higher prices of raw wool. Sheep growers would also have an opportunity of observing the manufacturing process and thus learn to recognize the characteristics of better quality wool.

Perennial weeds have retarded agricultural progress, since their first appearance in cultivated fields. They have grown and survived the destructive efforts of the farmer and agricultural scientist, over a great period of time. Many farmers have become discouraged and much valuable land has lain idle because of this wasteful weed persistence. These dismal consequences have stimulated constant effort at experimental stations to discover more effective methods of batlting the pest. The use of chemicals has been one of the most prominent weapons and, of the most recent chemicals tried, the chlorates are the most promising.

A series of experiments evaluated: 1) the influence of seed intake and gut retention time on seed passage , recovery , and germinability; 2) fecal seeding and broadcast /trampling as techniques to incorporate seeds into a well-established Agropyron desertorum (Fisch.) Schult. stand in Skull Valley , Utah; 3) intensive grazing as a means to reduce Agropyron biomass and increase establishment and survival of seeded species; and 4) the recovery and germinability of seed extracted from dung collected from the field. Two shrubs (Artemisia tridentata Nutt. ssp. wyomingensis Beetle & Young and Atriplex confertifolia Torr. & Frem.), a grass (Elymus elymoides (Raf.) Swezey) , and a forb (Sphaeralcea grossulariaefolia (H. & A.) Rydb.) were selected as representative native species. Holstein heifers were fed 15,000 , 30 ,000 , and 60,000 seeds of Artemisia , Sphaeralcea, and Elymus. Elymus recovery was negatively correlated to seed intake. Sphaeralcea had the highest percentage of recovered, undamaged seed, followed by Elymus and Artemisia. Sphaeralcea and Artemisia seed passage was highest on Day 1 then dropped sharply. Elymus passage and recovery were more consistent through time. Post-passage germjnability was highest for Elymus and Sphaeralcea on Day 1. Artemisia germjnation was neghgible. In the fall seeding, Sphaeralcea emerged in 6% of the subplots (half were volunteers). Overall seedling mortality was 93%. Elymus emerged in 63% of the dung pats, with 86% mortality. No Artemisia emerged. Drought and Anabrus simplex herbivory contributed to low seedling emergence and survival. In April 2003, similar treatments were applied, except Atriplex seed was substituted for Artemisia, and a third treatment was added (broadcast seeding/raking). No emergence was observed. Sphaeralcea had the highest seed recovery from dung collected in the field trials, followed by Elymus, Atriplex, and Artemisia. Sphaeralcea germinability was similar for seeds collected from both trials (11 %) and Elymus germination was highest in the fall seeding (13%). These studies indicate that: 1) physical seed properties (size, shape, density, seed coat) influence seed passage , recovery, and germination; 2) intensive grazing can reduce Agropyron biomass by 50% for 2 years; 3) broadcast/trampling may be effective for Sphaeralcea; and 4) an average-sized dung pat (714 g) may have ample germinable Sphaeralcea and Elymus seeds for plant establishment.

Plant nematodes belong to a large group of invertebrates known as round worms, They derive their name from the Greek word "nema," meaning thread. In literature some authors refer to nematodes as nemas. In England and many parts of the United States, plant-parasitic nematodes are called eelworms. While some damage to plants results from mechanical injury, salivary secretions injected by the nematode into the plant are usually the major cause of damage. Experiments conducted in the first part of the present century have demonstrated large differences in plant growth in soil infested with nematodes and soil freed of nematodes by chemicals. Any plant subjected to nematode attack is reduced in growth. The most important nematode which attacks and retards the growth of alfalfa in Utah is the stem nematode. This parasite has been reported in most of the major alfalfa-producing counties of the state. In certain areas the nematode is prevalent to such a degree that only resistant varieties can be grown if the crop is to remain for more than two or three years. In other areas stands and yields are reduced in varying degrees. In many additional areas it is not known if the stem nematode is present, since a complete survey of the state has never been made. The objectives of this investigation were to determine the distribution of the stem nematode of alfalfa through a complete survey of the state. The physical factors of the plant and soil which may be correlated with the presence of the nematode were likewise surveyed.