No description available.

No description available.

A complete factorial experiment using three nitrogen (44, 106 and 160 lbs N/acre) and three water rates (60, 100 and 130% consumptive use) examined the specific management criteria necessary for obtaining optimum yield and quality of drip -irrigated 'Jubilee' sweet coni. The crop was planted on I March and harvested on 10 June, with an 86 /50°F heat unit accumulation of 1738. When present, a nitrogen deficiency greatly decreased marketable yield, number of marketable ears/plant, mean ear weight, ear length and tip fill. Higher moisture rates generally had less effect on yield and quality than did N rates; however, increasing water rates significantly increased marketable yields and plant height, improved tip fill and lessened the occurrence of blank kernels. The effect of N and water rates on N and dry matter accumulation and on diagnostic plant tissue testing results for sweet corn are also presented. The maximum marketable yield obtained in this experiment was 7.8 tons per acre, using 160 lbs N/acre and 21.1 inches of irrigation water.

Gypsum was applied preplant on spring lettuce at rates of zero, 2 tons per acre, and 4 tons per acre. There were no significant differences in carton yields or in carton weights. Postharvest soil analyses showed that the application of four tons of gypsum per acre significantly increased the calcium and magnesium levels in the saturated paste solution. There were no significant effects of gypsum application on ESP and SAR values, nor in pH or sodium concentrations.

A field experiment using subsurface drip irrigation was conducted at the Maricopa Agricultural Center on a Casa Grande sandy loam to evaluate the effect of varying nitrogen rates on the growth and yield of 'Jubilee' sweet corn when applied with, and without the nitrification inhibitor, nitrapyrin (N-Serveᴿ). N treatments of 89, 134 and 2671bs. N/acre were applied as ammonium sulfate to one meter miniplots in three split applications between the V2 and the V10 growth stages. Individual N-Serveᴿ application rates were 0.5 lbs/acre. All solutions were applied through buried, perforated PVC tubing to simulate application through the buried drip irrigation system. The inclusion of N-Serveᴿ significantly increased dry matter accumulation, number of total ears and number of marketable ears /plant at all N levels. Plant tissue analysis suggested that enhanced uptake of ammonium -N as well as reduced leaching of nitrate-N contributed to this growth response to N- Serveᴿ.

In 1988, Arizona's early- season lettuce crop was plagued by disease and insect problems, both intensified by unseasonably high temperatures. In the western Arizona production area, an epidemic of lettuce infectious yellows (LIY) resulted in serious economic losses to growers. The yellows disease is incited by the LIY virus (LIYV), a plant virus transmitted by the sweet potato whitefly [Bemisia tabaci (Gene.)]. Disease symptoms in lettuce include stunted growth, rolling yellowing and /or reddening of infected leaves; necrotic lesions appear at or near the leaf margins at latter stages of the disease. LIYV has a wide host range which increases the difficulty of isolating lettuce fields from LIYV infected or whitefly-infested fields; also, whiteflies are resistant to insecticides. Therefore, host-plant resistance appears to be the most promising means of reducing losses due to this disease. To initiate a breeding program, commercial lettuce cultivars and breeding lines (Lactuca sativa L.), and related, cross-breeding wild lettuce species (L. serriola L. and L. saligna L.) were screened for resistance to LIYV in the western Arizona production area using natural inoculation by residence whiteflies.

Lettuce infectious yellows virus (LIYV), a recently recognized plant virus, causes dramatic yellowing symptoms and severe diseases in a wide range of vegetable crops in Arizona, adjacent southwestern states and Mexico. Until now, the only available diagnostic method was a time-consuming bioassay that used the insect vector to transmit the virus, with subsequent manipulation of indicator plants. A rapid, sensitive diagnostic technique (termed an indirect enzyme-linked immunoassay, called indirect ELISA) system was developed to detect lettuce infectious yellows virus (LIYV) in infected plant material. A virus specific antibody was made to viral capsid protein which was purified by polyacrylamide gel electrophoresis. The indirect ELISA system was optimized and used to detect viral antigen in greenhouse-inoculated melons. The system was subsequently adapted to detect LIYV in symptomatic and asymptomatic weed and cultivated plant species collected from infected fields near Yuma and in central Arizona. The indirect ELISA system described here allows for the detection of approximately 100 ng of virus per well. The LIYV was detectable in symptomatic (but not in asymptomatic) leaves of melon plants infected with the virus. In contrast, the virus could be detected in both symptomatic and symptomless cheeseweed plants collected in the field. The optical density readings for infected weed species were generally lower than those for cultivated species, such as melons, lettuce, and spinach, suggesting that there is less virus in the weed hosts tested than in infected, cultivated hosts.

Measles of honeydew melons is not a common problem, but melon growers should be aware that it can cause severe economic damage, under the right environmental conditions. At least one Pinal County grower suffered significant loss during an outbreak of this disease in September 1987.

No description available.

No description available.