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.

Early season infestations of sweet potato whiteflies, Bemisia tabaci ( Gennadius) were monitored in fields of cantaloupe, Cucumis melo L., near Yuma, Arizona. We used these data to describe the relationship between the proportion of infested leaves and mean adult population density for the entire field. This model was used to develop a binomial sampling plan based on a presence- absence approach. We evaluated the model with three independent data sets, and the level of agreement between the model and data was reasonable for pest management purposes. A minimum sample size of 200 leaves is suggested for maximum accuracy. By turning over 50 leaves in the four quadrants of a field and determining what proportion have whiteflies (i.e., are there whitefly adults on the leaf or not), growers can estimate field populations. We recommend that if 60% of the sampled leaves have whiteflies then it is time to make a pesticide application because that tells you that population levels are approaching 3 adults per leaf.

A study was conducted in 1995 to evaluate five application technologies in the field in terms of deposition efficiency, as well as to assess their abilities to control the sweet potato whitefly and thereby influence crop yield. The FMC and ESS-on treatments provided the greatest deposition on the ventral side of the leaves. The FMC system tended to maintain high ventral deposition efficiencies as the plants grew and the canopy closed, whereas the efficiency of the ESS declined. Differences in ventral deposition efficiency among treatments were not closely associated with differences in whitefly control, although the declining rate of ventral deposition for the ESS-on is also reflected in its declining superiority in adult insect control relative to the CDA and conventional systems. The ESS sprayer provided somewhat better whitefly control than the conventional treatment, and was also associated with a higher yield of #12 melons than the control and Admire treatments, but not better than the conventional treatment. Early control of adults was associated with reduced egg counts later in the season, suggesting that there may be long term control advantages with the ESS system. New application technologies need to be developed to obtain higher ventral deposition and maximum whitefly control, with minimum use of insecticides.

No description available.

The efficacy and field performance of new insecticides for control of insects on vegetables and melons under desert growing conditions has been investigated in small plot trials for the past several years at the Yuma Agricultural Center. Our objective has been to determine how new chemistries will fit into the growers management programs in Arizona. Thus, our research programs have been focused on studies to determine how to integrate these new chemicals into our local management programs in the most cost/effective way possible. This document was created to provide you with an overview of new insecticide chemistries being developed by the Agrichemical Industry for use in vegetables. The first part of this report concisely describes the new types of chemistries being developed The tabular information presented is a summary of the efficacy and activity of the new compounds based on research we have conducted at the Yuma Agricultural Center.

For the past 5 years, Arizona growers have been faced with the challenge of managing whiteflies populations to prevent yield reduction and loss of quality of their vegetable and melon crops. A large cooperative research effort was directed statewide to better understand how whiteflies develop on the numerous host -crops available and the environmental factors that influence their survival throughout the year. This information was used to develop short and long term management approaches for controlling whitefly populations. We quickly discovered that preventing whiteflies from colonizing plants was the key to successful management of whitefly populations in vegetable and melon crops. This report attempts to summarize what we presently understand about factors that influence the seasonal abundance of whiteflies in southern Arizona cropping systems. Non-chemical and chemical management approaches that have been developed by researchers and implemented by the agricultural communities are discussed

Bentazon (Basagran®) at 0.5 to 2.0 lb a. i. /A, halosulfuron (Permit®) at 0.025 to 0.10 lb a.i A, and pyridate (Lentagran®) at 0.25 to 1.5 lb a.i. /A were applied postemergence on cantaloupe and watermelon. Bentazon was marginally safe on cantaloupes and controlled purslane and pigweeds. Morningglory and Wright's groundcherry were not effectively controlled by bentazon. Bentazon appeared to be less injurious to watermelons relative to cantaloupes. Halosulfuron was safe on both cantaloupes and watermelons (<15% injury). Halosulfuron at greater than 0.05 lb /A was effective in controlling only Hyssop spurge and London rocket. In one test, halosulfuron gave acceptable control (85 %) of morningglory. Purslane and groundcherry were not controlled by halosulfuron. Pyridate was not safe on cantaloupes causing severe crop stand reduction. Pyridate was safer on watermelons and caused marginally acceptable injury, however, weed control was not effective against groundcherry, spurge or London rocket. Pyridate appeared to give acceptable control of morningglory in one test.

Whitefly populations were assessed under different IGR exposure levels, and compared to Admire. When used alone during the season Applaud, Knack, and Sterling significantly reduced immature colonization similar to the standard Admire application and significantly greater than the untreated melons. Applaud treatments, regardless of spray frequency, showed the most consistent reduction in immature whiteflies. Applaud through its vapor activity also appeared to provide a long residual period of control against nymphs. Single applications of Knack and Sterling were considerably less effective in preventing colonization than applying these material twice during the season. These compounds appeared to have considerably less residual activity, which is consistent with their modes of activity. All of the IGRs had a significant impact on the distribution of nymphs among the leaves on the primary vine. In addition, Applaud provided the best melon quality. We now have a good understanding of how the IGRs influence whitefly population growth, the residual mortality of the IGRs and proper application timing for whitefly management. This information will allow us to develop a simple and reliable method that growers and PCAs can use to assess product performance and time spray applications.