A range of population levels of sweet potato whitefly, Bemisia tabaci Gennadius was evaluated in three field experiments allowing measurement of the effect of whitefly numbers on melon quality and yield. An increase in total numbers of immature whitefly was associated with significant declines in harvested melon weight, a decline in number of boxes harvested, a decrease in fruit size, a decrease in percent sugars, and an increase in sooty mold. Regression analysis of individual whitefly life stages with yield parameters indicated that adult number was a more precise parameter and higher R2 values were obtained with increased range of whitefly population densities. Adults were sampled at the third leaf node in both locations. Nymph samples were taken at varying nodes from the base of the plant. Estimates of the mean adult whitefly density resulting in 5% and 15 % dollar yield loss were 3 and 10 adults per leaf Estimates of the mean total nymph density resulting in 5% and 15% dollar yield loss 0.5 and 2 (AZ) nymphs per cm² of leaf area, respectively.

A range of action thresholds for the control of sweet potato whitefly, Bemisia tabaci Gennadius were evaluated in field experiments with high population density of B. tabaci. Action thresholds for whitefly adults, based on seasonal whitefly averages that could result in 5% and 15 % dollar losses, of 3 and 10 adults per leaf, respectively, were tested. All thresholds were compared to weekly insecticide treatments and an untreated check The resulting best threshold treatment was 3 adults per leaf area which provided a 170% increase in net return over the untreated check. The 3 adult per leaf threshold resulted in 6 applications of insecticide, compared with 10 applications used in the weekly regime.

Imidacloprid is a new, chloronicotinyl insecticide currently being used to control sweetpotato whitefly (Bemisia tabaci Genn, also known as silverleaf whitefly, Bemisia argentifolii Bellows and Perring). Large growth and yield increases of cantaloupes (Cucumis melo L.) following the use of imidacloprid have caused some to speculate that this compound may enhance growth and yield above that expected from insect control alone. Greenhouse and field studies were conducted to evaluate the growth and yield response of melons to imidacloprid in the presence and absence of whitefly pressure. In greenhouse cage studies, sweetpotato whiteflies developed very high densities of nymphs and eclosed pupal cases on plants not treated with imidacloprid, and significant increases in vegetative plant growth were inversely proportional to whitefly densities. Positive plant growth responses were absent when plants were treated with imidacloprid and insects were excluded. Results from a field study showed similar whitefly control and yield responses to imidacloprid and bifenthrin+ endosulfan applications. Hence, we conclude that growth and yield response to imidacloprid is associated with control of whiteflies and the subsequent prevention of damage, rather than a compensatory physiological promotion of plant growth processes.

Most experimental treatments effectively reduced Bemisia tabaci [sweetpotato whitefly (WF) also known as silverleaf WF, B. argentifolii] adults and eggs in cantaloupes relative to the untreated check at 6 days after treatment of each of five applications. Acephate (Orthene®), buprofezin (Applaud®), bifenthrin (Capture®), endosulfan, fenpropathrin (Danitol®), naled (Dibrom®), and pymetrozine(CGA -215944, Ciba) treatments had the fewest adults and eggs. Insect growth regulator (IGR) materials in combinations, pyriproxyfen (S-71639, Valent) and fenoxycarb (Ciba),were more effective in reducing WF relative to the untreated check than when applied alone. Registered products, Dibrom®, endosulfan, and methamidaphos (Monitor®) were effective in combinations or in alternating applications.

Several experimental insecticide treatments alone or in combinations were evaluated and demonstrated efficacy against Bemisia argentifolii [silverleaf whitefly (WF) also known as sweet potato WF, B. tabaci]. At each rating date following each of four applications, the number of adult and immature WF were reduced relative to the untreated check CGA-215944 (Ciba) treatment combinations were similar at each rating date and significant differences could not be distinguished between the addition of fenoxycarb (Ciba) or CGA-59205 (Ciba). Combinations of insecticides or alternating with insect growth regulators (IGR's) also significantly reduced numbers of WF adults and immatures similar to the standard treatment of bifenthrin (Capture®) plus endosulfan. A single application of pyriproxyfen (Valent) was followed by different treatments [endosulfan followed by fenpropathrin (Danitol®) plus methamidaphos (Monitor®) followed by endosulfan] at each application date. Buprofezin (Applaud®) was combined or alternated with endosulfan at each application and similar reduction of WF was observed. Pyridaben (BASF) did not adequately reduce WF adults and immatures relative to the standard treatment in this test. The Ciba compounds and single or multiple applications of the IGR's, pyriproxyfen and Applaud were highly effective in substantially reducing WF immatures and adults in this test.

In small plot field testing, the new IGR's, buprofezine, pyriproxyfen, and fenoxycarb plus CGA-215944 , offered very good reduction of the WF adults and immature stages for several weeks. Combinations of the new insecticides and alternating weekly applications were effective in minimizing WF season-long. Pyrethroids, bifenthrin and esfenvalerate plus endosulfan treatments, were effective after early applications and nymph counts were elevated after the third application. Oxydemeton-methyl and imidacloprid treatments applied weekly compared favorably with the new chemistries to reduce adults and immatures. Pyridaben applied weekly reduced adult counts relative to the untreated check but immatures increased after the third application.

In a small plot field test on cantaloupes, abamectin (Agri-mek®), cyromazine (Trigard®), spinosad (Success®), and pyriproxyfen (Knack®) demonstrated efficacy to reduce the number of mined leaves caused by leafminers (Liriomvza sativae and L. trifolii). Multiple applications of Agri-mek and Trigard resulted in melons having the fewest number of mined leaves. Success and Knack were effective in reducing the number of mined leaves relative to the untreated check. All of the treatments provided effective control of leafminers for 14 to 21 days after treatment. Success exhibited a rate response with the highest rate showing the fewest number of mined leaves compared to the lower rate.

Cantaloupe growth was influenced by using imidacloprid (Admire®) insecticide to control, suppress, or reduce whiteflies. The growth rate of cantaloupe was evaluated at regular intervals after crop emergence and a rate response was observed with greater growth with respect to increase in Admire® rate. Following at planting time applications, at 3 and 4 weeks after treatment (WAT) cantaloupe plants had more foliar growth and a greater number of leaves with increasing Admire® rate. At 5 to 8 WAT, cantaloupe vines exhibited greater growth with increasing rates of Admire®.