The 4lb/gal (4F) formulation of oxyfluorfen was significantly safer than the 2 lb/gal (2XL) formulation on broccoli when applied at the 2 or 3-leaf stages of growth. At 6 days after treatment of the first application at the cotyledon stage of the broccoli, significant injury to the broccoli ranged from 30 to 66% for all oxyfluorfen treatments. Crop stand reduction did not occur with either formulation. The 4F formulation at 0.25 lb AI/A gave nearly the same weed control as the 2XL formulation at 0.063 lb AI/A. The 4F formulation applied at the broccoli cotyledon stage of growth provided longer effective weed control for more than 3 weeks after applications. Later applications gave effective weed control for a period of time between 1 to 2 weeks.

Studies were replicated over 2 years to further evaluate the residual efficacy of several selective, reduced-risk compounds that are now registered for use in head lettuce. In most cases, the Success, Proclaim, Avaunt and Intrepid provided excellent seasonal efficacy against beet armyworm and cabbage looper larvae. Their performance at stand establishment and harvest were also examined. Based on the results of these studies and additional trials conducted over the past several years, we now have sufficient information for optimizing their uses in our lettuce pest management program. Because they are uniquely different insecticide chemistries, they can be rotated throughout the season to prevent the rapid buildup of resistance. A table was constructed that offers suggested uses for each compound throughout the season. The results are ultimately are aimed at assisting growers and PCA’s in making sound decisions on choosing compounds for use in controlling beet armyworm and cabbage looper in head lettuce.

Several relative sampling techniques (direct visual counts, beat pans and sticky traps) were compared to absolute counts (plant wash) to determine sampling reliability for estimating western flower thrips population levels in lettuce. In numerous plantings of experimental plots of head lettuce, the relative sampling methods indicated similar thrips population trends throughout the season and all relative estimates of abundance were significantly correlated with absolute densities. However, both relative methods could only account for a proportion of the adult thrips infesting head lettuce plants, where they estimated about 30% of the actual absolute population. For larvae, beat pan sample estimated about 18-20% of the actual population density, whereas direct visual counts accounted for less than 10% of the thrips present. Comparison of sampling methods in insecticide efficacy trials indicated that beat pan and direct visual counts did not always accurately estimate treatment differences for adult. For densities of thrips larvae however, beat pan and visual counts methods did consistently provide accurate estimates of treatment differences in efficacy trials. Overall, both beat pan and direct visual count procedures are reliable thrips sampling methods that will generally provide precise estimates of thrips abundance necessary in lettuce pest management programs. Furthermore, these methods, and the beat pan in particular, also may serve as effective research tools that provide reliable estimates of treatment differences.

Studies were conducted in the spring of 2001 and 2002 to evaluate the interaction between starter and side dress fertilizer mixes with neonicotinoid insecticides and their performance against whiteflies in spring cantaloupes in Yuma, AZ. No incompatibility was observed between the fertilizers and the Admire and Platinum mixtures applied at planting and side dress, and both insecticides provided comparable control of whitefly populations regardless of fertilizer used. However, based on our experience in 2001, we suggest that growers use a dilute mixture with the final applied volume to avoid any potential "clumping" problems in the mix tank. In some cases the addition of the DuneUp® starter fertilizer appeared to improve plant growth, but was probably more due to the unique mixture of NPK rather than the combination with the insecticides. Based on the results of these studies growers should not hesitate to apply either Admire or Platinum with starter and side dress fertilizers in melon crops.

The effect of three different release rates (1x [label rate], 10x, and 20x the recommended rate of 10,120/acre) of the parasitoid Eretmocerus eremicus on sweet potato whitefly populations found in open fields of cantaloupe was evaluated against populations in untreated control plots. Parasitoids were released from a point source in the center of each of nine treatment plots. Whitefly population growth, encompassing all developmental stages, and rates of parasitism were monitored within a 33 ft radius surrounding the center point in all 12 plots over a 52-d period. The rates of sweet potato whitefly population increase during this time were equivalent regardless of the parasitoid release rate. Whitefly densities were not limited in any of our treatment plots when compared to those found in the control plots. Moreover, mean rates of parasitism did not increase with time nor did they differ among the three treatments or control plots (7.9 ± 6.5%). Finally, estimated rates of parasitism were density dependent responding positively to increasing host numbers. The ineffectiveness of this parasitoid in controlling whitefly populations in the field may be due to its high propensity to disperse at low host densities or to influxes of immigrating whiteflies. Hence, the use of E. eremicus alone is not an efficient means to reduce whitefly populations in melon crops in the southwestern United States.

Several small-plot studies were conducted in the spring of 2003 to compare the residual efficacy of several new reduced risk insecticides with a number of conventional aphicide compounds on head lettuce and romaine. Our efforts were primarily directed at determining efficacy against the foxglove aphid, a newly discovered pest in Yuma. In general, several new neonicotinoid foliar compounds provided good residual control of all aphid species including foxglove aphid. Other new compounds were less consistent. Admire, the standard soil systemic used in lettuce, was inconsistent against Foxglove aphid providing 85-90% control relative to >95% control against other aphid species present in the plots. Conventional aphid compound such as Capture, dimethoate, endosulfan, Orthene and MSR consistently provided good, economic control of Foxglove aphids in both head and romaine lettuce. Based on the results of these and previous studies, a sampling procedure and action threshold are recommended for foxglove aphid control in desert lettuce.

Replicated studies were conducted to examine aphid distribution and insecticidal control in a commercial cauliflower seed crop in 2001, and in large plots at the Yuma Agricultural Center in 2003. Results were generally consistent in both studies. The primary aphid species found colonizing pre-blooming crops were cabbage aphids, turnip aphids, and green peach aphids. During the bloom period (March-April), the population was almost exclusively cabbage aphid feeding on seed pods and extensions. During the pre-bloom growth period, green peach aphids tended to colonize plants slightly earlier and were found primarily on the older frame leaves low on the plant. In most cases, male and female plants were colonized to the same extent. Cabbage and turnip aphids did not appear to have a clear preference between older and younger leaves, and appeared to colonize males and females equally. Once the plant began to bloom and set seed, cabbage aphid was the primary species (>90%) found feeding on developing seed pods in both tests. These aphid populations were very susceptible to contact insecticides and quickly knocked down by both Capture and MSR. Of the selective, bee safe products, Pirimor provided the most consistent residual aphid control. Assail and Fulfill worked well against aphids on foliage, but did not provide comparable control on seed pods. Aphid densities were extremely high in the untreated check and resulted in almost complete loss of the crop in these plots. Seed yields were not taken due to heavy losses to Sclerotinia and bird damage.

Several studies were conducted during the past two growing season to examine the population growth, distribution and damage potential of the foxglove aphid on head lettuce in the Yuma Valley. Light populations of foxglove aphids were first found colonizing untreated head lettuce in small experimental plots at the Yuma Agricultural Center in the spring of 2001. In the spring of 2002 foxglove aphids reached high population levels at YAC on spring plantings, but were not reported in commercial fields. This past spring foxglove aphid populations were wide-spread throughout the Yuma Valley, particularly in fields near the Colorado river, adjacent to citrus orchards and residential areas, and not treated with Admire. Experimental studies suggested that foxglove aphids can reach economic levels on desert head lettuce, particularly crops planted during late November and December.

Courier, Knack, Assail, Calypso, and Oberon treatments on cantaloupe were effective in maintaining reduced numbers of WF eggs, immatures, and adults for 30 DAT. After 30 DAT, all treatments showed that WF adult counts began to increase. Courier, Knack, Assail, Calypso, and Oberon treated cantaloupe leaves had adult WF counts of one-half or less that of the untreated check and remaining treatments. The pyrethroid plus endosulfan treatments were effective for 7 to 13 DAT in reducing immature WF. After 21DAT, the pyrethroid plus endosulfan treatments and Actara showed a greater increase in the numbers of eggs, immatures, and adults compared to Courier, Knack, Assail, Calypso, and Oberon treatments. The seasonal average number of eggs, immatures, and adults was the least on Assail treated cantaloupes. Knack, Courier, Calypso, and Oberon treated cantaloupes consistently had less eggs, immatures, and adults compared to the untreated check.

Downy mildew of broccoli, cauliflower and cabbage is caused by the oomycete pathogen Peronospora parasitica. Cool moist environmental conditions favor the development of downy mildew on these crops. Several potential new fungicides were evaluated for control of this disease on broccoli in 2003. A moderate level of disease had developed by crop maturity. Actigard, Actigard alternated with Quadris, Acrobat+Maneb and DPX-KP481 were among the best treatments in this trial. Actigard is not a fungicide, but is classified as a plant activator. When applied to plants, this compound stimulates a defense response in plants to some diseases. Actigard also has performed well in previous trials. Several other new products and some chemistries that are currently available provided significant levels of disease control as well.