Aphistar provided the quickest reduction of the aphids after one application and continued residual control for up to 14 DAT-2. Following a second application and reduction of aphids, Pirimor, Provado, Fulfill, Actara, and Metasystox-R provided a varied degree of residual control of aphids between 5 and 14 DAT-2. A comparison of Fulfill rates indicated that the two rates were equally effective at 5 DAT-2 but the lower rate did not offer as long residual control compared to the higher rate. Endosulfan was moderately effective and did not provide acceptable control after 1 week.

Studies were conducted in 1998 and 1999 to evaluate three neonicotinoid insecticides for control of silverleaf whiteflies in melons and broccoli plots at the Yuma Agricultural Center. The results of these studies demonstrate that these insecticide uses offer vegetable growers management alternatives for controlling whiteflies comparable to what they have experienced with Admire®. In our spring trials, we applied Platinum® at planting, as a split application, and as a sidedress application. All methods provided whitefly efficacy similar to that provided by Admire. However, the split and sidedress applications provided more consistent residual control than Platinum applied at planting. Because of the mobility of the product in the soil, growers may have more flexibility for effectively applying the material post-planting. In addition, Assail, was applied as a foliar spray at various densities. Under spring growing conditions, applications of Assail provided significant whitefly control when initiated at low densities. Under high whitefly densities on fall melons and broccoli, application of Assail was capable of significantly reducing existing immature populations. These evaluations suggests that Platinum and Assail may be promising alternatives to Admire. We presume that it may allow growers to use the product in a responsive manner as a side dress (Platinum) or as a foliar (Assail) rather than having to rely on prophylactic Admire applications at planting.

The pyrethroid insecticides esfenvalerate (Asana®), bifenthrin (Capture®), or fenpropathrin (Danitol®) combined with endosulfan effectively reduced whitefly (WF, Bemisia argentifolii) counts at 1 week after treatment (WAT) following each of five applications. Asana, Capture, or Danitol combined with endosulfan effectively reduced WF counts at 1 WAT following each of five applications. Danitol treated melons exhibited fewer adult WF compared to Asana or Capture at most of the rating dates at 6 days after treatment (DAT) of each of the applications and also at 11 DAT of the last application. A single application of buprofezin (Applaud®) treatments or pymetrozine (Fulfill®) effectively reduced WF nymphs for 18 to 24 DAT and adults were reduced for 18 DAT. Fulfill exhibited a rate response where the higher rate reduced WF counts more than the lower rate.

Studies were conducted in three independent field trials to evaluate the efficacy of conventional and botanical insecticides against western flower thrips in head lettuce. Trials were conducted in spring lettuce under moderate and heavy populations pressures. Actara and Avaunt, two new experiential insecticides did not significantly control adults and provided only marginal activity against the larvae when applied alone. Combination of these products with either Lannate or Warrior significantly enhanced control, but usually not greater than that shown from the Lannate or Warrior applied alone. Several botanical products were evaluated (azadirachtin, pyrethrins, crop oils and garlic). Unfortunately, none of the botanical products significantly reduced thrips numbers to economically acceptable levels of control. Similar to previous studies, our results suggest that even the most efficacious products appeared to maintain thrips populations at constant levels and not necessarily reducing their numbers. More research needs to be conducted to determine the proper timing of applications to achieve optimal thrips using both conventional and botanical insecticides.

Success, Proclaim, and Avaunt were efficacious when applied alone or in combination with the pyrethroids, Warrior or Mustang. Warrior and Mustang alone also provided excellent control of the cabbage looper (Trichoplusia ni, CL) and diamondback moth (Plutella xylostella, DBM) at all rating dates for 3 weeks after a single application. Low infestation levels of the pests were attributed to the effectiveness of the insecticides.

At 3 days after the first application, RH-2485, Success, Proclaim, Avaunt, and Larvin reduced the total number of diamondback moth (DBM) larvae to less than 2.0 larvae per 10 plants compared to the untreated that had 7.0 larvae/10 plants. Alert, Kryocide, and S-1812 treated cabbage exhibited 4.0 to 5.0 larvae/10 plants and Lannate was intermediate with 2.7 total larvae/10 plants. Following a second application, Success and Proclaim completely controlled DBM for one week. Success, Proclaim, Alert, and Larvin continued to offer very good control of DBM for two weeks after the second application. S-1812 performed similarly to Lannate.

For a third year, a large block experiment was conducted at the Yuma Ag Center to compare the field performance of several lettuce IPM programs for control of lepidopterous larvae. Conventional, Reduced -risk , Bio-based and Modified IPM spray regimes were applied to control beet armyworm, cabbage looper and Heliothis species throughout the fall growing season. Differences in populations of total larvae among the treatments, relative to insecticide treatments and timing of application were observed at various times during the season. In general, the Conventional, Reduced -risk and Modified IPM approaches provided the most consistent control of lepidopterous larvae following each application. Harvest data showed that the spray regimes had a significant influence of head lettuce yield or quality. Maturity and quality were significantly reduced in the untreated control. An economic analysis shows that net returns varied widely among the management programs at different market prices. In conclusion, this study provides a strong data base to support the need for the development of experimental and biorational insecticide products as alternatives to conventional management programs in desert lettuce production. In addition, it demonstrates the dependance of IPM programs on a broad range of plant protection chemicals and control tactics.

Populations of cabbage looper were collected during 1998 from 12 geographical location in the United States, and were assessed for susceptibility to six new insecticides: Alert, Avaunt, Confirm, Intrepid, Proclaim, and Success, and to a standard insecticide, Pounce. There was no detectable evidence indicating insecticide resistance to any of the new insecticides. However, variability in response to Confirm, Proclaim, and Success warrants close resistance monitoring. Cabbage looper response to Pounce was extremely variable, and there was strong evidence for the occurrence of resistance. Populations from Jackson, MS, Sunderland, MA, and Whately, MA all exhibited high levels of resistance to Pounce with resistance ratios of 90.60, 93.50, and 76.30-fold respectively.

A season-long study was conducted to evaluate the efficacy of several conventional, experimental and bio-based insecticide combinations used in rotation against western flower thrips (WFT) in romaine lettuce. Results from this study showed that several insecticide rotational programs provided good control of WFT populations throughout the season. Adult abundance peaked just prior to the fourth spray on 28 March, whereas larvae numbers peaked about 2 weeks earlier on March 13. Fluctuations of larval and adult populations observed from weekly samples suggests that greater than 3 WFT generations developed during the experimental period. Averaged across all sample dates, the Success, Lannate and Warrior based rotations maintained adult and larval populations at significantly lower levels than all other treatments. The Bio-based, organic rotations (Neem/Garlic/COC/Sulfur/Diatect) did not differ from the untreated check. Percentage reduction of WFT larvae and adults compared with the untreated control was significantly greater following sprays which contained Success combinations. Consistent with reduction in WFT numbers, the Success/Lannate/Warrior, and Dimethoate based rotations resulted in significantly greater yields and less damage. Regression analysis suggests that larvae and total thrips abundance more consistently describes the variation measured in plant weights. Overall, this preliminary data further indicates that maintaining WFT abundance at low levels is important for maintaining romaine yield and quality.

Studies were conducted in the 1999/2000 growing season to examine the population dynamics and field distribution of aphid species on winter and spring head lettuce crops. Seven, 0.25 acre planting of head lettuce were established beginning in October with final harvest occurring in April. Plant samples were conducted weekly to estimate the numbers of both alate (winged) and apterous (wingless) green peach aphids, potato aphids, cowpea aphids and lettuce aphids. Lettuce aphids were more abundant this spring than anticipated, which may indicate that lettuce aphid may be a new pest for Yuma growers. However, based on a single years data, it is difficult to measure the threat that this aphid poses to the lettuce industry. Planting date and temperature likely has a strong influence on seasonal abundance of lettuce aphids. Similarly, the consistent appearance of cowpea aphids during the season was surprising , considering that it has seldom been observed on desert lettuce. Perhaps most surprising though was the low population abundance of green peach and potato aphids in out plots. Part of this unusual event may be due to the unseasonably warm, dry growing season that was experienced this year.