Several new insecticide chemistries were evaluated and compared with standard chemistries for residual efficacy against cabbage looper in lettuce. Four field trials were conducted at thinning, and heading stages of lettuce. These replicated trials clearly demonstrate that the new insecticides provide a solid 7 day residual efficacy (>90% control) following spray applications. Overall, Success at rates ranging from 4.5-6.0 oz/acre appeared to provide the most consistent residual activity on larvae present on plants at time of application. Confirm, appeared to have less consistent residual, but control was generally similar to Success. The newer compounds Proclaim and Avaunt, showed good residual efficacy for up to 7 days, and will be a welcome additions to the growers insecticide arsenal. Finally, the fact that all of these compounds are effective against large larvae, in part explains their consistent residual activity on lettuce.

A single application of buprofezin (Applaud7) at 0.38 lb AI/A had the fewest number of adult whiteflies (WF) on rating dates at 13, 21, and 27 days after treatment (DAT). The number of immature WF at 21 DAT of a single Applaud application ranged from 0.8 to 5.2 nymphs/leaf, significantly less than the untreated. Applaud treatments were effective in minimizing the immatures for 21 DAT of a single application and then numbers began to increase before 27 DAT. Applaud plus two subsequent weekly applications of bifenthrin (Capture7) plus endosulfan (Thiodan7, Phaser7) was almost similar to single applications of Applaud alone and adult numbers were also low. Weekly applications of the pyrethroids plus endosulfan reduced the adult WF relative to the untreated at 1 week after treatment (WAT). At 2 WAT of the third application, fenpropathrin (Danitol7) and Capture continued to show reduced numbers of adults and esfenvalerate (Asana7) was similar to the untreated. Danitol treatments had numerically fewer adults than Capture which was lower than Asana. The lowest adult and immature WF populations were observed season-long in the CGA-293343 (Novartis) treated cantaloupes. Both rates, 0.067 and 0.09 lb AI/A performed similarly and numerically slightly fewer nymphs were observed for the higher rate. CGA-293343 plus CGA-215944 (pymetrozine, Fulfill7) performed similar to the two rates of CGA-293343 alone.

A single application of S-1812 (Valent) at 0.15 and 0.20 lb AI/A effectively reduced Plutella xylostella (diamondback moth, DBM) in broccoli compared to the untreated check. S-1812 at 0.15 lb AI/A performed similar to thiodicarb (Larvin) at 1.0 lb AI/A. S-1812 significantly reduced the DBM at 5 days after treatment (DAT) and control was effective for up to 14 DAT. S-1812 was less effective against Trichoplusia ni (cabbage looper, CL) compared to DBM control efficacy or Larvin. S-1812 reduced the development of small CL to larger sized larvae.

CGA-293343 and Admire applied to the soil at planting time provided good control of WF at rating dates 34, 45, and 52 DAP. Cantaloupes treated with CGA-293343 at 0.09 lb AI/A showed a greater increase in number of immatures after 45 DAP compared to the CGA-293343 at 0.18 lb AI/A applied on melons. At 59 DAP, the higher rate of CGA-293343 continued to reduce the number of immatures compared to the lower rate and untreated check. Admire treated melons with or without a subsequent foliar insecticide treatments showed reduced WF nymphs at 45 and 52 DAP or 10 and 17 days after treatment (DAT) of foliar applications. Foliar applications of Applaud or Asana plus endosulfan did not significantly reduce WF immatures compared to a single at-planting time application of Admire. The application of either foliar treatment did not extend the length of control beyond that offered by the Admire treatment.

New soil injected and foliar insecticides were evaluated for their efficacy towards potato aphids in green leaf lettuce. The soil injected insecticides, Platinum and V10066, both appear to be viable alternatives to Admire, providing effective aphid control through harvest or ca. 90 days post-planting. Two foliar applications of Acetamiprid or Aphistar timed ca. 14 days apart beginning at the onset of aphid colonization provided superior aphid control over Provado or Fullfill, and control similar to that of the soil injected insecticides.

Proclaim and a normal use rate of 5 oz/ac of Success were highly effective against cabbage looper, Heliothis and beet armyworm. A low rate of 1.5 oz/ac of Success provided sufficient control of Heliothis and beet armyworm, but was weak against cabbage looper. While a low rate of 2.56 oz/ac of Warrior was not especially active against any of the target species. However, when this rate of Warrior was mixed with the low rate of Success, control across all the species was good, and was statistically similar to the higher rate of Success. Although Intrepid appeared slightly more active than its sister compound Confirm, it appears that it too will benefit from the addition of a pyrethroid for control of Heliothis and cabbage loopers on large lettuce plants.

Susceptibility to spinosad (Success®/Tracer®) of beet armyworm (Spodoptera exigua) from the southern U.S.A. and Southeast Asia was determined through exposure of third instar larvae to dipped cotton leaves. LC₅₀ values of field populations ranged from 0.6 to 14 μg spinosad/ml. Field populations were 3.0 to 70-fold less susceptible to spinosad than was a susceptible reference population. The least susceptible population was collected from Thailand. We hypothesized that this population was resistant to spinosad because: (1) it was significantly less susceptible to spinosad than all other populations evaluated and than any other reports in the literature; (2) it regained susceptibility while in culture; (3) it was collected from a region of very intensive insecticide use and severe insect resistance problems; and (4) it exhibited significant survivorship on field-treated cabbage leaves. Piperonyl butoxide (PBO), diethyl maleate (DEM), and S,S,S tributyl-phosphorothiolate (DEF) failed to synergize spinosad in this resistant Thailand population, and PBO failed to do so in the least susceptible domestic population evaluated, the Parker, AZ, field strain. However, the synergist and field residue studies were conducted using a Thailand population that had levels of resistance that declined while in laboratory culture.

During the past 5 years, the efficacy and field performance of several new insecticides for control of Lepidopterous insects on desert lettuce crops has been investigated in small plot trials at the Yuma Agricultural Center and in produce fields with commercial cooperators. The objective has been to determine how these new chemistries will fit into pest management programs in Arizona. Thus, research programs have been focused on studies to define use patterns for these insecticides chemicals that can be integrated into our local management programs in the most cost-effective way possible. This report was created to provide an overview of the new chemistries being developed, their field activity and characteristics, and guidelines for use in head lettuce. In addition, an approach for sustaining the long-term efficacy of these products is discussed.

The Western Growers Association and Arizona Cotton Growers Association worked cooperatively with a group of University of Arizona scientists, Arizona Department of Agriculture officials and regional pest control advisors to develop general guidelines for managing whiteflies and specific recommendations for Applaud and Admire use. This was achieved by identifying differences in crop production, insecticide use, and whitefly population dynamics on key host crops within three distinct growing regions in Arizona. Data was compiled that when graphically illustrated identified important, multidimensional interactions within cropping systems. Based on the patterns resulting from our analysis, initial recommendations have been formulated to harmonize chemical use across commodities by restricting Applaud use to only once per crop season in use windows, with additional guidelines for reducing the possibility of exposing successive whitefly generations to the same mode of action. The diversification and limitation of Admire and other active ingredients, and the employment of cultural practices are also be considered. Should this model of cooperation be successful, valuable and scarce modes of action may also be shared in the future within diverse, integrated use systems.

Whitefly populations in the Yuma area have been reduced to levels that growers can cost-effectively manage. Data from our studies suggest that these declines in pest populations are largely attributed to the use of Admire 2F (imidacloprid) soil treatments. Relative to the outbreaks in 1993-1994, whitefly populations during the past four growing seasons have remained at sub-economic levels on lettuce crops throughout the growing areas in Yuma This chemical has provided excellent control of whiteflies on fall lettuce, and aphids on spring lettuce. After 6 years of evaluation in commercial fields, the product appears to remain highly efficacious, maintaining good residual activity. Studies in 1998 on fall broccoli and melons crops further support this conclusion. Factors responsible for this sustained efficacy of Admire are discussed.