November 27, 2002
Vol. 1; Issue 5

Production Update: Planting of lettuces, baby mixes, spinach and cole crops continues at a steady pace, and harvest is in full swing for most commodities in all growing areas. In general, yields and quality appear to be good and no major production problems have been reported. Temperatures in the three major growing areas have been around normal, but are cooling down considerably (Table 1). Melon harvest is almost complete and should be finished by Thanksgiving weekend.

Pest Update: Overall, insect flight activity appears to be declining, with the exception of aphid movement (Table 2) which is beginning to pick up in the Yuma and Gila valleys. As reported two weeks ago, foxglove aphid has been found colonizing head lettuce in the Yuma Valley and this aphid species has been positively identified in 2 more lettuce fields this week. In all cases where colonization has been reported, Admire was not applied at planting. All the foxglove aphid infestations have been found in the Yuma Valley from Co12th to Co15th and Ave D to the west main canal. In addition, foxglove aphids have been found in Algodones, Mexico.

Although thrips activity as measured by sticky traps has been relatively low (Table 2), thrips populations in head lettuce and romaine have been quite heavy this fall. Western flower thrips have become a major pest of head, leaf and romaine lettuce because of their ability to build up to large numbers, resulting in head contamination (Fig 1), and excessive scarring of leaf tissue from thrips feeding injury (Fig 2). The only viable means of controlling thrips is with insecticides. Lannate (methomyl; E.I. duPont de Nemours & Co.) combinations and Success (Dow AgroSciences LLC) are currently the industry standards for thrips control in lettuce. We have recently been asked by PCA's whether Proclaim (emamectin benzoate, Syngenta Crop Protection, Inc.) has thrips activity. Proclaim provides excellent control of worms. Because thrips are not listed on the Proclaim label, we decided to conduct a short efficacy trial to ascertain the activity of Proclaim on western flower thrips.

Figure 3 below provides data illustrating that Proclaim applied at a moderate rate (3.2 oz/ac) does not provide significant efficacy against thrips in head lettuce. The trial was conducted at the Yuma Ag Center in small, replicated plots (4 beds * 45 ft). The data represents the residual efficacy at 3, 7 and 14 days after treatment (DAT) for each compound following a broadcast spray application made on October 29 (post-thinning ;12 lf stage) and November 13 (pre-heading; 20 lf stage). In general, the number of thrips adults and larvae in Proclaim-treated plots did not differ significantly from the untreated check on any of the post-treatment sampling dates (Fig 3). Although the product may be efficacious at higher rates, we do not recommend that Proclaim be used for thrips suppression. Rather, the product provides good residual control of beet armyworm and cabbage looper at 3.2 oz and should be integrated into worm management programs at this rate. For more information on thrips management in lettuce visit the following ACIS sites:

Management of Aphids and Thrips on Leafy Vegetables

Impact and Management of Western Flower Thrips on Romaine Lettuce (2000), PDF file, 203KB (http://cals.arizona.edu/pubs/crops/az1177/az1177-1f.pdf)

Management of Western Flower Thrips in Head Lettuce with Conventional and Botanical Insecticides (2000), PDF file, 187KB (http://cals.arizona.edu/pubs/crops/az1177/az1177-1g.pdf)

Table 1. Temperature recorded from AZMET stations at three Yuma growing locations.

Table 2. Insect activity measured from yellow sticky traps at at three Yuma growing locations.

Figure 1. Western flower thrips infesting the inner surface of a cap leaf in head lettuce, Yuma, Arizona, spring 1998

Figure 2. Western flower thrips feeding damage (scarring) to young head lettuce leaves (A), and to leaf tissue and midribs of romaine (B), Yuma, Arizona, spring 2001.

Figure 3. Abundance of western flower thrips adults and larvae in head lettuce plants following spray applications of Proclaim, Success and Lannate/Mustang, Yuma Agric. Center, fall 2002.

= use your "Back" button to return to ACIS
PDF documents require Adobe Acrobat Reader

AZMET Weather Data

Disclaimers--