November 17, 2003
Vol. 2; Issue 2

Production Update:

Planting of head lettuce, broccoli and cauliflower transplants continues, with romaine, mixed and specialty lettuce and baby spinach plantings starting to increase in acreage. Harvests of all commodities has begun in all production areas. Markets appear to be strong and for the most part quality is good. No reports of tipburn on lettuce. Temperatures are averaging in the low 60’s and high 50’s (Table 1). We did have significant precipitation on Nov 12 where rainfall exceeded 0.5 inches in some areas. Consequently, harvest of some crops was delayed. There have also been reports of downy mildew showing up on some cole crops. Melon harvest is almost complete, and overall, fruit quality was good-excellent this fall.

Pest Update:

Area-wide Trapping Network: Pest activity based on trap catches appears to be on the decline, with the exception of aphid flights near the Colorado river (Fig 1). Again, aphids have been identified primarily as non-lettuce infesting species (ie, cowpea aphid, alfalfa and grain aphids). We have picked up a considerable number of winged cabbage aphids on traps, so PCA should begin to closely monitor for their presence in fields. However, no colonization has been observed or reported from the field. Movement of whiteflies, leafminers and thrips has been light over the past 2 weeks, probably a reflection of the seasonal cool weather.

Foxglove Aphids are Back !

Winged foxglove aphids (Fig. 2) have been found on head lettuce in the Yuma Valley near the west main canal this past week (reported from Co.13th – Co. 15th). It’s probably not a coincidence that the earliest reports of foxglove aphids were found in this same general area last November. Although, no colonization by foxglove (Fig 3) has been reported in lettuce yet, these findings should serve as an indication to PCA’s and growers that foxglove aphids could potentially be present in large numbers again this winter and spring and should be on the look out for the foxglove colonies as the season progresses. Studies from last year showed foxglove colonizing untreated commercial lettuce as early as mid-December (Table 2). For more information on aphid scouting and management, please consult the following (http://ag.arizona.edu/crops/vegetables/insects/veginspub.html#aphid). Management of foxglove aphids has not been well studied, largely because it has only recently been found in commercial lettuce. However, insecticide efficacy trials from last season have shown that several registered insecticides provided adequate control of these aphids. Admire (12-16 oz) has been the standard for aphid control in the desert and is strongly recommended for foxglove aphid control in spring lettuce. Furthermore, given the recent discovery of winged foxglove aphids, and the projections by the National Weather Service (http://www.cpc.ncep.noaa.gov) that temperatures this winter will likely be warmer than the long-term averages, growers should consider applying Admire at higher rates (19-20 oz/acre) for late November and December plantings.

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

· Significant rainfall was recorded in the Yuma area on Nov. 11-12

Yuma Valley : 0.40 in

Gila Valley: 0.42 in

Roll /Wellton: 0.54 in

Fig 1. Sticky Trap Catches for the Yuma Valley, 2003-2004

Fig 2. Winged form (alate) of foxglove aphid found on lettuce

Fig 3. Wingless form (apterae) of foxglove aphid found colonizing lettuce.

AZMET Weather Data
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