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Desert Vegetable Advisory
 
Cooperative Extension
 
 

Yuma Agricultural Center, 6425 W. 8th St., Yuma, AZ 85364
Phone: 928-782-3836 FAX: 782-1940

 

October 15, 2002
Vol. 1; Issue 2

Production Update: Planting of lettuce and cole crops continues at a constant pace, with mixed and specialty lettuce and baby spinach plantings starting to increase in acreage. Temperatures are gradually declining, and the cooler evening temperatures (Table 1) are ideal for stand establishment. No serious production problems have been reported in the produce crops. However, a number of melon crops have tested positive for both potyvirus and whitefly-transmitted geminivirus in the Yuma Valley, as well as in the Imperial Valley. A few fields have shown symptoms of vine decline and may be suffering from Monosporascus cannonbolis or other related soil diseases. Samples have been submitted for positive identification.

Pest Update: Worm pressure continues to be heavy in some areas of the Yuma and Gila Valleys. Cabbage looper populations remain high, and beet armyworm pressure appears to be declining slightly. Flea beetles are still active and thrips can easily be found in head lettuce. No reports of significant diamondback moth on cole crops. Whitefly movement appear to be declining with the exception of the Gila Valley where trap catches peaked last week.(Table 2). Thrips movement remains low, but leafminer adult activity appears to have increased in the past few weeks. We are beginning to pick up winged aphid on sticky traps and lettuce plants in the Yuma Valley, but no colonization has been observed on plants. The aphids collected have consisted primarily of cabbage aphid, cowpea aphid and an unidentified green aphid.

Product Updates: Intrepid 2F (methoxyfenozide; Dow AgroSciences - label) insecticide was granted a label in Arizona last week and is now available for local use in leafy vegetables and cole crops. The product is an IGR (molt accelerating compound) with good residual activity at on cabbage looper and beet armyworm at appropriate rates. A "New" EPA Label for Avaunt WG (indoxacarb; DuPont - label) insecticide with a higher use rate range of 3.5 to 6.0 oz/ac (0.065 to 0.11 lbai/ac) for lettuce (head and leaf varieties) has been approved. The compound is effective against beet armyworm and cabbage looper as well. Both products are considered reduced-risk insecticides and have excellent fits in our Lettuce and Cole Crop IPM programs. Figure 1 below provides data illustrating the relative efficacy of these new compounds against Success and Proclaim. The trial was conducted at the Yuma Ag Center in small, replicated plots (4 beds * 45 ft). Tthe data represents the residual efficacy (5, 8 and 12 days after treatment) for several rates of each compound following a broadcast application made on thinning stage lettuce (4 leaves) on September 25. In general, all insecticide treatments provided the same level of beet armyworm and cabbage looper control at 5 and 8 DAT. By 12 DAT, residual activity of all the compounds had declined.

For more information on these compounds and how they fit within our Vegetable Pest Management Programs please visit the following ACIS web pages:


Table 1. Temperature recorded from AZMET stations at three Yuma growing locations.
  Temperature (°F)
Yuma Valley   Gila Valley   Dome Valley/Welton
Date Max Min Avg   Max Min Avg   Max Min Avg
Sep 2-6 108 78 93    108 76 92    110 75 92
Sep 6-10 - - -    96 75 86   95 73 84
Sep 10-13 100 69 84    104 68 86   101 70 86
Sep 13-18 104 70 87    106 69 88   106 70 88
Sep 18-23 103 67 85   105 65 85   103 64 84
Sep 23-27 107 69 88    109 67 88   108 64 86
Sep 27-30 95 69 82    95 64 80   96 63 80
Sep 30-Oct 4 83 57 70    85 54 70   85 51 68
Oct 4-Oct 8 93 55 74   95 54 75    94 51 73
Oct 8-Oct 11 97 60 78    99 58 79   99 56 77


Table 2. Insect activity measured from yellow sticky traps at at three Yuma growing locations.
  Mean Adults / Sticky Trap / Day
Yuma Valley Gila Valley Dome Valley/Welton
Date WF LM THP APH WF LM THP APH WF LM THP APH
Sep 2-6 2.4 0.1 0.1 - 14.1 0.1 0.1 - 34.3 0.1 0.1 -
Sep 6-10 1.9 0.9 0.5 - 8.5 0.2 0.1 - 16 1.8 0.4 -
Sep 10-13 17.1 3.3 0.3 - 20.1 0.9 0.1 - 24.8 2.4 0.4 -
Sep 13-18 14.5 5.7 0.5 - 6 0.2 0 - 53.3 0.7 0.2 -
Sep 18-23 10.3 2.6 0.4 - 6 0.8 0.1 - 19.5 2 0.4 -
Sep 23-27 4.3 1.6 0.3 - 5 1.2 0.3 - 17.8 0.8 0 -
Sep 27-30 5.6 0.4 0.2 - 1.7 0.1 0.2 - 2.7 1.6 0.4 -
Sep 30-Oct 4 6.3 0.3 0.1 - 0.9 0 0.3 - 1.3 1.1 0.2 -
Oct 4-Oct 8 4.4 3.2 0.3 0.1 13.4 0.6 1 - 2.8 3.1 0.5 0
Oct 8-Oct 11 1.1 4.8 0.4 0.1 20.7 1.1 0.8   1.6 3 0.1 0
WF=Silverleaf whitefly; LM= Leafminers; THP=Thrips 

Three graphs of the efficacy of various new insecticides against cabbage looper and beetarmyworm on head lettuce.

AZMETDetour sign Weather Data

Disclaimers--


For more information contact:
John C. Palumbo, jpalumbo@ag.arizona.edu Research Scientist (Entomology)
College of Agriculture, The University of Arizona, Tucson, AZ.

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document located at: http://cals.arizona.edu/crops/vegetables/insects/advisories/2002/vegadv101502.html
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