Desert Vegetable Advisory - March 20, 2004 (ACIS)

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

March 20, 2004
Vol. 2; Issue 6

Production Update:

Harvest of most produce crops is rapidly ending. There is still a small amount of acreage in the eastern part of the county (Tacna/Texas Hill areas) where lettuce and cabbage are still awaiting harvest. Vary little activity in the Yuma and Gila Valleys. What produce that is left will rapidly mature given the unusually high temperatures we have been experiencing over the past 2 weeks (Table 1). Quality is generally marginal due to high temperatures. Planting of melons appears to be complete, and crops are progressing well. Bees have been placed in several fields and growing conditions are ideal (Table 1). Pest pressure is light on melons, but growers and PCA’s should begin scouting for whiteflies and cabbage loopers as fruit set begins. In addition, leafminer adults (picture) have been observed in high numbers on seedling melons at the Yuma Ag Center and on trap catches (Fig 1).

Pest Update:

Area-wide Trapping Network: Based on our trap catches in the Yuma Valley, insect activity remains low for whiteflies, but leafminers and thrips numbers have increased significantly over the past week (Fig 1). Aphid flights are variable, but overall are declining.

Thrips adults (picture) can readily be found on produce crops and are reproducing at a high rate. This can lead to significant scarring of midribs and leaf margins. Control of adults is difficult as they are migrating from surrounding crops. However, caution should be taken to prevent the build up of immatures as they are primarily responsible for scarring damage to leaves and midribs (Fig 2). For more information see the paper below:

Thrips Management in Desert Lettuce: Understanding Crop*Insect Interactions (9/03 AZ Dept. of Ag. Specialty Crop Grant Report), PDF file, 667KB

Aphids: Aphid populations on produce crops have declined considerably. This is due in part to the high temperatures (reduce growth and reproduction) and the build up of natural enemies such as lady beetles and syrphid ( picture) flies. However, large numbers of alate (winged) green peach aphids ( picture) were observed over the past few weeks. Because this species is a know vector of a number of viruses, it is quite possible that the incidence of virus on spring melons crops could be higher this year. Crops treated with Admire have shown to have a lower incidence of virus in past years. PCA’s should pay close attention to crops not treated with Admire, and might consider side-dressing a systemic neonicotinoid such as Platinum to prevent aphid build up. For more information see the paper below:

Compatibility of Fertilizer and Neonicotinoid Soil Applications for Whitefly Control in Spring Cantaloupes (2003), PDF file, 132KB

Table 1. Temperature recorded from AZMET stations at three Yuma growing locations.
Week Ending	Temperature (°F)
	Yuma Valley			Gila Valley			Roll/Wellton
	Max	Min	Avg	Max	Min	Avg	Max	Min	Avg
6-Sep	107	81	94	106	79	92	107	78	93
13-Sep	103	72	88	102	70	87	103	69	86
20-Sep	106	68	88	106	66	86	106	65	95
27-Sep	101	71	85	100	69	84	97	68	82
4-Oct	102	71	85	101	68	84	102	70	85
11-Oct	96	68	81	96	67	80	95	65	79
18-Oct	100	68	84	101	67	83	100	66	82
25-Oct	102	62	81	103	61	80	100	57	78
1-Nov	84	58	71	84	55	69	83	54	68
8-Nov	73	49	60	77	46	59	73	43	57
15-Nov	73	52	62	74	50	61	74	48	59
23-Nov	74	48	61	74	45	59	75	43	58
30-Nov	68	44	57	69	39	53	69	39	51
7-Dec	75	41	57	76	39	55	76	35	52
14-Dec	67	41	54	68	39	53	67	36	51
21-Dec	68	40	54	68	38	53	70	32	49
28-Dec	67	43	55	68	42	55	69	40	55
4-Jan	61	37	48	61	35	48	64	33	47
11-Jan	67	41	54	67	39	52	69	35	50
17-Jan	73	46	60	76	45	59	75	47	57
24-Jan	67	43	54	69	43	55	69	41	54
31-Jan	68	40	53	69	40	53	68	37	52
7-Feb	68	39	54	68	39	53	68	36	52
14-Feb	67	37	54	66	36	52	67	32	51
21-Feb	74	45	59	75	42	58	75	42	58
28-Feb	68	46	57	68	44	56	70	42	56
6-Mar	68	44	57	69	45	56	69	44	56
13-Mar	88	53	72	88	52	70	90	52	70
20-Mar	93	53	73	94	52	73	94	51	72

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

Figure 2. Leaf scarring and rib bronzing on romaine lettuce from feeding caused by Western Flower Thrips

AZMET Weather Data
Search for Pest Photos

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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