Desert Vegetable Advisory - February 23, 2004 (ACIS)

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

February 23, 2004
Vol. 2; Issue 5

Production Update:

Planting of most leafy vegetable crops has ceased, with the exception of an occasional baby leaf or spinach field planting. Harvest of lettuce and cole crops appears to be on the decline and has been variable over the past week or so due to cold weather and sporadic rainfall earlier this week (Table 1). Soil temperatures remain low and ambient temperatures are forecasted to warm up slightly in the first 2 weeks in March (http://www.intellicast.com/). Markets appear to be steady and produce quality is excellent. Powdery mildew (more articles on powdery mildew) can be readily found on untreated head lettuce at the Yuma Ag Center. Planting of cantaloupe and honeydew crops continues. Seed corn maggots (picture) have caused some damage to emerging melons in eastern Yuma County.

Pest Update:

Area-wide Trapping Network: Based on our trap catches in the Yuma Valley, insect activity remains to be at seasonal lows for whiteflies and leafminers (Fig 1). Thrips activity appears low based on trap catches, but populations appear to be increasing on plants at the Yuma Ag Center. Aphid flight continues to fluctuate throughout the winter with high numbers of alates moving within the last week. This may be associated with both high winds and gradually declines in produce acres. The majority of aphids captured are cabbage aphids, green peach aphids, and cowpea aphids.

Seed corn maggot: As noted above, seed corn maggots have caused damage to emerging melon stands in cantaloupes being grown Yuma Co. Weather conditions are presently favorable for infestations (cool and wet weather). Based on our experiences in the desert, other conditions that favor maggot infestations are high organic matter in soils prior to planting (large amounts of plant residue not decomposed, specially when combined with application of manure ).

Aphids: Green peach aphids (GPA) (picture) remain abundant on untreated head lettuce at the Yuma Ag Center. In some plots we have measured > 100 aphids per plant and have observed significant contamination of harvestable heads. Admire is working well against GPA, as is Provado and Assail (registered only in CA) (Fig 2) . Dimethoate and endosulfan applied alone are only providing marginal control of GPA. Foxglove aphids and Lettuce aphids are continuing to build at levels similar to what we observed last season. Higher rates of Admire (>20 oz) are providing good control of these aphids thus far. Also with the increase in cabbage aphid alates detected on sticky traps, seed crop growers should begin closely monitoring for this aphid on pre-blooming and blooming crops.

For more information on control of these aphids visit:

Insect Management For Desert Lettuce Production (PDF file, 1.67MB)

Foxglove Aphids in Lettuce: Control with Reduced-Risk and Conventional Insecticides

Management of Aphids in Brassica Seed Crops with Selective Insecticides

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

Fig 1. Sticky Trap Catches for the Yuma Valley, 2003-200 Graphs of the mean number of aphids, whiteflies, thrips, or leafminers on sticky traps per day. From September 13, 2003 to February 2004.

Graph of the residual efficacy of various (8) insecticides against green peach aphid in head lettuce.

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.

Other Desert Vegetable Advisories