Pest		Threshold	Reference
	alfalfa caterpillar	6 or more larvae per sweep 10 non-parasitized larvae per sweep	UI CIS 908 (1995) University of California IPM Pest Management Database (1997)
	alfalfa weevil	30% plant terminals with feeding damage OR 20 or more larvae per sweep 10-15 larvae per sweep	UI CIS 908 (1995) UI Bulletin 547 (1990)
	armyworms	15 non-parasitized larvae per sweep (worms at least 1/2 inch long)	University of California IPM Pest Management Database (1997)
	blue alfalfa aphid	40-50 per stem 10-12 per stem on new regrowth	UI Bulletin 547 (1990) University of California IPM Pest Management Database (1997)
	grasshopper/crickets	15 grasshoppers per square yard	University of California IPM Pest Management Database (1997)
	pea aphid	100 per sweep on plants less than 1 foot tall OR plants are wilting and field is more than 2 weeks from cutting	UI CIS 908 (1995)
	pea leaf weevil	20% or more seedlings are defoliated	UI CIS 908 (1995)
	spotted alfalfa aphid	1 per stem in new seedlings, 10 per stem in established stands 20-30 per stem in mature stands, 1 per 2 stems in new seedlings (broadcast seedlings), 1 per 5 stems in new seedlings (row seedlings) Do not spray if there is 1 lady beetle adult per 5 to 10 aphids or 3 lady beetle larvae per 40 aphids 20-40 per stem in established stands	UI CIS 908 (1995) UI CIS 878 (1991) UI Bulletin 547 (1990)

Thresholds are not available for these pests: alfalfa seed chalcid; blister beetles; clover leaf weevils; clover root curculio; cutworms/armyworms, -army cutworm, -black cutworm, -spotted cutworm, -variegated cutworm; meadow spittlebugs; slugs; thrips; webworms; white grubs.

References: UI Bulletin 547 Idaho Forage Handbood, UI CIS 878 Spotted alfalfa aphid in alfalfa grown for seed and forage in Idaho, UI CIS 908 Control of alfalfa hay insects in Idaho, University of California IPM Pest Management Database (1997).

Revised: August 12, 2008

Webmaster:
nbell@uidaho.edu