How to Manage Pests
UC Pest Management Guidelines
Thrips are minute, slender-bodied insects usually possessing two pairs of long, narrow wings, the margins of which are fringed with long hairs. Some species cause injury by direct feeding, others by vectoring plant viruses, and still others are predatory on mites and small insects. Because of their high populations in alfalfa and their easily identifiable injury some have long considered thrips to be major alfalfa pests.
Thrips mouthparts form a lacerating-sucking cone, and the insects feed by rasping and lacerating the food tissues and then sucking-up the resulting juices. The rasping leads to deformed and crinkled leaves resulting from uneven growth around the injury (feeding) site. Feeding, particularly near the leaf mid-rib, causes curling and distortion of the leaves, which often have a cuplike or puckered appearance.
Western flower thrips have never been shown to cause economic damage in California. In fact, they often serve as alternate prey for a number of natural enemy species commonly found in alfalfa. Western flower thrips can be an effective natural enemy of spider mites. The cost of treatment (insecticide and application costs) is not justified for this species. In addition, disruption to natural enemy populations and the potential outbreak of other pests caused by insecticide treatment must be taken into account.
The exceptions to the "do not treat thrips" recommendation in alfalfa include the following: 1) very high populations of bean thrips and/or onion thrips. These species are relative newcomers to alfalfa and are considerably more destructive than flower thrips. 2) dryland alfalfa may be considerably more susceptible to thrips injury than irrigated alfalfa.
|The following materials are listed in order of usefulness, taking into account efficacy and impact on natural enemies and honey bees. When choosing a pesticide, also consider environmental impact. Not all registered pesticides are listed. Always read label of product being used.|
|(Lannate) LV||Label rates||48||7|
|(Lannate) SP||Label rates||48||0|
|MODE OF ACTION: A carbamate (Group 1A)1 insecticide.|
|COMMENTS: Restricted re-entry interval: 48 hours. Do not graze or feed livestock for 7 days after application. Do not apply when bees are present or apply more than 3.6 lb a.i./acre/season.|
|(Pounce) 3.2 EC||Label rates||12||see comments|
|MODE OF ACTION: A pyrethroid (Group 3)1 insecticide.|
|COMMENTS: Do not use more than 0.2 lb a.i./cutting. Do not apply to mixed stands with intentionally grown forage grasses and/or legumes. Preharvest interval is 0 days for 4 oz/acre and 14 days for more than 4oz/acre.|
UC IPM Pest Management Guidelines:
UC ANR Publication 3430
L. D. Godfrey, Entomology, UC Davis
E. T. Natwick, UC Cooperative Extension, Imperial County
P. B. Goodell, Entomology, Kearney Agricultural Center, Parlier
R. F. Long, UC Cooperative Extension, Yolo County