How to Manage Pests
UC Pest Management Guidelines
Border-strip harvesting involves leaving uncut strips of alfalfa at various intervals across the field. These serve as a refuge for natural enemy species and to retain lygus bugs in the alfalfa where they do no harm, thus keeping them out of neighboring crops such as cotton or beans where they cause significant damage. Research has shown that this practice significantly increases populations of parasites and predators of aphids, caterpillars, and other alfalfa insect pests.
To carry out border-strip harvesting, leave 10 to 14 foot wide uncut strips adjacent to every other irrigation border (or levee). At the subsequent harvest, these strips are cut with half of the alfalfa strip going into one windrow and the other half going into a second windrow to give a 50:50 blend of new and old hay. These windrows are then each combined with a windrow of newly cut (100% new) alfalfa making a blend of 25% old hay and 75% new hay. This technique minimizes quality problems from the older hay. Specific blends of old and new hay have been found not to significantly impact forage quality compared to 100% new growth alfalfa in most cases. Crude protein was not affected in five of nine cuttings (over 2 years) and Acid Detergent Fiber, used to calculate several quality parameters, was not impacted by blends that included 25% or less of old alfalfa.
At the following cutting, uncut strips are left adjacent to the alternate irrigation borders. As an alternative, uncut strips of alfalfa may be left adjacent to the crop to be protected, such as cotton or dry beans.
UC IPM Pest Management Guidelines: Alfalfa