Alfalfa harvest strategy effect on lygus bug (Hemiptera: Miridae) and insect predator population density: implications for use as trap crop in cotton


This study is summarised as evidence for the following.

Action Category

Leave part of the crop or pasture unharvested or uncut

Action Link
Natural Pest Control
  1. Leave part of the crop or pasture unharvested or uncut

    A replicated trial in 1990-1991 on alfalfa Medicago sativa strips in cotton Gossypium hirsutum fields (Godfrey & Leigh 1994) found that strips where each half was cut alternately every 14-17 days had more natural enemies (big-eyed bugs Geocoris spp., minute pirate bugs Orius spp. and damsel bugs Nabis spp.) than a completely cut alfalfa field (alternately-cut strips every 14 days: 50.8-184 individuals/1.9 m²; alternately-cut strips every 17 days: 148.8-181.7; completely-cut field: 39.3-101.5). However, alternately cut strips also had more lygus bugs Lygus hesperus (pest) than completely cut alfalfa (alternately-cut strips every 14 days: 43-66.6 individuals/1.9 m²; alternately-cut strips every 17 days: 38.6-103; completely-cut: 4.6-8). Uncut strips had high numbers of lygus bugs and natural enemies (128.4-191.4 lygus bugs/1.9 m², 87.1-339.4 natural enemies). Alfalfa strips (91.4 x 4.1 m) within the cotton crop or adjacent to it were established November 1989. Eight and twelve strips were studied in 1990 and 1991 respectively. Strips were cut completely on 30 April 1990 and 28 May 1991. There were three cutting treatments in both years, starting two weeks after the first cut: uncut, cut alternately every 28 days (one 2.05 m half strip cut, the other half cut 14 days later) or one alfalfa field cut completely every 28 days. In 1991, a 35 day alternate cutting treatment was also used (half the strip cut every 17 days). There were four replicates. Cuttings were not removed. Arthropods were D-Vac suction sampled weekly from May to August.


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