Habitat manipulation in lucerne (Medicago sativa L.): strip harvesting to enhance biological control of insect pests

Published source details Hossain Z., Gurr G.M. & Wratten S.D. (2001) Habitat manipulation in lucerne (Medicago sativa L.): strip harvesting to enhance biological control of insect pests. International Journal of Pest Management (formerly PANS Pest Articles & News Summaries 1969 - 1975, PANS 1976-1979 & Tropical Pest Management 1980-1992), 47, 81-88.
Share Tweet Email

Actions

This study is summarised as evidence for the following.

	Action	Category
	Leave part of the crop or pasture unharvested or uncut Action Link

Leave part of the crop or pasture unharvested or uncut

A replicated, controlled trial in 1997-1998 in a 4 ha alfalfa Medicago sativa field with strip- and conventional-harvesting in New South Wales, Australia (Hossain et al. 2001) found that predation and parasitism of Helicoverpa spp. (pest) eggs was higher in unharvested (36.7% eggs predated, 3.31% parasitised) than harvested strips (21.7% eggs predated, 0.85% parasitised). Total predator abundance (spiders (Araneae), red and blue beetles Dicranolaius bellulus and transverse ladybird Coccinella transversalis) was higher in the strip-harvested area (average 5.1-9.1 predators/0.4 m²) than the conventionally-cut area (1.2-7.6), and higher in unharvested than harvested strips. Helicoverpa spp. was less abundant in the strip- than conventionally-harvested area (0.1-9.2 individuals/0.4 m² vs. 0.7-27.6) but another pest, lucerne leaf roller Merophyas divulsana had similar numbers in both treatments (0.3-18.4 vs. 0.1-19.0); both pests were more abundant in unharvested than harvested strips. There were eight 200 x 14 m strips, split lengthways; one half cut a week before normal harvesting (harvested strip), one half cut two weeks later (unharvested strip). Subsequently, strips were cut when 10% alfalfa was flowering. Strips were vacuum-sampled five times. Helicoverpa spp. eggs were placed in strips to assess predation and parasitism rates. The 112 x 158 m conventionally-harvested block was cut three times, with three vacuum samples.