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Pasture production losses caused by natural infestations of black field cricket (Teleogryllus com modus Walker) were quantified on dairy pasture on clay or clay loam soils in Northland. In 1980 and 1981, summer and autumn rainfall was above normal and cricket densities were too low (2-5/m2) to influence pasture production. In the dry 1979, 1982, and 1983 years, cricket populations were moderate (8-22/m2) and significantly affected pasture production. Responses from baiting crickets ranged from 0.4 to 1.3 kg dry matter (DM) ha-1 cricket-day-l m-2. A loss of 0.8 kg DM ha-1 cricketday-l m-2 would mean that a field population of 20 crickets/m 2 could cause a pasture loss of 1600 kg DM/ha. Pasture loss from cricket attack occurred primarily during February-April when growth was severely restricted because of low soil moisture.

Widespread and severe pasture damage occurred on many farms in northern regions of Northland during the 1982-83 drought. Eight farms were investigated where black beetle, Heteronychus arator (Fabricius) (Coleoptera : Scarabaeidae), was assumed to be responsible for the damage. Black beetle adults, eggs of black field cricket, TeleogrylIus commodus (Walker) (Orthoptera: Gryllidae), and other insect pests were extracted by hand sorting and wet sieving soil cores taken from damaged pasture. The presence of black beetle larvae and crickets was also determined from an examination offrass and by noting the presence of tunnelling or soil fractures. Black beetle and crickets were the only insect pests found in abundance. Black beetle numbers were moderate (35/m2) or high (l09/m2) on the 2 farms with sandy soils (yellow-brown sands) but were low ( < 14/m2) on the 6 farms with clay (northern yellow-brown earths) or semi-volcanic soils (brown and granular loams and clays). Black field cricket egg densities were > 1000/m 2 and the frass recovered was predominantly from crickets on the 6 farms with clay and semi-volcanic soils. This suggested that cricket populations had been > 40-1 00/m2 and that crickets were responsible for the severe pasture damage that occurred on the 6 farms with clay and semi-volcanic soils, whereas black beetles were associated with the severe pasture damage that occurred on the 2 farms with sandy soils.

Synopsis During the first grazing year, a Ladino clover‐bluegrass mixture was more productive in terms of carrying capacity, gain per acre, and TDN consumption per acre than an Italian birdsfoot trefoil‐bluegrass mixture. The trefoil mixture was more productive the remaining two years of the test. Ladino clover was eliminated from the mixture by drouth. Continuous grazing killed the birdsfoot trefoil. The trefoil remained in the mixture when grazed with a rotation system of about two weeks grazing and four weeks rest.