Pasture mealybug (Balanococcuspoae) was found infesting two field trials evaluating the performance of selected strains of the endophyte Neotyphodium lolii in ryegrass (Lolium spp.) in Canterbury, New Zealand. Deterioration of endophyte-free plots relative to endophyte-infected plots had been observed. In Trial A, pasture mealybug were sampled in plots of the perennial ryegrass cultivar 'Grasslands Nui', without endophyte (nil), or infected with the wild-type endophyte, or the selected strains, AR1 and AR37. In Trial B, mealybug numbers on six ryegrass cultivars infected with AR1 or wild-type were compared with those on the same cultivars without endophyte. In sampling these trials, the presence of a root aphid, Aploneura lentisci, was also noted. Populations of mealybug in both trials were similar on all endophyte-infected treatments and significantly lower than populations on nil treatments. Neither AR1 nor wild-type appeared to reduce root aphid numbers, while AR37 may have had some effect. The amount of dead grass was significantly greater in nil than in endophyteinfected plots in Trial A, and yield of ryegrass was correlated with numbers of mealybug and root aphid present. Pasture productivity in nil treatments had recovered by spring, in the year of the outbreak. The presence of endophyte, strain of endophyte and cultivar were all significant factors affecting both total dry matter and green yield in Trial B. Pasture mealybug accounted for 55% of the variation in a decline in growth rate that occurred in this trial over the summer-autumn periods between 2000 and 2001, particularly in the nil treatments. Two years after the outbreak there was 25% less ryegrass and persistently lower pasture yields in nil plots. We conclude that pasture mealybug are capable of inflicting severe damage to endophyte-free ryegrass in Canterbury, particularly during dry summer-autumn periods.

The discovery in 1981 that ryegrass endophyte is responsible for ryegrass staggers has required a total revision of our understanding of ryegrassbased pastures. The effects on grazing livestock range from obvious clinical disorders to chronic impairment of productivity. On the other hand, endophyte infection is essential to ryegrass persistence in most of New Zealand, protecting the plant from some invertebrate pests and from over-grazing, and perhaps promoting its tolerance of moisture stress. Vigorous, endophyte-infected pastures sometimes include less clover than pastures relatively free of endophyte. Active compounds produced by the endophyte have been identified, and conditions causing high levels of them have been documented in part. Endophyte strains which do not produce the compounds responsible for livestock toxicoses offer exciting new possibilities in grassland agriculture. Keywords: invertebrate pests, mycotoxicoses, Neotyphodium lolii, perennial ryegrass, ryegrass staggers

A national series of six small plot trials were sown in 1996 and four in 1997 to evaluate the performance of six novel fungal endophytes in Grasslands Nui perennial ryegrass. These endophytes do not produce the mammalian toxins, ergovaline and lolitrem B, but produce peramine, a feeding deterrent to the major ryegrass pest, Argentine stem weevil (ASW). Trials included the naturally occurring endophyte (wild-type) which produces both toxins, and an endophyte-free (nil) treatment. Pasture production was measured regularly and samples were taken at least once each summer-autumn from all trials for assessment of ASW damage. Black beetle larval damage was recorded on three trials. The toxin-free endophytes, AR1, AR12, AR22 and the wild-type were equally effective at reducing ASW adult feeding and larval damage significantly below that which occurred in nil treatments. Ryegrass infected with AR1, AR12, AR22 and the wild-type endophyte was damaged less by black beetle larvae than ryegrass without endophyte. The effect of AR24 on insect damage was variable and two other toxin-free endophytes, AR17 and AR506, which had low infection rates, seldom reduced either ASW or black beetle damage. Yield differences between treatments were found on two of 21 sampling occasions between October and December and 12 of 30 sampling occasions between January and April. During summer-autumn, wild-type, AR1, AR12 and AR22 gave higher ryegrass yields than the nil, AR17 and AR506 treatments. In the second year of the 1996-sown trials, productivity of ryegrass with AR1 in the summer-autumn tended to be lower than that of the wild-type with significant differences occasionally occurring. Yield differences were correlated with either ASW or black beetle damage in North Island trials and with percent endophyte infection at all sites. Differences in yield at Lincoln, Canterbury, were attributed to pasture mealy bug. Three conclusions were drawn from these results: 1. Endophytes are very important for maximising ryegrass yield during summer and early autumn. 2. The effect of endophytes on yield is at least partly due to the insect resistance they impart. 3. The field performance of three toxin-free endophytes, AR1, AR12 and AR22, equalled that of the wild-type in terms of increased insect resistance but did not always match it in plant growth. Keywords: AR1, Argentine stem weevil, black beetle, endophyte strain, ergovaline, insect damage, lolitrem B, Neotyphodium lolii, ryegrass yield

and Gore were sampled every three months for three years. The white clover stolon material was dissected into three vertical classes: aerial, surface, and buried. Length and dry weight of stolon in each class were measured. The mean total weight of stolon and the distribution by weight of stolon in the three vertical classes varied among sites (P< 0.001). In addition, each year there was a highly significant (P <0.001) seasonal change in the vertical distribution of stolon at each site, with mean levels of approximately 80070 of stolon buried in winter and 40% in summer and autumn. At two sites, Wairarapa and Lincoln, exceptions to the seasonal. pattern of distribution of stolon were observed when low rainfall periods occurred. A significant negative correlation between threemonthly effective rainfall (rainfall minus Penman potential evapotranspiration) and weight per unit length of buried stolon indicated that thicker stolons comprised the bulk of the stolon population after dry periods. Regression analyses also indicated