Monitoring <i>Essigella californica</i> populations in Bay of Plenty forests

Abstract

Essigella californica (Monterey pine aphid) populations were monitored in the Bay of Plenty forests of Rotoehu and Kaingaroa over two years to determine what influence E californica has on the health of Pinus radiata and to identify any associated predators and parasites Populations were sampled throughout the canopy height of forests stands at three altitudinal ranges (lt;300 m 300600 m and gt;600 m above sea level) and three age classes (110 1120 and 2130 years old) Findings clearly show that although E californica populations vary markedly from one year to the next highest populations occurred in low altitude midaged P radiata in autumn Even at relatively high population levels in midaged stands E californica did not appear to have any visible effect on tree health The monitoring programme has shown that E californica cannot be considered a pest of P radiata in New Zealand

Monitoring Monterey pine aphids in Hawkes Bay forests

“…In general, few aphids were collected from the young tree age class. Similar results have been recorded in Bay of Plenty (Appleton & Gresham 2003) and Australia (Powell 2001). Powell found that older trees were most affected by the aphid, generally from the time of first thinning.…”

“…There was little visual evidence of MPA damage to trees in this study or other recent New Zealand studies (Appleton & Gresham 2003), but this does not necessarily indicate that this aphid does not cause economic damage to Pinus radiata. Phloem feeding insects can deplete carbohydrate reserves of trees, affecting their long-term growth and survival.…”

“…The size of MPA populations varied considerably between years and locations. In associated research many more aphids were found in Bay of Plenty forests than Hawke's Bay forests in both years, and more aphids were found in both areas in 2001-02 compared to 2000-01 (Appleton & Gresham 2003). Greatest numbers were recorded in April 2000 and 2001 in Bay of Plenty and April 2002 in Hawke's Bay.…”

“…It seems unlikely that natural enemies or emigration were important factors affecting MPA in this study because of the small number of natural enemies and the small number of winged adults found. Cold winter (and spring) temperatures may be important as smaller numbers of MPA were found at colder, higher elevation sites in Hawke's Bay in 2000-01 and in Bay of Plenty in 2000-01 and 2001-02 (Appleton & Gresham 2003). However, some of the greatest aphid numbers in Hawke's Bay in 2001-02 were found at the high elevation, medium aged class forest.…”

“…Two sampling methods were used. In both years beating, based on a protocol developed in Australia (Kent & Carnegie 2000) and used in similar research elsewhere (Appleton & Gresham 2003), was used. At each elevation and age class, 16-20 trees were selected.…”