Monitoring Monterey pine aphids in Hawkes Bay forests

Abstract

The Monterey pine aphid (Essigella californica) was recently found in New Zealand. To examine the seasonal biology and impact of this insect on Pinus radiata, aphids were sampled using beating and branch bagging methods over two seasons (October to April), from three forest elevations, and from three tree age-classes in Hawke's Bay forests. Many more aphids were found in 2001-02 than in 2000-01, with numbers peaking in January in 2001 and April in 2002. Few aphids were found from October to December. More aphids were recorded on trees in the medium and old age classes than in the young age class. There was no consistent pattern in aphid numbers in relation to elevation of forests. There was little visual evidence of aphid damage to trees but this does not mean that this aphid does not cause economic damage. Factors influencing the population dynamics of this aphid and sampling methods are discussed.

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

“…This study shows that in Bay of Plenty forests E. californica populations vary markedly from one year to the next, with highest numbers occurring in April in low altitude, midaged P. radiata. In comparison, Teulon et al (2003) found that E. californica populations were more numerous in older trees than in mid-aged trees in low elevation forests in Hawke's Bay. In our study E. californica was absent from forests above 600 m, whereas Teulon et al (2003) found it to be fairly abundant at this elevation.…”

“…In comparison, Teulon et al (2003) found that E. californica populations were more numerous in older trees than in mid-aged trees in low elevation forests in Hawke's Bay. In our study E. californica was absent from forests above 600 m, whereas Teulon et al (2003) found it to be fairly abundant at this elevation. The reason for the absence of E. californica at high altitude sites in Bay of Plenty can only be surmised.…”

“…In light of the Australian experience, it was decided to monitor E. californica populations at different altitudes and in different aged plantations across the Bay of Plenty region. This study was carried out in 2001-2002, in collaboration with scientists undertaking monitoring in Hawke's Bay forests (Teulon et al 2003).…”

Distribution and flight activity of the Monterey pine aphid in New Zealand

“…An interesting feature of the suction trap data is that, like foliage sample data (Teulon et al 2003;Appleton & Gresham 2003), numbers varied between sites and years but peak numbers occurred in late summer/early autumn. This late season abundance is interesting because most other conifer inhabiting aphid species have population peaks in spring and summer with a crash in late summer (Teulon et al 2003). Reasons for the MPA late season flight activity are not obvious and it would be interesting to investigate the role of climate and population density prior to production of winged morphs.…”

“…In New Zealand, damage appears to be limited to some needle yellowing at high density, and significant needle drop has not been recorded (Appleton & Gresham 2003;Teulon et al 2003). However Teulon et al (2003) suggest MPA may contribute to tree stress through depletion of carbohydrate resource in the roots, which in turn reduces timber yields and contributes to disease susceptibility. Long term studies assessing growth on trees treated with systemic insecticides to provide a comparison between trees with and without MPA would help determine the economic impact of this aphid.…”