Within‐tree and seasonal distribution of the pine woolly aphidPineus boernerionPinus kesiyatrees

Abstract

Summary1 The spatial and temporal distribution of pine woolly aphids, Pineus boerneri (Homoptera: Adelgidae) a pest of exotic pine trees in Malawi, was investigated in 5‐year‐old Pinus kesiya trees.2 Pineus boerneri was generally found to settle and reproduce on the outer shoot‐end sections of young P. kesiya trees. There was no evidence of preference for any particular levels of the tree canopy.3 The study suggests that the biological performance and, by implication, the pest status of P. boerneri in young P. kesiya trees can be influenced by external factors, particularly by the within‐tree and seasonal fluctuations in the level of nitrogen in the host trees, total rainfall and canopy structure.4 These findings are discussed in relation to possible management and control of P. boerneri in Malawi.

Infestation Density of Eucalyptus Gall Wasp,Leptocybe invasaFisher and La Salle (Hymenoptera: Eulophidae) on Five Commercially GrownEucalyptusSpecies in Tanzania

“…This type of crown structure receives light, moisture, and wind fairly equally in all parts, hence relatively equal distribution of gall wasps within the tree crown. Correspondingly, Chilima and Leather (2001) found that the pine woolly aphid (PWA) on 5-yr-old Pinus kesiya was generally settling and reproducing on the outer shoot-end sections of young P. kesiya trees and there was no evidence of preference for any particular levels of the tree canopy. Similarly, Madoffe (1989) and Petro (2009) reported that there was no evidence of preference of PWA damage to any particular levels of the tree canopy between tree crowns of P. patula and P. elliotii in Sao Hill, Tanzania.…”

Population dynamics of Thaumastocoris peregrinus in Eucalyptus plantations of South Africa

“…The data from this study, however, did not support this hypothesis at the Pretoria site (the only site with reliable rainfall data that could be used for this purpose). Rainfall during spring usually results in a flush of new leaves and shoots that are high in nitrogen, often leading to increases in numbers and feeding of other insects (Wolda 1978;Chilima and Leather 2001). Thaumastocoris peregrinus feeds on mature Eucalyptus leaves and possibly derives no benefit from this increased flush of shoots that usually occurring after first spring rainfalls.…”

Growth and nutrition of Pinus radiata in response to fertilizer applied after thinning and interaction with defoliation associated with Essigella californica

“…This response observed in phase I was repeated during phase II when applications of N and N + P both induced S deficiency and increased defoliation (see Table 4). Under these conditions levels of total N and free amino acids in foliage of P. radiata are expected to increase and this has been shown to boost the population density of aphids (Parry, 1974;Kainulainen et al, 1996;Holopainen et al, 1997;Chilima and Leather, 2001;Stadler et al, 2001;Day et al, 2004). Similar responses of P. radiata to N fertilizer were reported by Lambert (1986) who showed that N applied at high rates (400 kg ha À1 ) induced S deficiency and resulted in an imbalance between N and S with a commensurate increase in levels of free arginine in foliage; this increased infection levels of Dothistroma needle cast fungus.…”

“…The effects of nitrogen and phosphorus fertilizers on aphid populations and their activity have been reported as both positive and negative for several conifer species in their natural environment (Mitchell and Paul, 1974;Parry, 1974;Thomas and Miller, 1994;Kyto et al, 1996;Chilima and Leather, 2001;Straw and Green, 2001;Day et al, 2004;Williams et al, 2005). For example, Mitchell and Paul (1974) showed a significant increase in populations of aphids (Adelges cooleyi) on 7-yearold Pseudotsuga menziesii during the 1st but not the 2nd year following treatment with N fertilizer.…”

“…For example, Mitchell and Paul (1974) showed a significant increase in populations of aphids (Adelges cooleyi) on 7-yearold Pseudotsuga menziesii during the 1st but not the 2nd year following treatment with N fertilizer. Chilima and Leather (2001) showed that significant seasonal variation in population density and outbreaks of pine woolly aphid Pineus boerneri on young Pinus kesiya were linked to temporal increases in total N in foliage. In contrast, defoliation of 11-year-old Picea sitchensis associated with an infestation of green spruce aphid E. abietinum showed little difference between treatments of N fertilizers applied monthly at low rates but fertilized trees recovered more rapidly (Thomas and Miller, 1994).…”