Host utilisation by moth and larval survival of pine processionary caterpillar Thaumetopoea pityocampa in relation to food quality in three Pinus species

Abstract

1. The work reported here analysed host utilisation by the pine processionary moth Thaumetopoea pityocampa (Lepidoptera: Thaumetopoeidae), the relationship between moth oviposition patterns and larval performance, the chemical characteristics of the plant in relation to the performance of different larval instars, and the role of these factors in the outbreak capacity of the species. In order to do this, a combination of field and laboratory techniques was used to study three pine species differing in nutritional characteristics. 2. Moths oviposited in the three pine species analysed, although cluster pine received a lower number of batches. Late‐instar larvae were able to feed on all three pine species, however first‐instar larvae developed on Scots and black pine but died on cluster pine. Consequently, oviposition in cluster pine can be considered an oviposition mistake, and indicates that moths are rather unselective when ovipositing on different pine species. 3. Chemical analysis of needles suggested that the quantity of nitrogen was the main factor responsible for the difference in survival of larvae. 4. The oviposition pattern of the moth and the larval susceptibility to food quality in Thaumetopoea pityocampa agree with the theory that unselective oviposition of the moth is a precondition for eruptive dynamics in phytophagous insects. 5. The success of the larvae depends mainly on the probability of the moth finding a suitable host. This probability is determined strongly by the changes of structure and coverage in Mediterranean pine woodlands, due to human management.

Effects of drought and heat on forest insect populations in relation to the 2003 drought in Western Europe

“…The direct effects of temperature and drought on insects are likely to vary among species depending on the sensitivity of individual growth rates to increase temperatures [7], the life-stage at which they experience high temperatures and drought [3,26,42], their adaptation to warm, dry environments and climate extremes [27,67], and their capacity to escape unfavourable environmental conditions [58].…”

“…Eggs and young larvae are sensitive to high temperatures; an excess of heat or exposition to intense solar radiations may induce high levels of mortality [26]. The mortality of some larvae of T. pityocampa can also have an impact on the survival of the entire batch (group of larvae hatched from the same egg mass) because the ability to construct nests and consequently to survive over the winter, is dependent on the number of larvae per batch that reach late instars [27,42]. A large-scale survey carried by the French Forest Health Department in 2003-2004 [14,15] reported an overall increase in egg and larval mortality, particularly in continental zones where winter-nests are essential to survive winter temperatures; whereas the Atlantic coast, under oceanic influence, was less concerned [14,15].…”

“…[39,82]) and for the pine processionary moth (T. pityocampa) and the pinyon sawfly (Diprion pini L.). Young instars are usually the most sensitive to foliage quality [26,42,73], which may also have a negative effect on hatching rate [73,80,91,100]. For the pine processionary, mortality observed in 2003 [14,15] in young larvae could be the result of starvation because of a decrease in needle quality [42,43].…”

“…Young instars are usually the most sensitive to foliage quality [26,42,73], which may also have a negative effect on hatching rate [73,80,91,100]. For the pine processionary, mortality observed in 2003 [14,15] in young larvae could be the result of starvation because of a decrease in needle quality [42,43]. Lepidoptera hatching during a drought period are negatively affected by leaf texture changes; leaves become tougher because of the decline in water content (see ref.…”

Behaviour Patterns of the Pine Processionary Moth (Thaumetopoea wilkinsoni Tams; Lepidoptera: Thaumetopoeidae)

“…Although several studies have been published worldwide on Thaumetopoea pityocampa which has similar preferences to T. wilkinsoni [11][12][13][14][15] and specifically on the effect of its hairs [16][17][18][19][20][21] , few scientific studies have emerged regarding T. wilkinsoni [6,22,23] . Most workers have only casually broached the issue [8,24,25] .…”