Gonadal Development and Egg-Laying Response of Female White Pine Weevils Reared on Artificial and Natural Diets

Abstract

Reproductive processes in female Pissodes strobi (Peck) fed with a 5% ground bark artificial diet following summer emergence were studied. Females exposed to different temperature and photoperiod regimes were dissected every other week and their reproductive organs were observed to evaluate the maturation time according to the treatments. After 12 weeks, half the females were transferred onto lateral branch sections of white pine and the other half onto artificial diet supplemented with 10% ground bark of white pine, and their realized fecundity was determined. During the first 12 weeks, ovary development was detected but very few mature oocytes were found. No significant differences were observed for the maturation times between the different abiotic conditions used, but significant differences were observed in female egg-laying response on natural and artificial diets. Females that completed their sexual maturation at 24 °C and 16L: 8D laid over a 3-week period 14.4 ± 8.8 (mean ± SE) and 2.6 ± 2.6 eggs per female on white pine sections and artificial diet, respectively. Oviposition behaviour was compared with results from an earlier experiment conducted with spring-emerging white pine weevils on natural and artificial substrates. The egg-laying responses on white pine seedlings and on an artificial diet with a concentration of 15% ground white pine bark were 0.892 ± 0.124 and 0.171 ± 0.394 eggs per female per day, respectively.

White pine weevil performances in relation to budburst phenology and traumatic resin duct formation in Norway spruce

“…It has been shown that weevil egg production is sensitive to the quality of the ingested food. When females feed on unsuitable host tissues, they suffer an ovarian regression leading to a reduction in the number of oviposited eggs ( Trudel et al ., 1998 ). Similarly, the acceptance criteria of a host for oviposition appear to be crucial ( VanderSar, 1978;Sahota et al ., 1994 ;Alfaro et al ., 1996;Tomlin & Borden, 1994 ) and a reduction of egg production on hosts is observed with a weevil-resistant status.…”

Stimulating effect of bark polar fraction from the terminal leader of Norway spruce, Picea abies, on white pine weevil, Pissodes strobi, feeding and oviposition

“…The artificial diet (Trudel et al. 1998) was prepared with a relative moisture content of 50% (fresh weight basis) as suggested by Trudel et al. (1998) and was similar to the contents we measured (data not shown) in the spring terminal leaders.…”

“…Given the importance of nutritional quality for the development and reproduction process of white pine weevil (Xydias and Leaf 1964; Alfaro and Borden 1982, 1985; Lavallée et al. 1994; Trudel et al. 1994, 1998; Sahota et al.…”

“…Given the importance of nutritional quality for the development and reproduction process of white pine weevil (Xydias and Leaf 1964;Alfaro andBorden 1982, 1985;Lavalle´e et al 1994;Trudel et al 1994Trudel et al , 1998Sahota et al 1998), we propose that specific food components from the bark of Norway spruce terminal leaders could have an impact on the reproductive potential of female weevils.…”

Mechanisms of Resistance in Conifers Against Shoot Infesting Insects

“…In these situations, weevils may feed on highly resistant spruce trees, but reject them for oviposition. They may also fail to develop their ovaries, may sustain ovarian regression and the inhibition of the expression of genes involved in reproductive development (Gara and Wood 1989;Sahota et al 1994;Leal et al 1997;Trudel et al 1998). The precise mechanisms for induction of physiological regression are not known, but could range from simple starvation to complex endocrine effects.…”