Systemic Insecticide and Gibberellin Reduced Cone Damage and Increased Flowering in a Spruce Seed Orchard

Abstract

Insects feeding in conifer cones are difficult to control with nonsystemic insecticides. Newly developed systemic insecticides that can be injected into tree trunks may be a possible way of reducing both insect damage and negative side-effects to the surrounding environment, compared with conventional spraying. Several insecticides that could be injected into tree stems were tested on Picea abies (L.) Karst. In one experiment, insecticides (bifenthrin, deltamethrin, abamectin, and imidacloprid) were injected during flowering; in a second experiment two of these insecticides (abamectin and imidacloprid) were injected 1 yr before the expected flowering. In the second experiment insecticide treatment was also combined with treatments with the flower stimulating hormone, gibberellin (GA(4/7)). The only insecticide that reduced damage was abamectin, both after injection during flowering and after injection 1 yr before the expected flowering. Injections with GA(4/7) increased flowering and were as efficient as the conventional application method of drilling but abamectin was not effective in combination with the drilling method. There was no negative effect of the insecticide injections on seed quality. The injections were ineffective against the seed chalcid Megastigmus strobilobius (Ratzeburg), which was found to have an unexpected, negative effect on seed quality. Our results suggest that it may be possible to reduce damage from certain insect species, and to increase flowering by injecting abamectin and GA(4/7) in the year before a cone crop.

Seed quality attributes in seedling production of Norway spruce (<i>Picea abies</i> (L.) Karst.)

“…Therefore, the results on their frequency can be regarded as quite reliable. The prevalence of these insects is again comparable to the findings in previous studies (Nikula & Jalkanen 1990, Rosenberg & Weslien 2005, Rosenberg et al 2012. It is, however, interesting that although C. strobilella larvae were found commonly in the study material, the proportions of damaged seeds were relatively low.…”

“…The proportion of insect infested cones and seeds is highly variable in different years and at different locations. Rosenberg et al (2012) found that approximately 38% of cones were infested by E. abietaria or Eupithecia analoga (Diakonoff), in single year experiment in a seed orchard in central Sweden, while S. anthracina, M. strobilobius and P. abietina were present in very small numbers (<2%). In another study in central Sweden (Rosenberg & Weslien 2005) C. strobilella was found in 23% and 85% of cones in a research covering two consecutive years.…”

“…(Annila 1981, Annila & Heliövaara 1991, Seifert ym. 2000, Rosenberg 2003, Rosenberg & Weslien 2005, Rosenberg et al 2012. Spruce seed chalcid (Megastigmus strobilobius Ratz.)…”

“…are found inside the seeds. C. strobilella, S. anthracina and P. abietina lay their eggs in flowers while the other species oviposit in the developing cones (Annila 1981, Annila & Heliövaara 1991, Brockerhoff & Kenis 1996, Rosenberg et al 2012.…”

Intracone variation explains most of the variance in Picea abies seed weight: implications for seed sorting

“…However, in our seed orchard material, no statistically significant differences were observed among the clones. Rosenberg et al (2012) reported that as the number of spruce seed chalcid-infested seed in Norway spruce cones increased, seed weight decreased. Our findings do not support this.…”