Male-produced aggregation pheromone of Carpophilus sayi, a nitidulid vector of oak wilt disease, and pheromonal comparison with Carpophilus lugubris

Abstract 1 Carpophilus sayi, a nitidulid beetle vector of the oak wilt fungus, Ceratocystis fagacearum, was shown to have a male‐produced aggregation pheromone. 2 Six male‐specific chemicals were identified from collections of volatiles. The two major compounds were (2E,4E,6E,8E)‐3,5‐dimethyl‐7‐ethyl‐2,4,6,8‐undecatetraene and (2E,4E,6E,8E)‐3,5,7‐trimethyl‐2,4,6,8‐undecatetraene, in a ratio of 100 : 18. These compounds, in a similar ratio, were previously reported to be the pheromone of Carpophilus lugubris, a closely related species. The four minor C. sayi compounds (less than 4% as abundant as the first) were also alkyl‐branched hydrocarbons and consisted of two additional tetraenes and two trienes. 3 The pheromone of C. lugubris was re‐examined to refine the comparison with C. sayi, and C. lugubris was found to have the same additional, minor tetraenes as C. sayi, but not the trienes. 4 A synthetic mixture of the two major compounds was behaviourally active for both sexes of C. sayi in oak woodlands in Minnesota. The pheromone was tested in combination with fermenting whole wheat bread dough (a potent synergist of nitidulid pheromones). The combination of the 500‐µg pheromone dose and dough attracted at least 30‐fold more C. sayi than either pheromone or dough by itself. The synergized pheromone has potential as a tool for monitoring insect vector activity in an integrated management program for oak wilt. 5 Although C. lugubris was not present at the Minnesota test sites, two other Carpophilus species, Carpophilus brachypterus and Carpophilus corticinus, were clearly cross‐attracted to the synergized pheromone of C. sayi.     

Influence of cultural practices on edaphic factors related to root disease in Pinus nursery seedlings

Conifer seedlings grown in bare-root nurseries are frequently damaged and destroyed by soil-borne pathogenic fungi that cause root rot. Relationships between nursery cultural practices, soil characteristics, and populations of potential pathogens in the soil were examined in three bare-root tree nurseries in the Midwestern USA. Soil-borne populations of Fusarium spp. and Pythium spp. were enumerated as a function of soil depth in the upper 42 cm; red and white pine seedling root systems were assessed visually for signs of root rot. Soil organic carbon and resistance to cone penetration (as a function of depth) were augmented by saturated hydraulic conductivity (K_sat), water retention characteristic, texture and pH at selected depths. Cone index (CI) provided accurate ‘fingerprints’ of cultural practices in each nursery. A tillage pan due to rotary tillage was detected by CI in the Minnesota and Wisconsin nurseries, but no such tillage pan was indicated in the Michigan nursery, which did not use rotary tillage. Curves of CI also indicated differing maximum depth of tillage disturbance between nurseries; maximum rooting depth based on 3 MPa CI were different among nurseries. Vertical distribution of soil-borne Fusarium spp. reflected the vertical incorporation pattern associated with the type of tillage implement used to incorporate cover crop residue prior to Pinus seedling establishment. Peak numbers of Fusarium spp., from 250 to 950 colony-forming units (cfu g-1 dry soil) were recorded between 12 – 24 cm depth in two nurseries using a moldboard plow for incorporation while steadily decreasing populations, from 1800 to 250 cfu g-1 dry soil, were found from 0 to 15 cm in the third nursery using a disc. Vertical distribution of the Fusarium spp. also correlated with organic carbon levels, which suggested that cover-crop incorporation and conifer rooting had determined the location of soil-borne Fusarium spp. propagules. K_sat suggest that tillage pans caused by rotary tillage may impede drainage during nearly daily irrigation enough to cause physiological stress to the seedlings and predispose them to disease. Low levels of mortality (from < 1% to 5%) were observed in two-year-old Pinus seedlings while disease severity varied by nursery and seedling species. Tillage should be used to control depth placement of biomass residue and pathogenic fungal propagules, and adjusted to prevent tillage pans within the seedling root zone. More studies are needed to determine the impact of these cultural controls on the need and application depth of fumigation for pathogen control. This revised version was published online in August 2006 with corrections to the Cover Date.