(Z)-5-tetradecen-1-ol: A secondary pheromone of the yellowheaded spruce sawfly, and its relationship to (Z)-10-nonadecenal
The yellowheaded spruce sawfly,Pikonema alaskensis (Rohwer), was known to possess a potent secondary pheromone with the polarity of an alcohol, based on earlier studies with Florisil fractions. Purification of the 25% ether-hexane Florisil fraction (polarity as with alcohols) and the hydrolyzed 5% ether-hexane fraction (polarity as with esters) from 50,000 females yielded a total of ca 3μg of an active compound identified as (Z)-5-tetradecen-1-ol (Z5–14∶ OH). When added to 100 ng of (Z)-10-nonadecenal (Z10–19∶Al), which behaves as the primary pheromone in this sawfly, 0.5 ng of syntheticZ5–14∶ OH caused an 8.8-fold increase in the greenhouse bioassay response, compared toZ10–19∶Al alone.E5–14∶ OH caused a 2.8-fold increase. Only the combination ofZ5–14∶ OH andZ10–19∶ Al consistently elicited mating attempts among males. When Hercon® formulations ofZ5–14∶OH andZ10–19∶ Al were used together to bait traps, catches were up to four times higher than for theZ10–19∶ Al alone, but this increase was seen only after emergence and mating activity in the field population were virtually complete. TheZ5–14∶ OH was inactive alone, and at higher levels it depressed trap catches toZ10–19∶ Al. The Hercon formulations ofZ5–14∶ 0H andZ10–19∶Al together were as attractive as virgin females.Z10–19∶Al alone and the (Z,Z)-9,19 hydrocarbon dienes (found in all females and able to oxidize in air to produceZ10–19∶Al) were similar to mated females. ThusZ5–14∶:OH accounted for the difference in attractiveness between virgin and mated females.
(Z)-10-nonadecenal: A pheromonally active air oxidation product of (Z,Z)-9,19 dienes in yellowheaded spruce sawfly
Each of 10 (Z,Z)-9,19 hydrocarbon dienes (28–37 carbons) found in female yellowheaded spruce sawflies,Pikonema alaskensis (Rohwer), was synthesized and found to be attractive to males by field bioassay. These dienes oxidize slowly in air, major products being aldehydes. One product common to all the dienes, (Z)-10-nonadecenal (Z10–19∶Al), and one from the 29-carbon diene only, (Z)-10-eicosenal, initiated flight and caused upwind anemotaxis in males in a greenhouse bioassay.Z10–19∶Al was incorporated into Hercon® controlled release formulations and was active in the field. The aldehyde could be useful for monitoring sawfly populations.
Effect of Soybean Cyst Nematode (Heterodera glycines) on Yield of Resistant and Susceptible Soybean Cultivars Grown in Ohio.
Soybean (Glycine max) producers in Ohio rarely use soybean cyst nematode (Heterodera glycines, SCN)-resistant cultivars because of concerns over limited yield potential and lack of resistance to Phytophthora sojae. A two-year study was initiated to determine grain yield and nematode population increase on soybean cyst nematode-resistant cultivars in maturity groups II and III in production fields. Sites differed in soil texture, nematode densities, and P. sojae infestation at a number of locations in Ohio. Soil was assayed for nematode densities before planting and at harvest. Yields of resistant cultivars averaged 0% to 18% higher than those of susceptible cultivars in fine-textured soils with average preplant populations ranging from 463 to 14,330 SCN eggs/100 cm(3) soil. In coarse-textured soils, yields of susceptible cultivars were 21% to 56% less than the resistant cultivars with average preplant densities ranging from 1,661 to 15,558 SCN eggs/100 cm(3) soil. The reproductive index ranged from 0.1 to 5.5 for resistant cultivars and 0.4 to 112 for susceptible cultivars. In 1993, yield of P. sojae-susceptible, nematode-resistant 'Asgrow A 3431' was as high as yield of the P. sojae-resistant, nematode-susceptible cultivar 'Resnik' in a Phytophthora-infested field. The nematode-resistant cultivars Madison Experimental 131527 and Asgrow A3431 had higher yields than AgVenture AV1341 and susceptible cultivars Resnik and Kenwood when compared over five nematode-infested sites. Nematode-resistant cultivars were found to be excellent alternatives to currently grown susceptible cultivars for managing SCN where group III cultivars are used. However, better cultivar alternatives may be needed for sites with combined Phytophthora root rot and cyst nematode problems.