Delayed mating in tortricid leafroller species: simultaneously aging both sexes prior to mating is more detrimental to female reproductive potential than aging either sex alone

The effect of delayed mating on reproductive potential, longevity and oviposition period of female redbanded leafroller,Argyrotaenia velutinana(Walker) and Pandemis leafroller,Pandemis pyrusanaKearfott, was investigated in the laboratory. Virgin female or male moths of each species were held for 1, 2, 4, 6 or 10 days prior to pairing with one-day-old virgin conspecifics of the opposite sex. In addition, reproductive potential was assessed when both sexes of each species were aged for those periods prior to pairing. The expected reproduction of femaleA. velutinanawas reduced by 34, 53, 71 and 81% for 2, 4, 6 and 10-day delays in female mating, respectively. ForP. pyrusana, expected reproduction was reduced by 47, 74, 85 and 93% for 2, 4, 6 and 10-day delays in female mating, respectively. Increasing male age at mating in both species had a lesser effect on female reproductive output compared with increasing female age at mating. As maleA. velutinanaage at mating increased, the expected reproduction of femaleA. velutinanawas reduced by 15, 45, 54 and 70% for 2, 4, 6 and 10-day delays, respectively. Comparing maleP. pyrusanaof various ages at mating, expected reproduction was reduced by 14, 42, 64 and 79% for 2, 4, 6 and 10-day delays in mating, respectively. The decrease in female reproduction when both sexes were aged prior to mating was higher than when either sex alone was aged prior to pairing with a one-day-old virgin of the opposite sex. The expected reproduction of femaleA. velutinanawas reduced by 60, 83, 96 and 98% for 2, 4, 6 and 10-day delays in mating of both sexes, respectively. Only 7.5% of female eggs hatched when both sexes ofA. velutinanawere aged ten days prior to mating. When simultaneously aging both sexes ofP. pyrusanaprior to mating, expected reproduction was reduced by 71, 93, 96 and 99% for 2, 4, 6 and 10-day delays in mating, respectively. NoP. pyrusanaeggs hatched after a ten-day delay of mating for both sexes. For both species, female longevity increased and duration of oviposition period decreased with increasing female age at mating. Our results demonstrate that delayed mating in both females and males negatively affects female reproductive output in both species and that simultaneous aging of both sexes prior to mating has a greater effect than aging either sex alone. Our results suggest that laboratory studies that have paired aged females or aged males with conspecifics of optimal reproductive maturity have likely underestimated the effects of delayed mating on reproductive output.

Captures of two leafroller moth species (Lepidoptera: Tortricidae) in traps baited with varying dosages of pheromone lures or commercial mating-disruption dispensers in untreated and pheromone-treated orchard plots

A 2-year study conducted in 0.6-ha apple (Malus domestica Borkh.) blocks examined the effects of treatment with pheromone rope dispensers on captures of the obliquebanded leafroller, Choristoneura rosaceana (Harris, 1841), and the redbanded leafroller, Argyrotaenia velutinana (Walker, 1863), in traps baited with varying dosages of pheromone lures or Isomate®-OBLR/PLR Plus pheromone rope dispensers. In untreated blocks, captures of male A. velutinana were high and did not differ among (i) traps baited with a standard lure loading used to monitor this pest, (ii) lure loadings 10 and 100 times the standard loading, and (iii) traps baited with an Isomate-OBLR/PLR Plus pheromone rope dispenser. In pheromone-treated blocks, captures of A. velutinana in traps were reduced 94%–99% for all loadings tested (up to 1000 times the standard loading). The results for C. rosaceana were different. In untreated blocks in 2002, traps baited with 10 or 30 standard lures captured significantly more C. rosaceana than traps baited with a single standard lure; however, in 2003, traps baited with the standard lure loading captured significantly more moths than traps baited with 100 and 1000 times the standard loading. Also, traps baited with Isomate-OBLR/PLR Plus pheromone rope dispensers captured significantly fewer C. rosaceana than traps with standard lures in untreated blocks. In pheromone-treated blocks, traps baited with standard monitoring lures and lures with higher loadings (10 and 1000 times the standard) captured equivalent numbers of C. rosaceana; the capture of moths was reduced by only 50%–71%. We conclude that Isomate-OBLR/PLR Plus pheromone rope dispensers deployed in Michigan, United States of America, are effective in disrupting orientation of A. velutinana; however, they are not very effective for C. rosaceana. In addition, increasing lure loading above that of 1× monitoring lures (rubber septa or membrane type) does not appear to reliably increase the effectiveness of monitoring of males of either leafroller species in orchards where pheromone ropes are deployed at recommended densities.

Influence of Temperature on the Ovipositional Biology of the Redbanded Leafroller and Tufted Apple Bud Moth (Lepidoptera: Tortricidae)

Effects of constant temperatures of 10, 15, 20, 25, 30 and 35°C on the preoviposition period and the effects of a constant 25°C on oviposition, fecundity, and longevity of the redbanded leafroller, Argyrotaenia velutinana (Walker), and the tufted apple bud moth, Platynota idaeusalis (Walker), were investigated. Oviposition did not occur at 35°C for either species and only the redbanded leafroller oviposited at 10°C. The threshold for oviposition for RBLR was calculated to be 8.7°C with 29.4 DD necessary for oviposition, while the oviposition threshold for TABM was calculated to be 10.5°C with 33.5 DD needed for oviposition. The mean oviposition periods for the two species did not differ; however, tufted apple bud moth longevity was significantly greater at 25°C. Fecundity was greater for the tufted apple bud moth (301 eggs/female) than for the redbanded leafroller (221 eggs/female).

Comparative Sex Pheromone Biosynthesis in the Obliquebanded Leafroller, Choristoneura rosaceana, and the Redbanded Leafroller, Argyrotaenia velutinana, Moths

Biosynthesis of the major sex pheromone components of the obliquebanded leafroller, (Z)- and (E)-11-tetradecenyl acetates, is shown to proceed by Δ11 desaturation of myristate as in the related redbanded leafroller. A comparison between the amounts of deuterium label incorporated into the pheromone components from labelled myristic, palmitic and stearic acids gave a higher level of incorporation for the shorter chain acids, suggesting that Δ11 desaturation is a faster process than 2 carbon chain-shortening by β-oxidation.