The Chimeric Bud-Sport ‘Delicious’ (Red) Mutant Strain, It, Expresses Lethal-Effect Resistance Against the Obliquebanded Leafroller (Lepidoptera: Tortricidae)

Three ‘Red Delicious,’ Malus domestica Borkhausen (Rosales: Rosaceae), apple plantings, each representing a different sport, were evaluated for natural resistance against the obliquebanded leafroller (OBLR), Choristoneura rosaceana (Harris). The establishment of neonate larvae on apple foliage was not different between the three ‘Red Delicious’ plantings. Of the three ‘Red Delicious’ plantings, the one that most negatively impacted OBLR was the ‘It Delicious’ genotype. The ‘It Delicious’ genotype at the Sunrise Research Orchard exhibited essentially 100% mortality against OBLR when fed on spring and summer foliage, and mortality accumulated faster across instars than on other ‘Red Delicious’ plantings. The high mortality observed in the ‘It Delicious’ genotype points to the existence of a putative gene, which we propose as Cro1. The other ‘Red Delicious’ plantings, Columbia River Orchard and Tree Fruit Research and Extension Center Research Orchard treatments, showed negative impacts, especially when exposed to foliage from the summer compared to the spring period. Development rates in these treatments in spring were higher compared to summer, and there were direct relationships between development rates, pupal weights, and adult longevity for both males and females. These latter results suggest that sublethal effects could be present in these ‘Red Delicious’ cultivars, thus offering insights to a gene-pyramiding strategy for breeders to managing leafroller pests in Washington apple.

Parasitoid guild and parasitism rate of the obliquebanded leafroller in IPM orchards and adjacent woodlands

The obliquebanded leafroller (OBLR), Choristoneura rosaceana (Harris) [Lepidoptera: Tortricidae], a primary pest in Quebec apple orchards, can be naturally parasitized. Knowing that habitats around crop’s peripheries are reservoirs for natural enemies of pests, the objective of the present investigation was to assess parasitism and parasitoid guild composition associated with the OBLR. The two-year study included orchards under integrated pest management, their edges, and adjacent woodlands. Parasitism was assessed using sentinel OBLR larvae and considered spring, early summer and late summer. Parasitism rates between regions with different vegetation composition were not significantly different. The first year, late summer larvae showed higher parasitism in orchards (27%), compared to edges (7%) and woodlands (11%). The following year, larvae exposed in early summer had higher parasitism rate in edges (28%) compared to orchards and woodlands (17% in both zones). Nineteen parasitoid species parasitized sentinel larvae. The tachinid Actia interrupta (Curran), the most abundant species, represented 28 and 62% of species the first and the second year respectively. Our research demonstrates that natural biological regulation of the OBLR is the result of a highly diversified parasitoid guild and this should be taken into account in any Integrated Pest Management program.

Development of 2-phenylethanol plus acetic acid lures to monitor obliquebanded leafroller (Lepidoptera: Tortricidae) under mating disruption

We evaluated the effectiveness of 2-phenylethanol (PET) in combination with acetic acid (AA) as a binary lure for monitoring male and female obliquebanded leafroller, Choristoneura rosaceana (Harris). Studies were conducted in apple, Malus domestica Borkhausen, orchards treated with or without sex pheromone dispensers for mating disruption (MD). Open polypropylene vials, closed membrane cups, and rubber septa loaded with AA and/or PET in varying amounts were first evaluated in a series of trapping experiments. Membrane cups loaded with 800 mg of PET were as effective as 10-mg septa, but longer lasting, and were comparable to the open vials. A membrane cup AA lure was effective in tests, but further work is needed to increase its release rate and extend its activity. Catches of codling moth, Cydia pomonella (L.), and C. rosaceana were unaffected by combining PET with (E,E)-8,10-dodecadien-1-ol, the sex pheromone of codling moth, pear ester, (E,Z)-2,4-ethyl-decadienoate, and AA lures. Adding (E)-4,8-dimethyl-1,3,7-nonatriene to this blend to enhance codling moth catch, significantly reduced catches of C. rosaceana. PET+AA was a more attractive binary lure than AA plus phenylacetonitrile (PAN) for C. rosaceana. The addition of PET or PAN to traps already baited with the sex pheromone of C. rosaceana significantly reduced male catches. Traps baited with PET+AA placed in blocks not treated with MD caught significantly fewer C. rosaceana than traps baited with sex pheromone. In comparison, sex pheromone-baited traps in MD blocks caught ≤ 1 male moth per season which was significantly lower than total moth (> 10) or female moth (≥ 3) catch in these blocks with PET+AA. A high proportion (> 70%) of trapped females were mated in both untreated and MD-treated orchards. Further refinement of this binary, bisexual lure using membrane cup technology may allow the establishment of action thresholds and improve management timings for C. rosaceana.

Transovarial transmission of novaluron in Choristoneura rosaceana (Lepidoptera: Tortricidae)

The obliquebanded leafroller (OBLR), Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae), has become a significant pest of tree fruit production in North America within the past 25 years. Control of the OBLR has historically relied upon broad-spectrum insecticides like organophosphates, carbamates, and pyrethroids. However, with evidence of resistance development, newer chemistries have been developed to combat this pest. The effects of novaluron, a chitin synthesis inhibitor, were studied to determine if reduced egg hatch occurs after exposure to adults. The transovarial effects of this compound were tested through laboratory bioassays, looking at decreased egg hatch and also presence of novaluron in egg masses following adult exposure. Results from the study demonstrated a decrease in egg hatch after adult exposure. Analysis of egg mass using HPLC also demonstrated novaluron present in the eggs laid by treated adults. Along with the direct ovicidal and larvicidal properties of novaluron, this transovarial activity provides an important contribution to the overall control seen in the field.