Brunner, Jay F.

Gut, Larry J.

Undetermined

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1. Thresholds/Monitoring/SamplingMONITORING LEAFROLLERS WITH PHEROMONE TRAPSLarry J. Gut and Jay F. BrunnerWashington State UniversityTree Fruit Research and Extension CenterWenatchee, WA 98801The ability to monitor and prevent the establishment of leafroller (LR) populations is crucial tothe success of pheromone-based pest management programs. Detecting larval infestations beforethey reach damaging levels is very difficult. An alternative approach is to monitor leafrollerpopulations with pheromone traps.Pheromone dose: Standard load Pandemis leafroller (PLR) and obliquebanded leafroller (OBLR)red septa, and septa loaded with 10% of PLR pheromone and 5% of OBLR pheromone wereobtained from Trece, Inc. The effectiveness of pheromone traps baited with standard or low loadlures was directly compared in 35 orchards; PLR were trapped in 27 orchards and OBLR weretrapped in 20 orchards. For each species, Pherocon 1C traps (Trece, Inc.) baited with red septacontaining either the standard or low pheromone dose were uniformly distributed in orchards at adensity of one trap per 1.25 acres. The number of male moths captured was recorded weeklyand trap bottoms were replaced after a cumulative catch of 50 moths, more often if dirty. Tominimize position effects, traps were rotated each time they were inspected. Lures were replacedevery four weeks.Larval densities of the overwintering and summer generation, as well as fruit injury at harvest,were estimated in each of the orchards where traps were placed. Larval sampling was conductedtoward the end of each generation. The overwintering generation was sampled after petal fallwhen the population was comprised of late instar larvae feeding in spur shoot leaves. Densities ofthe summer generation were estimated in mid-summer when most individuals were late instarlarvae feeding in shoot tips. Twenty growing points per 20 trees were examined around each trapduring each generation. A sample of 25 fruits on each of 20 trees in proximity to each trap wasinspected for LR injury at harvest.Table 1 summarizes the average PLR and OBLR male catch per trap with standard and low loadpheromone lures during each flight period. Male captures were significantly lower in traps baitedwith a low dose of pheromone. Close to an 80% reduction in catch with a low load compared to astandard load lure was recorded for PLR. The effect appeared to be less pronounced for OBLR,with about a 60% reduction in catch in traps baited with the low dose of pheromone.Fewer than 10 moths per trap were captured during the OW flight in 16 of 27 orchards monitoredfor PLR and 11 of 20 orchards monitored for OBLR. At each study site, at least an 86%reduction in moth catch in traps baited with the low load compared to the standard load wasrecorded in these low catch orchards. In contrast, a less pronounced reduction in catch in lowcompared to high load traps was recorded in orchards where greater than 10 moths were capturedwith the low dose. The reduction in catch in these orchards ranged from 57 to 77%.Table 1. Pandemis and obliquebanded leafroller moth captures in pheromone traps baited withstandard or low load lures.Overwintering moth capture Summer moth captureNumber of Average per trap Percent Average per trap PercentSpecies orchards Stand. Low reduction Stand. Low reductionPLR 27 73.1 18.8 74 51.3 9.6 81OBLR 20 60.8 20.2 67 38.8 13.6 5617Fewer than 10 moths per trap were captured during the SU flight in 20 of 27 orchards monitoredfor PLR and 14 of 20 orchards monitored for OBLR. Thus, low catches were recorded in agreater portion of orchards during this SU flight than during the OW flight. The pattern ofreduction in moth catch in traps baited with the low load compared to the standard load in the SUwas similar to that recorded during the OW flight. The noticeable exception was the lesspronounced reduction in OBLR catch with low dose lures in orchards with high catches duringthe SU compared to the OW flight. Overall reductions of about 48% and 64% were observed inthe SU and OW flights, respectively.Relationship between captures and activity: PLR and OBLRmoth catch in low dose pheromonetraps during the OW flight was a good indicator of the level of larval activity. The percentage ofshoots or fruit fed on by either species of leafroller was consistently low in orchards with lowmoth catches in low load traps. Average fruit injury at harvest did not exceed 0.2% in low catchorchards at any of the study sites. Levels of leafroller feeding were substantially higher inorchards with relatively high moth catches in low load traps. Average fruit injury at harvestexceeded 1.0% in high catch orchards at most of the study sites.Captures of both PLR and OBLR males during the OW flight were highly correlated with fruitinjury at harvest. Somewhat unexpectedly, traps baited with either the standard or low load luresprovided similar relationships between catch and injury. Correlation coefficients for PLR fruitinjury and moth catch in standard and low load traps were 0.80 and 0.70, respectively.Correlation coefficients for OBLR fruit injury and moth catch in standard and low load traps were0.65 and 0.70, respectively. The strong correlation between LR moth captures in standard trapsand fmit injury appeared to be contrary to field observations of instances of high moth catchesbut low levels of infestation. Very few of these situations were recorded in the study reportedherein. The use of a much higher trapping density, one trap/2.5 acres compared to the industrystandard of about one trap/20 acres, and the positioning of the majority of traps in the interiorrather than the edge of orchards may explain this lack of false positive moth catches in our study.Longevity of lures: We evaluated the field life of standard and low load lures during the secondgeneration flights of PLR and OBLR. There was no significant change in the attractancy ofstandard or low load OBLR lures throughout the 45-day test period. The attractancy of standardand low load PLR lures also did not decline for 45 days. To the contrary, replacing the standardPLR lure appeared to have a negative effect on moth captures. Traps baited with new lurescaptured significantly fewer moths than traps baited with lures field aged for 27, 36 or 45 days.Trap design: We directly compared the effectiveness of a Multipher, delta, plastic cylinder andwing trap for capturing PLR or OBLR males. The delta trap performed as well as the industrystandard, wing trap, for both leafroller species. The Multipher trap was a highly effective trap forOBLR but was less effective for PLR. Significantly fewer PLR were captured in the Multiphercompared to the delta or wing traps. The plastic cylinder was a poor PLR and OBLR trap,capturing very few moths throughout the test.Trap maintenance issues also should be considered in choosing an effective trapping system. Thelow load trap is easier and less expensive to use than the standard trap because the reduced mothcatch in this trap means that fewer replacements of the trap bottom are required. The Multiphertrap shows promise as an option for trapping leafrollers. This is a non-sticky trap and should beless expensive and easier to maintain than the wing or delta traps. Our experience with theMultiplier trap suggests that the performance of this trap is highly influenced by the choice ofknockdown material.18

Monitoring leafrollers with pheromone traps

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Monitoring leafrollers with pheromone traps

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