HORTICULTURAL ENTOMOLOGY Phenology of Lacanobia subjuncta (Lepidoptera: Noctuidae) in Washington and Oregon Apple Orchards MICHAEL D. DOERR, JAY F. BRUNNER, AND VINCENT P. JONES Washington State University Tree Fruit Research and Extension Center, 1100 N. Western Avenue, Wenatchee, WA 98801 J. Econ. Entomol. 98(6): 2100Ð2106 (2005) ABSTRACT The phenology of Lacanobia subjuncta (Grote & Robinson) (Lepidoptera: Noctuidae) was investigated in 30 apple orchards in central Washington state and northeastern Oregon from 1998 to 2001 (57 total orchard-yr). Adult captures in pheromone-baited traps were Þt to a Weibull distribution to model emergence of the Þrst and second generations. Initial capture of Þrst generation adults was observed at 216.2 Ϯ 2.6 degree-days (DD) (mean Ϯ SEM) from 1 March by using a base temperature of 6.7ЊC. The model predicted that ßight was 5 and 95% complete by 240 and 700 degree-days (DD), respectively. Monitoring of oviposition and hatch was used to establish a protandry plus preoviposition degree-day requirement of 160.0 Ϯ 7.7 DD, as well as to provide data to describe the entire hatch period. Egg hatch was 5 and 95% complete by 395 and 630 DD, respectively. The start of the second ßight was observed at 1217.1 Ϯ 8.3 DD by using an upper threshold for development of 32ЊC and a horizontal cutoff. The model indicated that the second ßight was 5 and 95% complete by 1220 and 1690 DD, respectively. Second generation hatch was 5 and 95% complete by 1440 and 1740 DD, respectively. A discussion of the potential uses of these detailed phenology data in optimizing management strategies is presented. KEY WORDS Lacanobia subjuncta, degree-days, phenology model, pest management, Weibull distribution Lacanobia subjuncta (Grote & Robinson) (Lepidop- this study) averaged 44 d but ranged from 34 to 57 d. tera: Noctuidae) occurs throughout North America We feel this variation can be explained by differences and feeds on a variety of plants (Landolt 1997, Mc- in temperature accumulations between sites and Cabe 1980), including row crops, shrubs, trees, and years. Knowledge of the larval-age distribution in the several weed species (e.g., dandelion, bindweed, and Þeld is important for timing of sampling and insecti- mallow). In the mid-1990s, larvae of this insect became cide applications for management of L. subjuncta (Do- a pest of apples in central Washington state and parts err et al. 2004). Visual monitoring of larvae is labor- of northeastern Oregon (Brunner and Doerr 2000). intensive and also has proven to be a difÞcult method Insecticides are the primary means of control for L. for timing insecticide applications. To optimize insec- subjuncta. Although general information on the phe- ticide efÞcacy and minimize nontarget impacts, a nology of L. subjuncta is available, there is a lack of more precise determination of L. subjuncta phenology sufÞcient detail or predictive capabilities for making is necessary. integrated pest management (IPM) decisions. Landolt Doerr et al. (2002) reported lower temperature (1998) reported two generations on apples in Wash- thresholds for egg, larval, and pupal development and ington. He also reported that L. subjuncta overwinter estimated degree-days required to complete each im- as pupae in the soil and emerge as adults in May and mature life stage. However, these data alone were not June. Larvae of the Þrst generation are present from sufÞcient to develop phenology predictions that de- early June through July. A second adult ßight occurs scribed L. subjuncta development through the entire in July and August with larvae present in August and growing season. SpeciÞcally, information is needed on September. Landolt and Smithhisler (1998) discov- emergence of Þrst and second generation adults, de- ered that adult activity could be monitored with the gree-day requirements for any protandry and preovi- use of a sex pheromone; however, our experience has position period, and Þrst and second generation egg shown that trap captures do not provide a reliable hatch periods. Doerr et al. (2004) explained the im- method of timing insecticides. A random selection of portance of being able to predict a time after the 20 orchards from 2000 to 2001 studied for this current majority of egg hatch was complete but before the manuscript indicated the number of days from initial oldest larvae reach the fourth instar. They presented adult capture to an optimal spray timing (presented in data that suggested this would be an optimal time for 0022-0493/05/2100Ð2106$04.00/0 ᭧ 2005 Entomological Society of America December 2005 DOERR ET AL.: PHENOLOGY OF L. subjuncta 2101 applying insecticide inputs that could maximize con- bucket. To optimize collection of larvae, sampling was trol while reducing the need for further applications. conducted in a targeted, nonsystematic manner rather In this article, we develop a predictive model for Þrst than a random sample or structured sampling proto- and second generation adult ßight periods, estimate col. Targeted sampling of trees and weed hosts was the protandry plus preoviposition requirement, and conducted on plants showing recent damage typical of describe both egg hatch periods. Data from intensive L. subjuncta feeding. Visual inspection was done at Þeld sampling of larvae are presented along with a each orchard to locate areas of larval infestation. This discussion that explains how this information will be initial screening was done for 15Ð30 min, and any useful in optimizing management strategies, especially larvae located on trees or weeds during this inspection timing of insecticide applications. were collected. Trees with recent feeding damage were then sampled with a limb-jarring method (Burts and Retan 1973). A beating tray (45 by 45 cm) was Materials and Methods held under a tree limb showing feeding damage, and Adult ßight activity was monitored by placing one the limb was struck three times with a stiff rubber multipurpose bucket style trap (Unitraps, Phero Tech, hose. Dislodged larvae that landed on the tray were Inc., Delta, British Columbia, Canada) in each of 30 collected. Approximately 25Ð50 trees were sampled by apple orchards in central Washington and northeast- limb jarring at each orchard visit. Once a tree was ern Oregon from 1998 to 2001 (57 total orchard-yr). selected for limb-jar sampling, several limbs were sam- Traps were baited with an L. subjuncta sex pheromone pled to ensure that larvae that have moved from ob- lure (Peter Landolt, USDAÐARS, Wapato, WA), and vious feeding sites also could be collected. Weed hosts a 12.5-cm2 Vaportape II insecticidal strip (Hercon showing feeding damage were picked or cut off at Environmental Co., Emigsville, PA) was placed in the ground level and shaken into a 20-liter bucket. Dis- bottom of each trap to prevent moth escape. Lures lodged larvae were collected from the bucket. Weed were replaced at 6-wk intervals. Traps in each orchard hosts most prone to L. subjuncta infestations and thus were monitored once per week from full bloom in most sampled were lambÕs-quarter, Chenopodium al- apple, Malus domestica Borkhausen ÔDeliciousÕ, until bum L.; sow thistle, Sonchus sp.; bindweed, Convolvu- late summer of each year, and the number of adult L. lus arvensis L.; and mallow, Malva neglecta Wallroth. subjuncta males was recorded. Approximately 25 infested weeds were sampled at In 2000Ð2001, all immature life stages of L. subjuncta each orchard visit. However, this number was inßu- were monitored in six orchards from central Wash- enced by the amount of weeds in the orchard and the ington with high population levels (12 orchard-yr). relative infestation levels of trees and weeds, which The relative abundance of each life stage (eggs and varied from orchard to orchard. Larval sampling was L1ÐL6 instars) was determined by sampling orchard set at 2 person-h per day, and samples were conducted trees and ground cover weeds at regular intervals, two times per week (4 person-h per week). Larvae described in detail below, throughout the growing were collected and returned to the laboratory where season. Samples were generally collected three times head capsule width and instar stage were recorded per week, with one or two orchards visited per day. (Doerr et al. 2002). We collected 3,552 larvae over the Oviposition and egg hatch were monitored by ex- duration of this study. amining the underside of apple leaves. Fresh egg Temperature data were collected at each site by masses were ßagged and monitored daily for hatch. placing a max-min temperature recorder (Datascribe Orchard sampling for egg masses was set at two per- Jr., Avatel, Inc., Fort Bragg, CA) inside white Ste- son-hours per day (total for all orchards visited on that phenson weather shelter. The weather shelter was day), and sampling was conducted three times per placed within the canopy of a tree in the interior of the week (6 person-h per wk). Seventy-nine egg masses orchard. Degree-day accumulations at each site were were ßagged during the Þrst oviposition period in calculated using a single sine-wave method (Basker- 2000. The difference between initial adult male cap- ville and Emin 1969) from daily maximum and mini- tures and the Þrst observed egg mass at each orchard mum temperatures and a base threshold of 6.7ЊC (Do- was considered the preoviposition period, which in- err et al. 2002). Degee-day accumulations began at all cluded any protandry. During the second generation, locations on 1 March. The upper threshold for devel- detection of unhatched egg masses was difÞcult (only opment and the degree-day accumulation cutoff seven total egg masses from four orchards) because method were established using male moth ßight data. eggs were laid lower in the trees, on alternate hosts in The best combination of upper threshold and cutoff the orchard ground cover, or both.