Utilization of by the Lappet , panda Hübner (: ): Survival, Development, and Larval Performance Author(s): D. Calvo and J. Ma Molina Source: Journal of Economic Entomology, 97(3):957-963. Published By: Entomological Society of America DOI: http://dx.doi.org/10.1603/0022-0493(2004)097[0957:UOBBTL]2.0.CO;2 URL: http://www.bioone.org/doi/ full/10.1603/0022-0493%282004%29097%5B0957%3AUOBBTL%5D2.0.CO%3B2

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BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, research libraries, and research funders in the common goal of maximizing access to critical research. HORTICULTURAL ENTOMOLOGY Utilization of Blueberry by the Lappet Moth, Hu¨ bner (Lepidoptera: Lasiocampidae): Survival, Development, and Larval Performance

A D. CALVO AND J. M . MOLINA

Plant Protection. Entomology, CIFA “Las Torres-Tomejil”, Apartado OÞcial. 41200 Alcala´ del Rõ´o, Seville, Spain

J. Econ. Entomol. 97(3): 957Ð963 (2004) ABSTRACT The lappet moth, Streblote panda Hu¨ bner [1820] (Lasiocampidae), is a common species found in blueberry, Vaccinium spp. () Þelds of Western Andalusia. The biology of this species as well as the extent to which its larvae can use and survive on blueberry is unknown. In this study, the suitability to larvae of several blueberry cultivars was studied. Larvae were grown under controlled laboratory conditions on excised foliage of six blueberry cultivars. Survival, development, and food use were determined for Þrst and Þfth instars. According to our results, blueberry has become an alternative host for S. panda in southwestern Andalusia. Low growth rates and efÞciencies of use of food were observed. Lower gross efÞciency of growth was found for larvae fed blueberry ÔSharp- blueÕ, despite a higher apparent digestibility of this cultivar. Larvae reared on this cultivar had the highest mortality, increased developmental time, and used a greater part of metabolism for mainte- nance. Herbivore pressure may be increased with the widespread planting of the most suitable cultivars ÔMistyÕ and ÔOÕNealÕ, whereas ÔSharpblueÕ and ÔClimaxÕ seem to be the least suitable host . These data provide useful information for planning and managing blueberry orchards in the presence of S. panda populations.

KEY WORDS nutritional ecology, Vaccinium, host suitability, Lepidoptera, Lasiocampidae

STUDIES OF HERBIVORY ON crop plants can provide im- Many species infest blueberry, but they are portant information about the viability of new culti- locally variable in time and space, and few reach pest vars as well as facilitate the development of integrated status in European plantings (Pritts and Hancock management practices (Scriber and Slansky 1981, 1992). Blueberry was Þrst grown in the mid-1990s in Slansky 1990). Moreover, effective development and Huelva (southwestern Andalusia), providing a novel use of host plant resistance to manipulate pest host for native insects. At least 15 species of Lepidop- performance requires an understanding of the rela- tera have been found associated with blueberry in tionships between the attributes of crop plants and southwestern Andalusia (Molina 1998). Their rela- their impact on use by insect pests (Slansky 1990, tionship with this plant has not been fully character- 1993). ized. Among these species, Streblote panda Hu¨ bner Forage patterns by insect herbivores may reßect [1820] (Lepidoptera: Lasiocampidae) has been found constraints imposed by their host plants. Plant char- regularly since the introduction of the blueberry cul- acteristics inßuence the insectsÕ responses, affecting ture. The insect is now considered a pest of this small several phases of establishment (Saxena 1969). The crop (Molina 1998). S. panda is distributed in quality of food source, determined by nutrient avail- coastal and warm areas of the southeastern Iberian ability and presence of secondary compounds, affects Peninsula and North Africa, from the Atlantic coast of the time needed by larvae for completion of devel- Morocco through Egypt (Freina and Witt 1987). Fe- opment as well as the mass achieved at the end of the males lay their eggs in small groups on the food plant; larval stage (Scriber and Slansky 1981). In a crop larvae are polyphagous and gregarious during early species, cultivars may differ in phenology and chem- instars and usually remain on the same plant to com- ical and nutritional composition. These differences plete their development. Populations are able to use may cause dramatic changes in feeding behavior and several tree and species, in some cases affecting larval performance (Quisenberry and Wilson 1985; perennial crops (Zhang 1994). Slansky 1990, 1993; Chen et al. 2003; Rieske et al. 2003). Blueberry growers must consider S. panda during Through effects on metabolism and growth, these crop establishment in southwestern Andalusia. Al- characteristics can be used to determine potential though mature blueberry plants seem be able to sup- damage and relative susceptibility of plants (Smith et port the growth of this species, apparently without al. 1994). damage, younger plants can be completely defoliated

0022-0493/04/0957Ð0963$04.00/0 ᭧ 2004 Entomological Society of America 958 JOURNAL OF ECONOMIC ENTOMOLOGY Vol. 97, no. 3

(D.C., personal observation). Furthermore, blueberry 1990, Jordano and Goma´riz 1994, Foss and Rieske production depends upon a balance among foliage and 2003). fruit set (Maust et al. 1999); thus, feeding by this insect Larval Survival, Development, and Performance. could affect yield quality (grams per fruit) and quan- Larvae were taken from eggs laid by adults obtained tity (kilograms per tree). The steady increase of blue- from an experimental colony maintained at CIFA ÔLas culture in southwestern Andalusia would en- Torres-TomejilÕ (Alcala´ del Rõ´o, Seville, Spain) on hance the impact of this species. Arbutus unedo L. (Ericaceae). Survival, larval devel- Given the economic and social importance of ex- opment, and performance were assessed with no- panding blueberry cultivation in Andalusia, we eval- choice tests (Smith et al. 1994). All tests were con- uated in this study the larval performance, food use, ducted in a growth chamber at 25 Ϯ 1ЊC, 70 Ϯ 5% RH, and development of S. panda larvae on six low-chill and a photoperiod of 16:8 (L:D) h. blueberry cultivars. Differences in some nutritional After hatching, four groups of 10 neonates were components of host plants were examined for possible randomly chosen for each blueberry cultivar, isolated associations with suitability or assimilation. The infor- in plastic cages, and fed one of the test cultivars. Every mation of this study will provide tools for blueberry 2 days, new twigs with cut stems inserted into Eppen- growers to gauge the impact of S. panda populations. dorf tubes Þlled with distilled water were supplied and remaining leaves and frass were removed. We offered to larvae only totally expanded leaves; nonexpanded leaves were cut from twigs if present. Larvae were Materials and Methods observed daily. Survival was recorded after 7, 14, and Blueberry Plant Growth. Plants were grown at ÔEl 21 d from hatching. Further observations continued CebollarÕ Experimental Station (Moguer, Huelva, after pupation, to determine whether development Spain). Six blueberry cultivars were used: ÔOÕNealÕ, could be completed on the host plant. ÔSharpblueÕ, and ÔMistyÕ of the southern highbush type Freshly molted Þfth instars were selected for nu- (Vaccinium ϫ corymbosum L.), and ÔWindyÕ, ÔBonitaÕ, tritional studies. Fifteen larvae per cultivar were iso- and ÔClimaxÕ of the rabbiteye group (Vaccinium ashei lated in plastic boxes lined with moistened Þlter paper. Reade). All of these are low-chill cultivars and have Larvae were weighed daily along with frass produced, been recently introduced in western Andalusia. and foliage provided. Ingestion, growth, and egestion Plant Analyses. The study started in early June, were directly measured; metabolism was determined when egg hatching occurs in nature. Because the phe- by difference. Dry weight of experimental larvae was nology of the six blueberry cultivars used in this ex- estimated by multiplying fresh weight of larvae by the periment differed slightly, some measures for mini- mean dry weight percentage, determined from lots of mizing variation in leaf age were taken. Leaves were 10 additional larvae fed with each blueberry cultivar sampled weekly throughout the experimental period, and randomly sacriÞced at intervals during the exper- beginning when the laboratory feeding experiments iment. Dry weight of food offered was estimated from started and ending when larval development Þnished. the mean dry weight:fresh weight ratio of control Twigs of each cultivar, Ϸ25 cm in length, were cut and leaves cut at the same time as the leaves used as food. stored at 4ЊC for use as larval food. Food consumption and use parameters were esti- At each sampling date, additional samples of 60 mated by standard gravimetric techniques. Calculated leaves per cultivar were picked from 15 randomly use indices included the following: 1) approximate selected plants of the experimental plots. Fully ex- digestibility of food (AD); efÞciency with which di- panded leaves from the third to Þfth leaf position gested food is converted to body matter (ECD; net (counting from the tip) were selected and used for efÞciency of growth); and 2) efÞciency of conversion plant analyses. Leaves used for chemical determina- of ingested food to body matter (ECI; gross efÞciency tions were dried at 60ЊC for 48 h and ground to Þne of growth). Relative rates were based on the mean ϭ Ϫ powder in a mill. Total nitrogen content was measured exponential larval dry weight We (Wf Wi)/ as percentage of dry weight by the Kjeldahl technique ln(Wf/Wi), where Wf and Wi are Þnal and initial (Allen 1989). The percentage of leaf water was de- weights, respectively (Gordon 1968). Relative rates of termined gravimetrically, by the ratio of dry leaf to development calculated included relative consump- fresh mass. Approximate levels of total phenolics were tion rate (RCR), relative growth rate (RGR), relative determined using 80 mg of freeze-dried leaves, fol- excretion rate (RER), relative assimilation rate lowing the extraction method of Staedler-Martin and (RAR), and relative metabolization rate (RMR). AD, Martin (1982), and the Folin-Ciocalteau colorimetric ECI, and ECD are expressed as percentages, and rel- method for concentration determination (Allen ative rates are expressed in dry weight as milligrams 1989). Leaf thickness of blueberry cultivars during the per milligram per day (Waldbauer 1964, Scriber and studied period was also estimated. Leaves were indi- Slansky 1981, Smith et al.1994). vidually photocopied, weighed fresh, dried, and re- Molting was conÞrmed by checking boxes every day weighed. Their area was metrically calculated using for exuviae and head capsules. Two days after cocoon DtScan computer software (Kirchhof and Pendar formation, pupae were weighted and adult develop- 1993). The mean leaf speciÞc weight (milligrams of ment was allowed to proceed. fresh weight per square millimeter) was used as an Statistical Analysis. Water, leaf toughness, nitrogen, indirect measure of leaf toughness (Stamp and Bowers total phenolics, and foliar carbohydrates were ana- June 2004 CALVO AND MOLINA:BLUEBERRY UTILIZATION BY S. panda LARVAE 959

Table 1. Nutritional parameters of blueberry leaves used to rear S. panda larvae

Water Toughness Nitrogen Phenolics Carbohydrates Cultivar (% f.w.) (mg f.w./mm2) (% d.w.) (% d.w.) (% d.w.) OÕNeal 58.69 Ϯ 1.06a 0.28 Ϯ 0.006a 1.54 Ϯ 0.02a 2.54 Ϯ 0.37c 2.58 Ϯ 0.25c Sharpblue 59.61 Ϯ 1.41a 0.25 Ϯ 0.007b 1.47 Ϯ 0.02a 2.18 Ϯ 0.14c 3.54 Ϯ 0.33bc Misty 56.25 Ϯ 1.39a 0.28 Ϯ 0.006a 1.53 Ϯ 0.01a 3.72 Ϯ 0.25b 6.02 Ϯ 0.38a Windy 55.65 Ϯ 1.40a 0.31 Ϯ 0.006a 1.11 Ϯ 0.02b 4.77 Ϯ 0.61ab 2.51 Ϯ 0.29c Bonita 54.84 Ϯ 1.88a 0.32 Ϯ 0.005a 1.18 Ϯ 0.02b 5.99 Ϯ 0.64a 2.55 Ϯ 0.22c Climax 59.98 Ϯ 1.98a 0.29 Ϯ 0.009a 1.19 Ϯ 0.02b 5.76 Ϯ 0.60a 5.10 Ϯ 1.02ab F5,42 1.88 n.s. 4.93** 11,55*** 13.82*** 9.97***

d.w., dry weight; f.w., fresh weight; n.s., not signiÞcant. Data presented as mean Ϯ SEM. Means within a column followed with different letters are signiÞcantly different (P Ͻ 0.05; NewmanÐKeuls multiple range test). *P Ͻ 0.05; ** P Ͻ 0.01; *** P Ͻ 0.001. lyzed using analysis of variance (ANOVA), with blue- an increase in assimilation and production (growth) berry cultivar as the independent variable. Angular rates (Table 3). A signiÞcant larval growth suppression transformation, xЈϭarcsine (͌x), was used to nor- was observed for larvae fed ÔSharpblueÕ leaves. malize data before analysis. Larval performance was Use indices comparing AD, ECD, and ECI food analyzed using analysis of covariance (ANCOVA), efÞciencies among treatments are also given in Table with the initial weight of larvae as the covariate. The 3. An inverse relation between AD and ECD was logarithmic transformation: xЈϭlog (x ϩ 1) was used found (r ϭϪ0.62, n ϭ 6, P Ͻ 0.05). Digestion was most for these data (Dent and Walton 1997). SigniÞcant efÞcient in larvae fed ÔSharpblueÕ and ÔClimaxÕ; how- (P Ͻ 0.05) treatments means were separated by New- ever, these larvae had the lowest ECD, which re- manÐKeuls multiple range tests. Correlation coefÞ- ßected a higher proportion of assimilated food re- cients were used to detect associations between plant quired for maintenance. ECI was the highest in ÔMistyÕ nutritional factors and Þfth instar performance (Dent as a result of a superior ECD. and Walton 1997). All statistical calculations were Treatment differences were found in Þfth instar done with a microcomputer using the Statistix 4.1 duration (F ϭ 8.04; df ϭ 5, 71; P Ͻ 0.0001). Sex did not package (Analytical Software, 1996). signiÞcantly affect Þfth instar developmental time (F ϭ 2.51; df ϭ 1, 60; P Ͼ 0.1). S. panda Þfth instar developmental times were shorter for larvae fed ÔBo- Results nitaÕ leaves, whereas the developmental times were Blueberry leaves from different cultivars varied in longest for those larvae fed ÔSharpblueÕ leaves (Table nitrogen, total phenolics, soluble carbohydrates, and 3). Leaf toughness and Þfth instar developmental time toughness, but not in water content (Table 1). Foliage were correlated (r ϭϪ0.95, n ϭ 6, P Ͻ 0.01). of southern highbush cultivars had the highest mean Later on, differences in developmental time were concentrations of nitrogen and the lowest mean total not evident in suitable cultivars, and there were no phenolics levels. The estimate of leaf toughness was differences between treatment in total larval devel- lower in ÔSharpblueÕ. Leaf toughness and total phenols opmental time (F ϭ 1.52; df ϭ 4, 59; P Ͼ 0.1; Tables 3 of blueberry cultivars were associated (r ϭ 0.83, n ϭ and 4). The mean number of instars completed before 6, P Ͻ 0.05). Leaf nitrogen content of blueberry cul- pupation varied among larvae fed on leaves from dif- tivars was inversely related to total phenols content ferent cultivars (F ϭ 3.86; df ϭ 4, 60; P Ͻ 0.01; Table (r ϭϪ0.84, n ϭ 6, P Ͻ 0.05). 4). Pupation generally occurred after six instars in Percentage of survival of larvae varied among blue- larvae fed from most of the treatments, whereas those berry cultivars (Table 2). Survival of Þrst instars (age Ͻ 7 d) was lowest on ÔSharpblueÕ and ÔClimaxÕ. This Table 2. Survival of S. panda larvae reared on six blueberry tendency continued until pupation when only one cultivars adult emerged from larvae fed ÔSharpblueÕ and 66.7% in ÔClimaxÕ. ÔOÕNealÕ, ÔMistyÕ, ÔWindyÕ, and ÔBonitaÕ had Survival (%) Cultivar Adults similar values for percentage of survival. 7d 14d 21d Treatment differences in Þfth instar biomass gain (n ϭ 15) (F ϭ 7.20; df ϭ 5, 71; P Ͻ 0.0001) were found among OÕNeal 100.0 Ϯ 0.0a 100.0 Ϯ 0.0a 100.0 Ϯ 0.0a 100.0 blueberry cultivars (Table 3). Biomass gain was Sharpblue 95.0 Ϯ 0.03a 92.0 Ϯ 0.0b 67.0 Ϯ 0.1b 6.7 Ϯ Ϯ Ϯ greater for larvae fed on ÔMistyÕ leaves compared with Misty 100.0 0.0a 88.9 0.0b 88.9 0.0a 93.3 Windy 100.0 Ϯ 0.0a 100.0 Ϯ 0.0a 100.0 Ϯ 0.0a 93.3 those fed on ÔSharpblueÕ leaves. Mean initial weight of Bonita 100.0 Ϯ 0.0a 100.0 Ϯ 0.0a 97.5 Ϯ 0.0a 93.3 Þfth instars was correlated with mean larval gain (r ϭ Climax 81.3 Ϯ 0.0b 66.0 Ϯ 0.1c 53.0 Ϯ 0.1b 66.7 0.91, n ϭ 6, P Ͻ 0.05). F5,18 9.05*** 9.67*** 12,76*** Larval frass production was signiÞcantly inßuenced Data presented as mean Ϯ SEM, except for adults. Means within a by blueberry cultivar and food consumption. Fifth column followed with different letters are signiÞcantly different (P Ͻ instars compensated the high egestion and mainte- 0.05; NewmanÐKeuls multiple range test). nance costs by higher ingestion rates that resulted in *P Ͻ 0.05; ** P Ͻ 0.01; *** P Ͻ 0.001. 960 JOURNAL OF ECONOMIC ENTOMOLOGY Vol. 97, no. 3

Table 3. Development, weight gain, efficiency rates, and relative growth rates for fifth instars of S. panda reared on six blueberry cultivars

Blueberry cultivars Parameter OÕNeal Sharpblue Misty Windy Bonita Climax F5,71 Initial weight 63.9 Ϯ 2.8a 24.2 Ϯ 3.2c 61.9 Ϯ 3.3a 46.7 Ϯ 3.5b 45.2 Ϯ 3.2b 45.9 Ϯ 3.7b 18.39*** Duration (d) 13.9 Ϯ 0.9bc 18.4 Ϯ 2.5a 15.4 Ϯ 0.9ab 11.9 Ϯ 0.5cd 10.4 Ϯ 0.3d 15.3 Ϯ 0.9ab 8.04*** Gain (mg d.w.) 129.9 Ϯ 10.7ab 30.4 Ϯ 6.3d 145.0 Ϯ 12.2a 111.8 Ϯ 8.5abc 94.2 Ϯ 6.1c 92.4 Ϯ 5.6bc 7.20*** AD 41.1 Ϯ 1.2c 55.4 Ϯ 2.8a 45.2 Ϯ 1.3b 37.4 Ϯ 1.7c 44.9 Ϯ 1.3c 53.7 Ϯ 2.5ab 11.87*** ECD 14.4 Ϯ 0.9b 7.3 Ϯ 1.4c 21.7 Ϯ 0.9a 16.9 Ϯ 0.9b 12.8 Ϯ 0.8b 12.9 Ϯ 1.1b 11.53*** ECI 5.8 Ϯ 0.3bc 3.9 Ϯ 0.7d 9.7 Ϯ 0.3a 6.2 Ϯ 0.2b 5.6 Ϯ 0.2c 6.7 Ϯ 0.3b 20.78*** RGR 0.08 Ϯ 0.01b 0.05 Ϯ 0.01c 0.08 Ϯ 0.02b 0.10 Ϯ 0.00a 0.11 Ϯ 0.00a 0.08 Ϯ 0.00b 18.90*** RCR 1.38 Ϯ 0.07b 1.25 Ϯ 0.04bc 0.85 Ϯ 0.06d 1.70 Ϯ 0.07a 1.98 Ϯ 0.09a 1.15 Ϯ 0.06c 38.41*** RER 0.80 Ϯ 0.05b 0.56 Ϯ 0.04c 0.45 Ϯ 0.03c 1.05 Ϯ 0.14a 1.08 Ϯ 0.04a 0.53 Ϯ 0.03c 46.03*** RAR 0.57 Ϯ 0.03b 0.69 Ϯ 0.04b 0.39 Ϯ 0.03c 0.64 Ϯ 0.05b 0.90 Ϯ 0.06a 0.62 Ϯ 0.06b 13.04*** RMR 0.48 Ϯ 0.03c 0.64 Ϯ 0.04b 0.31 Ϯ 0.02d 0.54 Ϯ 0.05bc 0.79 Ϯ 0.06a 0.55 Ϯ 0.06bc 11.91*** n 15 7 15 15 15 13

d.w., dry weight. Data presented as mean Ϯ SEM. Means within a row followed with different letters are signiÞcantly different (P Ͻ 0.05; NewmanÐKeuls multiple range test). *P Ͻ 0.05; ** P Ͻ 0.01; *** P Ͻ 0.001. fed on ÔOÕNealÕ leaves pupated after occasionally Þve, blueberry cultivars. The failure of an insect to grow but typically six, instars. The gender of individuals well on a food resource may be due to a number of inßuenced (males: 5.93 Ϯ 0.20 instars; females: 6.45 Ϯ factors, including low food intake, poorly digested 0.34) the number of instars required for pupation (F ϭ food, inefÞcient incorporation of absorbed food, and 11.75; df ϭ 1, 60; P Ͻ 0.01). nonabsorption of one or more nutrients (Scriber 1977, The Þnal pupal mass was unaffected by blueberry Manuwoto et al. 1985, Slansky 1990, Stamp 1990). cultivar. Females were heavier than males (F ϭ 163.08; Digestive efÞciencies for a number of tree and shrub d.f. ϭ 1,57; P Ͻ 0.0001). The longest pupal develop- feeding Lepidoptera were summarized previously ment was observed in ÔMistyÕ, but no differences were (Scriber and Feeny 1979, Slansky and Scriber 1982). found among sexes (F ϭ 0.13; df ϭ 1, 58; P Ͼ 0.5; Table Compared with the mean values reported previously, 4). Þfth instars of S. panda show on blueberry an RCR near the mean, but an RGR 50% below the mean. Two types of blueberry cultivars have been intro- Discussion duced in Andalusia: southern highbush and rabbiteye. Few screening programs evaluate and recommend In June, when this study was conducted, fruit harvest blueberry cultivars based on pest susceptibility or re- of southern highbush cultivars (ÔOÕNealÕ, ÔSharpblueÕ, sistance. However, this type of study is at least com- and ÔMistyÕ) was almost completed, and plants had plementary to the typical fruit quality and yield studies new mature leaves. Rabbiteye cultivars (ÔBonitaÕ, conducted before the Þeld release of new cultivars ÔWindyÕ, and ÔClimaxÕ) had leaves and . Fructi- and the establishment of cultivar recommendations. Þcation of rabbiteye cultivars in Andalusia falls a The results of this study indicate that blueberry has month later than in southern highbush cultivars. Flow- become a host for S. panda in southwestern Andalusia. ering starts from January to March, depending upon Adverse effects such as low survival of younger larvae, the cultivar; in our region there are two vegetative protracted instar developmental time, and increased ßushes, one in JuneÐJuly and another in September. leaf consumption were observed for larvae on some Only ÔOÕNealÕ is deciduous in our region; all other

Table 4. Mean number of instars, developmental time, and pupal weight of S. panda larvae surviving to pupation and reared on six blueberry cultivars

Larval development Pupal development Sex ratio Cultivar n Instars Pupal weight (mg f.w.) (d) (d) (((:&&) OÕNeal 15 5.7 Ϯ 0.1b 57.3 Ϯ 2.6a 15.3 Ϯ 0.3b 1610.2 Ϯ 162.1a 12 : 3 Misty 14 6.1 Ϯ 0.1ab 58.5 Ϯ 2.1a 18.4 Ϯ 0.4a 1827.6 Ϯ 142.4a 6 : 8 Windy 15 6.2 Ϯ 0.1ab 68.7 Ϯ 1.7a 16.2 Ϯ 0.5b 1530.6 Ϯ 120.1a 11 : 4 Bonita 14 6.4 Ϯ 0.1a 67.3 Ϯ 2.4a 15.2 Ϯ 0.3b 1747.6 Ϯ 156.0a 7 : 7 Climax 10 6.2 Ϯ 0.1a 68.0 Ϯ 2.5a 16.0 Ϯ 0.4b 1589.3 Ϯ 172.9a 7 : 3 ϭ ϭ ϭ ϭ F4,59 1.52 n.s. F4,59 1.52 n.s. F4,58 10.64*** F4,57 2.20 n.s.

f.w., fresh weight; n.s., not signiÞcant. Data presented as mean Ϯ SEM. Means within a column followed with different letters are signiÞcantly different (P Ͻ 0.05; NewmanÐKeuls multiple range test). *P Ͻ 0.05; *P Ͻ 0.01; *** P Ͻ 0.001. No larvae reared on ÔSharpblueÕ survived at the end of the experiments; thus, this cultivar was not included in these statistical analyses. June 2004 CALVO AND MOLINA:BLUEBERRY UTILIZATION BY S. panda LARVAE 961 cultivars studied have leaves in fall-winter (J.M.M., creased growth and rapid development suggests high unpublished data). As in other plants, these differ- host plant suitability. Better performance of S. panda ences in blueberry phenology are likely associated larvae on ÔMistyÕ, ÔOÕNealÕ, and ÔWindyÕ implies that with differences in nutrient content, affecting plant herbivore pressure may be increased with the wide- quality and foliage availability (Barbosa and Greenb- spread planting of these cultivars, which could com- latt 1979, Lincoln et al. 1982, Martin 1988, Slansky and promise the growth and survival of young plants. Con- Wheeler, 1991, Osier et al. 2000). This implies differ- versely ÔSharpblueÕ and ÔClimaxÕ seem to be the least ent suitability as hosts for the neonate larvae by both suitable hosts plants for this species. However, there the presence and amount of new foliage during the are confusing effects of insect herbivore development hatching period, and the duration of high-quality fo- and host phenology that may have been enhanced by liage during development (Murugan and George 1992, the methodology used and by within cultivar variation Tikkanen et al. 1999, Keena 2003). Limiting effects of in chemistry (Stamp and Bowers 1990, Osier et al. poor water and nitrogen content on performance have 2000, Foss and Rieske 2003, Keena 2003). The vari- been reported among tree and shrub feeding Lepi- ability in larval responses between instars and culti- doptera larvae (Scriber 1977, Scriber and Feeny 1979, vars observed in this study emphasizes the need for Mattson 1980, Schroeder and Malmer 1980). In this additional studies to understand the inßuence and study, low levels of nitrogen and water were found in dynamics of cultivation management in S. panda pop- blueberry leaves, but southern highbush plants were ulation biology. Fertilization regimens, phytorregula- the richest in nitrogen and water, a fact that may tors use, and environmental modulators of plant phe- improve the survival and size achieved in these cul- nology and chemistry may be major variables affecting tivars (compare Tables 1 and 2). Furthermore, blueberry phenology and the stability and nature of polyphagous insects tend to have more stringent host blueberry cultivar suitability to this species (Barbosa acceptance standards as early instars, but these stan- 1993, Wheeler et al., 1998, Osier et al. 2000). Cultivar dards relax later in development (Barbosa 1978). mixing for blueberry fruit set improvement (Pritts and Thus, the phenological stage of blueberry plants at the Hanckock 1992) is a common management practice moment of larval hatching and establishment seems to that may be considered, because it can play an im- be very important and may be considered an expla- portant role in the spatial distribution of this herbivore nation for the differences observed, mainly due to its (Tikkanen et al. 1999) and thus in the effectiveness inßuence on the size achieved by early instars. and application of control measures (Krausen and The only nutritional factor that was correlated with Raffa 1996). Our results have implications for blue- larval performance was toughness. Toughness affects berry growers who want to minimize the impact of this the establishment of Þrst instars, increasing costs of lappet moth. Choosing blueberry cultivars that are less food acquisition and impeding food assimilation, suitable hosts could reduce the risk of defoliation, thereby affecting, survival, size, weight, and perfor- especially in newly established plants, helping to mance of successive larval stages (Stamp and Bowers dampen expanding populations of this defoliating spe- 1990, Slansky 1993, Jordano and Goma´riz 1994, Alonso cies. and Herrera 2000). Smaller larvae are less able to compensate for poor food quality, and although larvae Acknowledgments can adjust their feeding rates to maximize their growth, there is a limit, apparently narrower for early Funds for this research were provided by D.G. de Inves- instars (Reavey 1993). Additional molts associated tigacio´n y Formacio´n Agraria. Consejerõ´a de Agricultura y with a prolongation in stadium duration as observed in Pesca, Junta de Andalucõ´a Projects PIA #1301.02 and #03- rabbiteye cultivars is likely to be a response to in- 025; and Instituto Nacional Investigaciones Agrarias, MAPA, creased leaf toughness, allowing larvae to face the Project RTA #03-092. This article is based in part on a Ph.D. physical barrier imposed (Stamp and Bowers 1990, dissertation, which was funded by a Junta de Andalucõ´a Ph.D. Scholarship to D.C. Cambini and Magnoler 1997). Toughness has been reported previously as a source of resistance in Vac- cinium to other insect species (Etzel and Meyer 1986, References Cited Meyer and Ballington 1990). Allen, S. E. [ed.]. 1989. Chemical analysis of ecological ma- S. panda larvae seem to be capable of some com- terials, 2nd ed. Blackwell, Oxford, United Kingdom. pensation for low nutritional food value by increasing Alonso, C., and C. M. Herrera. 2000. 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Waldbauer, G. P. 1964. The consumption, digestion and utili- cornis. Technical Report A-98-3, U.S. Army Engineer Wa- zation of solanaceous and non-solanaceous plants by larvae terways Experiment Station, Vicksburg, MS. of the tobacco hornworm, Protoparce sexta (Johan). (Lep- Zhang, B. Ch. 1994. Index of economically important Lep- idoptera: Sphingidae). Entomol. Exp. Appl. 7: 253Ð269. idoptera. CAB, Wallingford, United Kingdom. Wheeler, G.S.T.D. Center, and T. K. Van. 1998. Inßuence of Pistia stratiotes plant quality on the growth and develop- ment of the biological control agent Spodoptera pectini- Received 27 June 2003; accepted 18 December 2003.