Host preference of the crapemyrtle aphid (Hemiptera: Aphididae) and host suitability of crapemyrtle cultivars.

Crapemyrtle aphids, Sarucallis kahawaluokalani (Kirkaldy), are a common pest of crapemyrtle (Lagerstroemia spp.) throughout the southeastern United States. Breeding programs have produced >100 crapemyrtle cultivars that vary in floral color, plant height, and disease resistance, but these programs did not evaluate insect resistance as part of the selection process. In this study, the host suitability of crapemyrtle cultivars and host preference of the crapemyrtle aphid were tested using the following seven crapemyrtle cultivars: 'Carolina Beauty', 'Byers Wonderful White', 'Apalachee', 'Lipan', 'Tuscarora', 'Sioux', and 'Natchez'. Host suitability or aphid preference may be affected by cultivar attributes of plant parentage, source of Lagerstroemia fauriei Koehne germplasm, and mature plant height. Host suitability was evaluated by measuring daily and total fecundity under no-choice conditions. Host preference of the crapemyrtle aphid was tested in a choice experiment that used eight crapemyrtle cultivars; the seven used in the no-choice experiment plus Lagerstroemia speciosa L. In the no-choice experiment, aphid daily fecundity was not different among the crapemyrtle cultivars, but aphid total fecundity was different for the factors cultivar, plant parentage, source of germplasm, and mature plant height. Crapemyrtle aphid host preference in the choice experiment indicated that there were differences among cultivar, parentage, source of germplasm, and mature plant height. Results from this study are useful for plant breeding programs that have the objective of producing aphid resistant cultivars.

Modeling egg distribution of Tinocallis kahawaluokalani (Kirkaldy) (Hemiptera: Aphididae) on Lagerstroemia indica L. (Lythraceae)

This is the first record of winter eggs of the holocyclic monoeceous crapemyrtle aphid Tinocallis kahawaluokalani (Kirkaldy) on Lagerstroemia indica L., in Brazil. The shiny black eggs were observed since early autumn, laid on small folds and crevices of the branches. In order to evaluate and model the egg abundance and distribution, four branches from the cardinal points of 10 plants of two age groups, 5-10 and 20-30 years-old, were collected randomly and cut in eight segments of 10 cm and the number of eggs was registered, in the winter 2001. The eggs were laid mainly on the middle portion of the branch, from 40 cm to 60 cm from the apex on the older trees (54 percent) and on 30 cm to 60 cm on younger ones (58 percent). The data fit in a longitudinal regression model that expresses the tendency of the egg distribution on the branches. The number of eggs was greater on the 20-30 year-old plants (61 percent) than on younger ones (39 percent). The average number (± CI 95 percent) of eggs was 70.5 ± 9.3 and 47.4 ± 12.5, respectively, for the older and younger tree groups. There was no correlation between egg distribution and the cardinal positions of the branches.

Este é o primeiro registro da ocorrência de ovos de inverno do afídeo holocíclico monoécio Tinocallis kahawaluokalani (Kirkaldy) em Lagerstroemia indica L., no Brasil. Os ovos, pretos brilhantes, foram observados a partir do início do outono, depositados nas dobras da casca e gemas dos ramos. Com o objetivo de avaliar a abundância e distribuição dos ovos, bem como modelar esse evento, quatro ramos dos pontos cardeais de 10 plantas de dois grupos etários, 5-10 e 20-30 anos de idade, foram coletados ao acaso e cortados em oito segmentos de 10 cm, registrando-se o número de ovos, no inverno de 2001. Os ovos estavam depositados principalmente na porção mediana dos ramos, entre 40 cm e 60 cm do ápice nas árvores mais velhas (54 por cento) e entre 30 cm e 60 cm nas jovens (58 por cento). Os dados ajustaram-se a um modelo de regressão longitudinal que expressa a tendência da distribuição dos ovos nos ramos. O número de ovos foi maior nas plantas mais velhas (61 por cento) que nas jovens (39 por cento), e o número médio de ovos (± IC 95 por cento) foi 70,5 ± 9,3 e 47,4 ± 12,5, respectivamente nos dois grupos etários. Não houve correlação entre a distribuição dos ovos e a posição dos ramos nos pontos cardeais.

Modeling egg distribution of Tinocallis kahawaluokalani (Kirkaldy) (Hemiptera: Aphididae) on Lagerstroemia indica L. (Lythraceae).

This is the first record of winter eggs of the holocyclic monoeceous crapemyrtle aphid Tinocallis kahawaluokalani (Kirkaldy) on Lagerstroemia indica L., in Brazil. The shiny black eggs were observed since early autumn, laid on small folds and crevices of the branches. In order to evaluate and model the egg abundance and distribution, four branches from the cardinal points of 10 plants of two age groups, 5-10 and 20-30 years-old, were collected randomly and cut in eight segments of 10 cm and the number of eggs was registered, in the winter 2001. The eggs were laid mainly on the middle portion of the branch, from 40 cm to 60 cm from the apex on the older trees (54%) and on 30 cm to 60 cm on younger ones (58%). The data fit in a longitudinal regression model that expresses the tendency of the egg distribution on the branches. The number of eggs was greater on the 20-30 year-old plants (61%) than on younger ones (39%). The average number (+/- CI 95%) of eggs was 70.5 +/- 9.3 and 47.4 +/- 12.5, respectively, for the older and younger tree groups. There was no correlation between egg distribution and the cardinal positions of the branches.

Type I error robustness of ANOVA and ANOVA on ranks when the number of treatments is large.

Agricultural screening trials often involve a large number (t) of treatments in a complete block design with limited replication (b = 3 or 4 blocks). The null hypothesis of interest is that of no differences between treatments. For the commonly used analysis of variance (ANOVA) procedure, most texts do not discuss agreement between actual and nominal Type I error rates in the presence of nonnormality, in this small b, large t, situation. Similarly, for the Friedman and the increasingly popular "ANOVA on ranks" procedures, it is not easy to find results concerning null performance given b small and t large. In this article, we therefore present results, from two different bodies of theory, that provide useful insight concerning null performance of these ANOVA and rank procedures when t is large. The two types of theory are (i) the classical approach based on moment approximations to the permutation distribution, and (ii) central-limit-theory-based asymptotics in the nonstandard t--> infinity situation. Both approaches demonstrate the validity of standard ANOVA and of ANOVA on within-block ranks, under nonnormality when t is large. Choice of the procedure to be used on a given data set should therefore be based on consideration of power properties. In general, ANOVA on ranks will be superior to standard ANOVA for data with frequent extreme values.