The development and reproduction of the citrus leafminer (CLM), Phyllocnistis citrella Stainton, were evaluated in six citrus genotypes in order to identify genotypes with resistance traits that could be applied in a program for the development of citrus varieties resistant to the citrus leafminer. Tests were conducted under controlled laboratory conditions (25 ± 1ºC, 70 ± 10% RH, and 14h photophase). Seedlings of each genotype tested were infested with eggs obtained from a stock colony of CLM maintained on 'Cravo' lemon (Citrus limonia L. Osbeck), and the duration and survival of the eggs, larval and pupal stages, pupal size and weight, fecundity and longevity of adults, and sex ratio were evaluated. No influence was observed on the duration and survival of eggs, larvae and pupae of P. citrella. However, pupae obtained in the hybrid C x R4 were significantly smaller and lighter than pupae from the remaining treatments. Adult females from the hybrids C x R4 and C x R315 were the least fecund. However, the lowest value for the corrected reproductive potential (CRP) was recorded in the hybrid C x R315, suggesting that this genotype is the least favorable for the development and reproduction of CLM. On the other hand, the highest CRP value obtained in the 'Rugoso' lemon confirms the susceptibility of this genotype, indicating it as the most suitable for CLM.

We aimed to characterize the population genetic structure within and among five Bemisia tabaci (Gennadius) populations collected from different host plants and geographic regions by using microssatelites as a molecular marker. Each population was represented by 19 specimens. The host plants and geographic origins of these populations were described as follows: Pop 1: Squash Barreiras (BA); Pop 2: Cotton Barreiras (BA); Pop 3: Soybean Campinas (SP); Pop 4: Tomato Cruz das Almas (BA); and Pop 5: Soybean Rondonópolis (MT). Six polymorphic loci were observed, which discriminated 31 different alleles in the studied populations, with a mean number of alleles per population of 3.30 (2.67 - 4.00). Using Fisher's Exact test, it was observed that at least three populations were in Hardy-Weinberg equilibrium for most of the studied loci (six). The dendrogram (UPGMA) separated populations into groups mainly related to the geographic origin of the samples. Only population 5 differed from the others at a 0.15 distance (74.5% group consistency). The most similar populations were 1 and 2, with a 0.01 distance (65.3%). This is in agreement with their geographic origins and it was not consistent with host specificity. The results suggest considerable gene flow (7.3%) among all whitefly populations and indicate that a better understanding of the gene flow in populations of B. tabaci associated with different hosts is required for the management of this insect.

A mosca-branca (Bemisia tabaci biótipo B) é uma das mais nocivas pragas da agricultura. Além de danos diretos, transmite vírus e também induz desordens fisiológicas, como o prateamento-das-folhas-da-aboboreira. No presente trabalho, avaliou-se o prateamento em folhas de cultivares de aboboreiras, submetidas à infestação artificial de B. tabaci biótipo B. Um experimento foi conduzido em condições de campo, em Campinas-SP, no ano agrícola 2003-2004, com 16 cultivares de aboboreira (Cucurbita spp.), sendo sete de hábito de crescimento rasteiro e nove de moita. Utilizou-se delineamento de blocos ao acaso, com 16 tratamentos (cultivares) e cinco repetições, sendo cada parcela formada por duas plantas. Procedeu-se à infestação da área experimental por meio de transplante de plantas de soja infestadas pela mosca-branca entre as aboboreiras, quando estas emitiram o terceiro par de folhas. A evolução do prateamento nas folhas foi avaliada a cada dois ou três dias, mediante uso de escala de notas variando de 1 (sem sintomas) a 5 (folha completamente prateada). 'Baianinha', 'Golden Delight', 'Caravela' e 'Arlika' apresentaram grau máximo de prateamento das folhas (média 5,0) enquanto 'Novita' (2,5), 'Atlas' (2,0) e 'Atlanta AG-303' (1,5) exibiram sintomas amenos, caracterizando-se como menos sensíveis a essa desordem fisiológica.

The silverleaf whitefly Bemisia tabaci biotype B is one of the most harmful insect pests for agricultural and vegetable crops. Beside the direct damage, it transmits pathogenic virus and induces plant physiological disorders, such as the squash silverleaf disorder. In this research we evaluated the development of leaf silvering in squash cultivars submitted to artificial infestation of B. tabaci biotype B. An experiment was conducted under field conditions, in Campinas, São Paulo State, Brazil, during the season 2003-2004. The germplasm (Cucurbita spp.) comprised of seven cultivars of summer squash and nine of bush squash. The experiment used a complete randomized blocks design, with 16 treatments (cultivars) and five replications. Each plot consisted of two plants. The artificial infestation was done when the plants emitted the third pair of leaves, by transplanting soybean plants infested with silverleaf whitefly between the squash plots. The leaf silvering was evaluated every two or three days, using a rating scale varying from 1 (no symptom) to 5 (leaves completely silvered). The highest level (5.0) was observed in 'Baianinha', 'Golden Delight', 'Caravela' and 'Arlika', while 'Novita' (2.5), 'Atlas' (2.0) and 'Atlanta AG-303' (1.5) showed light symptoms, indicating that these have low sensibility to this physiological disorder.