Sonia Maria Noemberg Lazzari

Correlation between the infestation level of Sitophilus zeamais Motschulsky, 1855 (Coleoptera, Curculionidae) and the quality factors of stored corn, Zea mays L. (Poaceae)

This experiment was carried out in order to evaluate the effect of Sitophilus zeamais on physical, physiological and sanitary quality of stored corn. Samples of 500 g of the hybrid OC-705, in three replicates, were conditioned in glasses covered with a screened lid, and kept in chamber at 25±2oC, 70±5% RH and 12 h of photophase, for 150 days. The infestation levels were 0, 5, 15 and 50 adults/replicate, for the storage periods of 30, 60, 90, 120 and 150 days. The moisture content, classification, weight loss, germination and internal infestation were evaluated monthly. Significant inverse correlations were verified between the number of insects and both the germination and the weight loss; also between the internal infestation and the germination and the standard type. The presence of S. zeamais showed a positive correlation with the weight loss, what means that the internal and external infestations contribute to the reduction of physiological and physical quality of corn seeds. The mean dry matter loss was 0,36%/day, corresponding to a consumption of 0,0001%/insect/month. As the result of those damages, the product suffered reduction of the commercial grade in 30 days, with significant loss in all quality factors.

Spatio-temporal analysis of insect pests infesting a paddy rice storage facility

The study describes the temporal and spatial distribution of the insect fauna collected in a paddy rice storage facility over two years, with major emphasis on the most abundant pests. The experiment, using 19 food-bait traps, was carried out in the county of Massaranduba, State of Santa Catarina, Brazil, from November 1997 to October 1999. During the whole survey, Sitophilus oryzae (L.), a primary pest associated to stored cereals, was the most abundant species in the storage facility (28,542 specimens captured). Other beetles were collected in remarkable numbers, both primary pests, such as Rhyzopertha dominica (Fabricius) (3,931 specimens), and secondary pests, such as Cryptolestes ferrugineus (Stephens) (4,075 specimens) and Oryzaephilus surinamesis (L.) (1,069 specimens). In general, various species showed very variable distribution and, depending on pest and year, all parts of the facility appeared infested. Pest populations were present both in processing area and in silos, at least in one of the two years survey. Analyzing different distributions, the various zones of the rice facility appeared to have different propensity to insect infestations, with the south-eastern silos and the grain pit with the conveyor belt as the most frequently infested. Moreover, variations between the 1st and 2nd year survey showed a strong decrease of total population numbers in the 2nd year, but in different ways, depending on the species considered. Such a result was probably due to the cleaning measures accomplished inside and outside the silos and in the processing area, including application of insecticide on the structure.

Combination of diatomaceous earth and powder deltamethrin for insect control in stored corn

The use of diatomaceous earth (DE) is a very efficient insect control measure in stored grain IPM due to its low cost, easy application, reduction of active ingredient residues, lower environmental contamination and operator safety. The objective of this research was to evaluate the efficacy of different dosages of DE mixed with powder deltamethrin for controlling Sitophilus zeamais in stored corn. Samples of 100 g of clean and dry corn, in three replicates, were submitted to the following treatments: DE (Keepdry®), at the dosages of 500, 750 and 1000 g/t; powder deltamethrin (K-Obiol®) at 0,5 g a.i. /t and 1,0 g a.i. /t; and combinations of the lowest and highest DE dosages with the two dosages of deltamethrin. Thirty adults of S. zeamais were placed in each vial with the treated grains and kept in environment chambers at 25oC. Mortality was evaluated from the 1st to the 28th day. In the treatments mixing DE with deltamethrin or deltamethrin alone, the mortalyti was registered since the first day. In the treatments using only DE, the first dead insects were recorded after the 3rd day, especially in the highest dosages. After the 7th day, however, there was no statistical difference among all treatments, except for the lowest dosage of DE which reached a satisfactory control level only by the 14th day. It was concluded that treatments using DE combined with low dosages of powder deltamethrin represent an efficient control measure against S. zeamais in stored corn because insect mortality is faster than in treatments using DE alone and residues of active ingredients are much lower than using the insecticide in high dosages.

Comparação dos sistemas de cultivo nativo e adensado de erva mate, Ilex paraguariensis St. Hil., quanto à ocorrência e flutuação populacional de insetos

This research was carried out in order to compare the occurrence of insects in two mate cultivation systems, native and high tree density. It was performed from August/2000 to September/2001, in a private property in Sao Mateus do Sul county, in Parana State, Brazil. Visual inspections of trees and light traps were used to evaluate insect populations in both areas. For Hedypathes betulinus (Klug) (Coleoptera, Cerambycidae), only six adults were observed in the dense area. Based on presence of sawdust at the basis of the trunk, it was obtained that the number of attacked trees did not surpass 11% in either area. For Gyropsylla spegazziniana (Lizer y Trelles) (Hemiptera, Psyllidae), the number of galls per tree was counted and it was observed that the population peak occurred from November to January. For Hylesia spp. (Lepidoptera, Saturniidae) and Thelosia camina Schaus (Lepidoptera, Eupterotidae), the presence of caterpillars on the trees was noticed from September to February, with the population peak in November and December. Adults of Hylesia spp. were more numerous in February and March. Two species that were not previously recorded for Brazil on mate were identified: Hylesia paulex Dognin (83%) and Hylesia remex Dyer (17%), collected with light traps. The mate caterpillar, T. camina was not collected with these traps. Nymphs and adults of Ceroplastes grandis Hempel (Hemiptera, Coccidae) were observed along the year on the branches, with population peak between April and June for the nymphs and from September to November for the adults. It should be considered that despite higher insect incidence in the dense area compared to the native area, the first presents higher yield, and that with a good pest management program the insect problems can be minimized.

Inibidores de amilase em híbridos de milho como fator de resistência a Sitophilus zeamais (Coleoptera: Curculionidae)

Sitophilus zeamais Motschulsky is one of the major pests of stored corn and it is mainly controlled by insecticides. However, due to the undesirable consequences of chemicals on the environment and human health other control measures have been investigated, especially the development of resistant plants. The presence of amylase inhibitors in corn kernels may interfere with the insect digestive process. This research was developed in order to evaluate resistance of corn hybrids to the attack of S. zeamais correlated with amylase inhibitors and nutritional composition of corn kernels. Adults of the maize weevil were exposed to grain samples of different corn hybrids at 27 ± 1°C and 75 ± 5% R.H. Biology, susceptibility index and grain consumption were evaluated. The results were correlated to the grain components (moisture content, ashes, lipids, proteins and carbohydrates) and with the amylase inhibitor activity. The amylase inhibitor activity was determined by incubating the amylase inhibitor with 0.2 units of amylase for 30 min at 25°C, and measuring the residual amylase activity determined by the iodine method. From the nutritional parameters evaluated, only the lipid content correlated significantly with the susceptibility index (r = 0.46). The amylase inhibitors obtained by the extraction with either ethanol or buffer were significantly and negatively correlated with the susceptibility index (r = -0.58), indicating that the inhibitors contribute to the resistance of corn hybrids to the attack of S. zeamais.

Ocorrência e flutuação populacional de Chrysopidae (Neuroptera) em áreas de plantio de Pinus taeda (L.) (Pinaceae) no sul do Paraná

The lacewings are very voracious predators of aphids. The objective of this research was to evaluate the occurrence of adult chrysopids in areas of Pinus reforestation where the giant conifer aphid Cinara spp. (Hemiptera: Aphididae) is causing severe damages. A total of 47 specimens were collected during one year and identified as: Chrysoperla externa (Hagen, 1861), Leucochrysa (Nodita) intermedia (Scheneir, 1851) and Leucochrysa (Nodita) vieirana (Navas, 1913). The captures in the area where the plants were one year old represented about 75% of the adults probably due to the high Cinara infestation on the trees in this area. The chrysopids were recorded mostly during the summer, possibly influenced by temperature.

Rearing method of Oryzaephilus surinamensis (L.) (Coleoptera, Silvanidae) on various wheat grain granulometry

Oryzaephilus surinamensis e uma das especies de insetos-praga mais comuns em graos e outros produtos armazenados, e tem ocorrido em grandes populacoes em praticamente todas as unidades de armazenamento de graos. Contudo, a criacao massal deste inseto, em laboratorio, para bioensaios diversos, nao tem sido uma tarefa simples, em funcao de seu comportamento alimentar, tamanho reduzido e alta mobilidade. Assim, o objetivo deste trabalho foi desenvolver um metodo simples e eficiente para a criacao de O. surinamensis, usando graos de trigo moidos a diversas granulometrias para obter grandes populacoes e estagios padronizados para bioensaios. Insetos adultos foram coletados em diversos armazens na regiao sul do Brasil; 100 especimes foram colocados em frascos de vidro, com graos de trigo moido a diferentes graus, mantidos a 25±0.5oC e 65±5% de umidade relativa. Os insetos foram mantidos por 10 dias para copula e postura dos ovos, sendo entao removidos. Ovos, larvas e pupas foram contados a intervalos de cinco dias; a longevidade dos adultos da segunda geracao foi avaliada. Os graos moidos a grau 20 representaram o melhor meio para a producao de progenie: 89% dos ovos foram produzidos no 5o dia; 30,5% das larvas no 10o; 43% das pupas no 30o e aproximadamente 63% dos adultos no 46o. Os adultos sobreviveram ate 450 dias. A criacao de O. surinamensis, nas condicoes descritas e transferindo os adultos apos 10 dias e repondo o meio quando a populacao aumenta muito, produzira um numero de insetos de cada estagio suficiente para diversos bioensaios de laboratorio.

Comportamento de adultos de diferentes raças de Rhyzopertha dominica (Fabricius) (Coleoptera, Bostrichidae) em superfície tratada com deltamethrin

The most important pest of stored wheat in Brazil, Rhyzopertha dominica (Fabricius, 1792), was tested at Embrapa Trigo, in Passo Fundo-RS, on filter paper impregnated with LC5, LC25, and LC50 of deltamethrin to verify alterations in its walking behaviour that may contribute for pest resistance management in grain storage. Insects of four strains were used, two resistant, BR6 and BR12, and two susceptible, BR4 and UK1, which were collected in storage facilities in Rio Grande do Sul and reared in the laboratory. Insects of the UK1 strain were brought from the laboratory of the Imperial College of Science and Technology, United Kingdom. The results showed differences in the walking behaviour between individuals of strains during the 24 h of the assessment period. Insects of the resistant strains reduced their walking activities on contaminated surface, in an attempt to avoid the insecticide .

Development and consumption capacity of Chrysoperla externa (Hagen) (Neuroptera, Chrysopidae) fed with Cinara spp. (Hemiptera, Aphididae) under three temperatures

The giant conifer aphids Cinara pinivora (Wilson, 1919) and Cinara atlantica (Wilson, 1919) (Hemiptera: Aphididae) are pests on Pinus spp. (Pinaceae) in the South and Southeast regions of Brazil. Larvae of Chrysoperla externa (Hagen, 1861) (Neuroptera, Chrysopidae) were observed feeding voraciously on these aphid colonies. In order to evaluate their potential as biological control agents, some biological parameters and their consumption capacity were studied in laboratory. Ten larvae were isolated in plastic vials and fed with aphids of small size (nymphs of 1st and 2nd instars) and 10 with aphids of medium size (nymphs of 3rd and 4th instars), maintained at 15oC, 20oC and 25oC, under 12:12 h photoperiod and 70 ± 10% RH, and observed daily. The egg incubation period was nine days at 20oC and four days at 25oC. The mean larval development period for C. externa was 59.5 days; 22.3 days and 10.9 days, respectively at 15oC, 20oC and 25oC. The pupal stage last 23.2 at 20oC and 11.1 days at 25oC. Unfortunately, data of egg and pupal development at 15oC are not available because the rearing chamber overheated. The mortality rate from egg to adult was 46.2% 46.6% and 20.2% at 15oC, 20oC and 25oC, respectively. The average aphid consumption of each C. externa larva to complete its development was 499.1; 341.7 and 215.1 small aphids, and 126.4; 105.6 and 67.0 medium aphids, at 15oC, 20oC and 25oC, respectively. About 80% of the total food consumption was by the 3rd instar larvae. Although the development was faster and viability higher at 25oC than at the other two temperatures, the consumption was the highest at 15oC because the larval period was much longer. Therefore, the larvae of C. externa can be regarded as potential biological control agents of Cinara spp. throughout the year and even in cool areas of Southern Brazil during some periods o the year.

Consumption of Cinara spp. (Hemiptera, Aphididae) by Cycloneda sanguinea (Linnaeus, 1763) and Hippodamia convergens Guérin-Méneville, 1842 (Coleoptera, Coccinellidae)

Adults and larvae of coccinellids were observed feeding on populations of the giant conifer aphids Cinara spp. on Pinus spp., in Southern Brazil. The objective of this research is to evaluate the consumption capacity of Cycloneda sanguinea (Linnaeus, 1763) and Hippodamia convergens Guerin-Meneville, 1842 (Coleoptera, Coccinellidae) on these aphid species, in order to obtain information for biological control programs. Ten larvae of each predator species were fed with aphids of small size (nymphs of 1st and 2nd instars), and 10 with aphids of medium size (nymphs of 3rd and 4th instars), maintained under 15oC, 20oC and 25oC, 12 h photophase and 70 ± 10% relative humidity. The aphids were counted every 24 hours, replacing those that were consumed. The total consumption of Cinara by the larvae of C. sanguinea was not statistically different at the three temperatures: 325.5; 322.2 and 324.8 of small aphids and 121.3; 140.4 and 109.9 of medium ones, respectively at 15oC, 20oC and 25oC. The consumption by H. convergens was higher than by C. sanguinea and increased noticeably with temperature: 444 aphids at 15oC; 491.3 at 20oC and 513.3 at 25oC, considering the small aphids, and 187.1; 205.1 and 216.6 of medium aphids at the three temperatures. The small aphids weigh about half as much as medium ones and were preferred by all larval instars probably because they are easier to manipulate than the large ones. Both predators, especially the 4th instar larvae, showed high consumption capacity on the Cinara nymphs at all temperatures and can be regarded as promising biological control agents.