Impacto do dano da mosca Contarinia sorghicola (Coquillett 1898), no tamanho do grão de sorgo.

Desde 1967 a mosca do sorgo vem sendo citada como um fator limitante para a cultura do sorgo granifero no Brasil. A obtencao de cultivares resistentes e o metodo de controle que tem recebido maior atencao por parte dos pesquisadores. Hoje, ja e conhecido que o principal mecanismo de resistencia do sorgo a mosca e nao preferencia para oviposicao. Tanto nos materiais susceptiveis quanto nos resistentes, o desenvolvimento de um simples individuo da mosca num espigueta e suficiente para destruir o grao. Entretanto, o impacto do dano da mosca no tamanho dos graos que escapam a infestacao permanece controvertido. Ha trabalhos em que foi observado aumento e em outros reducao do tamanho dos graos remanescentes em paniculas infestadas pela mosca do sorgo. Neste ensaio conduzido no Texas, USA, paniculas de dois hibridos (um resistente a mosca - Atx2755 x Tx2767 e outro susceptivel - ATx2752xT430) com niveis de infestacao entre o e 100% foram avaliadas. Foi observada uma baixa correlacao linear entre o peso de 1000 graos e outros parametros como: comprimento, diametro e peso da panicula; peso de graos e avaliacao de danos da mosca. Embora o peso de 1000 sementes tenha mostrado pequenas variacoes, a distribuicao das medias para os niveis de dano aproximou-se de uma funcao quadratica cujo tamanho de grao remanescente maximo ocorreu proximo aos 50% de espiguetas infestadas em ambos hibridos. Portanto, os resultados deste experimento sugerem que independente do tipo de hibrido, ha um pequeno incremento no tamanho dos graos, ..

The impact of sorghum midge damage on the weight of surviving kernels.

O efeito do dano da mosca do sorgo, Contarinia sorghicola (Coq.) no peso de 100 graos remanescentes a infestacao de panicula infestada foi avaliado em dois hibridos de sorgo ( um resistente e um susceptivel a esta praga).A diferenca do peso de 100 graos provenientes de paniculas com diferentes proporcoes de espiguetas danificadas pela mosca (0 a 100%) foi da ordem de 10 e 20% respectivamente para o hibrido resistente e susceptivel. Foi observado um baixa correlacao entre o peso de 100 graos e danos da mosca. Entretanto, nos dois hibridos, a distribuicao das medias de peso de 100 graos prevenientes de paniculas com diferentes proporcoes de espiguetas danificadas pela mosca aproximou-se deuma funcao quadratica. O peso maximo de 100 graos ocorreu quando as paniculas estavam com 40 e 50% de espiguetas danificadas pela mosca res pectivamente para o hibrido susceptivel e resistente. Isto indica que em paniculas sob leves infestacoes ha uma pequena compensacao do dano produzindo maiores graos e sob severa infestacao ha reducao do peso individual dos graos, que escapam a infestacao. Entretanto, esta compensacao do dano da mosca nao e suficiente para recuperar a perda causada diretamente as espiguetas infestadas

Impacto do dano da mosca do sorgo, Contarinia sorghicola (Coquillett, 1898), no peso de cada grão remanescente a infestação.

O efeito do dano da mosca do sorgo, Contarinia sorghicola (Coq.) no peso de 100 graos remanescentes a infestacao de panicula infestada foi avaliado em dois hibridos de sorgo (um resistente e um susceptivel a esta praga). A diferenca do peso de 100 graos provenientes de paniculas com diferentes proporcoes de espiquetas danificadas pela mosca (0 a 100%) foi da ordem de 10 e 20% respectivamente para o hibrido resistente e susceptivel. Foi observada uma baixa correlacao entre o peso de 100 graos e outros parametros como comprimento, diametro e peso da panicula; peso total de graos e danos da mosca. Entretanto, nos dois hibridos, a distribuicao das Medias do peso de 100 graos provenientes de paniculas com diferentes proporcoes de espiguetas danificadas pela mosca aproximou-se de uma funcao quadratica. O peso maximo de 100 graos ocorreu quando as paniculas estavam com 40 e 50% de espiguetas danificadas pela mosca, respectivamente para o hibrido susceptivel e resistente. Isto indica que em paniculas sob leves infestacoes, ha uma pequena compensao de dano, produzindo maiores graos, e sob severa infestacao, ha reducao do peso individual dos graos, que escapam a infestacao. Entretanto, esta compensacao do dano da mosca nao e suficiente para recuperar a perda causada diretamente as espiguetas infestadas

Resistance modality of hybrid sorghum to sorghum midge.

Using the sorghum midge, Contarinia sorghicola (Coq.), resistant hy-brid ATx2755 X Tx2767 and the susceptible hybrid ATx2752 X Tx430 several aspects of the resistance were examined under field conditions from 1982 to 1984 at College Station, Texas. Based on the number of oviposition adult midges trapped per flowering panicle, about 1/3 more female midges visited flowering panicles of the susceptible hybrid than the resistant. In addition, comparing the number of eggs laid by 20 caged females, it was shown that 4-5 times more eggs were laid in spikelets of the susceptible hybrid than spikelets of the resistant hybrid.Although and equivalent proportion of eggs was laid during and before anthesis in spikelets of both hybrids, a significantly lower proportion of eggs was laid in flowers of the resistant hybrid after anthesis. There aspects of adult ovipositional behavior were determined. About 25% more females were trapped on flowering panicles which had not been previously midge infested compared to when panicles had already been infested. Sorghum midge females searched the flowers of the resistant hybrid more rapidly than they did the susceptible; however, the time used attempting to oviposite waslonger. Also, the frequency of ovipositional sucess was much lower, about 4 times, in flowers of the resistant hybrid than in flowers of the susceptible hybrid. Development of midge immature stages in the spikelet of the resistant hybrid was affected

Thermal Requirements for Emergence of Overwintered Sorghum Midge (Diptera: Cecidomyiidae)

Emergence of overwintered sorghum midges, Contarinia sorghicola (Coquillett), was monitored during 1979, 1980, and 1981. Differences in emergence times and distributions among years was a function of soil temperature and rainfall. A heat unit accumulation model incorporating a rainfall adjustment factor was developed which described adult emergence in the spring. Adult midges initiated emergence after accumulating 431 centigrade heat units (based on mean daily to-cm soil temperatures starting 1 April) above a threshold temperature of 14.8°C, whereas, 679 and 977 heat units were required for 50 and 95% emergence, respectively. Sorghum midges that overwintered in johnsongrass spikelets emerged after similar heat unit accumulations as midges that overwintered in sorghum spikelets. The time that midges initiated diapause one year had little effect on the timing or distribution of emergence the following spring. No midges terminated diapause and emerged as adults during the same season that diapause was initiated. Of the diapausing midges, 23% failed to emerge until the second spring and 2.6% emerged the third spring, but times and distributions of emergence were similar for all years

Insect Pests Of Sorghum And Their Control

The insect pests that attack sorghum are presented. Crop damage is discussed in relation to pest species and plant part on which infestation occur namely, seedling, foliage, stem and panicle insects. The importance of the major species are discussed on a regional basis. Shootfly, midge, stem borers and head bugs in Africa and India; the greenbug and midge in the continental USA; midge, armyworm and greenbug in Central and South America and midge and Heliothis in Australia. A brief review of current control measures is given for each pest across regions highlighting differences between developed and developing countries. However, the more holistic pest management approach is applicable in all pest control situations and host plant resistance is seen as the major component required for mounting successful control strategies

Seasonal Abundance of the Greenbug and its Natural Enemies in Grain Sorghum in the Texas High Plains.

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Aphids on Texas Small Grains and sorghum.

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Sorghum insect identification handbook

This handbook has been published to help agricultural scientists and students to identify the common insect and mite pests of the sorghum crop at all stages of growth, and in storage. To create awareness about the benefit of natural enemies there is a section on the more well known predators and parasites of sorghum pests. General descriptions of the pests and color illustrations are provided to facilitate identification. There are brief descriptions of the biology, nature, and symptoms of damage together with suggested control measures. Chemical control should be applied only if really necessary, and a plant protection specialist should be consulted beforehand, if possible. It is always preferable to confirm the identity of pests with the help of professional entomologists and to collect specimens for future identification when the opportunity arises