Rhyzopertha dominica (Coleoptera: Bostrichidae) infestation on seeds of Sorghum drummondii (Poaceae) in packages sold in retail stores

ABSTRACT Insect damage to stored seeds is a challenge. Rhyzopertha dominica (Fabricius, 1792) (Coleoptera: Bostrichidae) is a major pest of seeds and grains in the world, but without record in seeds of the sudangrass (Sorghum drummondii (Poaceae)). The objective of this work was to report, for the first time, the occurrence and damage by R. dominica in S. drummondii seeds, sold in sealed packages in retail market. Four samples with 500 seeds each and without adult insects were separated from a package. The initial weight was obtained with a precision scale and the seeds were stored. The number of adult insects, the weight loss and the infestation rate of the seeds were evaluated 60 days later and the average between samples used to extrapolate the damage per package. An adult of R. dominica, on average, was obtained for each seven seeds and 54.06% of the seeds were damaged, with an average weight loss of 36.09%. This is the first report of R. dominica in sudangrass seeds and the damage inflicted shows that this insect may cause losses in the quantity and quality of seeds due to its rapid populational growth.

Produção de forragem de gramíneas anuais semeadas no verão / Forage yield of annual grasses seeded on the summer

No Rio Grande do Sul, a base forrageira para bovinos de corte e de leite é constituída, basicamente, por pastagens de gramíneas perenes de verão, com bom valor nutritivo (VN) durante a primavera e parte do verão, quando manejadas adequadamente. Entretanto, a forragem no outono e inverno tem baixa concentração de nutrientes, o que ainda é agravado pelas geadas. Um experimento com dois anos de avaliação com parcelas divididas no delineamento em blocos casualizados, com três repetições, comparou rendimento, distribuição de forragem e valor nutritivo em três épocas de semeadura (janeiro, fevereiro e março), alocadas nas parcelas principais, e cinco genótipos (milheto comum, capim-sudão ou aveia de verão, teosinto e os híbridos de sorgo BRS 800 e AG 2501C) nas subparcelas. As duas primeiras épocas de semeadura resultaram em maior rendimento de forragem (mais de 6,0Mg ha-1 de MS) que a semeadura de março, com elevado valor nutritivo (>15% PB). Os sorgos forrageiros foram mais produtivos que capim-sudão e teosinto. Milheto, capim-sudão e teosinto têm maior afilhamento que os sorgos forrageiros híbridos. Milheto tem maior teor de PB (20%) e menor de FDA (35%) nas lâminas foliares quando comparado aos sorgos e teosinto. É possível minimizar a crise forrageira conhecida como vazio forrageiro outonal com a semeadura em múltiplas datas de forrageiras anuais de verão, até o final de fevereiro na região do Planalto Médio do RS e estender o período de pastejo em até 60 dias, em período em que as pastagens perenes de verão têm baixa oferta de forragem ou baixo valor nutritivo e as forrageiras anuais de inverno não estão estabelecidas.

In the Rio Grande do Sul (RS) state, southern Brazil, the forage foundation of beef and dairy cattle operations is pasture of warm-season grasses, with high nutritive value (NV) during spring and part of summer seasons, if managed frequently. However, during cool-season, forage NV is very low and worsen by frosts. A 2-yr split-plot experiment on randomized complete block design with three replications compared yield, yield distribution, and nutritive value in three seeding dates (January, February, and March) allocated on main plots, and five forage grasses cultivars (common pearl millet, teosinte, sudangrass, and BRS 800 and AG 2501C sorghum hybrids) on subplots. The two first seeding dates had the highest forage yield, about 6.0Mg ha-1 of DM than March seeding date of high nutritive value forage (>150g kg-1 MS). Sorghum-hybrids genotypes yield more than teosinte and sudangrass. Pearl millet, sudangrass and teosinte had more tillering. Pearl millet had high CP (200g kg-1 DM), and lower FDA (350g kg-1 DM) concentrations on leaf blades compared to sorghums and teosinte. It is possible minimize fall forage shortage seeding annual forage grasses until end of February in the Planalto region of RS state, and extend the productive period, an additional 30 to 60-d, during a time of year when warm-season perennial grasses have low forage allowance or low nutritive value, and annual winter forages are not established.