Fumigant toxicity of allyl isothiocyanate to populations of the red flour beetle Tribolium castaneum

The phasing out of methyl bromide as a fumigant, the phosphine resistance problems in stored product insect-pests, and the ever-growing concerns with human health and environmental safety have been guiding the search of alternative fumigants. Allyl isothiocyanate (AITC) is the main component of mustard oil with reported pesticide activity and potential as a fumigant of stored foodstuffs. The fumigant toxicity of AITC was assessed in adults of 18 populations of the red flour beetle Tribolium castaneum (Coleoptera: Tenebronidae). These populations were all susceptible to AITC with negligible variation among them. Two of these populations were further used to test the AITC susceptibility of eggs, larvae (early and late instars), and pupae of T. castaneum. All of the developmental stages of both populations were similarly susceptible to AITC. No cross-resistance between phosphine and AITC was observed. Despite the significant variation in body mass, respiration rate, and fitness among the populations of T. castaneum, they were not correlated with AITC susceptibility. Larvae and adult malformations were observed when larvae and pupae were exposed to AITC. These results show the potential of AICT as an alternative fumigant against stored product insects

Modelagem das perdas causadas por Sitophilus zeamais e Rhyzopertha dominica em trigo armazenado Modeling of the losses caused by Sitophilus zeamais and Rhyzopertha dominica in stored wheat

Modelaram-se as perdas associadas à infestação de S. zeamais e R. dominica em trigo armazenado. Durante 90 dias de armazenagem, avaliaram-se a população de insetos, a umidade dos grãos, o percentual de grãos danificados por insetos, o peso hectolítrico e a perda de matéria seca da massa de grãos, em temperaturas de 16 a 36 °C. Segundo a Norma Brasileira de Classificação e Comercialização, o trigo que ultrapassar 1,5% de grãos danificados é classificado como "abaixo do padrão"e os modelos calculam que seria necessária uma população de S. zeamais de 180 insetos kg-1 para se atingir o percentual de 1,5% de grãos danificados, associado a umedecimento de 0,13%, redução no peso hectolítrico de 0,4 kg hL-1 e perda de 0,7% de matéria seca. Para R. dominica, uma população de 64 insetos kg-1 leva a 1,5% de grãos danificados, juntamente com o umedecimento de 0,07%, redução de 0,5 kg hL-1 no peso hectolítrico e perda de 0,5% de matéria seca. Em populações de mesmo tamanho, R. dominica foi mais prejudicial que S. zeamais. Dentre os fatores de perda e classificação comercial do trigo, o percentual de grãos danificados foi o mais influenciado pelo crescimento populacional dos insetos.<br>The losses in wheat storage associated with infestation of S. zeamais and R. dominica were modeled. In the course of 90 days of storage, insect population, moisture content, percentage of weight loss of insect damaged grains, test weight per hectoliter and dry matter loss of wheat grains were evaluated at 16-36 °C. In conformity with the Brazilian Classification and Commercialization Standards, the designation "below standard"is applied to wheat that contains more than 1.5% of insect damaged grains and the models predict that in case of S. zeamais a population of 180 insects kg-1 would be necessary to achieve 1.5% of damaged grains, associated with a moisture content of 0.13%, test weight reduction of 0.4 kg hL-1 and 0.7% of dry matter loss. For R. dominica, 64 insects kg-1 would be necessary to achieve 1.5% damaged grains, associated with a moisture content of 0.07%, test weight reduction of 0.5 kg hL-1 and 0.5% of dry matter loss. For equal size populations, the R. dominica was more harmful than S. zeamais. Among loss, grade and class factors for wheat, percent weight loss of insect damaged grains was more affected by the insect population growth

Associação de deltametrina com Acarophenax lacunatus e seu impacto sobre o desenvolvimento de Rhyzopertha dominica Association of deltamethrin with Acarophenax lacunatus on development of Rhyzopertha dominica

O objetivo deste trabalho foi avaliar a associação do inseticida deltametrina, aplicado em grãos de trigo, com o ácaro parasita Acarophenax lacunatus e seu impacto sobre o desenvolvimento de Rhyzopertha dominica. Grãos de trigo (13% de teor de água) foram tratados com diferentes doses de deltametrina (0,00, 0,125, 0,25, 0,375, 0,50, 0,625, 0,75, 0,875 e 1,00 mg i.a. kg-1). As unidades experimentais consistiram de placas de Petri contendo 30 g de grãos tratados, ou não, com o inseticida, infestados com 30 adultos de R. dominica. Cinco dias depois da infestação, foram inoculados cinco ácaros parasitas por unidade experimental, em sete repetições. As unidades experimentais foram armazenadas por 60 dias depois da infestação em câmara climatizada ajustada a 30&plusmn;1&deg;C, 60&plusmn;5% UR e escotofase de 24 horas. A taxa instantânea de crescimento de R. dominica apresentou índices negativos para as doses de deltametrina maiores que 0,25 mg i.a. kg-1. A. lacunatus associado a doses de deltametrina menores que 0,5 mg i.a. kg-1 reduz as fases imaturas de R. dominica.<br>The objective of this work was to evaluate the development of Rhyzopertha dominica on wheat grain treated with the insecticide deltamethrin and infested with the mite Acarophenax lacunatus. The experimental units were Petri dishes containing 30 g of wheat grain (13% moisture content) sprayed with different doses of deltamethrin (0.00, 0.125, 0.25, 0.375, 0.50, 0.625, 0.75, 0.875 and 1.00 mg a.i. kg-1) infested with 30 adults of R. dominica. Five days after the infestation, five mites were inoculated on each experimental unit, in seven replicates. All treatments were maintained under controlled conditions (30&plusmn;1&deg;C, 60&plusmn;5% r.h. and 24 hours scotophase) for 60 days after the infestation. The instantaneous rate of increase of R. dominica was negative under doses higher than 0.25 mg a.i. kg-1. The lowest number of immature R. dominica was observed with the interaction between deltamethrin doses smaller than 0.5 mg a.i. kg-1 and A. lacunatus