Stored Sorghum Research Articles

Moulds and mycotoxins in sorghum stored in traditional containers in India

Various traditional containers have been used in India for storage of sorghum grains. Sorghum is susceptible to fungal infestation and toxin elaboration. The present study relates to the mould and mycotoxin contamination (aflatoxin B1 and T-2 toxin) in stored sorghum in different storage containers viz. “Kotlu” (Storage rooms), earthenware pots, gunny bags and reed baskets. Aspergillus sp. and Fusarium sp. were the prominent genera and the “Kotlu” form of storage was most susceptible to fungal attack. Storage treatment had little effect on fungal contamination, but despite the fungal infestation, the mycotoxin contamination was found to be very low.

A study of the resistance of some sorghum seed cultivars to Sitophilus oryzae (L.) (Coleoptera: Curculionidae)

Experiments were conducted on some Nigerian and Tanzanian sorghum cultivars to determine their resistance to Sitophilus oryzae (L.), as indicated by the numbers of adults emerging from similar initial infestations. Further experiments were conducted to determine the differences and consequences of resistance to S. oryzae using selected stored sorghum seed cultivars. Differences in the numbers of emergent adults were highly significant ( P < 0.001) within both Nigerian and Tanzanian cultivars. Almost 2.5 times more adults emerged from the most susceptible Nigerian cultivar (CSH5) than from the least susceptible (FD1). Similarly 15.3 times more adults emerged from the most susceptible Tanzanian cultivar (336) than from the least susceptible (303). Resistance was found to be associated with fewer eggs laid (non-preference) and greater mortality of larvae in seeds (antibiosis). The two forms of resistance were associated since the number of eggs laid on different cultivars was significantly correlated with larval mortality in them ( r = 0.73, P < 0.02). Developmental periods were significantly longer in resistant than in susceptible cultivars. There was a significant positive linear relationship between developmental periods and larval mortality due to antibiosis.

Organophosphorus and synergised synthetic pyrethroid insecticides as grain protectants for stored sorghum

AbstractA field experiment was carried out on bulk sorghum stored for 26 weeks in concrete silos in South Queensland. No natural infestation occurred. Laboratory bioassays of treated grain, in which malathion‐resistant strains of insects were added to grain samples, indicated that all the treatments were generally effective. Deltamethrin (2mg kg−1)+piperonyl butoxide (8mg kg−1), fenitrothion (12mg kg−1)+fenvalerate (1 mg kg−1)+piperonyl butoxide (8mg kg−1), and fenitrothion (12mg kg−1)+phenothrin (2mg kg−1)+piperonyl butoxide (8mg kg−1) controlled typical malathion‐resistant strains of Sitophilus oryzae (L.), Rhyzopertha dominica (F.), Tribolium castaneum (Herbst) and Ephestia cautella (Walker). Pirimiphos‐methyl (6mg kg−1)+permethrin (1mg kg−1)+piperonyl butoxide (8mg kg−1) allowed some survival of adults and progeny production by S. oryzae after 12 weeks, and by one strain of R. dominica throughout. Chemical assays established that the residues and rates of breakdown of these grain protectants on sorghum conformed to the general pattern on other cereal grains. Residues at the conclusion of the experiment were below the individual Maximum Residue Limits recommended by the Codex Alimentarius Commission.

Grain protectants for the control of malathion‐resistant insects in stored sorghum

AbstractDuplicate experiments were carried out on bulk sorghum stored in South Queensland and in Central Queensland. Bioassays of treated grain, conducted during 6 months' storage, established that fenitrothion (12 mg kg−1)+ bioresmethrin (1 mg kg−1), and pirimiphos‐methyl (4 mg kg−1)+ carbaryl (8 mg kg−1), controlled typical malathionresistant strains of Sitophilus oryzae (L.), Rhyzopertha dominica (F.), Tribolium castaneum (Herbst), and Ephestia cautella (Walker). Chlorpyrifos‐methyl (10 mg kg−1)+ pyrethrins (1.5 mg kg−1)+ piperonyl butoxide (12 mg kg−1), and fenitrothion (12 mg kg−1)+ (1R)‐phenothrin (1 mg kg−1), also controlled the strains of S. oryzae, T. castaneum and E. cautella, but were only partly effective against R. dominica. Methacrifos (15 mg kg−1) controlled all the tested species except E. cautella. Chemical assays established that the residues and rates of breakdown of these grain protectants on sorghum conformed to the general pattern for other cereal grains; residues from the above treatments were below the individual Maximum Residue Limits recommended by the Codex Alimentarius Commission.

Observations on the breakdown of thiram at different moisture levels in stored grain sorghum

IT HAS been the common practice in some rural parts of India to store sorghum in underground pits during the glut season and release it to the market during the lean period after storage for 3-4 months. In some cases, due to inclement weather conditions during harvest, grain with relatively high moisture content is stored in underground pits. The relative humidity of the atmosphere in such storages will be 75-90%, (due to high moisture in the grain), and under such storage conditions fungal infection poses a serious problem. Although many potent antifungal agents are known, their use to prevent the fungal attack in storages has received little attention. It was found that under such storage conditions, sorghum with a moisture content of over 15% became infected with fungus within one week even in the presence of large doses (290-310 ppm) of thiram (tetramethylthiuram disulphide), while that with moisture content less than 15% was still free of infection for more than 90 days. In addition thiram even at 35 ppm on treated grain, has been reported to damage the egg production of hens, when the grain was fed to birds, both decreasing the total number produced, and causing soft shells (WAIBEL et al., 1955). The present study was undertaken to investigate the relationship between moisture content and the degradation of thiram so as to arrive at a critical moisture content for sorghum, above which thiram would be ineffective.

Control of insects infesting stored sorghum in Northern Nigeria

Store hygiene alone is not sufficient to prevent heavy infestation in unthreshed sorghum stored in sealed mud granaries in Northern Nigeria. Insects that infest before storage, mainly in the field, are liable to cause heavy damage in grain stored longer than six months. Threshing reduced populations of one of the major primary pests, Sitotroga cerealella (Oliv.) in stored grain, but other pests, particularly Sitophilus oryzae (L.) developed more quickly and “heating” was liable to occur if the grain were stored up to the end of the rainy season or longer. Two varieties of sorghum were found to differ in their susceptibility to stored product insect attack but neither was completely resistant. Although air-tight storage of threshed grain gave complete insect control in a large “Argentine” tank, little practical success was achieved in mud granaries treated with bitumen or in sealed clay pots. Some control was achieved in unthreshed sorghum stored in mud granaries treated several times with aluminium phosphide tablets at a rate of 16 tablets per ton. Dusting the surface of a bulk of heads with 0·5 per cent lindane was reasonably effective but a “sandwich” treatment was used in subsequent trials. A 0·5 per cent lindane dust application at a rate of 10 ppm threshed grain was the most effective and economic rate in grain stored in mud granaries for six months or longer. The treatment persists for at least 18 months. Control of insect infestation in grain stored in granaries made from plant materials is less effective because store hygiene is difficult, cross-infestation occurs more easily and a higher ventilation rate causes a faster loss of lindane. In early trials it was found that formulations of 0·5 per cent malathion on kaolin were unstable and thus in a later trial a stable two per cent flour-based malathion was used. Rates up to 15 ppm malathion were less effective than 10 ppm lindane in reducing insect damage. Treatment with two per cent flour-based carbaryl at rates up to 15 ppm were not effective. This series of investigations culminated in a recommendation that farmers could economically protect sorghum which is to be stored for more than six months in mud granaries if 0·5 per cent lindane dust is applied to unthreshed sorghum as a “sandwich” treatment, at a rate equivalent to 10 ppm threshed grain.