Eucalyptus grandis and Tagetes minuta leaf powders effectively protect stored maize against Sitophilus zeamais without affecting grain organoleptic properties

Abstract

Use of plant compounds in grain protection has shown great potential as an alternative to synthetic insecticides in Sub-Saharan Africa. This study investigated the efficacy of Eucalyptus grandis and Tagetes minuta ground leaf powders as grain protectants against Sitophilus zeamais in stored maize. Effect of leaf powders were evaluated on percent germination, percent weight loss of grain, insect infestation, grain colour and odour over 192 days (≈six months) duration. Leaf powders (2.5 and 5 g/kg), synthetic pesticide (Actellic Chirindamatura dust (0.5 g/kg)) and an untreated control were used as treatments. All plant powders significantly minimized grain damage and infestation 96 days post treatment (≈three months) and had no effect on percent germination of maize grains when compared to controls. However, variable responses dependent upon botanical plant cultivars and rate of application were observed from three to six months after application. Grain colour and odour were not affected by plant powders over six months of storage. E. grandis and T. minuta significantly reduce grain damage and insect infestation with no adverse effects on seed germination, colour and odour hence can be used as sustainable alternatives to synthetic insecticides in maize storage especially by smallholder farmers.

Effects of <i>Phytolacca dodecandra</i> Extracts on the Quality Parameters of Stored Maize Grains

“…The relatively high insect damage observed in this study could be due to high temperature and humidity that always prevails in coastal areas. This result are in agreement with Musundire et al, (2015) who reported that stored maize grains treated with plant powders of Tegetes minuta can reduce grains damage. Effect of Botanical Treatment on Colour and Odour Change in Maize Grains during Storage : Figure 6 shows the mean evaluation scores of colour for treated samples with P. dodecandra extracts as compared to those treated with actellic gold TM 2% dust and untreated maize grains.…”

“…Studies indicated that decrease in percentage germination of seeds in various crops after treatment with botanical extracts is attributed to phytotoxins, which are common in many plant species (Babu et al, 2014;Mendez & Mannuel, 2014;Mishra, 2014). However, some extracts have no effects on seed germination (Ogendo et al, 2004;Musundire et al, 2015) similar to our observations. Grains Damage during Storage: The level of grains damage was higher in untreated (negative control) maize grains than those treated with actellic gold TM and P. dodecandra extracts ( Figure 5).…”

“…Grain Colour and Odour: The change in colour and odour of untreated and treated maize grains were assessed on a monthly basis for five months consecutively. Grain sub-samples were assessed for change in colour and odour by modification of the method described by Musundire et al, (2015). The assessment method was done by using 1-5 scoring scale which define separately each of the two parameters.…”

“…The procedure was repeated on a monthly basis for five month and the same six panellists were retained over the entire assessment period. Blank scoring sheets were used for the different assessment dates to ensure that the previous data do not bias subsequent scores tests (Musundire et al, 2015).…”

“…The number of emerged seedlings from each Petri dish were counted and recorded after 7 days. The percentage germination was computed according to Musundire et al, (2015) as follows:…”