Evaluation of Eucalyptus tereticornis, Tagetes minuta and Carica papaya as Stored Maize Grain Protectants against Sitophilus zeamais (Motsch.) (Coleoptera: Curculionidae)

Abstract

Sitophilus zeamais (Motsch.) is an important storage pest of maize grain in several parts of Africa including Zimbabwe. Although synthetic pesticides are effective at controlling the pest, environmental and health hazards of these chemicals are of increasing concern. The study assessed efficacy of botanical leaf powders of Eucalyptus tereticornis, Tagetes minuta and Carica papaya in controlling S. zeamais using rates of 5 g, 10 g and 20 g per 200 g of open pollinated maize grain (variety ZM421). The trial was laid in a completely randomised design (CRD), with 12 treatments replicated three times. The grain was put in a freezer at-4 o C for a fortnight, before the botanicals were added, to kill any prior sources of weevil inoculum and eggs which might be already pre-existing in the grain. 200 g maize grain was infested with 200 three week old unsexed pure culture weevils in 750 ml jars. After 14, 28, 42, 56 and 70 days, weevils were sieved and their mortality determined. Percentage grain weight loss was assessed after 35 days post pests introduction. There were significant differences (p<0.05) in number of weevil mortality and grain weight loss among treatments and their application rates. The findings showed that conventional chemical control was most effective than all botanicals used. E. tereticornis was the most effective of all the botanical pesticides at an application rate of 20 g as evidenced by high weevil mortality and less grain weight loss. It was concluded that botanicals have storage pesticidal properties to suppress S. zeamais in maize grain and could be used as an alternative control option to synthetic pesticides.

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

“…Several studies have indicated efficacy of leaf powders and essential oils of most Eucalyptus spp. against many insect species including storage pests (Muzemu et al, 2013;Rajendran and Sriranjini, 2008;Mulungu et al, 2007;Talukder, 2006;Modgil and Samuels, 1998). Eucalyptus spp leaf powders for example, were shown to protect wheat grain against insect pests (Sitophilus oryzae (L.) Coleoptera: Curculionidae), Sitotroga cereallella (Olivier) Lepidoptera: Gelechiidae) and Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) for five months while essential oils of Eucalyptus camaldulensis and E. leucoxylon were shown to be lethal to the dates pest carob moth Ectomylois ceratoniae (Zeller) (Lepidoptera: Pyralidae) (Ben-Jemâa et al, 2013;Modgil and Samuels, 1998).…”

“…These include Lippia javanica L. (Gadzirayi et al, 2006), Lantana camara L. (Fusire, 2008) and T. minuta (Muzemu et al, 2013) leaves. Several studies have investigated the efficacy of Eucalyptus spp.…”

“…Several studies have investigated the efficacy of Eucalyptus spp. leaves as grain protectants with many showing a high degree of effectiveness against major storage pests such as S. zeamais (Muzemu et al, 2013;Mulungu et al, 2007;Modgil and Samuels, 1998). Similarly, several studies have investigated the insecticidal properties of T. minuta against storage pests (Muzemu et al, 2013;Shahzadi et al, 2010;Weaver et al, 1994).…”

Comparative laboratory efficacy of novel botanical extracts againstTribolium castaneum

“…reported that 59.37% out of 30,000 plants documented in the Royal Botanical Garden, Kew, UK, were found to have medicinal use. Many researchers have performed various studies of insecticidal plants for evaluating the properties and their effectiveness as repellents and antifeedants, and for their toxicity against various storage insects …”

Susceptibility of Maize Genotypes to Maize Weevil Sitophilus zeamais Motsch. (Coleoptera: Curculionidae)

“…In global, maize is an important crop for a small-scale farmer as food and feed resource (Mwololo et al, 2012). According to Muzemu, Chitamba, & Mutetwa (2013), maize is also the most important crop in Africa that significantly contributes to the national production. Markham, Bosque-Perez, Borgemeister, & Meikle (1994) mentioned that in Africa, losses by storage insect pests i.e.…”