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.

The potential of different water hyacinth compost application rates in influencing growth attributes, yield and heavy metal accumulation of lead (Pb), copper (Cu), nickel (Ni) and zinc (Zn) in tomato fruit was studied in Masvingo. Four treatments of water hyacinth compost rates of 0, 37, 55.6 and 74.1 t·ha −1 were each replicated three times and applied in a randomized complete block design set up. Results showed that water hyacinth compost application rates significantly affected plant height, days to maturity and yield but had no influence on the number of tomato fruits per plant. The plant height at application rate of 74.1 t·ha −1 was 25%, 56% and 63% higher than the control at week 6, 9 and 12, respectively. At application rates of 56.6 t·ha −1 , plant heights were 11%, 13% and 12% higher than the control whilst marginal plant height differences of −4%, 6% and 4% were recorded between application rate of 34.7 t·ha −1 and the control at week 6, 9 and 12, respectively. Tomato plants under compost rates of 34.7, 56.6 and 74.1 t·ha −1 in comparison to the control delayed maturity by 10, 17 and 20 days, respectively. Yields of 52, 55, 60 and 68 t·ha −1 were realized from hyacinth compost rates of 0, 34.7, 56.6 and 74.1 t·ha −1 , respectively. Heavy metal concentrations increased with increase in the water hyacinth compost rate but at all application rates, the average concentrations were 85%, 93% and 86% lower than the Codex Alimentarious Com-* Corresponding author. M. Mashavira et al. 546mission permissible levels for Pb, Cu and Zn. Water hyacinth compost at a rate of 74 t·ha −1 therefore can be used for increased tomato yield without exposing consumers to heavy metal toxicity.

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