The interaction between headbugs (Eurystylus sp.) and grain mould (GM) on sorghum was examined
in field trials carried out at Samaru, Nigeria in the 1995 and 1996 wet seasons. The results obtained
show that in all three sorghum cultivars tested, insect damage increased the number of fungal colonies
associated with the grain. This resulted in lower germination, 1000-grain mass and yield in such
treatments. Insect damage also altered the relative abundance of the common fungal flora species as,
following insect damage, Fusarium moniliforme (≡Gibberella fujikuroi), Phoma sorghina and
Curvularia lunata (≡Cochliobolus lunatus) were the most common fungi in decreasing order of
frequency as against the normal order of P. sorghina, F. moniliforme
followed by C. lunata. These
results are the first clear evidence of interactions between headbugs and GM in Nigeria.
Abstract. Pesticides are chemicals that kill or manage the population of pests. There are many different types of pesticides on the market today, but the most common are herbicides and insecticides, which kill or manage unwanted plants and insects. The benefits of pesticides include increased food production, increased profits for farmers and the prevention of diseases. Although pests consume or harm a large portion of agricultural crops, without the use of pesticides, it is likely that they would consume a higher percentage. More food is produced by farmers, thereby increasing profit. Pesticides also increase farm profits by helping the farmer save money on labor costs. Using pesticides reduces the amount of time required to manually remove weeds and pests from the fields. In addition to saving crops and livestock, pesticides have also had direct benefits to human health. It is estimated that since 1945, the use of pesticides has prevented the deaths of around seven million people by killing pests that carry or transmit diseases. Although there are benefits to the use of pesticides, there have also been many problems associated with their use. Pesticides do not always stay in the location where they are applied. They are mobile in the environment and often move through water, air and soil. The problem with pesticide mobility is that when they travel, the pesticides come in contact with other organisms and can cause harm. Pesticides have also been shown to disrupt the balance of an ecosystem. In many situations when a pesticide is used, it also kills non-pest organisms. This can drastically alter the natural balance of the ecosystem. By removing non-pest organisms, the environment can be changed to favor the pest. In addition to causing harm to wildlife, pesticides that travel from their original location are known to cause harm to humans. Human exposure to pesticides has caused poisonings, the development of cancer and the deaths of between 20000 and 40000 people worldwide each year. Another major problem associated with pesticide use is bioaccumulation and biological magnification. Bioaccumulation is when a substance builds up in the body because the body does not have the proper mechanisms to remove it. Many synthetic pesticides are not able to be broken down. Once they enter the body of an organism, they are permanently stored in the body tissue.
The objective of the research was to test the effect of sowing dates, intra-row spacing and biopesticides on the larval population dynamics of M. vitrata in Samaru, Nigeria. The experiment was laid out with biopesticides (B0; control, B1; Neem seeds kernel extract (NKE), B2; Maruca vitrata Multinucleopolyhedrosis virus (MaviMNPV) suspension and B3; Cyper diforce (30 g cypermethrin + 250 g dimethoate). The result at 10 WAS showed that varying sowing dates to SD3 significantly (P=.01) reduced mean population of M. vitrata larva in sampled flowers in all the years and the combine. MaviMNPV was effective in reducing pod borer populations (7.22, 6.11 and 6.67) better than NKE (10.19, 5.74 and 7.96) and Cyper diforce (7.41, 8.89 and 8.15). The control significantly recorded the highest mean (11.67, 12.59 and 12.13) population in all the years and the combined. Similarly, varying sowing dates to SD3 significantly reduced mean population (5.56, 5.00 and 5.28) of M. vitrata in cowpea pods sampled 10 WAS better than SD1 and SD2. Statistically similar effect of biopesticides was observed on mean population of M. vitrata, however, the control recorded the highest mean (22.59 and 13.89) in 2015 cropping season and the combined. High cowpea grain yield was obtained in SD2 (337.85, 689.10 and 800.66 kg ha -1 ) even though statistically similar with SD3 (244.89, 618.10 and 639.68 kg ha -1 ). Cyper diforce treated plots gave the highest yield of 394.56, 887.69 and 976.51 kg ha -1 during 2015 and 2016 cropping seasons and combine but was statistically at far (P=.01) with NKE and MaviMNPV. The interaction of SD2 and Cyper diforce gave the highest grain yield. The effect of sowing at SD2 and insecticide spray will give a better control of M. vitrata for an increased yield of cowpea in the study area.
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