Impact of parthenium weed (Parthenium hysterophorus L.) on production of maize and common beans in Arusha, Tanzania

Abstract

Introduction and spread of Parthenium hysterophorus is affecting crop production and farmer’s health. Impacts of this weed on crop production need be assessed and effective management measures be developed in order to reduce or prevent its effects. A study was therefore carried out in Arusha and Meru districts, to (i) describe the farmer’s perceptions about parthenium weed (ii) establish distribution and abundance of parthenium weed (iii) assess effective methods for parthenium weed control in maize fields. To achieve the above mentioned objectives, a field survey was conducted during the long rain season of 2017 in the study areas where 120 farmers growing maize and common beans were interviewed. List of villages and farmers were obtained from the district agricultural officers in the two districts. Three villages from Meru district (Mbuguni, Nasholi and Mareu) were selected randomly while Ilkerini, Losikito and Olorieni were randomly selected from Arusha district. Selection of 20 farmers from each village was also done randomly. On distribution and abundance of the weed, latitudes, longitudes and altitudes were recorded for every 10km intervals along the main arterial roads leading out of Arusha to Namanga, Kilimanjaro Airport, Mbuguni and Ilkerini using a hand-held GPS and simultaneously absence or presence and abundance were recorded. In order to identify effective methods to control the parthenium weed, a field experiment was carried out in a randomized complete block design (CRBD) with four replications at the Tropical Pesticides Research Institute (TPRI) in Arusha. The treatments included hand hoeing twice, dry grass mulch, cover crop (cowpeas) mulch, application of 2, 4-D twice, weed free and un-weed plot. Results showed that only 60% of the respondents in Arusha district were aware of the parthenium weed problem. Forty percent of farmers in Meru district reported to have known the weed. Overall, occurrence of parthenium weed in both maize and common bean fields was noted as non-significant. Although farmers reported to have managed other weeds effectively by hand hoeing, mulching and herbicides application, they were not actively managing parthenium weed. Few farmers (5.8) reported to have heard some farmers getting itchiness of hands, arms and legs as they come into contact with parthenium weed. Habitats, such as roadsides, arable lands, villages and towns are highly vulnerable to invasion by parthenium weed in Arusha and Meru districts. It was observed that parthenium weed was highly concentrated on roadsides and along water tunnels. For instance most (83.08%) farmers in Ilkerini village in Arusha District confirmed parthenium weed had infested their village. Additionally, 74% of farmers in Mbuguni village in Meru District also reported the weed to infest their fields. However few (39.15%) farmers in Olorieni village in Arusha District noticed the weed to infest their fields. Therefore Arusha municipality was highly infested with the weed considering its villages and the conducted survey routes being highly infested with the weed compared with Meru district. For example Ilkerini village and a road from Arusha Municipal to Namanga had 81% and 79% parthenium weed coverage respectively. Frequent observation of the weed was observed only in few areas, for instance along the road from Arusha municipal to Kilimanjaro International Airport 46% weed coverage was observed after 10km car driving and 42% after 40km car driving. Water drainage caused 50% weed coverage to be observed in Mbuguni village in Meru District. In addition, it was noted that road construction works and drainage water were main agents of disseminating seeds of parthenium weed. Before the first hand weeding, 2, 4-D application, dry grass mulch and cover crop (cowpea) hindered parthenium weed growth. Low populations and minimum parthenium heights were recorded in mulch treated plots. Dry grass and cover crop (cowpeas) mulches were the best parthenium weed control methods as they reduced parthenium weed height and population at maize maturity. The control methods did not significantly affect Maize grain yield (p>0.05). It is concluded that farmers were not aware of the health hazard caused by parthenium weed in the study areas. Thus proper and targeted control methods should be employed, especially on roadsides to mitigate the spread of the weed. Mulching was observed to reduce parthenium weed population; hence farmers should integrate such method with other control techniques like hand weeding, biological and chemical control in order to maximize maize and common beans yields.