Importance of wild crucifers for diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae) and its parasitoids in Kenya

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POTATO PRODUCTION PRACTICES AND LATE BLIGHT MANAGEMENT IN NYANDARUA COUNTY, KENYA

Potato is the second most important crop after maize for food and nutrition security in Kenya. Late blight is a major threat to potato production causing losses of up to 100% if not controlled. Poor production and disease management practices enhance the development and occurrence of potato late blight. A survey was conducted in Nyandarua County to assess potato production and disease management practices on the development and occurrence of late blight. Solvin’s formula was used to determine the sample of 105 farmers. Data on socio-demographic aspects, prevalent potato diseases, management options, and agronomic practices were collected and analyzed using SPSS version 25. Major findings reflected a positive correlation (r = 0.57, n = 105, p = 0.001) between the size of farms owned and the area under potato. Awareness of biological control practices and integrated disease management was 33.3% and 28.6%, respectively.  Practices largely influencing disease prevalence included the use of single variety (86.7%) and farm-saved seeds (74.3%), providing a medium for inoculum incubation. Averagely, 48.6% of farmers practice mono-cropping, and 13.3% leave plant debris in the field which enhances inoculum build-up and recurrence. An average of 65.8% use fungicides in a single class, leading to the pathogen developing resistance. It is therefore recommended that potato farmers adhere to good agricultural practices including crop rotation, intercropping, alternation of fungicide classes, use of biological control products, use of clean certified seeds, proper field sanitation, and primarily Integrated Disease Management to minimize the prevalence of late blight and the associated heavy use of chemical pesticides

Impact of Organic Vegetable Production System in Kiambu and Kajiado Counties of Kenya

The study was conducted to evaluate the impact of organic production system on profitability of smallholder vegetable production systems in the two counties so as to appraise its contribution to improvement of rural livelihoods. The study collected data on costs and returns for a sample of 208 smallholder vegetable farmers who were composed of 78 organic and 130 conventional farmers. Impact of organic production system was evaluated using propensity score matching technique. Organic vegetable production system was found to have a positive significant impact of increasing farm gross margin by US$0.58 representing 89.5% among smallholder producers in Kiambu and Kajiado Counties of Kenya. The study recommended promotion of organic production system as a tool that can be used to improve livelihoods especially in the rural areas

Reproductive potential of fall armyworm Spodoptera frugiperda (J.E. Smith) and effects of feeding on diverse maize genotypes under artificial infestation

Fall armyworm (FAW) Spodoptera frugiperda (J.E. Smith) has become a major threat to maize production in Africa. In this study, six maize genotypes were assessed for their resistance to FAW under artificial infestation in both laboratory and net house conditions. These included two FAW-tolerant hybrids (CKHFAW180294 and CKH191221), two commercial hybrids (WE2115 and CKH10717), and two open-pollinated varieties (ZM523 and KDV4). Larval development time and reproductive potential were assessed on maize leaves in the laboratory and a life table for FAW was constructed. The maize genotypes were also artificially infested with three FAW neonates at two phenological stages (V5 and V7) and reproductive stage (R1) in the net house. Leaf and ear damage scores were recorded on a scale of 1–9. Larval development time varied significantly between maize genotypes with the highest on CKH191221 (16.4 days) and the lowest on KDV4 (13.7 days). The intrinsic rate of natural increase for life tables varied from 0.24 on CKH191221 to 0.41 on KDV4. Mean generation time of FAW ranged from 17.6 to 22.8 days on KDV4 and CKH191221, respectively. Foliar damage was the lowest on CKH191221, and the highest on KDV4 at V7 infestation stage in week 1. CKH191221 had the lowest ear damage score, whereas ZM523 had the highest scores at V5 infestation stage. The highest and lowest yield reductions were observed on ZM523 (64%) at V7 infestation stage and CKHFAW180294 (6%) at R1 infestation stage, respectively. The results indicated the potential for developing tropical mid-altitude maize germplasm with native genetic resistance to FAW

Prioritization of invasive alien species with the potential to threaten agriculture and biodiversity in Kenya through horizon scanning

Invasive alien species (IAS) rank among the most significant drivers of species extinction and ecosystem degradation resulting in significant impacts on socio-economic development. The recent exponential spread of IAS in most of Africa is attributed to poor border biosecurity due to porous borders that have failed to prevent initial introductions. In addition, countries lack adequate information about potential invasions and have limited capacity to reduce the risk of invasions. Horizon scanning is an approach that prioritises the risks of potential IAS through rapid assessments. A group of 28 subject matter experts used an adapted methodology to assess 1700 potential IAS on a 5-point scale for the likelihood of entry and establishment, potential socio-economic impact, and impact on biodiversity. The individual scores were combined to rank the species according to their overall potential risk for the country. Confidence in individual and overall scores was recorded on a 3-point scale. This resulted in a priority list of 120 potential IAS (70 arthropods, 9 nematodes, 15 bacteria, 19 fungi/chromist, 1 viroid, and 6 viruses). Options for risk mitigation such as full pest risk analysis and detection surveys were suggested for prioritised species while species for which no immediate action was suggested, were added to the plant health risk register and a recommendation was made to regularly monitor the change in risk. By prioritising risks, horizon scanning guides resource allocation to interventions that are most likely to reduce risk and is very useful to National Plant Protection Organisations and other relevant stakeholders

Composition and abundance of wood-boring beetles of Acacia xanthophloea and their associated natural enemies in Thika, Kenya

Study was conducted on abundance, composition, and damage of wood-boring beetles on Acacia xanthophloea, and associated natural enemies. Infested wood samples were collected, placed in containers, and kept in the laboratory for emergence of beetles and natural enemies, which were identified and recorded. Distribution of heterostigmatic mites Tarsonemus sp. on Xyloperthodes nitidipennis was investigated. A total of 5,003 wood-boring beetles (Bostrichidae, Buprestidae, Curculionidae, and Cerambycidae), 1,162 predatory beetles (Histeridae and Cleridae), and 30 parasitoids (Chalcididae, Braconidae, Ichneumonidae, Pteromalidae, and Eupelmidae) were recovered. Xylion adustus accounted for 55.33% followed by X. nitidipennis (13.51%). Hister sp. was the dominant predator accounting for 17.36%. Highest Tarsonemus sp. mite load on X. nitidipennis was recorded on the abdominal sternites (25.66 ) followed by head (12.48) and thorax (9.86). Size of exit holes differed (df.1,4; F = 61.03; p < 0.0001) with 1–2 mm having a higher mean (523.2) followed by 2–3 mm (212.0)

Wood-boring beetles associated with Acacia xanthophloea in Nairobi and Machakos Counties, Kenya.

Naivasha thorn tree, Acacia xanthophloea, is grown for foliage, timber, shade and rehabilitation of soils in areas with high water tables in Kenya. Its production is threatened by insect pests, which cause major losses. Very little is documented on wood-boring beetles which cause considerable economic damage to lumber used in a variety of applications, and little is known about their natural enemies in Kenya. We conducted the study to evaluate the occurrence of wood-boring beetles on A. xanthophloea in two different regions of Kenya. Infested wood samples of A. xanthophloea with fresh exit holes were collected from three sites in Kenyatta University (KU), Nairobi and Mitaboni in Machakos, Kenya. The samples were placed in clear plastic buckets and kept at ambient temperatures 23±2°C, 65±10% relative humidity and 12L: 12D in a laboratory where they were observed daily for adult emergence. Adult beetles were collected every three days for identification and data recording. The experiment was replicated four times and data collected twice a week for 6 months. Data on abundance was subjected to analysis of variance using SAS software. A total of 5,850 and 4,691 beetles were collected where 2,187 and 3,097 were Bostrichidae, accounting for 37% and 66% in KU and Mitaboni, respectively. A total of 12 bostrichid species was identified, including Sinoxylon ruficorne, S. doliolum, Xylion adustus, Xyloperthodes nitidipennis, Xyloperthella picea, Xylopsocus castanoptera, Lyctus brunneus, Heterbostrychus brunneus, Xylopsocus sp., and Dinoderus gabonicus. The most abundant species in KU was Xylion adustus with 1,915 beetles accounting for 88.4%, and Sinoxylon ruficorne in Mitaboni with 1,050 beetles accounting for 33.9% of the total. Sinoxylon ruficorne was only recorded in Mitaboni while only 2 specimens of D. gabonicus were found in KU. The mean number of exit holes on A. xanthophloea differed significantly between sites, which corresponded approximately to the amount of economic damage caused by the beetles to the structural integrity of the lumber. In addition, a number of predators in the family Cerambycidae, Cleridae, Histeridae and parasitoids from Braconidae, Ichneumonidae, and Chalcididae were recovered, suggesting a need to conduct further studies to document these species' diversity, parasitism rates and efficacy for possible biological control

Abundance of Bostrichidae species recorded from <i>Acacia xanthophloea</i> ^* at Kenyatta University and Mitaboni from May 2016 –Feb 2017.

<p>Abundance of Bostrichidae species recorded from <i>Acacia xanthophloea</i> ^{<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0188773#t004fn001" target="_blank">*</a>} at Kenyatta University and Mitaboni from May 2016 –Feb 2017.</p

Mean ±SE number of exit holes of wood-boring beetles on <i>Acacia xanthophloea</i> at Kenyatta University and Mitaboni.

<p>Mean ±SE number of exit holes of wood-boring beetles on <i>Acacia xanthophloea</i> at Kenyatta University and Mitaboni.</p

Percent contribution of the family Bostrichidae recovered from <i>Acacia xanthophloea</i> at Kenyatta University and Mitaboni.

<p>Percent contribution of the family Bostrichidae recovered from <i>Acacia xanthophloea</i> at Kenyatta University and Mitaboni.</p