Incidence of Pests and Diseases in Tree Nurseries and Plantations in Kimondi Forest, Nandi County, Kenya

Increasing demand for wood is putting pressure on forest resources that are equally under threat from insect pests and diseases. Reported average annual forest loss stands at 0.2% globally, 0.8% in Africa, and 1.6% in Kenya. To meet the increasing demand for forest products in Kenya, the government and private sector have established plantations of non-native tree species dominated by Eucalyptus species, Cupressus lusitanica, and Pinus patula. To ensure successful forest plantation establishment and management schemes, there is a need for sufficient knowledge and understanding of tree growth conditions and threats including pests and diseases. This study aimed at determining the incidence of plantation and tree nurseries in Kimondi Forest, Kenya. Tree plantations were mapped into 2.5 Ha rectangular portion transects parallel to the forest roads.  In randomly selected portions, observations were carried out for disease and pest signs and symptoms on various tree parts (leaves, stem, roots, fruits, and twigs). In the tree nurseries, 3 m × 1 m rectangular quadrants were placed on seedling beds and similar observations were made. Collected data indicated a high incidence of nursery seedling pests (5.3 % leaves and 5.1%  stems) on Eucalyptus species and least on P. patula (2.4% leaves and 3% stems). Higher incidence of plantation pests (35.0% leaves of Eucalyptus sps.) and least on P. patula stems (1.2%) were recorded. On the other hand, twelve (12.0%) of C. lusitanica and (1.8%) Eucalyptus species plantation twigs were infested by pests. A high incidence of nursery seedling disease (9.8%) was observed on C. lusitanica leaves and least on P. patula stems (3.6%). Higher incidence of plantation diseases (32 %) on leaves of  Eucalyptus sps. and least on C. lusitanica stem (1.4%) was recorded. In both tree nurseries and plantations, roots and fruits remained free from pests and disease. Major tree pests and diseases identified in Kimondi forests include (Human, wildlife, livestock, Cinara cupressi, Gonipterus scutellatus, Pinus pini, and Leptocybe invasa) and (damping-off, Fusarium wilt, Botryosphaeria canker, cypress canker, and Mycosphaerella spp.) respectively. These results suggest a need for regular monitoring and intervention measures to control pest and disease infestation in the Kimondi forest.

pests and diseases identified in Kimondi forests include (Human, wildlife, livestock, Cinara cupressi, Gonipterus scutellatus, Pinus pini, and Leptocybe invasa) and (damping-off, Fusarium wilt, Botryosphaeria canker, cypress canker, and Mycosphaerella spp.) respectively. These results suggest a need for regular monitoring and intervention measures to control pest and disease infestation in the Kimondi forest.

INTRODUCTION
Increasing demand for wood and wood products has exerted pressure on natural forest resources throughout the world (FAO, 2007). These resources are currently under threat due to other factors including clearing forest land for agricultural production or settlements. According to FAO (2007), the world average annual forest losses stand at 0.2%, while that of Africa is about 0.8%.
The need to accommodate the increasing demand for tree products such as fibre and wood in Africa has therefore led to an increasing establishment of forest plantations using non-native tree species such as Eucalyptus, Cupressus lusitanica and Pinus patula species (Evans, 1992). These plantations have an important economic and social bearing for several countries in Africa providing a source of employment, wealth creation, the production of export capital as well as fuel and construction timber (FAO, 2007). Despite their importance, forest plantations using non-native species (exotic) are fragile and face unique threats mostly from pests and disease (Wingfield et al., 2001;Cock, 2003) due to a limited genetic base . Documented examples of major disease outbreaks in the history of forest plantations include Dothistroma needle blight of Pinus species in Chile, New Zealand and Kenya (Gibson, 1975); Phytophthora pinifolia in Chile (Durán et al., 2008); conifer aphid (Cinara cuppressivora) on Cupressus species in Eastern and Central Africa (Murphy, 1998;Day et al., 2003); the sirex wood wasp (Sirex noctilio) on Pinus species in South Africa (Tribe, 2003;Hurley et al., 2007), and the blue gum chalcid (Leptocybe invasa) on Eucalyptus species in many countries in Africa, Asia, the Middle East and Europe (Mutitu, 2003;Mendel et al., 2004;Nyeko, 2005;EPPO, 2006). Dothistroma septosporum led to the termination of P. radiata planting in many African countries, particularly those in East Africa (Gibson et al., 1964;Barnes et al., 2004). Similarly, the susceptibility of Eucalyptus to the snout beetle, Gonipterus scutellatus and Mycosphaerella leaf disease led to the partially discontinued planting of this species in South Africa (Lundquist et al., 1987).
The afforestation examples illustrate how forest pests and diseases raise serious concerns to developers of tropical tree plantation enterprises. Unfortunately, FAO observed that many people working with trees do not pay systematic attention to tree health until trees have died and it is too late for intervention (FAO, 2003).
Outbreaks of serious pests and diseases may still be a major threat to future plantation development in Kenya. Example devastating outbreaks of Psyllid, Heteropsylla cubana in plantations of Leucaena leucocephala in South East Asia, conifer aphids in plantations in East Africa and eucalyptus leaf diseases are only recent history (Nair, 2000).
In order to contain pest and pathogen problems, there is a need for knowledge and information regarding the occurrence of nursery and plantation insect pests and diseases. This study aimed at evaluating the incidence of pests and diseases of tree nurseries and plantations of Kimondi Forest, Nandi County, Kenya.

Study Area
This study was carried out in the Kimondi forest located in Nandi County, Kenya (Figure 1). It lies on latitude 0 0 18' and 0 0 32' N and longitude 37 0 05' to 37 0 23' E in the North Rift Conservancy. The soils are characterized as very shallow to deep and dark yellowish-brown to very dark brown, respectively. Soil types range from friable sandy loam to sandy clay loam and friable gravelly sandy clay loam to sand clay with 5 -50% fine to medium iron and manganese concentrations (Otieno et al., 2014)).

Figure 1: Map of the Study Area
Source: Adopted from KFS.
The Kimondi forest is mainly drained by both Kimondi and Sirua rivers which merge further downstream to form River Yala that finally flows into Lake Victoria (Mitchell, 2004). The forest is the source of water for the recently inaugurated Nzoia cluster II water project (supplies water to Kakamega town and its surroundings) and the Kobujoi water supply project (supplies water to Kobujoi and its surrounding) (Simon et al., 2016). Other rivers that drain water out of the Kimondi forest include Mokong, Orobo, Kundos, Gorgor, Chemogonja and Cheptaburbur. These rivers are perennial and therefore provide water for domestic and industrial use by the adjacent forest communities as well as have waterfalls, which can be harnessed for hydroelectric power generation (District Development Plan, Nandi South 2008-2012, GoK, 2008.

Target Population
The study targeted pests and diseases in both tree nursery seedlings and plantation species of Cupressus lusitanica (678.3 Ha), Pinus patula (147.5 Ha) and Eucalyptus species (48.8 Ha).

Sampling in Tree Nurseries
Tree seedlings within 10 portions of size 3 m × 1 m were sampled for this study according to Sokal and Rohlf (2012) as follows: Nursery beds of the three tree species (C. lusitanica, P. patula, and Eucalyptus species) were separately divided into equal portions of 3 m by 1 m along the nursery lengths. Each portion was numbered; then, 10 portions were randomly selected for the purpose of this study. Incidence of nursery pests and diseases were observed on the roots, leaves and stems of the seedlings within each portion.

Sampling in the Forest Plantations
The targeted plantations (Eucalyptus, C. lusitanica and P. patula) were separately mapped into 2.5 Ha rectangular plots (Figure 2). The plots were positioned in such a way that its long axis ran parallel with the planting rows.

Figure 2: Configuration of the 2.5 Ha Sample Plot Within a Plantation
The ratio of the length of road within the compartment (L) to the compartment area (A) was the same as the length of road (Ls) within the 2.5 Ha sample area (As).
Ground line transect walk was carried out along the road and a take-off point was randomly chosen along the distance abutting each of the 2.5 Ha sample plots per plantation species. Observations were made on 20 consecutive trees for incidences of pests and disease incursion. Across several rows, a further 20 consecutive trees were inspected for damage on the return journey to the road.

Determination of Diseases and Pests Incidence
In each sampled portion (nursery beds or plantations) number of diseased and pest-infested roots, leaves, fruits, twigs and stems were recorded separately and expressed as the proportion of total number in each set respectively according to Anonymous (2006)  Photographs of pest and disease-infested plant parts were taken and used for identification purposes.    Table 3 reports the incidence of diseases in Kimondi forest tree nurseries. 9.8% of C. lusitanica leaves were damaged by diseases in comparison with 8.0% in P. patula and 5.6% in Eucalyptus tree species.  (Gichora et al., 2017).    Logging, debarking, cuttings, uprooting All species

Plate 1: a)Galls of Leptocybe invasa on Eucalyptus Leaves; b) Debarked P. Patula Stem a b
Damage to trees is caused when the developing larvae of Leptocybe invasa produce galls on the leaf midribs, petioles and twigs. The galls cause the twigs to split, destroying the cambium. Small circular holes indicating exit points of adults from pupae are common on the galls. Repeated attacks lead to loss of growth and vigour in susceptible trees. Severely attacked seedlings show gnarled appearance, stunted growth, lodging, dieback and eventually die (Mendel et al., 2004;Nyeko & Nakabonge, 2008;Jhala, Patel & Vaghela, 2010;Petro, 2015;de Souza et al., (2014).
Termites attack on both Eucalyptus species and C. lusitanica seedlings was associated with debarked shoots slightly above and below the base level and the presence of anti-hills around the tree nursery. Petro (2015) previously observed termites as a major pest of nursery seedlings and young plantation of Eucalyptus species below age five. Termites debark the stems below and slightly above ground level, thus affecting the functioning of the physiological process of plant structures, thus leading to the death of seedlings in the nursery (Nyeko & Nakabonge, 2008). Other pests included humans, sap sacking Cinera cupressi and leaf defoliation caused by Pinus pini. These results are in agreement with the findings of Nyeko and Nakabonge (2008) and Gichora et al. (2017). Major diseases in the Kimondi forest were identified by observing disease signs and symptoms. Results are presented in Table 6.

Plate 3: a) Stem Canker of C .lusitanica; b) Mycosphaerella Sps on Eucalyptus Leaves a b CONCLUSION
A high incidence of nursery seedling pests (5.3% leaves and 5.1% stems) was observed on Eucalyptus species and least on P. patula (2.4% leaves and 3% stems). Higher incidence of plantation pests (35.0% leaves of Eucalyptus sps.) and least on P. patula stems (1.2%) were recorded. On the other hand, twelve (12.0%) of C. lusitanica and (1.8%) Eucalyptus species plantation twigs were infested by pests. A high incidence of nursery seedling disease (9.8%) was observed on C. lusitanica leaves and least on P. patula stems (3.6%). Higher incidence of plantation diseases (32 %) leaves of Eucalyptus sps. and least on C. lusitanica stem (1.4%) was recorded. In both tree nurseries and plantations, roots and fruits remained free from pests and disease, respectively. Major tree pests and diseases identified in Kimondi forests include (Human, wildlife, livestock, Cinera cupressi, Gonipterus scutellatus, Pinus pini and Leptocybe invasa) and damping off, Fusarium wilt, Botryosphaeria canker, cypress canker and Mycospherella sps.) respectively. These results suggest a need for intervention measures to control pest and disease infestation in the Kimondi forest.