ZEF Project Details

Strengthening Citrus production systems through the introduction of IPM measure

Keywords

African citrus greening disease, integrated pest management (IPM), vectors

Countries

Kenya, Tanzania

Summary

The proposed 3-year project brings together and unites the complementary strengths of icipe, University of Bonn, Texas A & M University-Kingsville, Citrus Research International (CRI), and National Agricultural Research Systems (NARS) from Kenya and Tanzania to address the most important and pressing insect pests and disease problem on citrus in Africa – mainly the African citrus triozid (ACT), Trioza erytreae, the false codling moth (FCM), Thaumatotibia leucotreta and Greening or Huanglongbing (HLB) disease vectored by T. erytreae. It is a response to accumulating evidence that managing these damaging pests and disease on citrus will increase production and improve the income generation capacity, food and nutritional security of small and medium scale producers in the 2 target countries. Direct feeding by ACT can cause the death of developing citrus flush shoots or abscission of leaves and up to 65% of such infestations are common. However, ACT is most importantly known for its transmission of the phloem-limited bacterium (Candidatus Liberibacter africanus [CLaf]) responsible for HLB, the most devastating disease of citrus which can cause 25 to 100 % citrus yield loss (Kilalo et al., 2009; Pole et al., 2010). The yield of affected trees is not only reduced considerably by continuous fruit drop, dieback, and tree stunting, but also by the poor quality of fruits remaining on the trees. Larvae of FCM also directly damage citrus by tunneling into fruits causing premature fruit drop resulting in 34-68% fruit loss (Ekesi, 2012). In addition to the direct damage, ACT and FCM are major quarantine pests limiting export of citrus to lucrative, quarantine sensitive markets. For both ACT and FCM, in sub-Saharan Africa (SSA) and outside of the Republic of South Africa (RSA), there is very little if any information on their biology and ecology, and the importance of indigenous natural enemies as a potential key mortality factors is unknown. Not surprisingly, in the two target countries, infestations by both insects attract widespread use of pesticides (MAFS, 2002; MoA, 2003), impacting negatively on their natural enemies. Some of these pesticides are UNEP listed persistent organic pollutants (POPs) whose toxic residues can seriously affect human health, and because of their frequent applications have resulted in rapid resistance development in ACT and FCM (Moore, 2002; Tiwari, et al., 2011), leading to an increase in production costs. A variety of environmentally more benign control approaches, including semiochemicals (e.g. attract and kill), bio-pesticides, bio-rationals, biological control and habitat management have been shown to be effective in ACT and FCM management, and can substantially reduce the use of synthetic pesticides. However, little has been done in the 2 target countries to exploit these alternatives on citrus. In the USA, Brazil and RSA, to manage HLB, the following measures are advocated: control of psyllid vectors through judicious use of insecticides or bio-pesticides; production of clean stock nursery in geographically isolated areas in secure insect-proof screen-houses and their certification; and encouraging growers to remove HLB-infected trees to reduce inoculum sources (Gottwald, 2010). This approach must be promoted in Kenya and Tanzania. Worldwide efforts at identifying citrus genotypes with tolerance to ACT and HLB are also receiving increased attention (Folimonova et al., 2009; Albrecht & Bowman, 2012). Unfortunately, in Kenya and Tanzania, little has been done to take advantage of these management practices to minimize HLB disease. The strategic research thrust of the proposed project therefore includes, but not limited to, understanding the abundance, distribution, dynamic, host plants and other ecological attributes of the target insect pests and disease as well as determining the host-pathogen-vector interactions of HLB to guide implementation of management methods. The role of natural enemies as major mortality factors in the dynamics of ACT and FCM will be established. Molecular tools will be employed to provide information on genetic makeup and population variation among the pests and the pathogen. Phenological and stochastic models will be utilized to assess the risk of pest and disease spread and establishment in different ecologies and under different climate change scenarios. We will also use a hyperspectral based mapping approach and random forest classification algorithm to map disease infestation rates (Malenovsky et al., 2007; Forkour et al., 2012) leading to accurate information on HLB distribution and spatio-temporal pattern, which will guide the NARS on where to establish geographically isolated insect-proof clean nursery stock within the target countries. We shall test and subsequently implement proven IPM technologies like bio-pesticides, as alternatives to frequent applications of synthetic pesticides (like POPs), alone or in rotation with ‘softer’ pesticides, bio-rationals (e.g. petroleum oils, botanicals), intercropping with guava, attractant/repellent, and attract-and-kill options. The project shall also screen for clean disease-free citrus planting materials and establish insect-proof nurseries with the clean stocks in locations identified to be free of HLB for later distribution to growers. Socioeconomic baseline studies to determine the impact of management interventions on citrus productivity, income generation, and producer livelihoods, is also built into the project. This will be followed by an ex post impact assessment on technology adoption. Technology transfer and training of NARS partners, growers, and graduate students (PhD and MSc) to increase knowledge on IPM is an integral component of the project to increase citrus production for improving the livelihood of producers and consumers in the target countries.

Methodology

Surveys, laboratory and field research, spatial modeling

Main Cooperation Partners