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The production of agricultural commodities faces increased risk of pests, diseases and other stresses due to climate change and variability. This study assesses the potential distribution of agricultural pests under projected climatic scenarios using evidence from the African coffee white stem borer (CWB), Monochamus leuconotus (Pascoe) (Coleoptera: Cerambycidae), an important pest of coffee in Zimbabwe. A species distribution modeling approach utilising Boosted Regression Trees (BRT) and Generalized Linear Models (GLM) was applied on current and projected climate data obtained from the WorldClim database and occurrence data (presence and absence) collected through on-farm biological surveys in Chipinge, Chimanimani, Mutare and Mutasa districts in Zimbabwe. Results from both the BRT and GLM indicate that precipitation-related variables are more important in determining species range for the CWB than temperature related variables. The CWB has extensive potential habitats in all coffee areas with Mutasa district having the largest model average area suitable for CWB under current and projected climatic conditions. Habitat ranges for CWB will increase under future climate scenarios for Chipinge, Chimanimani and Mutare districts while it will decrease in Mutasa district. The highest percentage change in area suitable for the CWB was for Chimanimani district with a model average of 49.1% (3 906 ha) increase in CWB range by 2080. The BRT and GLM predictions gave similar predicted ranges for Chipinge, Chimanimani and Mutasa districts compared to the high variation in current and projected habitat area for CWB in Mutare district. The study concludes that suitable area for CWB will increase significantly in Zimbabwe due to climate change and there is need to develop adaptation mechanisms.

A study was conducted to evaluate four common coffee (Coffea arabica) varieties in Zimbabwe for drought tolerance and ability to recover. The plants were subjected to drought stress for 21 and 28 days with evaluation of recovery done 14 days after interruptive irrigation. Coffee varieties were not significantly different in initial fresh and dry biomass before stressing (P>0.05). CR95 had significantly accumulated more (P<0.05)dry root mass (0.8 g) than the rest of the varieties after 21 days of drought stress. SL28 and CR95 had an 8.3% increase in dry biomass while Cat128 did not gain any dry biomass after 21 days of drought stress. CR95 had significantly more (P<0.05) total dry biomass after 21 days and 28 days of drought stress while SL28 was consistently the least in both periods. Cat129 had the highest recovery gains in dry root, dry shoot, and total dry biomass after 21 days and 28 days of drought stress. Initial root biomass was negatively correlated with changes in total fresh and dry biomass of young coffee (r>0.60) after both 21 and 28 days of drought stress, indicating that root biomass may be the most important factor determining drought tolerance in coffee varieties.

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Cercospora leaf spot is fast turning into a critically important diseasein Zimbabwe. The disease is caused by Cercospora coffeicola whichsignificantly reduces productivity and quality of coffee. Disturbingly,optimum sporulation of Cercospora coffeicola in culture remains a limitingfactor for microbial analysis and quantitative studies of Cercosporaleaf spot. Faced with this challenge, an in-vitro study was conducted atCoffee Research Institute, Manicaland, Zimbabwe to examine growth ofCercospora coffeicola in different nutrient media and to determine the bestmedia for Cercospora coffeicola analysis. Six nutrient media were assessed(corn meal agar, oat meal agar, Czapek Dox agar, malt extract agar, yeastextract agar and potato dextrose agar) for the growth of Cercosporacoffeicola. The laboratory-based experiment was duplicated, laid out ina Completely Randomized Design, replicated three times and based onCercospora coffeicola nutrient inoculation. Data were collected on radialgrowth, colour and texture of mycelium at 3 and 6 days after inoculation.There were significant differences (p < 0.05) in the growth of Cercosporacoffeicola in media after 3 and 6 days. Malt extract agar had the greatestradial growth (34 mm and 32 mm) of Cercospora coffeicola for trials 1and 2 respectively, whilst the least growth was in the oat meal agar (14.2mm and 15.7 mm) for trials 1 and 2 respectively. There were variations incolour and texture of mycelium with malt extract agar, potato dextrose agarand oat meal agar associated with darker colours and rough texture whilesmooth white mycelia were found in corn meal agar. After considering allnutrient media, malt extract agar was found to be the best media for thegrowth of Cercospora coffeicola in-vitro. On the basis of our findings, theauthors recommend the use of malt extract agar as the primary media foridentification and characterisation of Cercospora coffeicola.