Håvard Eikemo

Research Scientist

(+47) 916 95 954

Ås H7

Visiting address
Høgskoleveien 7, 1433 Ås




Researcher on fungal diseases, with potato as the main responsibility. Long experience with diseases on fruits and berries, and has also worked on vegetables. Works with disese warnings and modelling within NIBIO`s system for forekasting pests and diseases on plants, and also with climaitic data in Agrometeorology Norway. 

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The impact of Delphinella shoot blight (Delphinella abietis) and Grovesiella canker (Grovesiella abieticola) on subalpine (Abies lasiocarpa) and corkbark fir (A. lasiocarpa var. arizonica) in a provenance trial in Idaho (ID) was evaluated in 2013. Both pathogens were previously reported from North America on fir species. D. abietis had been found on subalpine fir in USA, but not in ID, and G. abieticola on grand fir (Abies grandis) in ID, but not on subalpine or corkbark fir. D. abietis kills current-year needles and in severe cases buds and shoots, and G. abieticola results in dead shoots and branches and can eventually kill whole trees. Significant differences between provenances in susceptibility to D. abietis and G. abieticola were observed in the provenance trial in ID. In general, subalpine fir was more susceptible to both diseases than corkbark fir. In 2013, D. abietis was also found on subalpine fir in the Puget Sound area of Washington State and G. abieticola was seen on white fir (Abies concolor), but neither disease was detected in native stands of subalpine fir in Washington State. Morphological features of both fungi were described from samples collected in the provenance trial in ID in May 2016.

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Delphinella shoot blight (Delphinella abietis) attacks true firs (Abies spp.) in Europe and North America. Especially subalpine fir (A. lasiocarpa), one of the main Christmas tree species in Norway, is prone to the disease. The fungus kills current year needles, and in severe cases entire shoots. Dead needles become covered with black fruiting bodies, both pycnidia and pseudothecia. Delphinella shoot blight has mainly been a problem in humid, coastal regions in the northwestern part of Southern Norway, but, probably due to higher precipitation in inland regions during recent years, heavy attacks were found in 2011 in a field trial with 76 provenances of subalpine fir in Southeastern Norway. However, the amount of precipitation seemed less important once the disease had established in the field. Significant differences in susceptibility between provenances were observed. In general, the more bluish the foliage was, the healthier the trees appeared. The analysis of provenance means indicated that, at least for the southern range, the disease ratings were correlated with foliage color. This study also includes isolation, identification, a pathogenicity test, a seed test and electron microscopy of the wax layer on the needles. The fungus was identified based on the morphology of spores and by sequencing the Internal Transcribed Spacer (ITS) regions of the ribosomal DNA. Koch’s postulates were fulfilled. The fungus was found present on newly harvested seeds and may therefore spread via international seed trade. When comparing the wax layers on green and blue needles, those of the latter were significantly thicker, a factor that may be involved in disease resistance.


The woodland strawberry (Fragaria vesca) has become the model plant for the economically important, but genetically complex, octoploid F. × ananassa. Crown rot caused by the oomycete Phytophthora cactorum is a major problem for the strawberry industry and the identification and incorporation of efficient resistance genes into superior cultivars are important for breeding. In the present study, two experimental populations were used in inoculation experiments under controlled greenhouse condition. Studies of a sparse diallel cross between resistant and susceptible F. vesca genotypes concluded that resistance to crown rot is inherited as a dominant trait under nuclear control. Subsequently, an F2 population derived from the grandparents Bukammen (resistant) and Haugastøl 3 (susceptible) collected in Norway, were phenotyped in infection experiments and genotyped using genotyping-by-sequencing. A 416.2-cM linkage map was constructed, and a single major gene locus was identified on linkage group 6 that we attributed to resistance to Phytopthora infection. We propose to name the resistance locus RPc-1 (Resistance to Phytophthora cactorum 1). Gene prediction of the 3.3 Mb QTL recovered 801 genes of which 69 had a potential role in plant disease resistance.


In an attempt to find alternative products to classical fungicides, several products with low toxicity were tested against powdery mildew of roses. These products included resistance inducers (Bion, BABA, and ROS), potassium salts (Resistim, monopotassium phosphate), and seed extracts. The best results were obtained with acibenzolar-S-methyl (Bion). The utilization of Bion as prophylactic treatment, watered at a concentration 0.1–0.2 mg/ml, together with good cultural practices can be enough to effectively control powdery mildew on roses. Treatments with Resistim reduced the disease incidence, but not always significantly compared to the controls. None of the other products had effect on powdery mildew.


Several non-chemical control agents are now registered and available for control of powdery mildews. However, there is little or no information about their efficacy against strawberry powdery mildew, caused by Podosphera aphanis. Trials were conducted to compare the performance of non-chemical control agents to chemical fungicides under laboratory, greenhouse and high plastic tunnel conditions. The treatments included: AQ10 (active ingredient is Ampelomyces quisqualis, a hyperparasite on powdery mildew), AQ10 + Silwet Gold (organosilicon adjuvant, enhances distribution and wetting), Vacciplant (active ingredient is laminarin, an extract from brown algae), JMS Stylet oil (mineral oil), Rape seed oil + detergent, Thiovit (wettable sulphur), Topas 100 EC (penconazole) + Candit (kresoximmethyl) and water as control. In the greenhouse, one quarter of the recommended dose was used either daily in one experiment or three times per week in another. In the field, half of recommended rates were applied twice weekly. Both in the greenhouse and tunnel experiments, the chemical control Topas + Candit and AQ10 + Silwet Gold significantly reduced disease severity. AQ10,Vacciplant and Thiovit were moderately effective when applied daily in the greenhouse trial, but not significantly different from the water control when applied three time per week in the greenhouse and twice a week in the tunnel experiment. In the plastic tunnel, the JMS stylet oil and Rape seed oil + detergent treatments caused severe phytotoxic reaction (necrosis). AQ10 used alone had the poorest performance in the tunnel. This indicated that the spreader either enhances the effect of AQ10 and/or the spreader itself had an effect. In laboratory experiments with powdery mildew grown on strawberry leaflets in Petri dishes, spore germination after treatments with water, Stylet oil, Candit and Thiovit were 74, 53, 8 and 7%, respectively. The effect of Thiovit found in the laboratory was not reflected in the greenhouse and plastic tunnel trials. We will further explore the protectant, curative and eradicative effects of the compounds included here.