The effect of crude extracts of neem (Azadirachta indica) leaf, neem seed and garlic (Allium sativum) at concentrations ranging from 5% to 30% of the material in 100 ml of Potato Dextrose Agar on mycelial growth of Fusarium oxysporum f. sp. lycopersici was assessed. All the extracts inhibited mycellial growth at various levels. Dry neem seed extract gavel 100% inhibition of mycelial growth. Fresh neem leaf extract reduced mycelial growth with increasing concentration while in garlic there were no differences in growth inhibition among the various concentrations used. However garlic extracts decreased sporulation with increasing concentration and cultures grown on extract amended agar plates remained viable.

A survey was conducted in February of 2004 on the outbreak of stem rot and wilt disease of pepper at the Kitabawa/Danzakara and Ajiwa irrigation sites in Northern Nigeria. Laboratory investigations revealed that it was elicited by Phytophthora capsici Leon. The disease caused severe loss in yield and USD 1 700.00 to USD 3 200.00 loss in revenue/ha. The disease was probably further aggravated by the presence of Fusarium sp. as well as ecto- and endoparasitic nematodes. Reasons for outbreak were elucidated and solutions proffered.

Three plant extracts viz. bulbs of Allium sativum L. (Liliaceae), seeds of Annona squamosa L. (Annonaceae) and leaves of Vitex negundo L. (Verbenaceae) were evaluated against cowpea wilt pathogen, Fusarium oxysporum f. sp. ciceris by mycelial dry weight method under laboratory condtions. The mean mycelium dry weights of F. oxysporum of methanol and benzene extracts of A. sativum obtained from 125 g of crused dry plant material (bulbs) were 0.0113 and 0.0174 mg, respectively. This was followed by methanol and petroleum ether extracts of A. squamosa (0.2396 and 0.2381 mg). They effectively controlled mycelial growth of cowpea wilt pathogen, however V. negundo extracts did not cause any significant mycelium growth inhibition when compared to other plant extracts tested. Among the three plant extracts, methanol extracts of A. sativum bulbs could possibly be used for controlling F. oxysporum.

Spectroscopy has become one of the most used non-invasive methods to detect plant diseases before symptoms are visible. In this study it was possible to characterize the spectral variation in leaves of Solanum lycopersicum L. infected with Fusarium oxysporum during the incubation period. It was also possible to identify the relevant specific wavelengths in the range of 380–1000 nm that can be used as spectral signatures for the detection and discrimination of vascular wilt in S. lycopersicum. It was observed that inoculated tomato plants increased their reflectance in the visible range (Vis) and decreased slowly in the near infrared range (NIR) measured during incubation, showing marked differences with plants subjected to water stress in the Vis/NIR. Additionally, three ranges were found in the spectrum related to infection by F. oxysporum (510–520 nm, 650–670 nm, 700–750 nm). Linear discriminant models on spectral reflectance data were able to differentiate between tomato varieties inoculated with F. oxysporum from healthy ones with accuracies higher than 70% 9 days after inoculation. The results showed the potential of reflectance spectroscopy to discriminate plants inoculated with F. oxysporum from healthy ones as well as those subjected to water stress in the incubation period of the disease.

Essential oils from four plants , i.e. geranium, rosa, lemon and mint were tested for their activity in vitro and in vivo against Rhizoctonia solani and Fusarium oxysporum f. sp. phaseoli, the cause of root rot and wilt of beans. In vitro, they were found to have an inhibitory effect against the mycelial growth of R. solani and F. oxysporum f. sp. phaseoli. Complete inhibition in fungal growth was observed at a concentration of 4% of each essential oil and Topsin M at 400 ppm as well. In greenhouse the four essential oils were tested as seed coating and/or foliar spray. Results of seed coating at a concentration of 1% clearly demonstrate a good protection of emerged bean seeds against invasion of R. solani and F. oxysporum f. sp. phaseoli compared with the fungicide treatment. A similar trend was observed in a lower extent when the essential oils were applied as bean seeds coating followed by seedlings foliar spray under field conditions. Obvious yield increase as bean green pods, in all treatments, was significantly higher than in the control.

This paper presents a preliminary report of Fusarium wilt of Roselle in the Nigerian savanna. Soil and plant samples were collected from eight experimental plots where plants showed Roselle wilt symptoms. Samples were analyzed for the presence of nematodes and wilt pathogens. The wilt causative organism Fusarium oxysporum was isolated together with nematodes of different genera. However, nematodes of the genus Helicotylenchus, Scutellonema and Hoplolaimus appeared to occur in higher densities than the others.