natural-products-in-plant-pest-management

30 S. Marín et al.way that depends on their concentration, substrate water activity and time ofincubation. Only the highest concentration assayed (3000 μg/g) showed theability to maintain antifungal activity during a 35-day incubation period.Ethanolic, methanolic and aqueous extracts of leaves, roots, scape andflowers of Agave asperrima (maguey cenizo) and Agave striate (espadin) havebeen tested for their capacity to inhibit growth and aflatoxin production byA. flavus and A. parasiticus on maize. Leaves and roots showed no inhibitoryeffect, and methanolic extracts from flowers were the most effective. It wasfound that 50% of the minimal inhibitory concentration of extracts (approximately20 mg/ml) produced aflatoxin reductions higher than 99% in maizein storage conditions (Sánchez et al., 2005).Natural maize phenolic acids such as trans-cinnamic acid (CA) andferulic acid (FA), alone or in combination, have been tested to control A. flavusand A. parasiticus growth and aflatoxin production on maize (Nesci et al.,2007). A combination of 25 mM CA + 30 mM FA was very effective in thecontrol of fungal growth and completely inhibited AFB 1production at alla wassayed (0.99–0.93 a wrange). However, some treatments, as a CA–FAmixture at 10 + 10 mM, could lead to stimulation of an A. parasiticus population,and stimulation of AFB 1could be possible in some treatments.Addition of whole or ground dry basil leaves at 50–100 mg/g to maizehas shown to be effective in the reduction of aflatoxin contamination in maizestored for 32 days, with reductions in the range of 75–94% (Atanda et al.,2007). The authors suggested that aflatoxins could be controlled by co-storingwhole dry sweet basil leaves with aflatoxin-susceptible foods in a verysimple manner.Aqueous extracts of leaves of some indigenous plants from Nigeria, suchas Ocimum gratissimum, Acalypha ciliata, Vernonia amyygdalina, Mangiferaindica and Azadirachta indica, had a significant inhibitory effect on F. verticillioidesdevelopment on maize, with Acalypha ciliata being the most effective(Owolade et al., 2000).The effect of cinnamon, clove, oregano and palma rose oils (500–1000 μg/g)on growth and FB 1accumulation by F. verticillioides and F. proliferatum inmaize grain, at 0.995 and 0.950 a wand at 20 and 30°C, have also been evaluated,resulting in different efficacies depending on the treatment conditions(Marín et al., 2003; Velluti et al., 2003). These essential oils have also been usedto study their effects on ZEA and DON production by F. graminearum in nonsterilizedmaize grain in the same initial conditions. In this case the efficacyof essentials oils was found to be poor, clove essential oil being that with abroader applicability (Marín et al., 2004).Ocimum vulgare (30 μg/g) and Aloysia triphylla (lemon verbena; 45 μg/g)essential oils were evaluated on F. verticillioides FB 1production on maizegrain. The oregano essential oil decreased the production level of FB 1, probablybecause of its content of monoterpenes (such as thymol, menthol andcinnamaldehyde) that act as antioxidants and inhibitors of toxicogenesis andsclerotial development. On the other hand, Aloysia triphylla increased theproduction of FB 1, probably because of the presence of myrcenone, alphathujone and isomers of myrcenone in the oil, compounds that showed