Introduction. In the water-savingand income-generating agroforestry cropping systems developed andpromoted by the ICRISAT in the Sudano-Sahelian zone of West Africa, particularlyin Niger, fruits of domesticated Ziziphus mauritiana (“applesof the Sahel”) are severely damaged by fruit flies (Carpomya incompleta),and chemical pesticide application poses economic, environmentaland human health problems. In the Bio-reclamation of Degraded Lands (BDL)system, apple of the Sahel is the main high-value crop, while inthe Dryland Eco-Farm (DEF), it is grown alongside watermelon. Sclerocaryabirrea (marula plum) is presently being investigated asa dryland tree species for fruit and oil production, either in orchardsor such systems as BDL. Materials and methods. To completepreliminary results of earlier studies published elsewhere, we collectedand incubated in 2010 ripe fruits of marula plum and watermelonin Sadoré, Niger, where the above-mentioned agroforestry systemsare developed, and we recorded emerging fruit flies. We also conducteda spot-spraying experiment (using GF-120) in an apple of the Sahel orchardin Niamey in 2010; we recorded undamaged and damaged fruits and incubatedthe latter. In the same orchard, we set up in 2011 a fruit fly trappingsurvey targeting the invasive species Bactrocera invadens (Chempac®traps using methyl eugenol as the attractant). Results and discussion.The results showed that only Ceratitis cosyra emergedfrom marula plums, and only Dacus spp. from watermelon.The GF-120 spot-spraying experiment showed that C. incompleta was notattracted / intoxicated, contrary to Ceratitis spp.and Dacus spp.; the sprayed trees yielded significantly moremarketable fruits than unsprayed ones; only C. incompleta emergedfrom damaged fruit. Detection trapping revealed for the first timethe presence of B. invadens in the Sahelian zone ofNiger, including at the time of apple of the Sahel fruit production. Conclusion. This, alongside results of earlier studies,suggests a repellent effect of GF-120 on the monophagous C. incompleta species(Trypetinae), while it is attractive to oligophagous/polyphagousDacinae fruit flies; some of them (e.g., Dacus spp.)damage watermelon, which is part of the DEF system, and producefruit at the same time as the jujube tree. The prospects for harnessingthese two opposite regulation pathways are discussed.

Seed germination of watermelon (Citrullus lanatus cv. Sugar Baby) was fully suppressed by intermittent far-red (FR) irradiation (1 min every 30 min). When the intervening dark period was increased, a linearly increasing final germination percentage was obtained. However, a 4-day intermittent FR treatment induced phytochrome-controlled dormancy and the longer the dark interval the deeper was the dormancy of the non-germinated seeds. When seeds were soaked in a fully inhibitory osmotic solution, no dormancy was imposed. However, a single FR pulse at the time of transfer induced partial, secondary dormancy; the kinetics of the imposition of dormancy followed a negative exponential curve (half-life 1.5 days; 3 days for the cultivar Crimson Sweet). Seeds osmotreated for 10 days in darkness and subsequently dehydrated (with and without a final FR pulse) acquired germination characteristics similar to those in light-requiring and dark-germinating achenes, respectively, of the lettuce cultivar Grand Rapids. In the light-requiring osmomanipulated seed population, the induction of germination was brought about by the low-energy reaction of phytochrome, chilling, dry storage and decoating. The transformation through osmomanipulation of the dark-germinating watermelon seeds (the inhibition of which required prolonged exposure to light) to positively or negatively photosensitive seeds (that responded to brief light pulses), might be attributed to the slow relaxation of existing meta-Fa and meta-Rb phytochrome intermediates to Pfr upon hydration.

Seeds of watermelon (Citrullus lanatus cv. Sugar Baby) germinated optimally in the dark, throughout the range 20–40°C. Germination was inhibited by continuous (c) irradiation with farred (FR), blue or white incandescent light; short pulses were ineffective. Intermittent FR could fully substitute for cFR; the effect of alternating red and FR pulses during 30-min dark cycles depended upon the timing of the illuminations within each cycle. It is concluded that germination in watermelon is controlled by the low-energy reaction of phytochrome. However, continuous and intermittent red light resulted in partial reductions in germinability. Opening the seed coat at the radicle end enhanced germination in the dark and reduced photosensitivity towards FR. The outer, lignified part of the testa exerted a mechanically restrictive force upon the expanding radicle; this force was estimated to be equivalent to 0.3 MPa. The kinetics, at 25°C in the dark, of the time course of germination and the escape from the inhibitory actions of cFR and osmoticum (0.5m mannitol) were all sigmoid curves, which, upon transformation to normal distributions, had different means, but statistically similar variances. The cFR-irreversible activation of germination by phytochrome and the mannitol-irreversible onset of radicle elongation preceded radicle protrusion (mean at 32 h, 25°C) by 8 and 6 h, respectively. From the results and data on imbition, it is concluded that activation of germination in watermelon takes place during the second, stationary phase of imbibition (20–30 h after sowing at 25°C).

Seeds of watermelon (Citrullus lanatus (Thunb.) Matsum. & Nakai var. Congo) were subjected to mild accelerated ageing treatments of 30 and 60 d at 30°C at a moisture content of 7.2%. In comparison to a cold-stored control, normal germination and viability were slightly (but not significantly) decreased by these treatments. Subsequent construction of survival curves during storage at 40°C, at seed moisture contents ranging from 10–18%, revealed that the prior 30°C ageing treatments prolonged survival under these conditions.

Pollination ecology was investigated in Citrullus lanatus (Thunb.) Matsum. & Nakai, which is a species vulnerable to pollinator loss. It was found that this species depends heavily on the honeybee, Apis mellifera L., as the main pollinator. Other pollen vectors identified include Xylocopa bees, halictid bees, Hypotrigona bees, flies and beetles. Phenologically, the plant was found to promote male fitness by producing numerous male flowers, which serve as pollinator attracting structures. Blooming sequence and A. mellifera visitation rates to these flowers are presented. This will enable farmers and pollination managers to better understand visitation patterns and to safeguard pollinators during pesticide application schedules.