Inflorescence rot disease also called Khamedj in North Africa caused by Mauginiella scaettae Cav. was reported for the first time by Cavara (1925) in Libya. The disease was reported subsequently in other North African countries and has also been reported from Arabian Peninsula and from Iraq. Recently the disease has been reported in Elx, SE Spain (Abdullah et al.2005). The disease is considered as the second most dangerous pathogen causing losses to date palm, next to FOa, the bayoud pathogen. The disease is considered to be of major economic importance in Iraq and Suadia Arabia. Severe outbreaks occurred in Basrah, Iraq in 1948-1949 and 1977-1978, causing 80% loss of the annual harvest. Losses up to 70% of the crop occurred in 1983 in the Katif province, Suadia Arabia ( Zaid et al.2002).
Disease symptoms: Infected spathes first showed rot symptoms when they begin to emerge in early spring . These symptoms were observed on the external surface of unopened spathes as brownish or rusty-colored lesions. The side of the spathe facing the infected flowers showed similar but milder symptoms. When the infected spathes split, symptoms appeared mostly nearly the top of the spathe and thereafter, a complete destruction of the flowers and strands occurred. Severely affected spathes at an early stage remain unopened and became dry.
Diagnosis and detection of the pathogen:
The major cause of inflorescence rot is considered to be the fungus Mauginiella scaettae Cav. However, other fungi such as F.oxysporum , F.moniliforme, F.solani, Trichothecium roseum, Botrytis aclada, Thielaviopsis paradoxa, Acremonium strictum and Memmoniella sp., have also been found associated with date palm rotted inflorescences and considered of minor importance. Mauginiella scaettae can be easily isolated from rotted inflorescence after surface disinfection of small pieces with 5% sodium hypochlorite solution and plated on suitable culture media such as malt extract agar, potato dextrose agar or potato carrot agar. Isolation can be achieved also after incubation of disinfected pieces in moist chambers and then picking up conidia which developed abundantly and streak them on a suitable medium. Inoculated plates should be incubated at 25 C. The fungus grows as white colonies with immersed and superficial mycelia. Mycelium is composed of branched hyaline septate hyphae. Colony reverse at first creamy to pale brown, becoming black in some isolates on potato dextrose agar. Sporulation are abundant showing powdery appearance . Immersed hyphae are 2-2.5 um wide, aerial hyphae measuring 3-4 um wide. Arthroconidia produced by segmentation of the aerial hyphae ,unicellular, or multicellular, hyaline , glistening white in mass, non-septate conidia, 6- 8X2.5-4um, septate conidia 6-14 X 3-4um ,2-eptate conidia 16-22 X 3.5- 4um, 3-septate condia 12-26 X 3.5-5um 4-septate condia,24-26 X 3.5- 4.5um and 6-septate conidia up to 35 um long. Pathgenicity test can be performed on detached inflorecence free of disease. Inoculation with spore suspension of the pathogen developed typical symptoms after 4 days. Biology and Epidemeology: The ultrastructure of the cell wall and the hyphal septa, together with the diazonium blue B test have shown that M. scaettae represents an anamorph of an unknown ascomycete.
Recently Abdullah et al.(2005) showed that sequncing of the Internal transcribed spacer (ITS) region of this fungus demonstrated that it is closely related to Phaeosphaeria I. Miyake clade B and in particular to P. triglochinicola which belongs to subclade B4. The majority of species of Phaeosphaeria form pseudoparenchymatous ascomata with bitunicate asci which mainly occurred on monocotyledonous plants. Al Ani et al. (1971) demonstrated that the pathogen is mainly preserved as mycelium in infected inflorescence remaining on palms from the previous season or remain within the infected leaf bases. Al Roubaie et al. (1987) suggested that the primary infection by M. scaettae probably occurred during the early stage of floral bud formation and prior to the envelope development of the spathes and their hardening. The availability of rain prior to the stage of flower bud formation and during the early stage of bud formation is probably responsible for creating favorable conditions for fungal growth ,when hyphae hidden between the leaf bases can grow and infect newly developed inflorescence (Abdullah et al.2005).
The disease is more serious in hot and humid regions or in areas with prolonged periods of heavy rains. Hussain and El Baldawy (1977) indicated that up to 52% of palms might be affected in Al Fao town in Basrah province, southern Iraq, where high humidity is prevailed, whereas proportions of the affected trees in the middle Iraq was ranging between 10-20%. Abdullah et al.(2006) demonstrated that conidia of M.scaettae germinated best at high % r.h. Maximum percentage of conidial germination (80.7%) occurred at 95% r.h. and declined sharply (20.8%) at relative humidity below 95% r.h. and no germination occurred below 80% r.h. Moreover, obvious increase in sporulation occurred according to the increase in relative humidity. The highest is being at 100% r.h. and the lowest occurred at 70% r.h( Abdullah et.al.2006) It is generally assumed that conidia of M. scaettae are very short lived and do not persist through the winter.
Control measure:
The first step in the control of inflorescence rot disease achieved by:
good management such as leaf pruning and collection and burning of all infected inflorescences. Application of several fungicides including 3% dichlone spray or 4% thirame spray at the rate of 8 litres per individual palm
