Guava die-back disease is a destructive disease. It causes serious yield losses and reduced guava fruits. Inspection of guava plant for die-back revealed that Beheira governorate had the highest frequencies of all isolated fungi from natural infected guava trees, followed by Alexandria, while Kafr El-Sheikh obtained the lowest frequency. Botryodiplodia theobromae gave the highest frequency of isolated fungi from natural infected guava trees during seasons 2015 and 2016, followed by Alternaria alternata, Alternaria sp., whereas Colletotrichum gloeosperiodes, Phomopsis sp., and Nigrospora sp. obtained minor frequency. The highest frequency of Botryodiplodia theobromae was observed at Beheira, followed by Alexandria governorate. Meanwhile, the lowest frequency was found at Kafr El-Sheikh. Pathogenicity test indicated that Botryodiplodia theobromae was the most pathogenic fungus. RAPD analysis of DNA by using three random primers exhibited five groups of DNA bands with first primer, six groups with second primer and five groups with the third primer and the overall similarities between isolates were arranged from 69 to 100% with P1, from 62 to 100% with P2 and from 33 to 100% with P3. The present study aimed to finding correlation between these isolates groups which resulted of RAPD, its pathogenesis and its geographical isolated locations. Ten isolates of B. theobromae represented ten locations of five governorates in Egypt were tested to evaluate the ability of pathogenesis in guava transplants cultivar Banaty at pots under experiments greenhouse conditions for artificial inoculation. The obtained results were exhibited that all tested isolates were clearly pathogenic to guava transplants and produced typical symptoms of guava die-back disease. Such isolates were differences of differed in their pathogenicity. The  ten isolates were coded according to their locations by three random primers (B.W.1, A.B.2, D.S.3, Q.K.4, A.A.5, B.N.6, K.Q.7, Q.S.8, D.B.9 and K.D.10). Isolate code No. Q.K.4 was the most virulent, followed by D.S.3 and Q.S.8, respectively which isolated of Qalyoubia and Damietta governorates. Meanwhile isolates K.D.10, A.A.5, K.Q.7 were moderately pathogenic, they were isolated from Kafr El-Sheikh and Alexandria, while A.B.2 and B.N.6 were the lowest pathogenic isolates isolated from Alexandria and Beheira governorates.

Acalypha shrubs Acalypha wilkesiana Mull.(Euphorbiaceae) found to be favorable host for the striped mealybug Ferrisia virgate (Cockerell)( Pseudococcidae) . This mealybug species is attacked all plant parts and caused considerable damages to this host. Some ecological aspects were carried out on F. virgata infesting acalypha shrubs throughout two successive years (2014-2015) and (2015-2016) in Qalyubiya Governorate. Results obtained showed that population density was more abundant during the second year than the first one, the annual means of total population were 62.02 and 52.01 individuals/leaf), respectively. Also, results revealed that, seasonal abundance of F. virgata found to be active from June to January of next year. The population density was reached its maximum activity on October during both years being 123.0 and 145.2 individuals /leaf for the first and second year, respectively. The prevailing main average temperature and relative humidity were ranging between 22.8°C, 24.2°C and 67%, 64% for the 1st and 2nd years, respectively. These conditions seemed to be favorable conditions for insect activity. After this activity period all stages of this species were disappeared from all plant parts. This phenomenon indicate that this mealybug species was overwinter during winter and spring seasons till the next summer. From these findings it could be stated that any control measurements must be early applied during June, at the beginning of activity period of this mealybug species. Also, results clarified that F. virgate was passed through two annual overlapping field generations on acalypha shrubs. Duration of the first generation was ranged between 80-85 days which occurred during summer months. While the second generation was lasted 75 days and occurred during autumn. Statistical analysis revealed that separate effect of each mean, two weeks earlier of the four selected weather factors on changes in population density of F. virgata most factors had insignificant effects except mean minimum temperature which had positive significant effects throughout the both years (r coefficient values were 0.589 and 0.677). While the combined effects of the four selected factors (mean minimum, maximum temperature, average temperature and mean percentage of relative humidity), two weeks earlier, had significant effects, as a group on the change in population density especially during (2014-2015) , the explained variance was 79.2% and F value 14.4.

Guava (Psidium guajava L.,) die-back disease caused by Botryodiplodia theobromae Pat., is a destructive disease, considered one of the most important and economic disease of guava. Amistar Top 325-32.5% E.C. gave the highest decreasing of linear growth and amount of growth of isolate code No., Q.K.4., followed by Camzin 50% W.P., Monceren 25% W.P. and Montro 30% E.C. Meanwhile, Ridomil Gold/Plus 42.50% W.P., Copral 50% W.P., Eminent 12.50% E.W. and Thiovat Jet 80% W.G. exhibited a lowest effect in reducing of linear growth and amount growth of B. theobromae isolate code No., Q.K.4. Amistar Top 325-32.5% E.C. was the most efficient fungicide in reduce disease incidence and disease severity infield of B. theobromae isolate code No., Q.K.4., followed by Camzin 50% W.P., Monceren 25% W.P., Montro 30% E.C. Meanwhile, Ridomil Gold/Plus 42.50% W.P., Copral 50% W.P., Eminent 12.50% E.W. and Thiovat Jet 80% W.G. showed a lowest efficient in reducing the disease incidence and disease severity. Soil drench method of fungicides application was the higher efficient method in elimination of percentage of disease incidence and disease severity followed by foliar spray application, relatively. Banaty transplant was the most susceptible cultivar to the all tested B. theobromae isolates, whereas cultivar Gizy Ahmr was the lowest susceptible with the same isolates, information about cultivar reaction of guava transplants against B. theobromae is still scanty.