Study of Heat and Cold Treatments for Fumigation of Piarom and Zahedi Dates

This study investigated the effectiveness of heat treatment (50°C, 60°C and 70°C for 1 h and 2h at 75-80% RH) and cold treatment (0°C and-5°C for 24h and 48h) in the control of storage pests in Zahedi and Piyarom dates. Before and after each treatment, the number of surviving adults, larvae, pupae and eggs were recorded and the percentage of infestation was calculated. The dates were treated at the selectedtemperatures in the first stage and then packed and stored in cold storage or at ambient temperatures for six months. The rate of infestation and microbiological and chemical analysis were recorded after two and four months of storage and six months after removal from storage. Plodia interpunctella, tribolium castaneum, lasioderma serricorne, oryzaephilus surinamensis, bartrachedra amydraula. and carpophillus sp. were collected from the infested dates. All treatments significantly decreased the percentage ofinfestation compared with the control group. Treatments at 70°C for 2 h and -5°C for 48h were the most effective in reducing the infestation. The results showed that treatment at -5°C for 48h reduced the infestation in the Zahedi and Piyaroum date fruits to 10% during storage. The type of storage and the length of storage interaction on the amount of infestation and percent acidity (as lactic acid) were significant. The rate of infestation and percent acidity in the samples in cold storage decreased significantly during storage. It was concluded that dry and semi-dry dates should be stored in cold storage to prevent the activity of microorganisms and pests.