Variety susceptibility

Chaaban, Sameh Ben, Chermiti, Brahim & Kreiter, Serge, 2012, Effects Of Host Plants On Distribution, Abundance, Developmental Time And Life Table Parameters Of Oligonychus Afrasiaticus (Mcgregor) (Acari: Tetranychidae), Papéis Avulsos de Zoologia 52 (10), pp. 121-132 : 121-132

Variety susceptibility to O. afrasiaticus

In addition to Deglet Noor variety, the susceptibility of Alig, Kentichi and Bessr varieties to O. afrasiaticus was assessed, by counting motile stages on dates collected weekly from 15 th April to 4 th November 2006 and from 1 st May to 17 th November 2007. Hibernating O. afrasiaticus populations were monitored twice a month during the rest of the year. Samples of 10 date fruits were collected from each of ten trees for each cultivar.

Date fruits, sorghum leaves and pinnae were individually placed in plastic bags, kept in an insulated cooler with ice, brought to the laboratory and stored at a temperature of 4°C. On removal samples, motile forms of O. afrasiaticus were counted under a stereomicroscope.

Mite development and life table construction

Mite cultures

Date palm fruits (var. Deglet Noor) that was well-infested with spider mites ( O. afrasiaticus ), were collected from the Segdoud oases located near Tozeur, Southern Tunisia, in July 2006. With several hundred spider mites of all stages from these dates a stock colony was started on sorghum plants (Sorghum sp.) .

One month later hundreds of females and males were randomly selected from the laboratory culture and placed together on each of rearing units containing dates of Alig, Bessr, Kentichi and Deglet Noor and on pinnae of Deglet Noor, to lay eggs. The obtained eggs were conserved until they reached maturity and will be used for experiments.

This was done to ensure that mites with which we started the experiments were produced from food that was ingested from the date or leaf type on which we determined the intrinsic rate of increase (rm). The spider mite populations in the colonies were never below several hundred individuals.

All colonies, were kept in a room at 25 ± 1°C, 62.5 ± 12.5% relative humidity ( R.H.) and a 16:8 h (L:D) photoperiod.