تأثير التبريد في بعض الجوانب الحياتية للأطوار المختلفة لدودة ورق القطنSpodoptera littoralis (BOISD)‎ (Ledipoptera : Noctuidae)‎

Abstract EN

Field investigations conducted during two seasons at six ecologically different governorates in Egypt, revealed that the larval and pupal populations of S.

littoralis in the soil under Eg5ptian clover plants in qpring (March and April) were positively and significantly correlated with the minimu.m temperatures of the preceding winter (December and January).

Drop of minimum temperattues by l'C.

decreased spring population by 1.5 larvae and/or pupae/ m2.

Laboratory investigations emphasized that cooling afrected the various aspects of the biology of the different stages of S.

littoralis.

Effect of cooling varied according to temperahue, period of exposure, and pupal age at the time of exposure to cold.

Cooling effects included: prolongation of incubation period, decrease of egg-hatchability, decrease of rate (or o/o) of pupation, emergence of malformed moths and decrease of egg-layrng capacity.

Coolin g eggs at 3'C.

for 12-24 hours increased incubation period to 4.86.8 days, and decreased hatchability to 8048oh, compared to 3.3 days and 88o/o, respectively, for the check.

Under the same cooling conditions, low temperature reduced the strrvival rate of the different larval instars from 92-100% for the check to 56-9lyo.

Third and 4th -instar larvae were the most sensitive to cooling, whereas 5th and 6th instars were the most tolerant.

Exposure of 0- (newly - formed), 3- and 6-days old pupae to low temperatures of 12,9,6 and 3'C.

for 1, 3, 5 and 7 days decreased the percentage of moth emergence from 93%for the check to 90-2 4yo with 5-29oh of the emerged moths being malformed.

Cooling pupae under the above-mentioned conditions decreased egg-laying capacity of emerged moths.

Females emerged from non-cooled pupae laid an avetage of 1718 eggs, while those emerged from pupae receiving cooling treatments laid 160- L273 eggsl female.

Eggs laid by moths emerging from newly-formed, 3-days old and 6-days old pupae cooled at 9'C.

or less for 5 days or more,6'C or less for 5 days or more, and 3'C for 7 days, respectively, failed to hatch.

Tolerence of pupae to adverse effects of cooling increased with increase of pupal age.

Cooling effects increased with increase of exposure period and/or decrease of temperature.