No abstract

This work is the first study to investigate the efficacy of the commercial formulation of Beauveria bassiana (Broadband) to control adults of red palm weevil (Rhynchophorus ferrugineus (Olivier)). This fungus could be applied as one of the biological tactics in controlling red palm weevil. Bioassay experiments for medium lethal concentrate and medium time to cause death of 50% of red palm weevil adults were carried out. The result showed that the LC50 of B. bassiana (Broadband) was 2.19×10(7) and 2.76×10(6) spores/ml at 9 and 23 d of treatment, respectively. The LT50 was 13.95 and 4.15 d for concentration of 1×10(7) and 1×10(8) spores/ml, respectively, whereas 1×10(9) spores/ml caused 100% mortality after 24 h. Additionally, a red palm weevil pheromone trap was designed to attract the adults to be contaminated with spores of Broadband, which was applied to the sackcloth fabric that coated the internal surfaces of the bucket trap. The mating behavior was studied to determine direct and indirect infection of the spores from male to female and vice versa. The results showed a high efficacy of Broadband suspension at 1×10(9) spores/ml; 40 ml of suspension at this concentration treated to cloth in a trap caused death of contaminated adults with B. bassiana spores directly and indirectly. The 100% mortality was obtained even after 13 d of traps treatment with 40 ml of the suspension at 1×10(9) spores/ml.

Cypermethrin deposits on sprayed (3, 6, 9, 12 and 15 g ha-') radish leaves caused a significant antifeedant effect on third instar larvae and adults of mustard beetles.There was a significant inverse relationship between feeding and dose for both stages. In the case of adults on deposits of 1, 3 and 6 g ha-', feeding was reduced by 60-75% but no mortality was recorded. Much less uniform feeding was associated with higher application rates (9, 12 and 15 g ha-I) with low mortality at the two highest doses. The mean areas of the individual holes eaten by larvae or adults in either control or treated leaves, did not differ significantly. The number of holes eaten was negatively related to application rate. The antifeedant effect was observed with low concentration of both technical and formulated cypermethrin.

Lethal and sublethal eff ects of ten insecticides commonly used in date palm production in Saudi Arabia were assessed in the laboratory against adults of Trichogramma cacoeciae, an important egg parasitoid of the dried fruit moth Ephestia calidella. Bioassays were conducted according to the standard protocol of the International Organization for Biological Control IOBC/WPRS/Working Group 'Pesticides and Benefi cial Organisms'. Our results showed that cypermethrin, deltamethrin, malathion, phenthoate, methomyl, and carbosulfan were moderately harmful (IOBC Class 3) to the parasitoid. The botanical insecticides azadirachtin and matrine were moderately harmful (IOBC Class 3) and slightly harmful (IOBC Class 2), respectively. The insect growth regulator pyriproxyfen was slightly harmful, whereas bistrifl uron was harmless (IOBC Class 1). Regarding sublethal eff ects, the parasitism ratios compared to control were reduced by pyriproxyfen and azadirachtin to 49.0% and 58.0%, respectively; hence they are classifi ed as slightly harmful insecticides (IOBC Class 2). Bistrifl uron and matrine were harmless (IOBC Class 1) as parasitism ratios were reduced by 9.2% and 27.6%, respectively. Longevity of adults exposed to bistrifl uron and matrine (3.6 and 3.3 days, respectively) and to pyriproxyfen and azadirachtin (1.7 and 1.3 days, respectively) was signifi cantly lower than that in control (4.67 days). In semi-fi eld tests, residues of most insecticides on leaves of tomato, a common host plant of lepidopteran pests parasitized by T. cacoeciae, were considered moderately harmful to harmful based on parasitoid mortality at 24 h post-treatment whereas they were slightly harmful at 7 and 14 days post-treatment.

Diluted cypermethrin EC was sprayed on to radish plants in the laboratory and its toxicity to mustard beetle was assayed. Doses at or below an equivalent of 3gha-' (LD,) were used to measure sublethal eflects. A substantial reduction in egg laying occurred even at doses as low as 1 and 1-5 g ha-'. This was due to two factors, the toxicity factor and the antifeeding factor. Insects showing sublethal symptoms of poisoning laid fewer eggs, the reduction being proportional to the dose. On treated leaves, oviposition behaviour was abnormal, eggs being laid on the surface instead of in niches excavated by the female. Feeding was reduced on treated leaves and a positive correlation was demonstrated between the amount of feeding and the proportion of eggs laid in niches. A reduction in hatching occurred when eggs were not laid in niches.Doses of 3gha-' killed the first instar larvae even seven days after application. The effects on adult feeding and oviposition of a sublethal dose of 3 g ha-' persisted for a period up to 20 days post-treatment.