Damages from white grubs in young cork oak plantations of the Mamora forest:biology and proposal of chemical control against the most important species

Abstract: During cork oak regeneration tests performed in the Mamora forest, seedlings sufferedmassive attacks from white grubs. Their mortality rate reached 41 to 68% according to years andsites. Sphodroxia maroccana Ley (Coleoptera; Melolonthidae), an endemic species of theMamora forest, is the main pest present in the regeneration parcels. The other causes of seedlingwithering are principally the summer drought and weeding work. The polyphagous opportunisticS. maroccana became obviously a pest under unbalanced anthropogenic influence. Adults appearevery year in summer, since early June till mid-September. The life-cycle lasts up to five yearsfor females and three years for males. The female, larger than the male, is unable to fly. Thelarvae attack roots and collars of cork oak seedlings. Chemical control achieved by usinggranulate systemic insecticides (Carbosulfan 10% and Chlorpyrifos 10%) induced a significantdecrease of seedling mortality.