pɹˈaɪmɚɹi ɪnfˈɛkʃən ɪz mˈeɪnli kˈɔːzd baɪ ðɪ ɐskˈɑːspoːɹz ðæt ˌoʊvɚwˈɪntɚɹ ɪnðə fˈɔːlən dəbɹˈiː ænd ðə dˈɛnsᵻɾi ʌv ðiːz spˈoːɹz ɪnðə spɹˈɪŋ ɪz dᵻɹˈɛktli ɹᵻlˈeɪɾᵻd tə ðə spˈiːd ænd ɪntˈɛnsᵻɾi əvən ˈæpəl skˈæb ˈaʊtbɹeɪk.
Primary infection is mainly caused by the ascospores that overwinter in the fallen debris and the density of these spores in the spring is directly related to the speed and intensity of an apple scab outbreak.