Embrapa has reported that there are higher instances of pests resistance to the Cry1Ac gene used in B.t soybeans in the 2021/22 crop year, particularly in sunflower looper (Rachiplusia nu). Conditions that have led to the emergence of pest resistance reportedly include the low adoption of structured refuge areas and the indiscriminate use of insecticides. Refuge areas are calculated portions of the total cultivated area that must be planted with crops that do not contain B.t genes, nor can the area be treated with foliar B.t applications, in order to maintain a B.t-susceptible pest population. It has been suggested that a 20% structured refuge be planted to reduce rates of pest resistance. Embrapa cites research that indicates that insecticides against defoliating caterpillars should be applied only when defoliation is equal to or greater than 30% during the vegetative stage of soybean or 15% during the reproductive stage. Despite the identified instances of resistance in sunflower looper, it has been noted that the ability to control Velvetbean caterpillar (Anticarsia gemmatalis), soybean looper (Chrysodeixis includens), tobacco budworm (Chloridea virescens) and Bud borer (Crocidosema aporema) by Cry1Ac remains high.