| Habitat modification,especially in non-crop habitats,often plays a key role in protecting natural enemies of arthropods and enhancing their biological pest control in adjacent crop fields.Little research has been conducted in the cotton producing areas of Xinjiang on the biological control efficacy of functional plants along cotton fields against the major pest,cotton aphid,Aphis gossypii Glover.In this thesis,we investigated the ecological effects of Glycyrrhiza uralensis Fisch weed strips on major predatory natural enemies in cotton fields and assessed their biological control services against cotton aphids at multiple spatial and temporal scales in agricultural landscapes.The main findings are as follows:1.The 2-year systematic survey showed that in 2020,the total number of arthropods in cotton fields with licorice weed belt was 2 classes and 8 orders and 18 families and 19 species,and the total number of cotton fields without weed belt was 2 classes and 8 orders and 15 families and 17 species.In 2021,the total number of arthropods in cotton fields with licorice weed belt was 2 classes and 8 orders and 16 families and19 species,and the total number of cotton fields without weed belt was 2 orders and 8 families and 13 families and 17 species.The cotton fields were mostly Hemiptera,mainly Aphididae,followed by Thysanoptera,mainly Thripsidae;in 2020,the total arthropods in the licorice belt were 2 orders,11 families,45 species;in2021,the total arthropods were 2 orders,12 families,46 species.Most of them are Hemiptera on licorice,mainly Aphididae and Psyllidae.2.The presence of licorice strips increased the number of families(S),richness(R),diversity index(H′),and evenness(J)of arthropod communities in adjacent cotton fields,and decreased the dominance(D)and dominance concentration(C)of arthropod communities in cotton fields.The presence of licorice strips increased the stability and diversity of arthropod communities in cotton fields and increased the percentage of the dominant natural enemy Hippodamia variegate Goeze.3.The analysis of rubidium(Rb)labeling method showed that trace amount of Rb existed in natural background;the retention period of Rb in adult H.variegate was about 15 d;the transfer distance of adult and larvae of H.variegate from licorice to cotton field was different,the detection rate of Rb was highest for larvae in cotton fields at 0-5 m from the licorice weed belt,and the other distances were 5-10 m > 10-20 m in order;the detection rate of Rb for adults was 0-15 m > 30-50 m > 15-30 m > 50-100 m in order..The Rb marker technology can effectively evaluate and track the transfer of H.variegate between the licorice belt and cotton fields4.This study showed that the presence of licorice strips increased the number of predators before the occurrence of cotton aphids in cotton fields.the number of predators in cotton field with licorice weed strips increased by 4.3 and 2.2-fold in 2020 and 2021 compared to the cotton field without weed strips,and aphid population abundance decreased by 17.5% and 61.2%;compared to the ratio(PAR)in cotton field without weed strips,the predator-to-aphid ratio(PAR)increased at the peak of the pest(July)by 9.7-fold and 8.9-fold,respectively,and significantly increased by 4.0-fold and 9.0-fold in the late season(August),the two periods with the highest PARs.The exclusion cage assays indicated that predators were key to biological control of cotton aphids and that licorice strips significantly increased natural enemy abundance and predation on aphids.The biological control service index(BSI)was 2.8-fold higher in 2020 and 1.4-fold higher in 2021 in cotton fields located 5 m from the licorice belt compared to the cotton field without weed strips.In summary,licorice can be used as an effective banker plant as a source bank to provide natural enemies to adjacent cotton fields and to improve the pest control capacity of natural enemies in cotton fields. |
PDF Full Text Request