Ants protect aphids and reduce parasitism in bell peppers.

The presence of the ant Tapinoma ibericum reduces the success of the parasitoid Aphidius colemani in control of Aphis gossypii In greenhouse-grown bell peppers in southeastern Spain, the exclusion of ants increased the number of mummies per plant by 22,2% and decreased the number of aphid colonies. Fruit weight did not vary between treatments.

This study evaluated the impact of the mutualistic interaction between ants and aphids on biological control in four experimental greenhouses in Almería. The region has the largest area of ​​protected horticulture in Europe. Pepper cultivation occupies approximately 12.500 hectares, with annual production exceeding 893 tons.

The researchers conducted an ant exclusion experiment over two consecutive growing seasons, in 2018 and 2019. Each greenhouse received 16 pepper plants infested with ants. Aphis gossypiiHalf of the plants remained accessible to the ants. The other half was isolated with physical barriers at the bases of the pots.

Parasitoid released

After the aphids were established, the authors released the parasitoid. Aphidius colemani at a dose of 30 mummies per greenhouse. The team monitored the abundance of aphids, the number of colonies, the quantity of mummies, and the presence of spontaneous natural enemies weekly for four weeks.

The total abundance of aphids did not show a consistent pattern between years. In 2018, plants without ants showed a trend of lower numbers of individuals. In 2019, the opposite occurred. In the data set, the presence of ants did not consistently alter the total density of the insect.

Number of colonies

The number of colonies, however, provided a clear answer. Plants with access to Tapinoma ibericum They showed an average of 38,8 colonies per plant. Plants without ants registered 30,2 colonies. The spatial aggregation of aphids increased in the presence of ants.

The most consistent effect was observed in parasitism. Plants without ants showed an average of 65,9 mummies per plant. Plants with ants recorded 38 mummies. The statistical model indicated a 22,2% increase in the abundance of mummies when ants were excluded.

The authors interpret the result as evidence of direct interference by ants on the oviposition of the parasitoid. The presence of Tapinoma ibericum makes access difficult Aphidius colemani to the colonies. Aggressive behavior reduces the success of parasitism.

natural enemies

The community of natural enemies also changed according to the treatment. The exclusion of ants increased the abundance of Chrysoperla carnea sl, Scymnus sp. It is Nesidiocoris tenuisThese organisms showed a lower number of individuals on plants with ants.

The predator Aphidoletes aphidimyza The study showed an inverse pattern. Its abundance increased in plants with ant access. Spiders and hoverflies did not show a significant difference between treatments.

The data indicate the presence of Tapinoma ibericum reorganizes the assembly of natural enemies. In plants with ants, biological control occurred with greater participation of Aphidoletes aphidimyzaIn plants without ants, the diversity of predators increased.

Productivity showed no statistically significant difference. In 2019, the fruits of plants with ants registered an average fresh weight of 59,6 grams. Plants without ants registered 50,9 grams. Dry weight also did not vary significantly.

The study concludes that Tapinoma ibericum promotes spatial aggregation of Aphis gossypii and reduces parasitism by Aphidius colemaniThe interaction did not result in a decrease in performance under the evaluated conditions. The authors suggest that the combination of Aphidoletes aphidimyza Using Aphidius colemani can increase the efficiency of control in areas with the presence of mutualistic ants.

Further information at doi.org/10.1111/1744-7917.70249