Reduced macadamia nut quality is linked to wetter growing seasons but mitigated at higher elevations

Abstract

Climate and insect pests are vital variables that affect crop production. Climate change will alter the magnitude and timing of precipitation, but how rainfall and temperature interact to affect insect pest damage in agriculture is poorly understood. Here, we explore the interacting effects of elevation and contrasting weather conditions (a wet vs. dry year) on macadamia nut quality, which is strongly affected by insect pests. For two years, we sampled macadamia nuts at 40 plots, stratified across ten farms along an elevational gradient in subtropical Limpopo province of South Africa. As measures of nut quality, we related total kernel recovery, nut immaturity, and kernel insect damage to precipitation and elevation. Higher rainfall reduced nut quality in all three response variables, while colder temperatures at higher elevations mitigated this effect. Our findings suggest that future warmer temperatures, more intense and wetter rainy seasons could lead to lowered macadamia nut quality even at higher elevations and economic losses to the industry.

Keywords

• Agriculture
• Climate change
• Insect pests
• Rainfall
• Southern Africa
• Subtropical