Effect of soil-applied complex fertiliser on an insect–host plant relationship: Liriomyza trifolii on Solanum tuberosum

Insects respond to very low levels of nutritional and non‐nutritional compounds in plants, which influence their acceptance and colonisation of the plant or plant part, and thereby their growth and development. Plant nutrient levels can vary within and between plants, and are influenced by external factors such as fertiliser treatments, irrigation regime, and light. Soil levels of nitrogen, potassium, phosphorus, calcium, and magnesium can have significant effects on the amounts of these nutrients in the plant, and thereby on pest infestation. This study reports on the influence of seven different NPK fertiliser rates in potted potato (Solanum tuberosum cv. Mondial) plants on the nitrogen, phosphorus, potassium, calcium, and magnesium levels in the leaves, and the concomitant influence on infestation by, and development of, the serpentine leafminer, Liriomyza trifolii Burgess (Diptera: Agromyzidae). Results showed that increases in nitrogen in the potato leaves increased larval and pupal survival, and pupal and adult body weight and length. Potassium and phosphorus, on the other hand, decreased the host suitability of potato plants to L. trifolii, and were detrimental to the pest.     

The influence of humidity on emergence in Dacnusa sibirica Telenga (Hymenoptera: Braconidae)

The effects of four humidities (33, 55, 76 and 93% relative humidity) and four ages (0–1, 2–3, 4–5, 6–7 days) of parasitized Chromatomyia syngenesiae puparia on adult emergence in the leafminer parasitoid Dacnusa sibirica were examined in the laboratory. Parasitized puparia harvested at 0–1 days were susceptible to low humidities resulting in a significantly reduced parasitoid emergence. Aging of the puparia appeared to protect the developing parasitoid from low humidities. Increasing humidity produced a corresponding increase in the longevity of the adult parasitoid.