Effect of seedling damage by redlegged earth mite, Halotydeus destructor, on subsequent growth and development of yellow lupin, Lupinus luteus, in the glasshouse

Abstract

Redlegged earth mite (Halotydeus destructor) causes feeding damage to some pulse species at the seedling stage. To quantify the effect of this damage on subsequent plant growth and development, an experiment was conducted in the glasshouse using yellow lupin, Lupinus luteus cv. Motiv, which is highly susceptible to the mites. After emergence, plants were infested with 0, 100, 150, and 250 mites/plant, collected from the field. Fourteen days after application, mites were removed. Damage to plants was estimated at seedling stage, flowering time, and maturity. At seedling stage (on Day 14), feeding damage scores to cotyledons and true leaves were greater at higher mite densities. Damaged plants produced fewer nodules, fewer lateral roots, and less dry weight than the control. On Day 35, severely damaged plants failed to recover and on the surviving plants, cotyledons and true leaves died earlier than on the plants without damage. On Day 78, when plants were flowering, the surviving plants produced fewer nodules and branches, and less dry weight per plant than the control. The flowering time of plants with the mite treatments was delayed by up to 6 days compared with the controls. The final shoot dry weight, pod number, seed number, and seed yield per pot were significantly reduced by the mite treatments. Feeding by H. destructor on seedlings of yellow lupin caused a reduction in seed yield of 58% at the highest mite density treatment. This significant economic loss needs to be confirmed under field conditions, but it signifies the need to develop appropriate control measures for this pest.