Control of Thrips on Eggplant, 1985

Transplants were set 19 Feb ’85, 0.75 m apart on 6.09-m long by 4.57-m wide plots, at the Waimanalo Experiment Station, Waimanalo, HI. Each treatment plot consisted of 3 rows. Treatments were replicated 4 times in a randomized complete block design. Treatments were applied 25 Apr; 9, 21 May; 4 and 18 Jun by hand using a ‘Maruyama Power Sprayer’, with a single nozzle which was operated at 100 psi to deliver 100 gal/acre. Thrips counts were made on leaves and fruits on 18 Apr, 1 May and 13 Jun. On 16, 28 May and 24 Jun thrips counts were conducted only on leaves, due to the absence of fruits in most plots. Populations of thrips were recorded by examining 6 randomly selected leaves (third fully expanded leaf from tip) per plot together with 6 young fruits (ca. 5 cm long). Prior to counting, thrips were fixed in place by application of an aerosol hairspray over both surfaces of sampled leaves and all over the sampled fruits. Thrips pressure was high from the second month after transplanting (Apr). Untreated control plots were very badly infested, resulting in the arresting of terminal plant growth, very few flowers and fruits. Plants in these check plots had smaller, deformed and thickened leaves and highly deformed fruits when they were present. Although the melon thrips counts were low on these malformed leaves and fruits, they do not represent the true severity of the infestation. The deformation caused by heavy thrips infestations resulted in these leaves and fruits becoming unsuitable for subsequent thrips feeding.