Cucumber Insecticide Trial, 2014 *

The study was conducted at the Mountain Horticultural Crops Research Station in Mills River, NC. ‘Dasher II’ cucumber seeds were field planted on 4 Jul on black plastic mulch with drip irrigation. Plots consisted of single 25-ft-long beds on 10-ft centers planted with a single row of cucumbers spaced 12 inches apart within rows. Plants were grown using a staked trellis system. Treatments were replicated four times and arranged in an RCB design. All insecticide treatments were made with a CO ₂ -powered backpack sprayer delivering 71 gpa. Materials, rates, and application dates are listed in the tables. All plots were sprayed with a standard fungicide program.

Cucumber beetles were monitored by shaking 10 plants and recording the number of adult insects observed flying away. Aphids were monitored by recording the number of apterous aphids on 10 leaves per plot. Flower thrips and insidious flower bugs were monitored by removing five flowers per plot, placing them in a vial of 50% ETOH, and counting dislodged insects under a stereomicroscope. Mature fruit were harvested from the same 18 consecutive plants from each plot on 6 and 26 Aug and 2 Sep. Fruit were graded for insect damage, which consisted of surface scarring caused by adult cucumber beetle feeding, and fruit infested with pickleworm larvae. All data were subjected to two-way ANOVA and means were separated by LSD ( P  = 0.05).

Thrips and cucumber beetles were relatively low in this trial, and on 6 Aug the 16.4 oz rate of IKI-3106 was the only treatment to significantly reduce numbers below the check ( Table 1 ). Cucumber beetle populations were extremely low, with ≤0.5 beetles recorded in any plot, and no significant differences among treatments. On 6 Aug, there were significantly more aphids in the check (approximately 2 per leaf) than in the treated plots (<0.6 per leaf), and by 26 Aug populations had reached 18.9 per leaf in the check and over 30 per leaf in the standard treatment. The pyrethroid applications in Aug clearly flared aphid populations in the standard treatment, while both IKI-3106 treatments maintained densities below an average of 2 per leaf. Despite the low cucumber beetles recorded in plant beatings, fruit scarring caused by adult beetles reached almost 10% in the check. Scarring was generally lower in the insecticide treatments compared with the check, but these data were highly variable, and there were no significant differences among treatments after the first harvest date. Pickleworm damage was relatively low until the last harvest date when almost 11% of fruit were damaged. All insecticide treatments provided excellent pickleworm control.

Author notes