Effect of Simulated Rainfall on the Control of Colorado Potato Beetle (Coleoptera: Chrysomelidae) and Potato Leafhopper (Homoptera: Cicadellidae) with At-Plant Applications of Imidacloprid, Thiamethoxam or Dinotefuran on Potatoes in Laboratory and Field Trials - Agricultural Chemistry - page 194

4.5

Low rainfall

c

4

3.5

Venom
Admire
Platinum
Ck

3

c

2.5

2

1.5

a
a

1

a

a

0.5

a

0

23-Jun 25-Jun 27-Jun 29-Jun 1-Jul 3-Jul 5-Jul 7-Jul 9-Jul

4.5

High rainfall

4

c

Venom
Admire
Platinum
Ck

3.5

c

3

b
b

2.5

2

b

1.5

a

a

1

a

0.5

0

23-Jun 25-Jun 27-Jun 29-Jun 1-Jul 3-Jul 5-Jul 7-Jul 9-Jul

Figure 5. Effect of two levels of simulated rainfall on damage caused by potato leafhopper on potatoes
treated with neonicotinoids at planting, Bridgeton, NJ. 2007.

4. Discussion

The CPB mortality bioassay showed that imidacloprid and thiamethoxam were more toxic
to CPB larvae than dinotefuran during May and early June, but mortality of CPB larvae for
all treatments declined over time (Fig. 1). It is likely that the continual simulated rainfall was
partially responsible for this decrease in efficacy since dinotefuran, the most soluble
material, was effective against CPB larvae early with the low amount of simulated rainfall,
but was not effective at any time with the high amount of rainfall, suggesting that the
material was leached from the soil before the potato plants had enough root matter to
absorb the insecticide. Mortality would also decline over time because the material is no