University of Maryland Extension

Examining an Organic Control for Flea Beetles on Eggplant

Author: 
Dr. Gerald Brust - IPM Vegetable Specialist


Gerald Brust, Caragh Fitzgerald, Dave Clements,
Jon Traunfeld, and Bryan Butler

Dececember 2006

Summary

One of the most difficult to control pests in organic production systems is flea beetles. Flea beetles can build to very large populations in a relatively short period of time. The adults feed on solanaceous plants, i.e., potato, tomato, and especially eggplant, to the degree that they can significantly reduce plant growth and vigor. The feeding appears as ‘shot-holes’ in the foliage to the point of killing the plants or reducing yields by 10-50%. Flea beetle larvae feed on the roots of the solanaceous plant further weakening it. There are no good organic controls for beetles, leaving organic producers who want to grow eggplant that have a severe flea beetle population to abandon the crop.

A recently developed organic control has come available called ‘Surround’. It is a very finely formulated clay product and when applied to the plant acts as a very thin barrier to feeding from certain insect pests that does not reduce yield because of being covered with the material. It has been used extensively in fruit tree production, but less so in vegetable production. Previous studies examining the use of ‘Surround" have shown poor results with chewing beetles. However, those studies started applications of the material after there was feeding damage to the plant. Our study examined the unique application timing of Surround at the transplant stage before the plant was placed in the field. Thus building a layer of feeding protection before the pest could begin feeding. In addition plant coverage with Surround was much more thorough via greenhouse applications. We compared early applications of Surround with later applications of the material (after flea beetle feeding started) with no applications of the material.

By spraying transplants in the greenhouse before they went to the field we could significantly decrease flea beetle damage and increase yields as compared with later sprays and significantly increase yields compared with no application (Table 1). There were no significant interactions between variety of eggplant used and any treatment. Flea beetle populations were moderate in 2006 and treatments will need to be examined again when populations are greater.

Table 1. Yields of eggplant for each spray treatment and mean damage rating to plants.

Yield (lbs) Treatment Damage Rating (1) Treatment
19.000 a Early Spray       2.4 a Early Spray
16.833 ab Late Spray       5.3 b Late Spray
12.167 b No Spray       7.4 b No Spray

Means with different letters are significantly different at the p<0.05 level. 1Rating system is 1-10 with 1 representing little damage and 10 representing severe damage (defoliation).

 

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