Home gardeners and commercial vegetable growers in the coastal region of Texas growing greens (mustard greens, turnip greens, collard greens, Chinese cabbage, bok choy), have increasingly been experiencing problems with a leaf-feeding insect. This pest has been identified as Microtheca ochroloma Stal (Coleoptera: Chrysomelidae), the yellowmargined leaf beetle. This species was introduced from South America to New Orleans in 1945 on grapes from Argentina. Since then it has spread to Alabama, Louisiana, Mississippi, Florida and Texas.
The first published report in Texas was from Harris County collard greens (1977), but there are specimens in the Texas A&M University insect collection from Galveston County dated 5 June 1975. In addition, the collection contains specimens from Fort Bend, Lamar, Waller and Walker counties. The beetles have also been observed in Brazos and Matagorda Counties, and more recently in Wharton County. The actual distribution of the yellowmargined leaf beetle is probably more wide spread than reported.
Host plants for the yellowmargined leaf beetle include mustard greens, turnip greens, collard greens, Chinese cabbage, bok choy, radish, irish potato, watercress and roses. Both the larvae and adults feed on foliage Adult beetles are dark brown to blackish in overall color with lightcolored (white to yellowish) margins along the wing covers (elytra). The wing covers are also marked by rows of pits. Adults mate shortly after emerging from pupae and females deposit approximately 83 eggs during their lifetimes. Larvae hatching from eggs are dark brown to black and have three pairs of short legs behind the head.
Adults and fully grown larvae are about 3/8 inch long. There are three larval stages or instars prior to pupation, and about 23 days are required for development from egg to adult. Several generations can develop in the field esch year, with young adults leaving their hosts to enter a resting stage (estivation) about midJune, and remaining there until October. Thus, damage is prevalent during the spring and fall production periods, and beetles are scarce in the summer months.
Larval and adult feeding produces irregularly-shaped holes and damaged leaf margins. Because young leaves occur close to the ground in the middle part of the plant and are obscured by the older leaves, damage may go unnoticed until populations are large and damage is extensive. Difficulties in control that have been reported were probably due to inadequate coverage of young foliage with insecticide rather than to a lack of effectiveness of the product used. Higher pressure and volume of water used during application of sprays should help ensure adequate coverage. In addition, better control should be achieved by initiating treatments when populations are first detected.
Control has been successfully achieved by some growers who reported using some compounds labeled for other pests on these crops such as carbaryl (Sevin ), diazinon or mevinphos (Phosdrin ), which is fortunate since no insecticide products are labeled or officially recommended specifically for the control of the yellowmargined leaf beetle. According to regulations by the Environmental Protection Agency (EPA, FIFRA Act as Amended, Section 2ee), "applying a pesticide against any target not specified on the labeling if the application is to the crop, animal or site specified on the labeling" is not included in the phrase to use any registered pesticide in a manner inconsistent with its labeling unless the product label specifically restricts its use to specific target pests listed. Thus, the use of other products labeled for use on plants attacked by the yellowmargined leaf beetle is legal and may also provide control insecticide this pest.
The USER is always responsible for the effects of pesticide residues on his livestock and crops, as well as problems that could arise from drift or movement of the pesticide from his property to that of others. Always read and follow carefully the instructions on the container label.
The information given herein is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by the Cooperative Extension Service is implied.
Educational programs conducted by the Texas Agricultural Extension Service are open to all people without regard to race, color, sex, disability, religion, age or national origin.
1990
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Last modified: March 18, 1997 by Edgar Cross