Controlling Caterpillars and Loopers on Ornamentals

From BASF: The Chemical Company Website

By Paul Pilon

Caterpillars and loopers and not considered major pests to greenhouse and nursery crops; however, it is not uncommon for them to be seen consuming the foliage of numerous annuals, perennials, and woody ornamentals.  When they are present, caterpillars and loopers can quickly ravage the foliage and reduce the marketability of the plants the feed on.

Caterpillars and loopers are the immature or larval stages of a number of insects, namely butterflies and moths. There are numerous types of caterpillars and loopers consisting of various shapes, sizes, and colorations.  This diverse group of larvae includes various types of armyworms, caterpillars, cutworms, leafrollers, and loopers.

Caterpillars only cause injury to plants while they are in the larval stage.  Once they become adults they either do not eat or only feed on nectar.  Caterpillars have strong jaws, allowing them to consume large amounts of foliage, tender stems, and even flowers.  Many times, their feeding causes serious plant injury, leaving behind ragged, unmarketable plants.  Caterpillars are usually host specific, feeding on certain types of plants or plants within a particular family. The damage left behind varies with the species present and includes the consumption of part or entire leaves, rolling of leaf tissue, or tunneling through stems and leaf surfaces.

Due to the large number of caterpillar species that feed on ornamentals, it is difficult to make generalizations about their life cycles. Many species lay eggs in the soil, while others deposit their eggs on plant parts.  There are several species that hide during the day emerging at night to feed, and others feed only during the day. Pupation is another way many species differ; some species pupate in the soil and others on the plant. Depending on the species and temperatures, the life cycle from egg to adult takes 3 to 4 weeks.

Routine scouting programs can provide early detection for most caterpillar infestations. Besides the damage to plants, the occurrence of fecal deposits (frass) on plant leaves is a good confirmation that caterpillars are present. If the populations are high and they go undetected, significant injury to crops can occur, resulting in reduced plant quality and possibly crop losses. Although sticky cards can be used to detect adult butterflies and moths, they are not as effective at detecting pest populations as they are for other insect pests, such as western flower thrips.

Depending on the population, control methods can range from simply removing these pests by hand to controlling them using various biological or chemical strategies. Growers can reduce the occurrence of caterpillars by reducing weeds in and near the production facility. Adult moths and butterflies often lay eggs in certain weed species or have pupae overwintering in the plant debris, which may enter the crop area.  Using lights at night near the production site often attracts adult moths into the facility, where they could lay eggs on host plants. Growers should reduce the use of lights to avoid luring moths into the production area. Adults of many species can also be monitored using pheromone or black light traps. 

The most common biological method of controlling caterpillars and loopers is using the bacterium Bacillus thuringiensis var. kurstaki (Bt). Multiple applications of Bt is usually necessary to provide adequate control. Several biorational products provide effective control of caterpillars including: azadirachtin, spinosad, tebufenozide, and Beauveria bassiana

The most effective insecticides for controlling caterpillars and loopers include acephate, chlorfenapyr, cyfluthrin, bifenthrin, fenpropathrin, and permethrin.  These products are most effective when they are applied to the younger, more susceptible life stages.

The mention of specific active ingredients does not constitute an endorsement or recommendation of, or discrimination against similar products not mentioned. ALWAYS READ PRODUCT LABELS AND USE THEM AS DIRECTED ON THE LABEL.