Article of the Month - January 2005

South Florida Beef - Forage Program

"Article of the Month"
January 2005

Tropical Soda Apple

Jim Selph - Extension Agent IV, Livestock DeSoto County

The South Florida Beef Forage Program met in December after the Florida Cattlemen's Association December Quarterly and have decided to follow up on what was reported at that meeting. With the general concern that was voiced by many over TSA, the Beef Forage group of agents and specialist decided that we would work on developing rearing sites at many of the county Extension office locations throughout the South Florida Beef Forage Program area. Our goal is to begin to increase dramatically the number of the leaf eating beetles available and to facilitate the spread of this biological control agent to as many acres of pastures and range as possible. We will need help in constructing the rearing facilities both financially and in volunteer labor. Contact your local extension Livestock Agent if you are interested in assisting in this effort. A 10X27 shade house for raising the Leaf Beetles can be built for less than $500.

TSA is a plant that originated in Argentina and Central Brazil. It has now spread over a large area of the Sub-tropical world. We don't want it spreading over a large area of DeSoto County. The plant is readily identified by its immature fruit which are green with white mottling, similar to watermelon. Cattle don't consume the leaves of the plant, but will eat the fruit. After consuming the fruit, seed will pass through the digestive tract and will be deposited in the droppings. Seeds of the TSA tend to move through the cow's digestive system at different rates. Those seed that move through in 1 or 2 days are very viable. The longer they stay in the cow's digestive tract though, the less viable the germination. This is only a fact for mature cows, bulls, steers, etc. When bringing in replacement females from highly infected areas, holding them up in a small area is a wise choice to help control the area of TSA that might need to be treated. Calves do consume the fruit and we are waiting on the data that reflects the viability of seeds passing through calves digestive tracts.

Biology of Gratiana boliviana,
the First Biocontrol Agent Released to Control Tropical Soda Apple in the USA

J. C. Medal, D. Gandolfo and J. P. Cuda

The TSA leaf beetle, Gratiana boliviana Spaeth (Coleoptera: Chrysomelidae) was approved by the USDA-APHIS-PPQ for field release in Florida on May 7, 2003. The initial release of G. boliviana in Florida began 2003 on May 14 in Polk County. Subsequent releases were made on June 17 in Alachua County, September 5 in Hendry County, and November 11 in Sumter County. A release in the fall of 2004 has been made in DeSoto County. This beetle lay eggs individually ( Figure 1 ) on TSA leaves and petioles. Eggs are initially white in color but turn light green during the incubation period. Each egg is enclosed by two translucent brown membranes. The egg case is attached to the leaf surface by one extreme. A female can produce on average 300 eggs. Incubation of the egg takes 5-6 days at a temperature of 25°C.

Figure 1 Gratiana boliviana egg

Larvae are cream-colored with a small green spot in the anterior half. Each segment of the body has two lateral processes and a pair of long caudal processes or small forks that arise from the last abdominal segment. Like most tortoise beetles, larvae carry the cast skins on the anal forks with the posterior end of the larva bent forward ( Figure 2 ). The five larval instars can be completed in 15-18 days. Larval feeding is concentrated mostly in the upper third of the plant canopy. Infested plants are easily detected by clusters of small to medium size holes made by the feeding larvae. As feeding progresses, the plants may exhibit large areas of defoliated leaves. Almost complete defoliation has been observed in enclosed cages when the beetle's natural enemies are excluded.

Figure 2 Gratiana boliviana larva

The pupal stage ( Figure 3 ) is completed in about 6-7 days. The pupae are green colored and dorsal-ventrally (from top to bottom) flattened. Pupae are attached to the leaf by the last abdominal segment. The most common pupation place is the underside of leaves. In severely defoliated plants, some pupae can be found on the petioles and stems.

Figure 3 Gratiana boliviana pupa

General coloration of the young adult is light green. Along the margin of the elytra (front wings) there is a continous yellow band. The rest of the elytra is light green with irregular yellowish areas between rows or depressions ( Figure 4 ). Mature adults turn a uniform yellow. Females and males can be distinguished by examining the underside of the body. In males, two somewhat rounded orange testes can be observed, one on each side of abdomen. In females there is a pair of white ovaries. Characters for separating the sexes can be observed 3-5 days after eclosion (hatching). Pre-oviposition (pre-egg laying) period takes from 9 to 12 days. Longevity of females averages 3 months.

Figure 4 Gratiana boliviana adult

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