The time is fast-approaching for Mid-South rice producers to begin scouting fields for yield-robbing pests. Researcher Jim Robbins describes seven common insect pests that can cause problems in your rice.
Get out your looking glass, sweep nets and rubber boots. The time is fast approaching to begin scouting your rice fields for yield-robbing pests.
While rice water weevils and stinkbugs have traditionally posed the most serious pest-related economic threat to rice producers, other insects also have the potential to put a dent in rice yields.
Which of these insects growers need to look for was the subject of a presentation by researcher Jim Robbins Feb. 21 at the Mississippi Agricultural Pest Management Association's annual meeting in Greenville, Miss.
Robbins, an entomologist with the Delta Research and Extension Center in Stoneville, Miss., says there are primarily seven pests with the potential to rob Delta growers of rice quality and yield, beginning with the rice stinkbug.
“A tremendous amount of damage is caused by this insect. In fact, I would consider the rice stinkbug the Delta's number one rice pest problem,” he says.
Smaller in size than many other species of stinkbug, the rice stinkbug is a brown, shield-shaped insect with points on its shoulders. It feeds by sucking juice from developing rice kernels, which causes blanking in the rice head and the degradation of any remaining rice kernels.
Rice stinkbugs usually begin migrating into rice fields shortly after the crop begins heading. Often, they move into rice fields from surrounding grassy areas, such as ditches.
Recommended insecticide treatments include applications of Pencap M, methyl parathion, and Karate, according to Robbins. “While all of these products seem to work to control the stinkbug, methyl parathion may be slightly more economical and Karate may provide some residual control,” he says.
Rice water weevil
Second on Robbins list of rice pests is the rice water weevil. Rice water weevils, which have the potential to substantially limit rice yields, are similar in appearance to boll weevils but are smaller in size. Rice water weevil larvae are small, leg-less, C-shaped, white worms. In comparison, the adult weevils are grayish-brown, broad-nosed insects about one-eighth inch in length.
Fields in rice production for several years are usually more susceptible to rice water weevil infestations than rice fields recently brought into production. In addition, weevil populations are often higher in areas with open water, such as around levees or in areas of thin stands.
The rice water weevil larvae eat up the roots of the rice plant — the adults cause leaf scarring.
For those growers with a history of rice water weevil infestations, Robbins recommends a preventive treatment, using the insecticide Icon. “This product seems to be economical if you have a history of weevil problems in your rice field,” he says.
Past history is also a good indicator of whether or not a field will become populated with chinch bugs, which feed primarily on the rice stems just above the soil. Chinch bugs most often populate a field between emergence of the rice plant and the establishment of a permanent flood.
“Getting a flood on the affected field as soon as possible is the most economically feasible control method for the chinch bug,” Robbins says.
When treating chinch bugs with an insecticide, entomologists often recommend applying the pesticide either late in the afternoon or early in the morning when chinch bugs are most active.
According to Robbins, growers battling high chinch bug populations can spot-treat with methyl parathion 4EC or with Pencap-M 2EC.
Another emerging rice pest is the fall armyworm. “The fall armyworm can be one of the most significant pests in rice because it doesn't appear every year and is often not noticeable until significant damage to the rice crop has already occurred,” says Robbins. “You can lose a crop because of this one insect species. Populations often occur only one out of every five or six years, which means you are often not looking for it.”
A late-season rice pest which, according to Robbins, has caused “a lot of heartache” among rice growers is the grasshopper. Often found along the borders of rice fields, grasshopper populations usually begin building at the initiation of heading through the grain-fill period. Symptoms of grasshopper injury include “blanks” and mangled grain.
Recommended control treatments include applications of Sevin 80S, Sevin XLR 4L, and malathion.
Although high populations of grasshoppers can cause substantial damage to a rice crop, they also serve as a beneficial insect, eating the eggs of the rice stinkbug and the rice stalk borer
Rice stalk borer
The rice stalk borer can often be found burrowed in a rice stem, usually at the time of head emergence.
Rice stalk borer moths are about 1 inch long with pale-white wings that have small black spots. The wing edges are marked by a row of metallic gold scales with distinct black dots
The bad news, according to Robbins, is that no effective control method is currently available for this insect.
Another insect that is emerging as a problem insect in Delta rice fields is the maize billbug. Mostly found on or near rice levees, the maize billbug causes rice plants to break off at the base of the plant and damages the rice heads.
“The maize billbug is rarely economically important in this area. However, in some of the Delta fields I've checked, it's a real problem,” Robbins says.”