Our tomato plants are looking strong and healthy; however, a few weeks ago I noticed an odd tomato plant looking very sickly. It was completely wilted, and it was the only plant looking like this. Upon closer inspection, I noticed a whole in the stem. It was obvious this plant wasn’t going to make it so I cut if off at the base, and left a sucker which is maturing nicely. I am thankful for that sucker because this is the only plant I have of this variety of tomato this year. We have at least 20 varieties of tomatoes growing this year.
I am always curious what disease or pest is causing distress to my vegetables so I sliced into the plant stem to see what I could learn. I eventually found the persistent pest working his way up the stem: A Stalk Borer
This is our first experience with this pest. Luckily, we haven’t had any other issues. We are simply observing, and will keep this information in mind for the future. I would like to work on trying to cut down on some of the potential host plants in the area, but still building up our beneficials’ habitat. We will not spray, but will work with managing cover crops.
Here are a few photos that we took and then info follows that I found online (http://ipm.ncsu.edu/AG271/corn_sorghum/stalk_borer.html):
Stalk Borer and damaged tomato stem
Papaipema nebris (Guenee),Noctuidae, LEPIDOPTERA
Adult – The forewings of this moth are basicallyreddish- or grayish-brown marked with distinct white spots or obscure smoky areas. The outer third is paler and bordered by a thin white line. The hind wings are grayish brown on the upper surface and fawn gray below. The wingspan ranges from 25 to 40 mm in diameter.Egg – The longitudinally ribbed egg may be spherical or slightly flattened and measures 0.4 to 0.6 mm in diameter. White when first deposited, it gradually turns brownish-gray or amber before hatching.
Larva – Basically brown, the early larval instars have a dark brown band around the middle and brown or purple longitudinal stripes on all but the first four segments. The mature larva is solid white or light purple and may reach a length of 31.8 mm. Color plate.
Pupa – About 16 to 22 mm in length, the light brown pupa gradually darkens as it matures.
Distribution – The stalk borer occurs in all areas east of the Rocky Mountains from southern Canada to the Gulf of Mexico. Highest populations are associated with fields and fence rows with large-stemmed weeds. Economically significant infestations are most common in the Piedmont, particularly in no-till plantings.Host Plants – Stalk borers tunnel in almost any large- stemmed plant. Their host range encompasses at least 44 families and 176 species of plants. Some cultivated crops subject to infestation include corn, cotton, potato, tomato, alfalfa, rye, barley, pepper, spinach, beet, and sugarbeet. Although many weedy plants are infested, giant ragweed is preferred.
Damage – Stalk borers migrating from an earlier host infest corn seedlings 6 to 60 cm (2 to 24 inches) high, causing two types of injury. Larvae that enter the plant through the lower stalk tunnel upwards, severing the leaves from below. In this case, infested stalks are hollow and apparently healthy green leaves wilt and die. Other larvae climb plants, enter from the top, and feed on buds and rolled leaves. As they unfurl, the new leaves display ragged holes which increase in size as the leaves display ragged holes which increase in size as the leaves develop. Both forms of injury result in destruction of tassels, production of suckers and deformation of the upper plant. Soon after borers enter the seedlings, the stems often break. Frass is usually evident around the base of more mature infested plants. Once past the “whorl” stage, however, corn is somewhat resistant to the stalk borer and recovers more readily from damage. Damage is sporadic but most commonly associated with the border rows of conventionally planted corn and with no-till plantings.
Life History – Stalk borers overwintering as eggs on weedy plants. In May, the newly emerged larvae feed as leaf-miners on broadleaf plants or as stem borers on grasses. On all hosts, larvae eventually bore into the stem and feed until they kill or outgrow their host. When this occurs, they emerge at night and tunnel into new plants, including seedling corn. Developing through 7 to 16 instars, stalk borers mature in their second host. Late in July, the borers emerge, construct individual cells in the soil, and begin a 4-week pupal period. Stalk borer moths emerge in late summer and deposit eggs singly or in masses between the leaf sheath and stems where they remain until the following spring. One generation occurs each year.
Stalk borers cannot be controlled once they have entered the plant; therefore, control measures should concentrate on prevention. Destruction of weeds in fields and along fence rows results in the elimination of many primary hosts from which the borers infest corn. Where applicable, systemic insecticides may be effective when applied in areas of highest potential damage. For specific control information, consult the current North Carolina Agricultural Chemicals Manual.