Fruit-Insect Pest Management

Insect Note #C-1 (Revised)

Prepared by:
K. A. Sorensen, Extension Entomologist

Dated 6/94
Placed on the Web 4/95 by the Department of Entomology, NCSU

Chestnut Insects

Of the 16 insects reported from Asiatic chestnuts, only weevils, mites and treehoppers cause damage in North Carolina.

Chestnut Weevils

The most destructive are the small and the large chestnut weevils; both species are native to North America. Adult weevils puncture the burs with their long curved beaks and feed on the nuts. They lay eggs in the nuts and these hatch into legless larvae or "worms" which devour the kernels. After nuts fall to the ground, much time is spent inside as larvae and pupae before adults emerge.

The small chestnut weevil (Curculio auriger (Casey) Coleoptera: Curculionidae) in the adult stage is often referred to as a "snot beetle" or curculio. It is about 1/3 inch long, 1/8 inch wide and dark brown with patches of yellowish hairs on the hind legs and underside of the body. The beak or snout is approximately as long as the body.
The females drill holes in the chestnut bur with their beaks, then insert eggs into the cavity. Eggs hatch in about 10 days.
The larvae are about 1/4 inch long and white when full grown. After feeding 4 or 5 weeks within the nut, they chew exit holes, leave the fallen nut and enter the ground where they form earthen cells 3 to 10 inches below the surface. Larvae remain in these cells throughout the winter and following summer. In the fall (one year after entering the soil) they pupate, spend a second winter in the soil and emerge as adults in late spring or early summer. Adults mate, feed, and the females begin to lay eggs in early August.
The large chestnut weevil (Curculio proboscideus (Fab.) Coleoptera: Curculionidae) adults resemble small chestnut weevil adults except they are larger and have a beak longer than the body. Adults are brown in color, 1/2 inch long and 1/5 inch wide. Females chew holes through the bur and into the nut to make a suitable place in which to lay eggs. Each female lays about 25 eggs which hatch in about one week. Larvae feed 6 to 10 weeks then chew their way out of fallen nuts and enter the ground where they spend the winter and spring. Larvae pupate in late spring and early summer. Adults begin to appear about the first of August.

Mites

Several species of mites attack chestnuts causing brownish, scorched appearing foliage. Leaves at first turn reddish-brown along the veins and later take on a dingy, grayish-rust color, due in part to shed skins and webs. Prolonged infestations can damage trees and the chestnut crop.

Treehoppers

Several species of leafhoppers attach chestnuts. These insects are generally about 3/8 inch long, green to bronze in color with various colored spots or stripes. They have a greatly expanded area of the thorax just back of the small head.

Young nymphs which resemble adults are usually dark in color with bright markings and spines.

Control

Chestnut Weevils - At the present time, there are no insecticides registered specifically for control of the small or large chestnut weevils.

Mites - The following materials at the suggested rates may be used to control mites on chestnuts:

Insecticide       Rate/100 gals    Rate/1 gal              Remarks
______________________________________________________________________________
Malathion 25% WP      2 lbs         1 tbsp       Repeat treatment if necessary
Kelthane 35% WP       1 lb          0.5 tsp        "        "     "      "
Kelthane 18.5% EC     1 qt          2 tsp          "        "     "      "
Ethion 25% WP         1 lb          0.5 tbsp     2 applications/season prior
                                                   to shuck split
______________________________________________________________________________

WP = wettable powder; EC = emulsifiable concentrate

READ AND FOLLOW LABEL DIRECTIONS

Treehoppers - No chemicals are registered for control of these pests on chestnuts.

Home Plantings - When chestnut trees are used for shade and ornamental purposes, some weevil control is obtained where diazinon or Lorsban has been used to control white grubs in turf or grass beneath the trees. Apparently, the soil treatments also kill chestnut weevils when they drop to the ground.

Both species of weevils spend a period of time on the ground before flying to the trees and still more time from the time they reach the tree branches and twigs until egg laying begins. The first soil application of an insecticide should be made one week after catkins begin to bloom or by June 15. The second application should be made about August 1.

The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsements by the North Carolina Cooperative Extension Service nor discrimination against similar products or services not mentioned. All pesticide recommendations provided in this publication apply to pest control in North Carolina. Individuals who use chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain information about product usage in your locale and examine a current product label before applying any chemical. The information presented on pest biology is based on conditions in North Carolina and may not be applicable to your locale. For further information, we recommend that you contact the Cooperative Extension Service office in your county.