William F. Lyon
Roger N. Williams
|Common Name||Scientific Name|
|Picnic Beetle||Glischrochilus quadrisignatus (Say)|
|Dusky Sap Beetle||Carpophilus luqubris Murray|
|Strawberry Sap Beetle||Stelidota geminata (Say)|
|Dusky Sap Beetle||Picnic Beetle|
Sap beetles often fly to ripening or damaged raspberries, strawberries, melons, early apples, tree wounds, corn, tomatoes, and osage orange fruits. They may bore into the fruit, eat a portion and make it unfit for human consumption. The picnic beetle is essentially a secondary invader of damaged plants and decomposing plant tissue, but in undamaged ear corn silks and ripe raspberries, it can be a primary invader. The strawberry sap beetle is a primary invader of ripe and nearly ripe strawberries. As a nuisance, sap beetles may congregate in annoying numbers on screen doors, around garbage cans, invade homes, backyards, picnic areas, food processing plants, and roadside fruit and vegetable stands.
One of the identifying characteristics of all sap beetles is their "knobbed" antennae.
Picnic beetle adults are about 1/4-inch long and black with four orange-red spots on the wing covers. Eggs are milky-white, sausage-shaped, and about 1/32-inch long.
Dusky sap beetle adults are about 1/8-inch long with short wing covers and are uniform dull black in color.
Strawberry sap beetle adults are slightly less than 1/8-inch long, light to dark brown, oval, and somewhat flattened. Larvae of all three are white. Pupae are white, turning cream-colored and later tan before adult emergence.
All of the sap beetles in Ohio overwinter as adults in protected places such as decaying vegetation, debris or fruit buried in the ground. In the spring, picnic beetle adults come out of hibernation and mate. Egg laying begins in April and continues in May and June. Females lay 5 to 15 eggs per day, scattered at random near decomposing plant material rather than on the material itself. Larvae develop in spilled grain, feed, corn ears, waste onion piles, and soil saturated with juices and food material in contact with the soil. Full-grown larvae leave their food when mature, wander through the soil and change to the pupa stage. Adults then emerge in June and July. The cycle from egg to adult takes about 30 to 35 days. There is usually only one generation per year.
Newly emerged adults do not lay eggs but congregate on screen doors, around garbage cans, in picnic areas and parks, and about anywhere food is grown or being served. They are a general nuisance, attracted to sweet or fermented plant juices. Beetles are found on cracked tomatoes, damaged sweet corn ears, overripe muskmelons, strawberries, and raspberries.
The life cycle of the dusky sap beetle is about 30 days with three to four generations per year. Some females lay more than 300 eggs and live as long as 147 days. The strawberry sap beetle primarily attacks strawberries. Sap beetles also disseminate organisms that cause rots in the fruits. Some sap beetles bore into the fruit, devour a portion, and lay eggs. Larval damage is usually only slight and often goes unnoticed.
It is helpful to harvest sweet corn, tomatoes, melons, berries and other produce immediately as soon as they ripen. Remove any damaged, diseased, and overripe fruits and vegetables from the area at regular intervals. The collecting of apples, peaches, melons, tomatoes, and other decomposing fruits and vegetables and by burying deep in the soil or destroying is needed to eliminate beetle food sources.
Research has shown that picnic beetles prefer banana, whole wheat bread dough, and muskmelon. As a bait, muskmelon rinds or pineapple scraps, sprinkled with a pesticide, kills the strawberry sap beetle and other scavenger beetles attracted to the fruits and vegetables. Take extra precautions to keep treated baits away from humans, domestic animals and other non-target organisms. Bait trapping shows some promise in the reduction of beetle populations. Place traps several feet away from the picnic table or outside the garden. Discard trap contents frequently, every three or four days, and rebait traps with pineapple scraps and a bait consisting of stale beer, vinegar, molasses and water with yeast. Research has shown that carbaryl (Sevin) hardly kills sap beetles. Malathion gives better control and azinphosmethyl (Guthion) the best control. However, no pesticides are legally labeled for home owner use.
Raspberries can be protected somewhat with repeat sprays of malathion as sap beetles begin to enter the fields. Treat three to five days before the first picking date. Use malathion 25 percent WP at the rate of four to five pounds per 100 gallons of water. Do not use malathion liquid as it can cause burning of the plant leaves. There is a one-day waiting period between application of malathion and harvest. Some sweet corn growers have reported limited success in killing sap beetles with carbaryl (Sevin). Read the label and follow directions and safety precautions as to which crops can be sprayed and the waiting period interval for harvest to avoid illegal chemical residues.
This publication contains pesticide recommendations that are subject to change at any time. These recommendations are provided only as a guide. It is always the pesticide applicator's responsibility, by law, to read and follow all current label directions for the specific pesticide being used. Due to constantly changing labels and product registration, some of the recommendations given in this writing may no longer be legal by the time you read them. If any information in these recommendations disagrees with the label, the recommendation must be disregarded. No endorsement is intended for products mentioned, nor is criticism meant for products not mentioned. The author, The Ohio State University and Ohio State University Extension assume no liability resulting from the use of these recommendations.
All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.
Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.
TDD No. 800-589-8292 (Ohio only) or 614-292-6181