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Conrad Bérubé |
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Tuber Flea Beetle
family: chrysomelidae |
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Potato IPM: Tuber Flea Beetle Tuber flea beetles and aphids are the key pests around which IPM is structured. Potato flea beetle, Epitrix tuberis, causes subepidermal burrowing that causes cosmetically unacceptable damage (1-2 beetles in one hundred plants at beginning of season can result in late season damage). These Chrysomelids are easily recognized by their expanded hind femurs. The 8-10 holes per leaf that adults cause are relatively insignificant, damage is primarily caused by larvae. Adults and pupae peaks occur in middle of June, beginning of August and end of September. Tuber flea beetles seem to come in from one direction predominantly. The adults can overwinter in brush and soil of old potato fields. Mustard and lambsquarter may harbor the flea beetles. If plants are less than a foot tall then they need to be examined visually. On windy days the beetles will not be as active on upper sides of the leaves. Time of day is not so important for sampling accuracy. Generally a sweep catches about 1% of beetles. Synthetic pyrethroids are the weapon of choice for the beetles. Outside edge or localized sprays are generally effective for control of flea beetles. Flooding of fields can kill many of the overwinterer beetles may survive on high ground, pastures, or headlands. When rouging of volunteers with beetles occurs the beetles may move into new crop. These volunteers may also serve as potential sources of inoculum of pathogens of blight and leaf-roll virus. The larvae are evident from late May throughout growing season. Beetles can increase two hundred fold each generation. Peaks occur in mid-July, early August and late September. Damage in early season is often small channels that can be peeled off. Later in the season the suberization forces the larvae to bore through the skin and into spud causing cosmetic damage and down-grading. IPM focuses on controlling the first generation of beetles so that only mop-up and spot-treating is necessary later in the season. Field rotation is first line of defense to reduce flea beetle population (otherwise you may get beetle populations building up in center of field). Monitor only gives three days of protection after spraying. Ideally its nice to have growers break field into sections (that are larger on edges that historically have had beetles there before or have prevailing winds). If you can get them to plant outside first the outer edges will plant from inside-out because it gives them more turning room). The impetus in IPM is to do timely (early-season) with something harsh (Cymbush, Decis) which will give long-term protection at a time when there are not a lot of beneficials in the field. (Cymbush and other synthetic pyrethroids are toxic to fish but less so to humans and other mammalian species). Monitor, Sevin, Thiodan and other OP and Carbamates offer less residual activity than the synthetic pyrethroids. The peak beetle population tends to be several rows in from the edges (so when they're in the borders, sample towards the center until they're no longer detected). About five seconds per plant is adequate for an experienced scout to detect all the beetles on one plant. Wind and fatigue can impact the accuracy of sampling for beetle (accuracy is better in the morning when it's calm and scouts are fresh). Beetles tend to move under the leaves at night or in adverse environmental conditions. Visual plants). Sweeping is only about 3-4% accurate (but more convenient).
15-20 paces between sampling plots: on plants less than a foot tall do a visual inspection of 10 plants in a row or, if sampling across rows, choose two plants from each of five rows. If plants are greater than a foot tall, make ten consecutive full-circle sweeps (such that each sweep shares a single tangential point with the previous circle-- the intent being to sweep one hundred plants) and count the resulting beetles — THE THRESHOLD IS ONE BEETLE PER ONE HUNDRED PLANTS. If beetles are found to be above threshold take sufficient samples to delimit the area of infestation (to determine whether border spray will be sufficient or if the whole field should be treated.
Tuber Flea Beetle Epitrix tuberis Gentner This beetle is the most serious insect pest of potatoes in British
Columbia. It has recently been found in Alberta and appears to
be moving eastward.
Injury: Adults primarily feed on potato leaves, giving them a shot-holed appearance. This damage is seldom of economic concern. The larvae inflict the main damage by feeding on the tubers, causing pimples, surface channels, and shallow networks of fine tunnels. Vacant tunnels are lined with brown, corky skin and must be removed by deeper peeling; this reduces the marketability of table potatoes.
Tuber flea beetles overwinter as adults, buried in the soil in
and around potato fields. Winter survival appears highest in elevated,
grassy headland regions unaffected by flooding. There are two to
three generations a year, beginning with the overwintered adults
from late May to late June. Mating and
Systemic insecticides (applied to the soil at seeding) or fouler sprays will control adults before they lay eggs. Foliar sprays can be timed according to sweep-net samples taken weekly beginning in early June. Volunteer potato plants are potential breeding areas and should be rogued or treated. For further details on sampling and control contact your local agriculture representative.
Tuber flea beetles and aphids are the key pests around which IPM is structured. Potato flea beetle, Epitrix tuberis, causes subepidermal burrowing that causes cosmetically unacceptable damage (1-2 beetles in one hundred plants at beginning of season can result in late season damage). These Chrysomelids are easily recognized by their expanded hind femurs. The 8-10 holes per leaf that adults cause are relatively insignificant, damage is primarily caused by larvae. Adults and pupae overwinter during which time there is much mortality. Three peaks occur in middle of June, beginning of August and end of September. Tuber flea beetles seem to come in from one direction predominantly. The adults can overwinter in brush and soil of old potato fields. Mustard and lambsquarter may harbor the flea beetles. If plants are less than a foot tall then they need to be examined visually. On windy days the beetles will not be as active on upper sides of the leaves. Time of day is not so important for sampling accuracy. Generally a sweep catches about 1% of beetles. Synthetic pyrethroids are the weapon of choice for the beetles. Outside edge or localized sprays are generally effective for control of flea beetles. Flooding of fields can kill many of the overwinterers. Beetles may survive on high ground, in pastures, or headlands. When rouging of volunteers with beetles occurs the beetles may move into new crop. These volunteers may also serve as potential sources of inoculum of pathogens of blight and leaf-roll virus. The larvae are evident from late May throughout growing season. Beetles can increase two hundred fold each generation. Peaks occur in mid-July, early August and late September. Damage in early season is often small channels that can be peeled off. Later in the season the suberization forces the larvae to bore through the skin and into spud causing cosmetic damage and down-grading. IPM focuses on controlling the first generation of beetles so that only mop-up and spot-treating is necessary later in the season. Field rotation is first line of defense to reduce flea beetle population (otherwise you may get beetle populations building up in center of field). Monitor only gives three days of protection after spraying. Ideally its nice to have growers break field into sections (that are larger on edges that historically have had beetles there before or have prevailing winds). If you can get them to plant outside first the outer edges will serve that much more as a trap crop (but growers seem to like to plant from inside-out because it gives them more turning room). The impetus in IPM is to do timely (early-season) with something harsh (Cymbush, Decis) which will give long-term protection at a time when there are not a lot of beneficials in the field. (Cymbush and other synthetic pyrethroids are toxic to fish but less so to humans and other mammalian species). Monitor, Sevin, Thiodan and other OP and Carbamates offer less residual activity than the synthetic pyrethroids. The peak beetle population tends to be several rows in from the edges (so when they're in the borders, sample towards the center until they're no longer detected). About five seconds per plant is adequate for an experienced scout to detect all the beetles on one plant. Wind and fatigue can impact the accuracy of sampling for beetle (accuracy is better in the morning when it's calm and scouts are fresh). Beetles tend to move under the leaves at night or in adverse environmental conditions. Visual sampling is about 30-35% accurate (accuracy increases for smaller plants). Sweeping is only about 3-4% accurate (but more convenient).
MINISTRY OF AGRICULTURE AND FOOD. Tuber Flea Beetle Epitrix tuberis Gentner In Canada, it occurs mainly in British Columbia. It was first reported in the Lower Fraser Valley in 1940 and has since spread to all of the major potato-growing areas on the Mainland and Vancouver Island. By 1967, the tuber flea beetle had spread north to Quesnel in the Cariboo and east to Yahk in the Kootenay area.
Potato
Adults chew small, round holes in the leaves, creating a shot-hole appearance. Beetles feed on upper and lower leaf surfaces and on leaf petioles and flowers. Unless damage to the foliage is severe, the crop yield is not reduced. A shallow network of fine tunnels is produced by larvae or worms feeding in the potato tuber. Vacant tunnels are lined with brown, corky skin. Rough pimples and cracks are formed on the surface where larvae enter or where tunnels converge; cracks resemble common potato scab. The marketability of table potatoes is reduced because damaged tubers are rough looking and must be peeled deep to remove the brown thread-like tunnels. The germination of seed potatoes is not affected. Main or late crop potato varieties are most severely attacked.
Adults are shiny black beetles about 3 mm long which jump quickly when disturbed. Larvae are white, with brown heads and 12mm long when mature.
Adults overwinter in the soil and emerge from early May to late June. Each female lays about 90 eggs in the soil near the developing tubers. Larvae feed for about three weeks on the tubers and pupate in the soil. There are up to three generations a year; these overlap. First-generation larvae feed from early June to early July, second generation from early July to early August, and third generation from early August to early September.
Early in the growing season make visual observations to detect beetles or beetle feeding damage on the potato foliage. After the foliage is 15 or more centimetres high, the population of beetles should be measured by net-sweeping. Sweeping is reliable only under conditions of low wind and bright sunlight with the temperature above 21°C. Use a 38 cm net and take five samples of 25 net-sweeps each, per ha. Sample throughout a field at regular 10-day intervals throughout the growing season. Twenty-five samples (each of 25 net-sweeps) is enough for fields of 4 ha or larger if the samples are taken diagonally from corner to corner in two directions. Continue treatments if there is an average of more than one beetle per 10 net-sweeps. Net sweeping is most effective when conducted on an area-wide basis.
Insecticides are applied either to the soil or to the foliage to kill beetles as they lay eggs or feed. Foliar treatments must be timed properly or damaged tubers will result. Volunteer and untreated potato plants are potential breeding-sites for beetles and should be destroyed or treated.
MINISTRY OF AGRICULTURE AND FOOD. Flea Beetles Mainly:
Occur in most vegetable-growing areas in British Columbia. Economic damage occurs only when populations are high.
Cole crops: broccoli, kohlrabi, brussels sprouts, radish, cabbage, rutabaga, cauliflower, turnip, kale, potato, tomato
Feeding damage is most severe on seedlings and transplants early in the season or on mature crops near harvest. Small, round holes are chewed through the leaves, producing a shot-hole effect. Larvae feed on the roots.
Adults are 1. 5 to 3 mm long, black or bronze beetles. Their hind legs are well developed for jumping. The legless white larvae are in the soil, and therefore seldom seen.
Depending
on species, there are one or two generations a year. Adults overwinter
in the soil. Eggs are laid on or near the roots
where larvae feed. Mature larvae pupate in the soil near the
host plant. Adults emerge in early August for single-generation
species.
Last-generation adults feed on foliage
Insecticides
should be applied when damage is first observed. Heavy populations
of beetles may migrate from adjacent crops, therefore
monitoring (sequential observation) is essential to prevent
severe, sudden damage. |
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