European corn borer

Egg

Females lay their eggs in clusters of 15–20 on the underside of the leaf.

Damage

• The caterpillars spread over the plant and, in sheltered places (in the leaf axils, under the cob husks), bore into the stem, where they feed.
• The caterpillars first bore into the leaf stalks and leaf sheaths, then damage the stem, the inflorescence, the shank, the cob and the grain.

When to look

• The moth flight usually coincides with the start of tassel emergence in maize.
• In the Steppe, flight of first-generation moths was recorded from the end of the third ten-day period of May (Odesa oblast), and in the other oblasts in the first half of June. Even before they appear in maize, millet and sunflower crops, the moths first fly on thick-stemmed weeds.
• In the Forest-Steppe, moth flight lasted from mid-June to mid-July. It was counted as the number of individuals per light, food-bait or pheromone trap per day.

How to count

The moths are active at dusk and at night. Their flight intensity is counted per 10 steps or per light trap per night.

No rate and no spray timing here: both come from the label and the register.

Agronomy

• Pest numbers are limited by chopping and ploughing in post-harvest residues, constant monitoring of crops and of fields intended for crops attractive to the pest, and keeping to the timing of agronomic operations.
• Against pyralid moths, weeds are destroyed, row crops are sown early and the inter-rows are cultivated after the first-generation caterpillars have pupated. Areas with a high density of caterpillars are disc-harrowed and given deep autumn ploughing.

Biological control

• In the main maize-growing zones, especially in the Forest-Steppe, the volume of Trichogramma releases should be increased during the pest's egg-laying period.
• To protect hemp, Trichogramma (100–150 thousand per hectare) is released at the start of and during mass egg-laying by European corn borer females.
• Against pyralid moths, the pyralid form of Trichogramma is released in 3–4 rounds at 5-day intervals.

Yield loss

It can cause up to 25% loss of maize grain yield. The damage it does to maize plants becomes an entry point for infections.

Generations a year

In the Steppe it developed in two generations, and in the Forest-Steppe and Polissia in one. In Zakarpattia oblast the second generation developed facultatively.

Overwintering

Plant residues infested with caterpillars that were not chopped or incorporated into the soil are the foci from which the pest spreads.

Favourable conditions

• Moderate air temperature with high humidity can lead to an increase in moth numbers, higher fecundity of females and the hatching of a large number of caterpillars. Unfavourable conditions during flight and mating can reduce the fecundity of the moths.
• Laid eggs die en masse from drying out. Atmospheric drought can also cause heavy mortality of caterpillars of the first instars.
• Excessive humidity and low air temperature slow the development of caterpillars and pupae and cause partial mortality among them, in particular because they are more affected by diseases.
• Repeat maize crops and crops bordering unploughed fields after thick-stemmed crops need the most attention.

Natural enemies

Eggs of both the first and the second generations are parasitised by the natural Trichogramma population.

Every fact rests on a quote from its source, and each quote was checked against the page it is printed on.

1. Зайцева І. А., «Сільськогосподарська ентомологія. Курс лекцій», навчальний посібник, 237 с. · Дніпровський державний аграрно-економічний університет, Дніпро, 2021 · p. 89, 150
2. EPPO Global Database · European and Mediterranean Plant Protection Organization
3. Прогноз фітосанітарного стану агроценозів України та рекомендації щодо захисту рослин у 2025 році · Держпродспоживслужба, НААН, НАН · p. 13, 14, 15, 16
4. Photos: botanygirl, iNaturalist, CC BY 4.0 · Keith Weller, Wikimedia Commons, Public domain · aarongunnar, iNaturalist, CC BY 4.0 · Donald Hobern from Copenhagen, Denmark, Wikimedia Commons, CC BY 2.0 · Donald Hobern, iNaturalist, CC BY 4.0