Common Broccoli Problems
Yellow flowers may appear before the heads are ready to harvest during periods of high temperatures. Planting too late in the spring or failing to give the plants a good start contributes to this condition. Premature flower development also may be caused by interrupted growth resulting from extended chilling of young plants, extremely early planting, holding plants in a garden center until they are too old or too dry, and severe drought conditions. Small heads that form soon after plants are set in the garden are called "buttons" and usually result from mistreated seedlings being held too long or improperly before sale or planting. Applying a starter fertilizer at transplanting gets the plants off to a good start but cannot correct all the difficulties mentioned.
APHIDS: Watch for buildup of colonies of aphids on the undersides of the leaves.
CABBAGE WORMS: Three species of cabbage worms (imported cabbage worms, cabbage loopers and diamond back moth worms) commonly attack the leaves and heads of cabbage and related cole crops. Imported cabbage worms are velvety green caterpillars. The moth is white and commonly is seen during the day hovering over plants in the garden. Cabbage loopers ("measuring worms") are smooth, light green caterpillars. The cabbage looper crawls by doubling up (to form a loop) and then moving the front of its body forward. The moth is brown and is most active at night. Diamondback worms are small, pale, green caterpillars that are pointed on both ends. The moth is gray, with diamond-shaped markings when the wings are closed. The damage caused by diamondback larvae looks like shot holes in the leaf.
The larval or worm stages of these insects cause damage by eating holes in the leaves and cabbage head. The adult moths or butterflies lay their eggs on the leaves but otherwise do not damage the plants. The worms are not easy to see because they are fairly small and blend with the cabbage leaves. Cabbage worms are quite destructive and can ruin the crop if not controlled. They are even worse in fall plantings than in spring gardens because the population has had several months to increase. About the time of the first frost in the fall, moth and caterpillar numbers finally begin to decline drastically. It is impossible to safeguard your crop against every possible kind of insect and disease, but most damage can be prevented. Use paper or metal collars to prevent cutwork damage. Apply a sage vegetable dust such as a combination of rotenone and pyrethrum. Use Dipel or Thuricide organic products to keep caterpillars such as the cabbage worm under control.